**APPENDIX II**

**Analysis of the use of returned Martian samples to support the
investigations described in the MEPAG Goals Document.**

**Prepared by ND-SAG**

**Compilation as of February 28, 2008.**

Note that the Goal, Objective, and Investigation headings plus the blue
text are quotes from the 2006 MEPAG Goals Document, available on the
MEPAG web site http://mepag.jpl.nasa.gov/reports/index.html.

**I. GOAL: DETERMINE IF LIFE EVER AROSE ON MARS**

**A. Objective: Assess the past and present habitability of Mars**

**A1. Investigation: Establish the current distribution of water in all
its forms on Mars**

***Team leads: [Des Marais]{.underline}, McLennan, Nealson***

Water on Mars is thought to be present in a variety of forms and
potential distributions, ranging from trace amounts of vapor in the
atmosphere to substantial reservoirs of liquid, ice and hydrous minerals
that may be present on or the below the surface. The presence of
abundant water is supported by the existence of the Martian perennial
polar caps, the geomorphic evidence of present day ground ice and past
fluvial discharges, and by the Mars Odyssey GRS detection of abundant
hydrogen (as water ice and/or hydrous minerals) within the upper meter
of the surface in both hemispheres, at mid-latitudes and above. To
investigate current habitability, the identity of the highest priority
H~2~O targets, and the depth and geographic distribution of their most
accessible occurrences, must be known with sufficient precision to guide
the placement of subsequent investigations. To understand the conditions
that gave rise to these potential habitats it is also desirable to
characterize their geologic and climatic context. The highest priority
H~2~O targets for the identification of potential habitats are: (1)
liquid water \-- which may be present in as pockets of brine in the
near-subsurface, in association with geothermally active regions (such
as Tharsis and Elysium), as super-cooled thin films within the lower
cryosphere, and beneath the cryosphere as confined, unconfined, and
perched aquifers. (2) Massive ground ice -- which may preserve evidence
of former life and exist in a complex stratigraphy beneath the northern
plains and the floors of Hellas, Argyre, and Valles Marineris, an
expectation based on the possible former existence of a Noachian ocean,
and the geomorphic evidence for extensive and repeated flooding by
Hesperian-age outflow channel activity. (3) The polar layered deposits
-- whose strata may preserve evidence of climatically-responsive
biological activity (at the poles and elsewhere on the planet) and whose
ice-rich environment may result in episodic or persistent occurrences of
liquid water associated with climate change, local geothermal activity
and the presence of basal lakes.

This investigation would help to explore the hypothesis that Martian
life exists today. To support the search for evidence of currently
habitable environments, the depth and geographic distribution of the
most accessible liquid H~2~O targets must be known with sufficient
precision to guide mission site selection. This investigation would
include both present-day water and evidence for recent liquid water. For
example, samples that indicate aqueous activity during the geologically
recent past (e.g., the most recent 100 million years) might demonstrate
that habitable environments persist today in the subsurface.

Relatively recent habitats might include the following:

> \(1\) Liquid water in near-subsurface brines, in geothermally active
> regions, and as confined, unconfined, and perched aquifers beneath the
> cryosphere.
>
> \(2\) Massive ground ice that might have sustained habitable
> environments during recent climate changes, including those associated
> with excursions to higher obliquities.
>
> \(3\) Polar-layered deposits that might preserve evidence of liquid
> water associated with climate change, local geothermal activity and
> the presence of basal lakes.
>
> \(4\) Diurnal and/or seasonal water cycling during
> hydration-dehydration reactions of hydrous minerals (e.g.
> MgSO~4~•*n*H~2~O). (but is it a habitable environment? -- not likely
> given the low water activities due to salinity and thin film behavior)

Important measurements would include the following:

> \(1\) Abundances of water in crustal materials, ices and atmosphere.
> These measurements would help to reconstruct crustal inventories and
> characterize the potential for recent habitability.
>
> \(2\) Oxygen and hydrogen isotopic compositions of these water
> reservoirs. Isotopic measurements would help to determine the sizes of
> these reservoirs and they also could help us characterize processes
> that exchange water between the atmosphere, crust, minerals and ice
> deposits.
>
> \(3\) Composition of salts or other species that might indicate the
> solute compositions and the water activities of any aqueous phases
> that existed during recent geologic epochs. The solute contents of
> water affect its capacity to sustain a habitable environment.

Because a Mars sample return mission could not access liquid water
directly, it would be critical to document the geological and
environmental contexts of the collected samples in order to infer the
nature of any recent aqueous environments. For example, a sample from a
rock ejected from a large impact crater during the geologically recent
past might provide evidence that a subsurface aquifer exists even today.
Salt deposits resulting from evaporation or sublimation of water could
provide evidence of water transfer from the subsurface to the
atmosphere. An icy sample would contain existing water. In all cases,
samples require field observations to document their contexts and
origins. The scales of imaging during a Mars sample return mission
should range from orbital through rover panoramic camera to microscopic
imager.

**Sample types needed.** Water-containing phases. Other materials that
water has altered either physically or chemically might indicate water
activity in the geologically recent past. These materials might
indicate, for example, that habitable environments exist today in the
deep subsurface or perhaps existed intermittently near the surface.

**Sample diversity needed.** A suite of samples that would allow
collective characterization of both the geologically recent water
reservoirs in the atmosphere, ices, regolith and deep subsurface and the
processes that link these reservoirs.

**Physical condition (rock, pulverized rock, etc.).** Intact rock
samples, such as chips and cores, would be optimal because they best
preserve any fluid inclusions, microtextural relationships or
environmentally labile hydrated phases. Pulverized rock might be useful
to identify relatively more stable hydrated phases if samples are not
heated to the point where such phases are degraded. The same would apply
to ice samples until they are hermetically sealed for return.
Atmospheric water and trace gases that are quantitatively trapped and
hermetically sealed also would add value to this investigation.

**Contamination types and limits that affects this investigation.**
Water and any materials having exchangeable oxygen and hydrogen in
spacecraft materials might affect the abundance and stable isotopic
composition of hydrated samples. Amounts that exceed the equivalent of
1000 ppm water in the samples might substantially alter hydrated
minerals present at the level of one weight percent in the samples and
therefore could create potentially serious levels of contamination. The
stable isotopic composition of any exchangeable oxygen and hydrogen in
spacecraft materials should be characterized.

**Sample number and mass.** The requirements for mineralogical context,
the expected abundances of hydrous phases and the contamination concerns
call for individual sample sizes in the range 1 to 5 grams, especially
in order to evaluate textural relationships. On the other hand, sizes on
the order of \~1 gram or less should be sufficient for most chemical and
isotopic analyses. A suite of \~5 samples would be desired to
characterize variations in hydration and water-rock interactions.

**Vulnerability of samples to degradation effects (T, volatile loss,
etc.).** Temperatures that exceed maximum Mars ambient temperatures at
the site of sample collection are expected to alter any ices and also
the most sensitive hydrated minerals. Partial pressures that are lower
than those at minimum Mars ambient partial pressure would similarly
cause degradation of these phases. Alteration of hydrous phases and ices
would compromise some isotopic analyses and most textural analyses for
samples with substantial water.

**Maximum sample temperatures for sample integrity.** Keeping samples
below maximum Mars ambient conditions would achieve 100% of the
objective. Sample handling and storage temperatures that exceed 50^o^C
almost certainly would seriously degrade some samples that contain
polyhydrated phases (e.g., see figure, below). Samples of ice should be
kept below temperatures where they sublimate rapidly after acquisition
and before storage in hermetically sealed containers. Storage containers
for all hydrous samples should be hermetically sealed.

![](media/image1.jpeg){width="4.679861111111111in" height="3.28125in"}

**Impact of degradation on the investigation.** Elevated temperatures
would alter phases perhaps to a point where the original hydrated phases
could not be reconstructed. Loss of volatiles during acquisition and
handling might fractionate the composition of those that remain to the
point where original isotopic compositions could no longer be inferred.
At the very least, sealed sample containers coupled with sample
characterization on Mars should maximize the possibility of
"reconstructing" degraded samples.

**Required/preferred sampling hardware.** Rock and ice corers that
achieve minimal heating during sampling would be required. Sample
handling should heat the samples only minimally. Sample processing
probably should be achieved outside the rover body to remain at or below
Mars ambient conditions. The most thermally sensitive samples should be
stored individually in hermetically sealed containers within one sol of
sampling.

**Data needed for sample choice and in situ characterization.** Image
the rock outcrop or regolith sampling site to document their macroscale
textures and any indications of their composition and origin. Performing
spectroscopic (NIR or MIR) and elemental abundance measurements to guide
selection of optimal samples should be a priority. An *in situ*
pyrolytic analysis of candidate samples could assay the abundance and
composition of water or other key volatile species.

**Estimate of required mobility range.** This requirement would be very
site-specific. High latitude sites on ice might require horizontal
mobility ranging from zero to a few 100 meters, but drilling to depths
of several centimeters to meters. Mid- to low-latitude sites might
require mobility of several kilometers to access sample diversity.

**Additional comments.** Hydrated or water-containing samples tend to be
sensitive to elevated temperatures or prolonged exposure to conditions
where water vapor pressure is lower than in their original environments.
These samples should be acquired and processed at or below maximum local
ambient conditions. Sensitive samples should be stored in hermetically
sealed containers as soon as possible. There should be capability for
sealing samples as quickly as possible, preferably within minutes to
hours if needed but certainly within one sol. They would require similar
confinement and storage conditions in the sample receiving facility on
Earth.

\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_

**A2. Investigation: Determine the geological history of water on Mars,
and model the processes that have caused water to move from one
reservoir to another.**

***Team leads: [Des Marais]{.underline}, Carr, McLennan,** Grady,
Westall*

In order to assess past habitability, we need to start with
understanding at global scale the abundance, form, and distribution of
water in Mars' geologic past. A first-order hypothesis to be tested is
that Mars was at one time warmer and wetter than it is now. This could
be done in part through investigation of geological deposits that have
been affected by hydrological processes, and in part through
construction of carefully conceived models. One key step is to
characterize the regional and global sedimentary stratigraphy of Mars.
It is entirely possible that Mars had life early in its history, but
that life is now extinct.

The aqueous history of Mars can be divided into three eras: (1) the
Noachian for which we have evidence that suggests widespread episodic
precipitation and the consequent fluvial erosion, lacustrine
sedimentation, weathering and groundwater activity, (2) the
post-Noachian which is characterized largely by dominantly dry
conditions punctuated by episodic floods widely spaced in time, and (3)
the recent geologic past for which the water story is dominated by gully
formation, glacial activity, thin aqueous alteration rinds on exposed
surfaces and changes at the poles.

*Noachian era (4.1-3.7 Gyr ago).* This is the era for which we have the
best and most abundant geomorphic evidence for warm climatic conditions.
Desired samples include sediments from deltas, and from layered
sequences both in local lows such as craters and from the more extensive
Noachian 'etched' terrains. Samples should include both clastic and
chemical sediments, and be taken from as diverse a suite of
stratigraphic horizons as is practical. Sedimentary structures, the
size, sorting and rounding of grains, and the distribution of soluble
minerals would all help understand the environment under which the
sediments accumulated. Also desirable would be samples rich in possible
weathering products such as phyllosilicates. Sequences of samples from
soil profiles would be particularly important for determining climatic
conditions under which the soil profiles formed. Given the high rates of
volcanism and meteorite impacts and seemingly widespread presence of
water in Noachian times, hydrothermal activity was likely. Should any
such sites be found they would be of high priority for sampling. Other
possible samples that would complement the more accessible upper
Noachian samples are samples from sections deep within the Noachian,
such as those at bases of cliffs in eastern portions of canyons
dissecting Noachian-aged rocks. Finally, sediments from the Noachian
near the south pole may preserve a record of conditions at the poles
during this early era, and should Noachian marine deposits be
identified, they would be strong candidates for sampling.

*Middle Mars History (3.7 Gyr to 0.1 Gyr ago).* This era encompasses
most of the history of the planet and is characterized by extremely low
rates of weathering and erosion, formation of the canyons, formation of
most the planet's large flood features and the possibly the consequent
episodic accumulation of large bodies of water. In addition, ice-abetted
processes appear to have been pervasive in mid to high latitudes. The
era appears to have been mostly dry and cold. Key water-related issues
are whether there were any short, warmer, climatic excursions and if so
when they occurred, how long they lasted, and whether there were ever
large standing bodies of water in enclosed areas such as the canyons,
Hellas and the northern plains. As with the Noachian, the most valuable
samples for understanding the water story would likely be sediments.
Possibly the thickest sequence of stratified sediments so far identified
from this era are within the canyons. Some of these post-Noachian
sediments are eroded by young valley networks. Samples would be needed
from both the stratified sediments and from the deposits left by the
superimposed streams, and they should include both the salt-rich
fractions and those that are salt poor. Samples also would be desirable
from post-Noachian sedimentary sequences that occur in local lows within
the predominantly Noachian uplands, particularly where there is
supplementary evidence that water was involved in their deposition.
Samples also would be desired of layered deposits from more extensive
low areas, such as Utopia within the northern basin, should any be
identified. Such samples would indicate whether bodies of water had in
fact ever occupied these areas and if so what kind of depositional
regimes prevailed. As with the Noachian, if any hydrothermal deposits
are identified, they would be of interest, and in the event that
mineralogical evidence of substantial (cm+ - thick) young weathering
profiles is found, they would be of high priority for sampling. Samples
of Hesperian and lower Amazonian plains around the South Pole might
provide clues about water activity and climate in middle Mars history.
Water ice has played a significant role in the evolution of the
landscape in the mid to high latitudes. In the fretted terrain, in
particular, large fractions of ground ice are probably present near the
surface. The ice is probably old, and might be of interest for its
isotopic composition and presence of other volatiles.

*Recent (\<100 My) Mars history.* The main geologic objectives of
samples from this era would be first to determine if indeed there has
been any recent activity at the surface involving liquid water, and
second to determine the effects of astronomical motions on the
distribution of water and ice. Present day liquid water has been invoked
to explain gullies, together with their associated bright streaks and
dark streaks. The origin of both features is, however, controversial.
Alternative suggestions for the gullies are that they formed by dry mass
wasting or with liquid water but during a former period of high
obliquity. The dark streaks have also been attributed to dry mass
wasting. Samples of deposits at the ends of the gullies could resolve
these issues and have broad biological and geological implications. The
recent history of the redistribution of water as a result of
astronomical perturbations may be recorded in the polar layered deposits
(and perhaps further afield in near-surface regolith deposits at mid- to
low-latitude). The sampling of polar deposits should include both light
and dark bands at various stratigraphic levels. At both poles samples
should also be taken of the stratigraphic units below the uppermost
layered sequence.

Two major issues could confront the selection of samples that would lead
to a better understanding of the history of water. The first would be
our ability to confidently identify where the desired samples could be
collected. The difficulty of identifying water-processed samples is
illustrated by Gusev crater, where geologic evidence from orbital
imaging strongly, but falsely, suggested that lake deposits might be
accessible near the landing point. The second issue would be our ability
to date the samples and so determine the sample's historical contexts.
Dating the age of sedimentation, sedimentary processes and ices is
difficult on Earth. It would be much more difficult on Mars where we
would have far less supporting stratigraphic and chemical data. The
types of samples listed below are narrowly directed toward understanding
water-related processes, but their selection should be accompanied by a
sampling program directed at dating the samples, and this might require
a complementary suite of samples.

**Sample types needed.** Materials that water has altered either
physically or chemically. Examples of key rocks include aqueous clastic
and chemical sediments, and aqueously weathered soils, and cemented
eolian features. Examples of key minerals desired in samples include
phyllosilicates, sulfates, carbonates, SiO~2~ minerals, other hydrous
minerals, soluble salts (e.g., halides, nitrates, etc.) and minerals
associated with hydrothermal activity.

**Sample diversity needed.** A suite of aqueous sediments in layered
sequences should be taken from appropriately diverse stratigraphic
horizons that would allow their depositional environments to be defined.
A variety of sedimentary structures, the size, sorting and rounding of
grains, the distribution of soluble minerals would all help understand
the environment under which the sediments accumulated. Sequences of
samples from soil profiles would define the processes and conditions of
soil formation. Should hydrothermal deposit be discovered, sequences of
samples along paleo-temperature, paleo-flow lines and/or paleo-redox
hydrothermal gradients would help to define their environments of
formation, including potentially the fluid compositions.

**Physical condition (rock, pulverized rock, etc.).** Intact rock
samples such as chips and cores would be optimal because they best
preserve any fluid inclusions or environmentally labile hydrated phases
in addition to textural evidence of aqueous processes. Pulverized rock
might be useful to identify relatively more stable hydrated phases if
sample are not heated during collection and handling to the point where
such phases would be degraded.

**Contamination types and limits that affect this investigation.** Water
and any materials having exchangeable oxygen and hydrogen in spacecraft
materials might affect the abundance and stable isotopic composition of
hydrated samples. Amounts that exceed the equivalent of 1000 ppm water
in the samples might create serious levels of contamination. The stable
isotopic composition of any exchangeable oxygen and hydrogen in
spacecraft materials should be characterized.

**Sample number and mass.** The requirements for mineralogical context,
the expected abundances of hydrous phases and the contamination concerns
would call for individual sample sizes in the range 1 to 5 grams,
especially for textural analyses. Note however, that all chemical and
isotopic analyses likely could be performed with samples on the order of
\~1 gram. The composition of host phases, together with the anticipated
need to sample stratigraphic sequences (minimum 3-5 samples), soil
profiles (minimum 3-5 samples) or geochemical gradients (minimum 3-5
samples) indicate that at least ten samples would be required to achieve
this investigation.

**Vulnerability of samples to degradation effects (T, volatile loss,
etc.).** Temperatures that exceed maximum Mars ambient temperatures at
the site of collection are expected to alter any ices and also the most
sensitive hydrated minerals. Partial pressures that are lower than those
at minimum Mars ambient partial pressure would similarly cause
degradation of these phases. The stability of hydrated sulfate minerals
is also highly sensitive to relative humidity and control or, at the
least, monitoring relative humidity would be a priority.

**Maximum sample temperatures for sample integrity.** Same as for
Investigation A1: Keeping samples below maximum Mars ambient conditions
would achieve 100 percent of the objective. Sample handling and storage
temperatures that exceed 50^o^C almost certainly would seriously degrade
some samples that contain polyhydrated phases. Samples of ice should be
kept below temperatures where they sublimate rapidly after acquisition
and before storage in hermetically sealed containers. Storage containers
should be hermetically sealed.

**Impact of degradation on the investigation.** Many sample types
containing waters of hydration, hydroxyl groups or phyllosilicates would
suffer alteration at elevated temperatures (see comments for
Investigation A1). Elevated temperatures would alter phases perhaps to a
point where the original hydrated phases could not be reconstructed.
Loss of volatiles might fractionate the composition of those that remain
to the point where original compositions could no longer be inferred.
Elevated temperatures could decompose certain minerals and disrupt
microscale diagnostic sedimentary textures. Accordingly, sealed
containers would be a priority in order to preserve all components and
maximize the possibility of "reconstructing" materials altered during
sampling and transport to Earth.

**Required/preferred sampling hardware.** Rock and ice corers that would
cause minimal heating during sampling. Sample handling that would heat
the samples only minimally. Sample processing probably should be
achieved outside the rover body to remain at or below Mars ambient
conditions. The most thermally sensitive samples should be stored
individually in hermetically sealed containers as quickly as possible
but certainly within one sol of sampling.

**Data needed for sample choice and in situ characterization.** Image
the rock outcrop or regolith sampling site to document their macroscale
textures and any indications of their composition and origin. Perform
spectroscopic (NIR or MIR) and elemental abundance measurements to guide
selection of optimal samples.

**Estimate of required mobility range.** The need to land at a safe
(flat) site would require mobility of several km in order to approach
and sample key localities such as stratigraphic sequences, hydrothermal
deposits, etc. and to perform observations of geological and
environmental context.

**Additional comments.** Hydrated or water-containing samples tend to be
sensitive to elevated temperatures or prolonged exposure to conditions
where water vapor pressure is lower (or possibly higher) than in their
original environments. These samples should be acquired and processed at
or below maximum local ambient conditions. Sensitive samples should be
stored in hermetically sealed containers within one sol of sampling.
They would require similar confinement and storage conditions in the
sample receiving facility on Earth.

\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_

### **A3. [Investigation:]{.underline} Identify and characterize phases containing C, H, O, N, P and S, including minerals, ices, and gases, and the fluxes of these elements between phases**. 

***Team leads: [Pratt, ]{.underline}**Des Marais, Grady, Eigenbrode*

Assessing the availability of biologically important elements and the
phases in which they are contained would allow a greater assessment of
both habitability and the potential for life to have arisen. Detailed
investigations for carbon are the primary focus of Objective B and
therefore will not be further expounded upon here. Nitrogen, phosphorous
and sulfur are critical elements for life (as they are on Earth), and
the phases containing these elements and fluxes of these elements may
reflect biological processes and the availability of these elements for
life. They are often intimately associated with carbon and their
distribution is commonly controlled by water and oxidation states, so
interpreting these elemental cycles in terms of C, H, and O is extremely
valuable to understanding habitability. The redox chemistry of S is of
interest because of its known role in some microbial metabolic
strategies in terrestrial organisms and the abundance of sulfate on the
surface of Mars.

The geochemical and biogeochemical cycles of carbon are intimately
linked to five light elements that are the principal heteroatoms in
biogenic and abiogenic organic matter. With the notable exceptions of
graphic or diamondoid carbon, heteroatoms serve to balance charge in
materials with chains and/or rings of carbon as the backbone of the
molecular structure. In biogenic organic matter, heteroatoms impart
specific functionalities related to chemical reactivity or 3-dimentional
shape. Heteroatoms are extracted from the surrounding environment during
growth and are released back to the surrounding environment during
decomposition following reaction pathways that often involve substantial
kinetic isotope effects. Consequently, changes in elemental ratios or
stable isotopic compositions of gases, liquids, and minerals are
important lines of evidence for inferring the presence of extant or
extinct life. Sedimentary materials deposited or precipitated in the
presence of liquid water would be the most important target rocks for
investigating heteroatomic links in the carbon cycle on Mars.
Hydrothermal or mesothermal mineral deposits along fracture or gully
flow paths for geofluids would be additional priority targets for
sampling. Fresh rather than weathered samples would be a priority given
the reactivity and valence variability of carbon, nitrogen, and sulfur.

Due to the close links among these elements, this investigation
substantially overlaps Goal 1, B1: Determine the distribution and
composition of organic carbon on Mars. It is also linked to Goal 1, A4:
Determine the array of potential energy sources available on Mars to
sustain biological processes, because many of these elements are
important in biological metabolic cycles. The investigation requirements
described here are exactly the same as those in Goal 1, B3: Characterize
links between C and H, O, N, P, and S because the sample needs would be
identical.

**Sample types needed.** Rocks cores or rock fragments would be the
types of samples needed to study minerals that are sensitive indicators
of links between C and H, O, N, P, and S. Direct evidence of carbon
cycling could be found in sedimentary organic matter, minerals
containing hydrocarbon-bearing fluid inclusions, minerals containing
sorbed organic acids, and methane-bearing clays or zeolites. Hydrogen
and oxygen are common in many minerals and aqueous fluids, so links to
the carbon cycle would be established primarily through stable isotopic
compositions of sedimentary deposits containing phyllosilicates,
carbonates, and hydrated evaporates. Oxidized and reduced forms of
nitrogen are relatively uncommon in minerals so samples containing
nitrates, ammonium minerals, and ammonia-bearing clay or zeolite
minerals would be high priority targets for sampling. Phosphate minerals
can incorporate Fe(II), Fe(III), Mn(II), and Mn(IV), thereby providing
evidence of changes in redox, commonly associated with decomposition of
organic matter. Similarly, carbonates can serve as sensitive indicators
of reducing aqueous conditions by incorporation and preservation of
Fe(II) and Mn(IV). Evidence of sulfur associated with carbon cycling can
be found in sulfate minerals containing Fe(II) or Fe(III), elemental
sulfur, metallic disulfides, and metallic monosulfides.

**Sample diversity needed.** Scientific objectives would be diversity
driven and necessitate sedimentary or hydrothermal/mesothermal rocks
units and evidence of geological diversity within rover range. A suite
of \~5 samples would provide a good estimate of initial diversity.

**Physical condition (rock, pulverized rock, etc.)**. Fresh rock
collected by impact fracturing or coring would be required to maintain
sample integrity.

**Contamination types and limits that affect this investigation.**
Contamination by refined hydrocarbons (waxes, lubricants, and greases),
soft plastics, and solid rocket fuels (nitrogen, carbon, and sulfur
constituents) would be highly problematic even at low ppm or high ppb
levels. Specific levels that would be required are similar to those
listed in Goal 1, B1, "Determine the distribution and composition of
organic carbon on Mars" due to the similar nature of required samples.

**Sample number and mass.** Sample number depending on variation in rock
type and the currently unknown concentrations of CHNOP and S. Sample
mass in the 1-2 gm range with a few samples in the 5-10 g range to allow
for molecular characterization of trace-level organic constituents if
they are abundant enough. Specific constraints on abundances are
described in Goal 1, B1: Determine the distribution and composition of
organic carbon on Mars. Sample requirements would be the same for this
investigation

**Vulnerability of samples to degradation effects (T, volatile loss,
etc.).** Samples for this investigation would be highly vulnerable to
degradation associated with oxidation and or hydration due to reactive
character of potential electron donors (non-aromatic organic matter and
minerals containing reduced metals). Specific constraints for organic
compounds are listed in Goal 1, B1: Determine the distribution and
composition of organic carbon on Mars. For minerals containing CHNOP and
S, samples are less vulnerable to degradation, but volatile loss could
significantly changes trace component concentrations.

**Maximum sample temperatures for sample integrity.** Storage and
transportation conditions would need to remain at or below maximum
ambient surface temperature for surface samples and at or below
collection temperature for subsurface samples. See specific constraints
for organic compounds under Goal 1, B1: "Determine the distribution and
composition of organic carbon on Mars." For minerals containing these
elements, little degradation is likely at 50°C for less than a few hours
in the absence of hydrous phases. However, oxidative processes are
likely present if water is released during heating, which would
significantly damage sample integrity.

**Impact of degradation on the investigation.** See specific effects for
organic compounds under Goal 1, B1: Determine the distribution and
composition of organic carbon on Mars. Redox reactions catalyzed by
water would substantially reduce the value of samples due to changes in
bonding of these elements.

**Required/preferred sampling hardware.** An impact tool or corer on a
rover arm that could extend 10 cm or more away from the rover footprint
would be preferred.

**Data needed for sample choice and in situ characterization.**
Millimeter-scale imaging, mineralogical information, and elemental
composition would be required for sample collection.

**Estimate of required mobility range**. Hundreds of meters to a few
kilometers would be needed to obtain sample diversity.

**Additional comments.** All samples would need to be individual package
in gas-tight glassy containers. Temperatures would need to be maintained
well below the freezing point of concentrated sulfate brines. Head-space
gas could be Martian atmosphere or an inert gas and oxidant-resistant
seals would be rquired.

\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_

### **A4. [Investigation:]{.underline} Determine the array of potential energy sources available on Mars to sustain biological processes.** 

***Team leads: [Pratt]{.underline}, Nealson***

This investigation would allow identification of the potential of Mars
to have harbored or continue to harbor life. Biological systems require
energy. Therefore, measurement of the availability of potential energy
sources would be a critical component of habitability, and understanding
how life might use them is a critical component of designing
scientifically robust life detection experiments. Sources of energy that
should be measured may include chemical redox, pH gradients, geothermal
heat, radioactivity, incident radiation (sunlight), and atmospheric
processes.

Energy for life can come from sunlight or chemical disequilibrium.
Solid, liquid, and gaseous species on Mars provide chemical energy that
could be used by life. Thus, the characterization of oxidation contrasts
and the energy available for various potential biological reactions
would provide a context in which to understand potential energetically
useful metabolisms. Such analyses would be greatly enhanced by the
return of virtually any sample of rock, regolith, regolith gas,
atmospheric gas, or ground ice obtained from Mars would enhance our
understanding of energy sources.

The wide range of samples that would be useful for this investigation
means that sample requirements would overlap those of many other
investigations. In addition, much of the characterization could be
accomplished *in situ*. Thus, this investigation would place few
constraints on specific samples, and it should be viewed as a
supplementary benefit for sample return rather than a driving influence
on landing site or sample characteristics.

**Sample types needed.** Any sample category would be useful, and the
following sections are divided into these groupings: 1) Sedimentary
rocks; 2) Hydrothermal rocks; 3) Low temperature weathered rocks; 4)
Igneous rocks; 5) Regolith; 6) Dust; 7) Ice; and 8) Atmospheric gases.

**Sample diversity needed.** Suites of rocks with contrasting oxidation
states would be required for types 1, 2, 3, 4, and 5. Particular
attention should be paid to variations in rock units likely to contain
Fe- and Mn-bearing minerals, metallic monosulfide or disulfides, and
organic carbon. These phases often have multiple oxidation states and
have the potential to serve as electron acceptors or donors in metabolic
pathways.

Regolith samples (5) from multiple sites and at multiple depths (e.g. 2,
5, and 10 cm below the surface) would be needed to assess the influence
of bedrock on chemical composition and horizonation of regolith. This
would provide information on oxidation gradients that could be used by
biological processes.

Single samples of dust (6) and atmospheric gases (8) would be sufficient
to address this investigation. However, multiple samples of pore gases
within regolith would be necessary to provide constraints on energy
available in volatiles within the regolith.

Stratigraphically constrained samples of ground ice (including water
ice, CO~2~ ice, and clathrates of CO~2~ and/or CH~4~) would be needed to
assess the current upward flux of volatiles as well as the potential for
periods of high obliquity to impact the availability of energy from
release of previously sequestered volatiles in ices and hydrated
minerals.

**Physical condition (rock, pulverized rock, etc.)** Intact samples of
rock would be most useful, although oxidation state variations could be
characterized in pulverized rock. Gas samples must be collected separate
from other samples, as must ice samples.

**Contamination types and limits that affect this investigation.** Rock
and regolith samples would have low sensitivity to parts-per-million
level contamination from refined hydrocarbon lubricants or plastics,
moderate sensitivity to parts-per-million level contamination from
industrial metals, and low sensitivity to parts-per-million level
contamination from industrial glasses or enamels. Ice samples would have
high sensitivity to contamination from hydrocarbons and metals due to
the possibility of inducing phase changes or having diffusion of
contaminants in water films at grain boundaries.

**Sample number and mass.** Suites of \~5 samples of each type with a
minimum mass of 2-3 grams are would be necessary for this investigation.

Concentration of methane, carbon dioxide, and water vapor as well as
isotopic composition of hydrogen in methane and water vapor and isotopic
composition of carbon in methane and carbon dioxide from regolith gas
would be important scientific objectives for assessing available energy.
Twenty milliliter gas samples containing 30 nanomol of water vapor could
be analyzed for the hydrogen isotopic composition of hydrogen using
commercial IR instrumentation. A regolith gas sample containing about 50
micromol of methane or carbon dioxide would be needed for duplicate
determinations of the carbon isotopic compositions in a return sample
using routine gas source mass spectrometry. Assuming 1 ppt methane at
0.01 atmosphere, each return gas sample would need to be about 5 ml in
volume. Development of more precise analytical techniques would allow
smaller gas samples.

**Vulnerability of samples to degradation effects (T, volatile loss,
etc.).** Due to interest in potential electron donors for metabolism,
fresh-rock samples collected as cores or chips would need to be
protected from exposure to atmospheric oxidants and to moisture.
Volatile loss would be a particular problem for hydrated minerals and
ices. Temperature sensitivity would be a serious problem if hydrated
minerals decompose or dehydrate. Although alteration temperatures are
mineral specific, keeping the sample at or below maximum ambient
temperature at the sample site would be the best way to ensure the
integrity of hydrated minerals. Ice samples would require maintaining
samples at or below the temperature of the ice at the time of sampling.

**Maximum sample temperatures for sample integrity.** For non-hydrous
rock and regolith samples, a maximum temperature of 50°C for several
hours would not impair this investigation for inorganic components.
Volatile organic components could be lost and would begin to react at
temperatures and pressures above ambient Martian conditions, and
disequilibrium gas components, such a CH4, may also react at
temperatures of 50°C. Temperatures of 10°C would be much preferable.
Hydrous minerals should be maintained at ambient martian conditions to
maintain oxidative disequilibrium. Ices, if returned must be maintained
at -10°C or colder temperatures to limit redox reactions and volatile
loss during return to earth.

**Impact of degradation effect on the investigation.** Degradation of
gases, ices, and hydrated minerals would significantly reduce the
scientific value to below justification for return samples because the
reconstruction of initial redox conditions are probably not possible.
Partial oxidation and hydration of rock and regolith samples would still
allow for significant scientific study of material below the zone of
alternation. Anhydrous samples are unlikely to be subjected to
significant oxidative equilibration, unless they are organic-rich.

**Required/preferred sampling hardware.** Sampling hardware needs would
be highly variable depending on type of sample. A method for collecting
intact, fresh rock samples would be highly desirable. Stratigraphically
preserved, solid ice samples would be needed. Gas samples might need
concentration to sample a sufficient number of moles for isotopic
analyses.

**Data needed for sample choice and in situ characterization.** Visual
images with millimeter-scale resolution and spectral data on mineral and
bulk elemental composition for rock and regolith samples would be needed
to identify the most appropriate samples. Gas analysis capable of
detecting methane and water vapor concentrations in regolith gas samples
and the composition of volatiles from ground ice would significantly
improve the quality of gas samples.

**Estimate of required mobility range**. A minimum mobility of 100's of
meters to a kilometer away from landing contamination would be essential
for clean samples of trace volatiles. Access to multiple rock units
would be required for collection of a diverse suite of samples to
characterize variability in oxidation states.

**Additional comments.** Both biogenic and abiogenic organic matter in
gaseous, liquid, and solid states are significant potential energy
sources for life. Although the concentration of organic constituents at
or near the surface may be low, a few larger rock samples (5 to 10 g)
should be collected in order to fully inventory the concentration and
composition of organic matter.

\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_

**B. Objective: Characterize Carbon Cycling in its Geochemical Context**

### **B1. [Investigation:]{.underline} Determine the distribution and composition of organic carbon on Mars.** 

***Team leads: [Eigenbrode]{.underline}, Benner, Conrad, Glavin,
Steele***

The spatial distribution and composition of organic carbon have not been
characterized, but are instrumental in understanding the biological
potential of Mars. (Methane and other simple reduced carbon molecules
are included as "organic carbon" in this context.) Abiotic synthesis of
organics, delivery of organics to Mars via meteorites, and possible
biological production of organics must all be evaluated in the context
of carbon cycling on Mars. Characterizing the molecular and isotopic
composition of organic carbon is essential for determining the origin of
the organics shown in Table 2, which includes the types of organic
materials that need to be detected and deconvolved from each other.
Investigations would require sufficient spacecraft cleaning and
verification to avoid likelihood of contamination, in addition to
careful planning of specific methods to identify and exclude forward
contamination at the experiment level. Example measurements include
analysis of the concentration and isotopic composition of organic
carbon, characterization of the molecular structure of organic carbon,
or identifying and monitoring reduced carbon (e.g., methane) fluxes.

Organic materials are a key component of a biological carbon cycle, and
they may play an important role in the carbon cycle of a planet without
life. They have a variety of sources including primary biologic,
subsurface abiogenic (i.e. from serpentinization), and meteoritic
origins, in addition to secondary diagenetic derivatives of the former.
A suite of organics in a single sample could be derived from more than
one of these sources. An understanding of the geological and atmospheric
processes that influence organic carbon distribution, preservation, and
alteration would assist in the identification of organic carbon and,
once detected, provide contextual support for understanding organic
carbon distribution and composition.

The investigation of the distribution of carbon on Mars could be
approached on several levels, which could be viewed as interlocking
investigations. Different approaches would be suitable for specific
sub-investigations, such as:

> *Sub-investigation A. Stability and spatial distribution of exogenous
> organic carbon (meteoritically delivered)*
>
> For this question, we must consider the distribution on a planetary
> scale as well as on smaller spatial scales associated with crater
> impacts, sedimentary structures associated with aqueous alteration
> such as down-cut channels indicative of fluvial transport, and
> volcanic lava flows. In addition to lateral distribution and
> association with sedimentary structures or other morphological
> relationships, we would also want to understand distribution with
> depth, not only as a function of gardening, but also as a function of
> the stability of the meteoritically-predicted organic molecules while
> under attack by radiation and putative chemical oxidant(s). Therefore,
> assessment of exogenous organic carbon distribution would entail
> several spatially distributed sets of measurements, potentially
> associated with a variety of specific geologic environments and
> temporal ranges and each including a depth profile. Rover-accessible
> geological diversity within traversible rover range would support this
> approach; however, measurements to assess latitudinal variations would
> require multiple missions.
>
> *Sub-investigation B. Distribution of indigenously produced organic
> carbon*
>
> There could be several types of indigenous organic carbon on Mars: (1)
> abiotically produced (either by deep alteration of igneous rock or
> sedimentary alteration subsequently, or by prebiotic synthesis in a
> reducing or mildly reducing environments) and (2) potentially biogenic
> organic carbon. The optimal geologic settings for finding these
> records may differ. The abiologically produced organic C associated
> with mafic-rock weathering might be more likely within basalts that
> were hydrothermally altered. The possible biogenic or biologically
> affected organic carbon might be better detected in aqueous deposited
> sediments as in a delta and/or lacustrine setting or spring.

Because we want to know the same distributions for sub-investigations A
and B, a diversity of geologic samples would be required. That being
said, to answer the really big question: What is the global cycling of
carbon on Mars, we need to understand the different organic carbon
sources, fluxes and sinks, as well as the partitioning of carbon between
organic and inorganic phases, including gases. Thus, carbon isotope
measurements of CO~2~ released from carbonate (if we find any), the
atmosphere, and any organic material would be VERY important in order to
understand the impact of a potential biosphere an metabolic isotopic
fractionation, the source of any organic carbon detected (e.g.,
indigenous verses exogenous).

The requirements and strategies for addressing this investigation
largely overlap with other goal 1 investigations (A3-4, B3-4, and C1).
Moreover, addressing other investigations (Goal 1: B2-3, C1-4, and
others) would provide complementary support for this investigation and
would be necessary to build an understanding of carbon cycling on Mars.

**Sample types needed.** Rocks samples containing or in association with
reduced carbon should be given the highest priority. These might include
sedimentary rocks, mafic basalt and peridotite, regolith, and mineral
precipitates from aqueous solutions. Geologically diverse samples that
include samples with reduced minerals also would be a high priority.
Samples containing halogenated salts, precipitated cements, and
phyllosilicates, which may assist in organic preservation should be
considered within geological context of potential sampling sites.
Selecting samples that are more likely to contain organic carbon and to
preserve organics during the process of acquisition to analysis would
improve the likelihood of success in detecting, characterizing, and
structurally inspecting organic carbon.

Samples most likely to have been preserved reduced carbon would have
been shielded from the effects of ionizing radiation (galactic and
solar) on the Martian surface from the time of deposition to sample
acquisition. Aquatic basins and geological materials contribute to this
shielding. Quick removal from the surface condition (e.g., burial or
cementation) would likely enhance chances of organic carbon
preservation. Sub-investigations should include sample collection from
various depths in the subsurface or alternatively from geological
materials that have been recently exhumed or eroded, exposing
radiation-shielded terrain.

**Sample diversity needed.** A diverse sample suite including samples
containing reduced carbon would be desired. Sample suites should include
lithologic, spatial, and/or temporal diversity from geologically related
materials over spatial scales of 2 m or more (with respect to depth,
geomorphology or stratigraphy to the lateral range of a rover).

**Physical condition (rock, pulverized rock, etc.).** Consolidated
sediments, unweathered and weathered rock fragments, or core material
would be required by this investigation and depend on the specific
approach. Rocks pulverized by a drill bit or unconsolidated sediments
have high surface area making them more susceptible to alteration and
contamination by rover-hosted and terrestrial organics; they would not
be appropriate for determining microscopic textural, chemical and
isotopic spatial relationship using Earth-based analytical tools, which
would be an important driver for sample return.

**Contamination types and limits that affect this investigation.**
Forward contamination by organic polymers, lubricants, biomolecules,
dust and other compounds containing carbon could critically affect this
investigation and must be minimized and monitored. Some Earth-based
instrumentation that would be used on returned samples (e.g. ToF-SIM) is
sensitive enough to detect organics adsorbed from the air after seconds
of exposure.

Flight hardware should be decontaminated for organics as much as
possible in addition to biological load as defined by current planetary
protection requirements. A comprehensive organic molecular inventory for
the mission would be necessary to establish chemical relationships and
establish a resource for cross-checking for Earth-contaminants. Sets of
witness plates (e.g., silica wafers, molecular absorbents) should be
employed to measure contamination during the mission. In particular,
witness plates would record contaminants derived from the rocket descent
and other landing effects, such as bag inflation. They would collect
evidence of the organic "noise" necessary for deciphering signatures
from samples. Separate, additional sets of witness plates should be used
to record contamination during curation and processing upon return,
where individual witness plates would serve different analytical
applications. Every effort should be made to minimize sample handling.
All tools and containment vessels should be made of metal, glass, or
ceramic decontaminated for organics. Every effort must be made to avoid
exposure to solid plastics (including fluorinated polymers if possible)
and plasticizers leached into liquids and gases.

Samples should be transferred to storage containers quickly, preferably
autonomously within minutes but no longer than one communication cycle.
Samples should be stored in sealed aluminum, electropolished stainless
steel, or similar low-organic containers. See below for additional
sampling requirements.

**Sample number and mass.** It is difficult to estimate how much sample
material would be necessary to address this investigation in the absence
of detected organics on Mars. Assuming only exogenous reduced carbon is
present and the mass influx of meteorites and IDPs is 3 x10^9^ to 6 x
10^10^ g/yr to the surface of Mars (Flynn, G. J. and McKay, D. S., 1990,
J. Geophys. Res. 95, 14497-14509), meteoritic material could account for
between 2 to 29 wt. % of total Martian surface soil. Applying a
conservative estimate of \~1 wt. % of meteoritic material in the soil, a
1 g sample of Martian regolith would have 10 mg of IDP material
containing 1 mg of carbon (10 wt.% carbon in IDPs). Thus, a conservative
estimate of exogeneous carbon would suggest parts per thousand
concentrations of reduced carbon in Martian soil if none of it decays.
However, this estimate is inconsistent with a negative result for ppb
concentrations of organics in the soil by Viking, suggesting that
organics are being oxidized to CO~2~, the IDP influx estimates are in
error, and/or organic matter from IDPs is diluted by transported
sediments. In the absence of additional constraints on organic
concentrations and organic composition in rocks and regolith, we must
assume that organic carbon is present in trace quantities that may
challenge the detection limits of many analytical instruments. Thus, our
recommendation would be to collect as much sample as possible. One to
ten grams of sample are recommended for characterization, spatial
distribution, isotopic and molecular composition using a range of
analytical tools and assuming total levels of organics in the martian
regolith of 10-100 ppb.

**Vulnerability of samples to degradation effects (T, volatile loss,
etc.).** The structural components in organic matter will continually
react until metastability is reached. Reactions include stereochemical
changes, structural rearrangents, bond cleavage and reaction with other
chemical species (e.g., water, oxidants, halogens, metals, and other
organics). Changes in temperature, pressure, and redox conditions
promote alteration and increases in temperature and pressure can lead to
volatile loss. Mineral phases may also undergo reconstructive phase
transformations, changing microscale geochemical conditions and
influencing organic molecule stability and inclusion chemistry. Organic
biosignatures of both isotopic and molecular nature are particularly
vulnerable to alteration and loss. These processes occur naturally in
most environments; however, post-acquisition conditions could obscure or
destroy the organic structures present at the time of acquisition.

**Maximum sample temperatures for sample integrity.** Due to the lower
atmospheric pressure on Mars, volatiles could be lost from samples by
moderate heating above Martian surface conditions. They would need to be
trapped and contained. Heating followed by cooling could lead to
migration of low molecular weight organics from the interior of the
sample to outside the sample where the migrated molecules could condense
on sample and container surfaces. Whereas refractory organic matter such
as ancient organics can withstand temperatures of 120-200°C, more labile
organics containing functional groups, which are common of biomolecules,
will begin to degrade at temperatures above 50°C, although significant
alteration of amino acids does not begin until 250°C at Martian
pressure. Temperatures below 50°C would be are highly desirable, with
temperatures below 10°C substantially improving sample integrity.

**Impact of degradation effect on the investigation.** Degradation of
organics after sampling would significantly reduce the quality of
samples and limit results of this investigation if less refractory
organics are present. However, if any organics are present, some of the
more stable phases are likely to be preserved, providing substantially
more information than is currently available about the organic inventory
on Mars. Much more characterization of these organics could be
accomplished in returned samples than is possible from *in situ*
analyses.

**Required/preferred sampling hardware.** A coring device or other
method for providing intact rock samples would be preferred for sampling
materials that are not strongly oxidized in the surface environments.
Alternatively, an impact chisel or drill might suffice for specific
sub-investigations.

**Data needed for sample choice and in situ characterization.**
Geological context at regional to microscopic scales could provide key
insight into the sources, specific processes of formation of organics if
they formed *in situ* (e.g., catalytic mineralogical assemblages for
abiogenic carbon), patterns indicative of ancient and extant ecosystems
(e.g., stratigraphic, geomorphic, and geochemical facies in association
with organic composition), and preservation and alteration mechanisms
that influenced any organic compounds. This geological and geochemical
context is critical for understanding the distribution and factors that
influence organic compositions or a paucity of organics. Panoramic
stereo images from the acquisition platform linked to high-resolution
remote sensing images should be used to assess the regional and local
morphological, structural, and stratigraphic geology and macroscale
textures. In addition, *in situ* characterization of mineralogical
assemblages and associations would be necessary to guide sample
selection. In particular, an *in situ* survey of the local
geochemistry/mineralogy and presence of reduced chemical species would
be necessary for sample selection and establishing geological context.
Although these methods might detect ppm reduced carbon, an independent
test for sub-ppb reduced carbon (i.e., below Viking detection limits)
would be desired.

For this investigation, more contextual information would improve our
chances of selecting the optimal samples for return to Earth. *In situ*
detection of reduced carbon would be strongly desired for sample
selection; however, a positive reduced-carbon observation would not be
required in the absence of organic detections by missions prior to
sample return. Sample sets that include samples with detectable reduced
carbon would have the greatest utility in assessing sources and
processes influencing organic composition. However, samples lacking
reduced carbon might be useful for understanding factors influencing
organic carbon preservation, alteration, and loss.

**Estimate of required mobility range.** Sufficient mobility to obtain a
diversity of samples and contextual data would be required for this
investigation.

**Additional Comments.** Samples with a very low surface area would be
less likely to be compromised by alteration reactions and contamination.
Drill core or rock fragments would be preferable and allow for a greater
variety of analyses on Earth (including spatially resolved spectroscopic
analyses), as well as contributing to optimal preservation conditions
and protection from contamination. They would also maintain *in situ*
geochemical relationships, which provide key contextual data for
understanding the processes influencing organic carbon distribution and
composition.

Preservation of organics from recent biological activity would require
substantially more restrictive sample return conditions than organics
from abiotic processes or preserved from ancient life because they are
more reactive and volatile. (Abiotic and old biotic organics have,
presumably, already reacted significantly with their environment,
eliminating many of the compounds of greatest interest in recent
communities.) If evidence for recent biological activity is obtained
prior to sample return, every effort to preserve these less stable
organics should be made. To minimize alteration to organic structures,
samples should ideally be maintained under the following conditions:

-   At pressure conditions within the bounds of ambient conditions
    experienced on Mars for the sample to preserve volatiles

-   At temperatures not to exceed the upper bound of ambient Mars
    conditions for the sample (or 50C) for any longer than absolutely
    necessary, and ideally at -20°C for short-term storage to preserve
    reactive functional groups such as double bonds in carboxylic acids,
    -80°C for long-term storage (\>1 yr) to preserve nucleobases
    sequences if present, and at 4°C during analytical use.

-   Under inert conditions to minimize reactions such as oxidation and
    reduction, and maintain ambient pH conditions.

-   Under as much protection as possible from cosmic radiation exposure
    until returned to Earth in order to minimize radiation induced bond
    cleavage and subsequent reactions.

Recommendations for sample validation and curation include:

-   Surfaces and gases of the sample container should be examined for
    carbon in their initial returned state.

-   Intact samples should have context imaging on the \~100 micrometer
    scale prior to storage.

-   Organic cleanliness must be verifiable to the detection limits of
    instrumentation prior to launch for *in situ* instrumentation and
    during curation and analysis upon return.

-   Introduction of contaminates and alteration of sample chemistry must
    be carefully considered before physical sample alteration (crushing,
    slicing, etc.) in order to avoid compromising the sample for other
    investigations.

\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_

### **B2. [Investigation:]{.underline} Characterize the distribution and composition of inorganic carbon reservoirs on Mars through time**. 

***Team leads: [Des Marais]{.underline}**, Sumner, Grady, Westall,*

Transformations of carbon between inorganic and organic carbon
reservoirs are a characteristic of life. Evaluating carbon reservoirs
and the fluxes among them is critical to understanding both the modern
and geological evolution of carbon availability, and the inorganic
carbon reservoirs are an important link in the cycle. The distribution
of these reservoirs can also reveal critical habitability information
because they can record climate records. Potential measurements include
continued searching for carbonate minerals from orbit, *in situ*, and in
returned samples, characterizing CO~2~ fluxes on various time scales
globally and locally, and measuring the isotopic composition of any
inorganic reservoir.

Carbonates sequester more than 80% of Earth's total crustal inventory of
carbon, and their analysis conveys critical paleoenvironmental
information. Carbonates would be key exploration targets on Mars for the
same reasons they are important on Earth. However, recent surface
environments on Mars are inimical to carbonates due to their destruction
by impacts, radiation, and acidic weathering reactions. Carbonate-rich
bedded deposits analogous to continental platform deposits on Earth have
not been identified on Mars, and they might be very rare or absent
either because they did not form or because of preservational
challenges. In contrast, a substantial fraction of the Martian crustal
carbon inventory might reside as carbonates sequestered within
subsurface fractures. Carbonate inventories could be characterized
either by retrieving samples wherein carbonates have been protected from
degradation or by identifying minerals and lithologies that contain
phases that replaced former carbonates.

In the following, we assume that the only carbonate detected prior to
sample return is within dust or in trace quantities in fractures in
rocks.

**Sample types needed.** Detection of trace Mg-carbonate has been
reported in Martian dust. Thus, a sample of dust would be required.

Intact samples of rocks that might contain carbonate minerals would be
needed to evaluate the presence or absence of carbonates, and to
evaluate geochemical spatial heterogeneity of carbonate minerals if
present. Such rock samples could include sedimentary rocks, hydrothermal
rocks, and altered igneous rocks.

**Sample diversity needed.** Only one sample of dust would be required
because the Mg-carbonate appears globally distributed. Contamination by
a small component of regolith would be acceptable.

Should aqueous sediments in layered sequences containing carbonate be
detected, samples should be taken from appropriate stratigraphic
horizons where depositional environments to be characterized to allow
investigation of processes leading to the sedimentary accumulation of
carbonate. Hydrothermal and altered igneous rocks might harbor
carbonates in cracks, voids or alteration zones. Should hydrothermal
deposit be discovered, sequences of samples along paleo-temperature,
paleo-flow lines and/or paleo-redox hydrothermal gradients would help to
define their environments of formation, including potentially their
carbonate contents. Fractures, voids, and surface alteration features of
altered rocks should each be sampled.

**Physical condition (rock, pulverized rock, etc.).** One dust sample
would be required for characterization of magnesium carbonate in dust.

Intact rock samples would be required for characterizing the spatial
relationships within carbonates and between carbonates and host rocks if
carbonate is present as a phase within other rock types. Pulverized rock
might be useful for chemical analyses of any carbonate phases but would
not retain the highly valuable spatial information that sheds light on
processes leading to the formation of carbonate.

**Contamination types and limits that affect this investigation.**
Samples should not be exposed to acidic conditions, CO~2~ or moisture
that might alter the chemical and isotopic composition of any trace
carbonate phases. Storage containers should be hermetically sealed to
limit contamination.

**Sample number and mass.** One gram of dust with 1-3% Mg-carbonate
would be sufficient to characterize the elemental and isotopic
composition of the carbonate known to exist on Mars. The requirements
for mineralogical context in rock chips and cores and the expected
(relatively minor) abundances of carbonates calls for individual sample
sizes in the range 1 to 5 grams. Chemical and isotopic analyses likely
could be performed with samples \<1gram.

The absence of carbonate detections in rocks on Mars makes estimating
sample number necessary for this investigation difficult. However, an
initial documentation of the presence or absence of carbonate could be
performed by sampling diverse phases within geological contexts where
carbonates might be expected. Stratigraphic sequences or altered bedrock
should be sampled (minimum 3-5 samples), as should soil profiles
(minimum 3-5 samples) and geochemical gradients (minimum 3-5 samples),
depending on the landing site. Thus, at least ten samples would be
required to initially evaluate the presence or absence of carbonate in
the landing area within the context of this investigation. If carbonates
are present, they could be characterized within the 1 to 5 gram sample
sizes needed to evaluate the presence of carbonates.

**Vulnerability of samples to degradation effects (T, volatile loss,
etc.).** Temperatures that exceed maximum Mars ambient temperatures at
the site of collection might alter some hydrous bicarbonate and
carbonate minerals that could be present. For example, sodium
bicarbonate decomposes at \~50^o^C and ikite decomposes at 7°C.

**Maximum sample temperatures for sample integrity.** Keeping samples
below maximum Mars ambient conditions would achieve 100% of the
objective. Sample handling and storage temperatures that exceed 50^o^C
would degrade hydrous bicarbonates. Anhydrous carbonates are stable at
least to 100^o^C or above, but finely disseminated carbonates might
begin to exchange isotopically with water vapor above 50^o^C.

**Impact of degradation effect on the investigation.** Elevated
temperatures could decompose certain minerals and disrupt microscale
diagnostic sedimentary textures. Decomposition of bicarbonates could
compromise reactive geochemistry within the sample. Carbonates might
begin to exchange isotopically with water, etc. above 50^o^C. Carbonates
might begin to react with other phases above 100^o^C. Sealed containers
would be a priority in order to preserve all components and maximize the
possibility of "reconstructing" any materials altered during sampling
and transport to Earth.

**Required/preferred sampling hardware.** Rock corers that achieve
minimal heating during sampling would be the preferred sampling
technique for intact rock samples. Dust collection hardware should
include non-magnetic grains if present.

**Data needed for sample choice and in situ characterization.** Image
the rock outcrop or regolith sampling site to document macroscale
textures and any indications of their composition and origin.
Mineralogical and elemental abundance measurements would guide selection
of optimal samples, particularly if carbonates are identified.

**Estimate of required mobility range.** The need to land at a safe
(flat) site would require mobility of several km in order to approach
and sample key localities such as stratigraphic sequences, hydrothermal
deposits, etc. and to perform observations to acquire geological and
environmental context.

\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_

### **B3. [Investigation:]{.underline} Characterize links between C and H, O, N, P, and S**

***Team leads: [Pratt, ]{.underline}**Des Marais, Grady, Eigenbrode*

The carbon cycle is intimately linked to H, O, N, P, and S, particularly
in the presence of life. Identifying connections among the geological
cycles of these elements would substantially aid interpretations of the
carbon cycle and might provide indicators that could be used to
interpret biological potential. Potential measurements include
mineralogical characterization of samples containing C, N, P, or S,
isotopic and oxidation state characterization of S-containing phases,
and identification of reactions involving any of these elements.

In the current absence of detection of organics, this investigation
currently entirely overlaps Goal 1, A3 Identify and characterize phases
containing C, H, O, N, P and S, including minerals, ices, and gases, and
the fluxes of these elements between phases. Please see sample
requirements listed under Goal 1, A3.

\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_

### **B4. [Investigation:]{.underline} Preservation of reduced compounds on the near-surface through time**

NOTE FROM REVIEWER: I don't know what to do with this section. As
originally conceived, the investigation was a place-marker for
understanding the oxidant in the regolith that may have removed the
organic carbon; thus, its presence in Objective B. However, as worded
and interpreted by the ND-SAG subgroup, it is much broader. I find it so
broad that it seems nearly impossible to fit into the context. I would
be more comfortable restricting it to the surface oxidant, but I do not
want to unilaterally discard the other sample considerations. Please
advise.

***Team leads: [Westall]{.underline}, Benner,** Steele, **Zent***

The surface of Mars is oxidizing, but the composition and properties of
the responsible oxidant(s) are unknown. Characterizing the reactivity of
the near surface of Mars, including atmospheric (e.g., electrical
discharges) and radiation processes as well as chemical processes with
depth in the regolith[^1] and within weathered rocks would be critical
to interpreting the paucity or possible absence of organic carbon on the
surface of Mars. Understanding the oxidation chemistry and the processes
controlling its variations would aid in predicting subsurface
habitability if no organics are found on the surface. Potential
measurements include identifying species and concentrations of oxidants,
characterizing the processes forming and destroying them, and
characterizing concentrations and fluxes of redox sensitive gases in the
lower atmosphere.

*Aaron Zent's comments about the "Viking Mars Oxidant:"* Oxidation: It
is very unlikely that the species that were responsible for either the
absence of organics in the Viking samples, or their unusual chemical
behavior in the Viking biology experiments, could be sampled *in* situ
and returned to Earth without significant re-equilibration once removed
from the Martian surface environment. The key requirement for preserving
the chemical nature of the soil surfaces to the extent possible would be
to keep the sample at low temperature, and to control the relative
humidity such that the chemical activity of surface H~2~O does not
exceed its nominal value at the sampling site. This might be
prohibitive, and any attempt to rigorously control the atmospheric
ambient is likely to be unsuccessful, based on the lunar experience with
fine-grained samples. It would be far more important to maintain the
sample at Mars-ambient temperature, or ideally colder.

I would like also to weigh in on the subject surficial interactions
between regolith particles and the atmosphere. I would again argue that
it is very unlikely that the surface state of the regolith particles
could be maintained in their original condition. Rather, I would again
argue for maintaining the samples at low temperatures in order to
prevent any surface alteration due to high H~2~O activity. In addition,
I would argue that it would be key to acquire samples from more than one
depth.

I infer from the proposed measurements described by McLennan and
Aharonson that there would be limitations on the depth-sampling
capabilities of the nominal sample-return lander. Nonetheless, I would
argue that depth-resolved samples capable of capturing any vertical
inhomogeneity observed in imagery would be key. It would be potentially
disastrous to scoop up a few cubic centimeters of surface material and
then extrapolate that to the entire regolith (which everybody will do)
if we could discriminate inhomogeneity in the near-surface regolith.
Therefore, a key recommendation I would make would involve vertically
resolved sampling of the regolith.

**1. Are samples of specific character, geologic setting, or landing
site) required to answer this question?**

To test the preservation of reduced compounds in the near surface
through time, we would need to select a variety of samples that include
typical surface material, such as weathered basalt, sedimentary
materials (relatively friable sulphate-rich sediments, sands derived
from weathered basalt), as well as atypical materials, for instance any
identified hydrothermal deposits (for instance silica). The fresh basalt
(if available) would act as a control sample as it would contain
magmatic carbon.

Surface materials in the regolith appear to be to a greater or lesser
extent altered by oxidation processes and the effects of concentrated
acidic brines over long periods of geological time. Such materials would
represent an "end-member" sample of martian material, potentially
containing carbon, that has been significantly altered (implying also
alteration of the carbon) probably in succeeding episopdes.

We already know that volatile organics are readily lost from most
surface materials on Mars but certain natural materials, such as silica
in the form of chert (amorphous, hydrated Si02) is particularly
impervious and it is possible that surface silica, if found, could
contain a variety of organic components including volatiles, especially
in the younger rocks.

Preservation through time -- Comparison with terrestrial organics
through time suggests that there will be a gradual loss of functional
groups with increasing age of the sample, simply because of
time-dependent degradation (like the racemisation of chiral molecules).
Therefore, even if we could identify ancient silica, and, although it
would contain "hermetically-sealed" organics (of abiogenic and/or
biogenic origin), the latter would probably be represented by PAHs
(mostly alkanes).

***1.1. Sample types needed (in order of priority based on likelihood of
preserving carbon in an unaltered a form as possible)***

-   Volcanic water-lain sediments that have not seen aqueous alteration
    since they formed and therefore have a pristine carbon signal (do
    they exist on Mars?)

-   Hydrothermal deposits - silica

carbonates?? (very leaky)

Fe minerals

-   Volcanics that were extruded under water and have an alteration rind
    (do they exist)

-   Evaporites (very leaky)

-   Volcanic sediments that have been obviously processed by water and
    contain aqueously-formed alteration products

-   Volcanic rocks as fresh as possible

-   Weathered basalts

We would need these samples from both the surface and the near-surface.
We would need to get below the zone of oxidation which would be
different depending on whether we would be dealing with rock outcrop,
rocks of different composition and texture (porosity), or regolith. With
outcrop perhaps even a few cm or less would be sufficient in an
impervious rock (like chert) but deeply weathered basalt or friable
basaltic sediments probably would need to be sampled at a greater depth
(decimetres to 1 m? This would need to be modelled).

***1.2. Sample diversity needed***

See above

***1.3. Physical condition (rock, pulverized rock, etc.)***

\- Any rock samples need to be integral because the interior mineral
matrix will protect any organics from eventual loss or contamination.

\- Friable rocks are likely to disintegrate during transport.

\- Sand/dust samples are already disintegrated, although there may be
slight cementing due to subliming/evaporating frost (?). Any delicate
cement would probably not survive transport back.

***1.4. Contamination that affects this investigation:  Types and
limits***

Each sample would need to be placed in a separate, hermetically-sealed
container. Organic compounds should not be used in the instruments used
for sample collection nor in the containers and seals.

***1.5. Sample number and mass***

Minimum surface and subsurface sample of the regolith. Should also take
a sample of rocks of different composition (if present within reach of
the landing site or rover capabilities; see above comment regarding
sample diversity).

I.e. minimum sample number of 4 of each \> 1 g.

***1.6. Vulnerability of samples to degradation effects (T, volatile
loss, etc.)***

The biggest problem would probably be disintegration of a friable sample
with possible subsequent loss of volatiles, if relatively volatile
components are present to begin with. This is why the sample containers
would need to be hermetically sealed so that, if volatiles are liberated
during transport (time), they would at least be collected within the
container. Exposure to temperatures above 40 °C, would contribute to
volatile loss. As Steve Benner noted in his contribution, if you have
extracted volatiles in the sample container, there is a possibility that
they could further degrade any organics left in the sample.

***1.7. max sample temp to achieve objective***

≤ 40°C

***1.8. Impact of degradation effect on the investigation***

See comments in 1.6.

***1.9. Required/preferred sampling hardware***

Scoop and drill/mole without organic components

***1.10. Data needed for sample characterization, sample selection
decisions***

Observational and geochemical/mineralogical data to determine the
composition of the sample, its origin, and its status (e.g., loose
regolith, friable sediments/weathered volcanics, solid rock).

***1.11. Estimate of required mobility range***

As much as possible to obtain as wide a variety of samples as possible,
i.e., at least 2 km

***1.12 Special requirements for sample acquisition, storage, and Earth
analysis?***

\- Characterisation of the sample site/materials before acquisition

\- Storage in separate, hermetically-sealed containers

\- No organic components in sample acquisition tools or storage
containers

\- Care in opening the containers on Earth so that any eventual
volatiles liberated during ttransport could be analysed.

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## C. Objective: Assess whether life is or was present on Mars 

## C1. [Investigation:]{.underline} Characterize complex organics. 

***Team leads: [Eigenbrode]{.underline}, Benner, Conrad, Glavin,
Steele***

The identification of complex organics that can only be produced
biologically is a very strong biosignature, if forward contamination by
terrestrial organics can be excluded. Measurements for this
investigation must include appropriate methods to identify and exclude
forward contamination as a source of the target materials. To this end
new instruments must be developed for cleaning and monitoring of
spacecraft contamination. Instruments must be required to produce
procedural blanks that allow accurate measurements by that instrument to
be undertaken. This would entail that the critical path of
contamination, i.e., the path the sample takes to the instrument, be
cleaned to a level below the detection limit of the instrument. Example
measurements might include characterization of organics such as DNA,
nucleotides, chlorophyll, etc. for extant life; hopanes, steranes,
isoprenoids, etc., for fossil life; or cumulative properties and/or
distributions of organics such as homochirality.

One of the first assessments of biological processes would consist of
characterization of complex organics. The distribution of organics on
Mars is currently unknown beyond the observation that they are not
abundant at sites investigated to date. Thus, this investigation
currently entirely overlaps Goal 1, B1 Determine the distribution and
composition of organic carbon on Mars. Please see sample requirements
listed under Goal 1, B1 for this investigation.

**Additional comments.** Complex organics could be present in various
forms including biomolecules, cross-linked humic-like macromolecules,
and kerogen. Within each subgroup, the structural and heteroatomic
nature could vary. Although the sampling requirements for addressing
this investigation and the vulnerability to alteration and contamination
are the same as those described in section B1, most analyses of complex
organics would require specific sample preparation targeting types of
organic material. For instance, wet-chemical extraction or hydrolysis by
water or acid might be necessary prior to analysis of amino acids,
amines, carboxylic acids, etc. that are bound in large molecular
structure or within the mineral matrix. Various unbound components are
accessible by solvent extraction, as is necessary for hydrocarbons such
as polyaromatic hydrocarbons, alkanes, and possibly lipids. In both
cases, derivatization of active functional groups might be desired to
focus the analysis on specific compound groups, such as in the chiral
analysis of amino acids. More general organic characterization by
pyrolysis-MS and GCMS, Raman, etc. might serve as a guide for
determining appropriate sample quantities and preparation techniques.

Molecular information yields increase when structural integrity is
maintained during processing for both unbound and bound complex
organics. Thus analytical techniques that involve minimal processing
would be preferred. The analytical suite would need to structurally
identify and resolve a breadth of compounds, their isotopic composition,
and heteroatomic content in order to identify molecular biosignatures,
exogenous and indigenous abiogenic organics. As with all investigations
of organic carbon on Mars, the geological and geochemical context of
samples must be well documented during sample selection and upon return
in order to assess sources and processes influencing organics,
especially biological sources. Moreover, the distribution and isotopic
composition of inorganic carbon and simple organic volatiles are
necessary to build the framework for understanding the biogeochemical
cycling of carbon on Mars.

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### **C2. [Investigation:]{.underline} Characterize the spatial distribution of chemical and/or isotopic signatures.**

***Team leads: [Des Marais]{.underline}**, Eigenbrode, Pratt, Sumner*

The spatial distribution of chemical or isotopic variations can be a
biosignature, if the distribution is inconsistent with abiotic
processes. Example measurements might include imaging of the
distribution of organics on a surface or in minerals; identifying
correlations among isotopic values and elemental concentrations that
reflect biological processes; or the presence of reduced and oxidized
gas phases in disequilibrium.

A biosignature is an object, substance and/or pattern whose origin
specifically requires a biological agent. The usefulness of a
biosignature is determined by both the probability of life creating it
and the improbability of nonbiological processes producing it. Living
systems can create biosignatures as remnant expressions of their
complexity, for example, complex organic molecules or organismic
structures such as cells, leaves or skeletons. Living systems also
create biosignatures as byproducts of their energy harvesting processes.
Examples include the accumulation of sedimentary organic carbon or
stable isotopic patterns in sulfate and sulfide minerals or reduced
carbon and carbonates. This investigation would address samples that
might contain traces of chemical or isotopic biosignatures.

**Sample types needed.** Samples from materials that experienced
formerly habitable environments would be prime candidates for this
investigation. In particular these are substances that contain the
elemental building blocks of life, in particular C, N, H, S, P and
certain transition elements such as Fe and Mn.

**Sample diversity needed.** Aqueous sediments in layered sequences
should be taken from appropriately spaced stratigraphic horizons that
allow their depositional environments to be characterized. Igneous
bedrock and float might harbor evidence of C, N, S and P minerals in
cracks, voids or alteration zones. Should a hydrothermal deposit be
discovered, sequences of samples along paleo-temperature, paleo-flow
lines and/or paleo-redox hydrothermal gradients would help to define
their environments of formation, including potential biogenic signatures
in textures or elemental and isotopic distributions.

**Physical condition (rock, pulverized rock, etc.).** Rock chips and
cores would be optimal because they would best preserve minerals
containing C, N, S and P and the information contained in their spatial
distribution. Pulverized rock might be useful for chemical analyses of
any of these phases, but would not preserve the micron-scale spatial
gradients targeted in this investigation.

**Contamination types and limits that affect this investigation.**
Samples should not be exposed to conditions that might alter the
chemical and isotopic composition of any trace C, N, S and P phases.
Returned samples should be hermetically sealed.

**Sample number and mass.** The requirements for mineralogical context,
the expected (relatively minor) abundances of these minerals and
contamination concerns would call for individual sample sizes in the
range 1 to 5 grams, especially for textural analyses. Chemical and
isotopic analyses likely could be performed with samples \<1 gram. The
composition of host phases, together with the anticipated need to sample
stratigraphic sequences (minimum 3-5 samples), soil profiles (minimum
3-5 samples) or geochemical gradients (minimum 3-5 samples) indicate
that at least ten carefully selected samples would be required for this
investigation.

**Vulnerability of samples to degradation effects (T, volatile loss,
etc.).** Temperatures that exceed maximum Mars ambient temperatures at
the site of collection might alter any bicarbonates and polyhydrated
sulfates present. Large changes in relative humidity can alter nitrates
and polyhydrated sulfates.

**Maximum sample temperatures for sample integrity.** Keeping samples
below maximum Mars ambient conditions would achieve 100% of the
objective. Sample handling and storage temperatures that exceed 50^o^C
would alter hydrated minerals and could affect oxygen isotopic patterns.
Finely disseminated minerals might begin to exchange isotopically with
water vapor above 50^o^C. Storage containers should be hermetically
sealed.

**Impact of degradation on the investigation.** Elevated temperatures
could decompose certain minerals, destroying spatial elemental and
isotopic gradients and disrupting microscale diagnostic sedimentary
textures. Sealed containers would be a priority in order to preserve all
components and maximize the possibility of "reconstructing" any
materials altered during sampling and transport to Earth.

**Required/preferred sampling hardware.** Rock corers that achieve
minimal heating during sampling. Sample handling that would heat the
samples only minimally.

**Data needed for sample choice and in situ characterization.** Image
the rock outcrop or regolith sampling site to document their macroscale
textures and any indications of their composition and origin. Perform
spectroscopic (NIR or MIR) and elemental abundance measurements to guide
selection of optimal samples.

**Estimate of required mobility range.** The need to land at a safe
(flat) site would require mobility of several km in order to approach
and sample key localities such as stratigraphic sequences, hydrothermal
deposits, etc. and to perform observations to acquire geological and
environmental context.

\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_

**C3. [Investigation:]{.underline} Characterize the morphology or
morphological distribution of mineralogical signatures.**

***Team leads: [Westall]{.underline},** Sumner*

Sedimentary and weathered rocks can preserve biosignatures in the
distribution of grains and minerals or in the morphology of biologically
produced minerals. Example measurements might include micron to
nanometer imaging and chemical analysis of crystals or morphological
characterization of sedimentary lamination to regional or global scale
characterization of sedimentary stratigraphy.

Geological setting -- Samples from rocks that have been influenced by
water would be required -- either formed by
deposition/precipitation/extrusion in water, or water flowing through
cracks in the rocks (runoff water, standing water, hydrothermal fluids).
Weathered surfaces (altered by water) can also contain morphological
biosignatures.

Characterisation of the morphology and distribution of mineralogical
biosignatures would require intact samples because morphological
signatures depend on spatial distributions of features. Potential
mineralogical biosignatures must be evaluated within the context of the
rocks. Loose sand and powders do not conserve the context although they
may contain biologically-produced minerals. On a larger scale than
returned samples, biolaminations may be of the order of tens of microns
to centimeters. These should be imaged prior to sample collection.

**Sample types needed.** Highest priority samples would be intact
sedimentary rocks that formed in bodies of standing water because they
can support biofilms with significant morphological expression and
aggrading environments readily preserve biofilm morphology. Chemical
sediments formed in evaporitic and hydrothermal environments would be
high priority due to the prevalence of mineral precipitation that
promotes preservation of morphological signatures. Water induced mineral
precipitation within cracks in rocks, including volcanic rocks can also
capture morphological biosignatures. Duricrusts, desert varnish, and
weathered horizons can also preserve small-scale morphological
biosignatures. Volcanic rocks extruded under water can encapsulate or be
colonized by micro-organisms that leave morphological biomarkers.

**Sample diversity needed.** Diversity including the rock types above
would be desired. A suite of samples representing these rock types at
the landing site would be needed.

**Physical condition (rock, pulverized rock, etc.).** Intact rock
samples would be necessary, including lithified rock as well as friable
sediments or weathered volcanics.

**Contamination types and limits that affect this investigation.** There
would be less of a problem of cross-contamination with mineral
biosignatures than there would be with chemical ones but it is important
to be able to relate each individual sample to its microhabitat and the
*in* *situ* documentation of that habitat in order to make reliable
interpretations of the potential mineral biosignatures within samples.
Thus, the samples would need to be isolated from each other to prevent
cross contamination during transport. Sampling with a clean tool would
be desirable.

**Sample number and mass.** A suite of 5 samples of 5 grams each would
be desired. Sample size would be determined by the need to resolve
spatial variations on the centimeter and finer scale more so than mass.
Samples would need a dimension of 1 cm or more in at least one direction
to allow adequate spatial evaluation.

**Vulnerability of samples to degradation effects (T, volatile loss,
etc.).** The main degradation hazard would be the loss of integrity of
delicate (friable) rocks, especially if they are stratified or if the
mineralogical biosignature of interest becomes loosened from its
mineralogical matrix. Textures would be degraded if temperatures are
sufficiently high to induce phase changes in hydrous minerals or a
substantial concentration of volatiles are lost.

**Maximum sample temperatures for sample integrity.** Temperature
degradation can destroy mineralogical biosignatures preserved in
hydrated phases. Temperatures equivalent to ambient martian environments
for the sample would be strongly desired and would be required for
hydrous samples. Anhydrous samples could probably withstand temperatures
of 20°C during sample return with a short exposure to 50°C on landing
without compromising the highest priority scientific investigations.

**Impact of degradation on the investigation.** Loss of integrity of
delicate samples would significantly limit the quality of results for
this investigation. The degradation of hydrous samples would also
destroy textural information, possibly destroying biosignatures.

**Required/preferred sampling hardware.** Clean coring or a mechanical
finger to pick up rock fragments that are clearly related to the
underlying rock context.

**Data needed for sample choice and in situ characterization.** The
sample would need to be imaged prior to collection to document in situ
structures (sediment lamination, biolaminations) and the relationships
between potential biominerals/mineralogical biosignatures and the host
rock and surrounding environment. The host rock mineralogy and
geochemistry would need to be characterized to determine the composition
of the sample and to provide environmental context. Characterization of
host rock would be especially important for small samples.

**Estimate of required mobility range.** As much as possible to obtain
as wide a variety of samples as possible, i.e., at least 2 km

\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_

### **C4. [Investigation:]{.underline} Identify temporal chemical variations requiring life.**

***Team leads: [Steele]{.underline},** Benner, Nealson*

Extant life may be active, producing observable temporal changes in
chemistry over the time scale in which a lander experiment may be
functional. Monitoring systems that may harbor life is an excellent way
to identify the presence of life. However, possible abiotic reactions
need to be thoroughly understood and forward contamination needs to be
identified or excluded. It is critical that measurements capable of
being contaminated include appropriate methods to identify and exclude
forward contamination as a source of the signatures being monitored.
Example measurements might include monitoring the flux of gases thought
to be biologically-produced; monitoring oxidative changes in a way that
excludes abiotic reactions; or performing experiments to look for
metabolic processes.

The identification of temporal chemical variations requiring life would
be the most important analytical tasks for returned samples due to
planetary protection considerations in addition to looking for evidence
of life on Mars. The critically important planetary protection
evaluation of returned samples would drive sampling requirements beyond
those articulated here, which focus on the scientific aspects of
identifying temporal chemical variations requiring life. However, the
following requirements could form the basis for defining sample
requirements for planetary protection.

The Viking experiment to monitor the kinetics of reaction and gaseous
release of the Martian regolith with a medium over time is one of the
mainstays of terrestrial microbiology. Monitoring changes in morphology
of interesting features has also revealed the nature of contaminants in
Martian meteorites on Earth. Extant and viable life will affect its
surroundings, changing the concentration of key nutrients and waste
products. There is no reason to assume that an extant Martian organism
would do anything less. There are however, fundamental difficulties
associated with undertaking these observations as illustrated with the
Viking experiments. Namely: ensuring no abiotic reactions cause a false
positive (although these reactions would be of interest in themselves),
ensuring that no terrestrial contamination is involved, ensuring the
integrity of the sample during acquisition, storage, transport, curation
and experimentation on earth. Temporal changes might be monitored in a
variety of ways, imaging of the same sample over a period of time
(Toporski and Steele 2007), radioisotope uptake and release, gaseous
exchange, culturing etc. Throughout this process, it would be essential
to conduct analysis at appropriate time steps to garner the most
information while ensuring that during measurement the analysis would
not be compromised i.e., all the gas would not be removed from the
headspace in the first time step.

**Sample types needed.** Ideally subsurface samples would be best to
answer this goal. However, it is likely that, if present, Martian biota
would adapt similar survival techniques to earth biota and retire within
rocks and become endolithic in character. Obviously samples that contain
evidence of organic carbon, hydrated minerals and the presence of known
redox couples that could be exploited by life would have a high
priority. Any returned samples with liquid or solid phases should be
subject to analysis for temporal changes requiring life.

**Sample diversity needed.** Given the unknown nature of possible
Martian organisms and the absence of positive detections of organics on
Mars to date, sample diversity can not yet be defined. However, all
returned samples should receive attention particularly those containing
organic carbon

**Physical condition (rock, pulverized rock, etc.).** This goal
represents a diverse range of investigations, some of which could and
should be undertaken on fresh fracture surfaces, some on pulverized
material that would be handled in such a way as to ensure NO organic or
microbial contamination to the samples.

**Contamination types and limits that affect this investigation.** A
single terrestrial microbe would potentially compromise these
investigations, given that terrestrial microbiota can thrive on organic
material within Martian meteorites. Organic contamination may be
tolerated up to a concentration below the detection limits of the
instrumentation used to measure it, particularly if conditions did not
favor reactions that would produce temporal changes.

**Sample number and mass.** As previously alluded to, most samples would
have to be processed. All investigations on this material could be
carried out on \~6 g of pulverized material (assuming 3 samples at 2
grams per sample), plus a variety of fresh fracture surfaces (\~3
samples of 1g per samples from diverse areas of the whole sample.

**Vulnerability of samples to degradation effects (T, volatile loss,
etc.).** We have no way of knowing what a Martian organism may be
vulnerable to. However, it would seem prudent to subject the samples to
Martian ambient conditions during sample return.

**Maximum sample temperatures for sample integrity.** Ambient Martian
conditions would be required to avoid disruption of any microbial
ecosystems present.

**Impact of degradation on the investigation.** Degradation would result
in a null result.

**Required/preferred sampling hardware.** Sterilized instruments would
be required for sampling.

**Data needed for sample choice and in situ characterization.**
Detection of any biosignature from images or the detection of organics
prior to sampling would increase the reliability of results by providing
context for the sample.

**Estimate of required mobility range.** Sufficient mobility to obtain
sample diversity would be desired.

**Additional comments.** Sterilization of instruments and other hardware
that would contact or could contaminate the sample would be strictly
required.

**GOAL II**

**[Introduction and Synthesis]{.underline}**

> This Goal focuses on understanding the climate evolution and history
> of Mars through atmospheric processes, surface-atmosphere interaction,
> climate history expressed in polar layers, and understanding
> atmospheric conditions critical to safe landing of spacecraft. Many of
> the specific objectives and investigations related to dynamical
> processes of the atmosphere which need to be measured in--situ and so
> are largely irrelevant to sample return. Sample return was found to
> support only specific investigations under Objective B: Mars Ancient
> Climate and Climate processes. Investigations B.1 and B.3 are related
> and linked to the determination of noble gasses and trace atmospheric
> constituents, both of which would benefit from a return atmospheric
> sample and analysis of gas inclusions in return rocks. Investigation
> B.4, records of past climates, has strong synergy and overlap with
> many of the Goal III objectives and sample return requirements for
> Goal 3 would satisfy the needs for this investigation as well.
> Investigation B.5 of polar ice and layered deposit stratigraphy would
> benefit from the return of a sample of ice, or small core. Return of
> specialized atmospheric and/or ice samples is expected to profoundly
> impact our understanding of climate evolution and history as outlined
> in the Goal.

**II. GOAL: UNDERSTANDING THE PROCESSES AND HISTORY OF CLIMATE ON MARS**

The fundamental scientific questions that underlie this goal are how the
climate of Mars has evolved over time to reach its current state, and
what processes have operated to produce this evolution. These extremely
important scientific questions are in accord with several key science
objectives found in the NASA Solar System Exploration Roadmap (2003).
Mars climate can be defined as the mean state and variability of its
atmosphere and exchangeable volatile reservoirs (near the surface)
evaluated from diurnal to geologic time scales. An understanding of Mars
climatic evolution rests upon gaining a full understanding of the
fundamental processes governing its climate system, and thus upon
obtaining detailed observations of the current (observable) system. Goal
II also is in line with the recent recommendation of the Solar System
Exploration Survey \[2002\], which calls out the clear need for Mars
upper atmosphere measurements to properly characterize current volatile
escape rates. The Objectives below are given in priority order.
Objective A is crucial to understanding the present state of the entire
atmospheric system (from the surface-atmosphere boundary to the
exosphere). It forms the baseline for interpreting past climate on Mars.
Objective B focuses upon specific investigations that would measure key
indicators of the past climate of Mars. Finally, Objective C highlights
mission critical atmospheric measurements that would reduce mission risk
and enhance overall science return, benefiting all future missions to
the planet. No attempt has been made to prioritize these risk mitigation
and engineering related measurements since all are important.

# A. Objective: Characterize Mars' Atmosphere, Present Climate, and Climate Processes (investigations in priority order) 

Our understanding of the composition and dynamics of the present Martian
atmosphere is the basis for understanding past climate on Mars.
Investigations of both the upper and lower atmosphere are essential
because they are one large, interconnected system. Measurements of both
atmospheric regions would enable us to explore different suites of
processes that play unique roles in understanding the Martian climate
and its evolution. In short, a ground-to-exosphere approach to
monitoring the Martian atmospheric structure and dynamics is needed for
a proper characterization of the present day climate of Mars.

**1. [Investigation:]{.underline} Determine the processes controlling
the present distributions of water, carbon dioxide, and dust by
determining** **the short and long-term trends (daily, seasonal and
solar cycle) in the present climate. Determine the present state of the
upper atmosphere (neutral/plasma) structure and dynamics; quantify the
processes that link the Mars lower and upper atmospheres.**

**[Implications for sample return]{.underline}**.

Discussion Leads: **Steve Bougher**

The processes and detailed atmospheric characterizations outlined in
this broad investigation would be best addressed with a combination of
global orbiter, network, and landed/rover measurements conducted over
multi-year (continuous) timeframes. A single returned atmospheric sample
would not contribute to the completion of this investigation.

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**2. [Investigation:]{.underline} Search for microclimates.**

Detection of exceptionally or recently wet or warm locales,
exceptionally cold localities, and areas of significant change in
surface accumulations of volatiles or dust would identify sites for *in
situ* exploration. This requires a global search for sites based on
local surface properties (e.g., geomorphic evidence, topography, local
thermal properties, albedo) or changes in volatile (especially H~2~O)
distributions.

**[Implications for sample return]{.underline}**.

Discussion Leads: **Vicky Hipkin**

This objective, as it stands, focuses on detecting environments and not
on characterizing these. In this case sample return would not be
relevant.

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**3. [Investigation:]{.underline} Determine the production/loss,
reaction rates, and global 3-dimensional distributions of key
photochemical species (O~3~, H~2~O~2~, CO, OH, CH4, SO2, etc.), and
their interaction with surface materials.**

**[Implications for sample return]{.underline}**.

Discussion Leads: **Joel Levine** and Don Bogard

Because a returned atmospheric sample would be in a different
environment, photochemical species would undergo substantial equilibrium
changes relative to that in Mars\' atmosphere.  Interpretation of
atmospheric composition and chemistry would be very difficult, if not
impossible.  Gas inclusions in returned rock samples would be unlikely
to provide useful information on photochemical state of the martian
atmosphere. Therefore sample return is not seen as relevant to this
investigation.

\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_

**B. Objective: Characterize Mars' Ancient Climate and Climate
Processes**

**Through Study of the Geologic and Volatile Record of Climate Change**
**(investigations in priority order)**

Understanding the ancient climate and climate processes on Mars requires
interdisciplinary study of the Martian surface and atmosphere. The
investigations described below would focus on quantitative measurements
(concentrations and isotopic compositions) of important atmospheric
gases in the atmosphere and trapped in surface materials. It also would
require study of geologic features to search for the record of past
climates.

**1. [Investigation:]{.underline} Determine the stable isotopic, noble
gas, and trace gas composition of the present-day bulk atmosphere.**

These provide quantitative constraints on the evolution of atmospheric
composition and on the sources and sinks of the major gas inventories.
It is important to understand the temporal and spatial variability of
atmospheric composition. This investigation would require high-precision
isotopic measurements of the atmosphere.

**[Implications for sample return]{.underline}**.

Discussion Leads: **Don Bogard.** James Farquahar, Veronika Heber, Kurt
Marti

**Current and Anticipated Knowledge.**

Measurements from Earth and on Mars by Viking demonstrated significant
isotopic fractionations of H and N in the martian atmosphere, which
indicate substantial atmospheric loss of these species over time.
Measurements of martian meteorites have demonstrated analogous isotopic
fractionations in atmospheric Ar and Xe, but curiously not Kr.
Atmospheric composition of Ne is very poorly known. Although these data
suggest the martian atmosphere possibly experienced both an early
massive loss and a continuing loss by different mechanisms, details of
its evolution are poorly known. Further, direct measurements from orbit
of H loss from the upper atmosphere suggest that the present atmospheric
D/H ratio could have been produced in a far shorter time than the age of
Mars, which implies periodic internal degassing of water may replenish
atmospheric H. More detailed understanding of such atmospheric loss
mechanisms have implications for understanding evolution of the Earth's
atmosphere. Because atmospheric fractionation during planetary escape
must be interpreted in terms of initial composition and condensed
buffers (e.g., hydrates and carbonates), this investigation is closely
linked with investigation B-3, which would address ancient atmospheric
volatiles trapped in martian samples.

Carbon dioxide is the principal carrier for both carbon and oxygen in
the martian atmosphere, and a high precision determination of its
isotopic composition has the potential to provide very important
constraints on the steady state carbon and oxygen cycles (source and
sink flux terms) of present-day Mars. Further determination of the
isotopic fractionation of carbon and oxygen isotopes between carbon
dioxide and other atmospheric species has the potential to provide
additional information that would be important in placing constraints on
these element cycles. Viking measurements of atmospheric C and O were
only accurate to ±5%, whereas C measurements in meteorites demonstrate
the expected isotopic fractionations on a smaller scale that are
produced during solid/liquid/gas phase chemical reactions. The H
isotopic compositions measured in meteorites are much lighter than that
of the atmosphere, exhibit variations, and the initial (interior) D/H
ratio is still controversial. All volatile data acquired from meteorites
represent components incorporated at earlier times, and may or may not
be the same as the atmospheric composition today. For trace,
chemically-reactive species in the atmosphere, only the Viking
compositional data exist.

**Required Measurements**. The isotopic abundances of all abundant
and/or chemically unreactive species in the martian atmosphere (e.g.,
CO~2~, N~2~, Xe, Kr, Ar, Ne) should be accurately measured. Where
feasible abundances of minor species (H, He, CO, sulfur compounds)
should also be measured. Measurement of ^14^C activity might also be
desirable. These measurements would be performed by mass spectrometry
and other appropriate techniques in multiple terrestrial laboratories.
Gas handling procedures and measurement techniques differ among the
gases, and returned volatiles would have to be subdivided.

Most noble gases and abundant volatile species could be measured on a
gas sample size of 0.1 to 100 pico moles.  Some species could be
measured on the same sample, e.g., noble gases, whereas others would
require separate gas splits.  The table below gives an approximate
amount of gas in pico moles needed for a single analysis and the volume
of Mars atmosphere at ambient conditions that would be needed to supply
this analysis amount.  This assumes Mars atmosphere is 0.007 that of
Earth\'s at STP.

  --------- ---------------------- ---------------------------------------
  **GAS**   **Assumed for          **Mars Atmosphere Required in cubic cm,
            Analysis**             ambient**

  Xe        0.1 p-mole, e-9 cc     2

  Kr        0.1 p-m,  e-9 cc       0.5

  Ar        1 p-m,  e-8 cc         0.0001

  Ne        1 p-m,   e-8 cc        1

  CO~2~     100 p-m,  e-6 cc       0.1

  N~2~      10 p-m,  e-7 cc        0.02

  H/D       5 nano-mole (e-4 cc)   \~50
  --------- ---------------------- ---------------------------------------

From this \~ 100 cubic cm of Mars atmosphere at ambient conditions would
be sufficient for multiple analyses of noble gases and abundant
species.  Note, however, these numbers for H/D in water are approximate
only.  Note also that the head space inside a container of solid
samples, if hermetically sealed, could possibly satisfy the above sample
sizes.

**Samples Needed.** Determination of the current martian atmospheric
composition would require return of an atmospheric sample. Atmospheric
noble gases, CO~2~, and N~2~ could possibly be returned in the same
container as solid material, but advantages and disadvantages of a
separate atmosphere container, especially for other minor components,
should be evaluated. The atmospheric gas container should be constructed
in such a way that the gases can be readily removed without
contamination in a terrestrial lab. Several isotopic abundances could be
measured in an atmospheric sample of 100 cm^3^ collected at Mars ambient
(\~0.7 cm^3^ STP). However, measurement of several rarer isotopic
abundances and multiple analyses in different labs would probably
require a much larger sample. The possibility of compressing an
atmospheric gas sample above Mars ambient pressure should be
investigated.

**Special Requirements.** Sufficient hermetic sealing to prevent gas
loss during return would be important, and the reliability of the actual
seal might be an issue. Whereas measurements of noble gases, CO~2~, and
N~2~ should be straightforward in a returned atmospheric sample, the
less abundant, chemically reactive species (e.g., O~2~, H~2~O, CO,
sulfur compounds) likely would be altered during return. Special
consideration should be given to volatile outgassing of the atmospheric
container, especially during hermetic sealing operations. Consideration
should also be given to chemical reactions of the gas sample with the
returned container. Measurement of these trace species might better be
performed on Mars.

\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_

**2. [Investigation:]{.underline} Determine the rates of escape of key
species from the Martian atmosphere, their correlation with seasonal and
solar variability, their modification by remnant crustal magnetic
fields, and their connection with lower atmosphere phenomenon (e.g. dust
storms). From these observations, quantify the relative importance of
processes that control the solar wind interaction with the Mars upper
atmosphere in order to establish the magnitude of associated volatile
escape rates.**

**[Implications for sample return]{.underline}**.

Discussion Leads: **Steve Bougher and Bruce Jakosky**

Isotopic ratios analyzed from an extracted atmospheric sample would
serve as a "tie point" and general aid in our understanding of volatile
escape rates determined for the II.B.2 investigation. However, a direct
link between an atmospheric sample and quantification of volatile escape
rates is missing. Thus, analysis of an atmospheric sample would
complement Investigation II.B.2. However, such a returned and analyzed
atmospheric sample would be most directly relevant to investigations
II.B.1 and II.B.3.

\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_

3.  **[Investigation:]{.underline} Determine how the stable isotopic,
    noble gas, and trace gas composition of the Martian atmosphere has
    evolved through time.**

These provide quantitative constraints on the evolution of atmospheric
composition and on the source and sinks of water and other major gas
inventories. Requires high precision dating and isotopic measurements of
Martian meteorites and returned samples, and high precision *in situ*
measurements of samples on and beneath the surface (e.g., polar
layered-deposits or strata exposed in Valles Marineris).

**[Implications for sample return]{.underline}**.

Discussion Leads: **Don Bogard,** James Farquahar, Bob Pepin, Veronika
Heber, Kurt Marti, and Monica Grady

**Current and Anticipated Knowledge.**

The most current, sketchy knowledge about evolution of atmospheric
composition through time derives from analyses of martian meteorites,
which contain volatiles of varying and often unknown age. These
meteoritic volatiles occur in various phases, including adsorbed on
solid surfaces, shock-implanted into solid silicates (including impact
melt), and as chemically condensed phases such hydrates and carbonates,
likely precipitated by ground water interactions with silicates or by
chemical reactions induced by impact heating. Other martian surface
samples might contain subsurface ices. An important approach to gaining
new information would be to analyze various volatiles in different types
of samples of determined age.

An important element in understanding atmospheric evolution is knowing
the primitive, starting composition of atmospheric volatiles and the
physical method by which they were introduced into the atmosphere, i.e.,
by interior degassing or late-stage accretion (e.g., from comets). The
isotopic composition of most atmophile elements are either too poorly
known or are too fractionated to currently address this question
directly, but the atmospheric Kr isotopic composition resembles the
solar composition. Further, heavy noble gases in a few meteorites (e.g.,
Chassigny) also indicate a solar-like starting composition. The crustal
^15^N/^14^N ratio measured in some meteorites is very different from the
atmospheric ratio and similar to, thought not exactly like, the
terrestrial composition. Samples from the Earth's interior show
solar-like Ne and possibly Ar. It also would be important to determine
the primitive (starting) D/H composition in order to assess possible
short-term variations over time produced by interior degassing and rapid
atmospheric loss. Models that have been suggested for atmospheric loss
processes strongly utilize measured isotopic compositions of atmospheric
species.

The martian interior likely is poorly degassed of its volatiles.
Measurement of the ^40^Ar/^36^Ar ratio (where ^40^Ar derives from the
decay of ^40^K over geologic time) in ancient atmospheric gas trapped
within samples of known age could directly address the martian degassing
history. Further, measurement of the ^129^Xe/^132^Xe and ^136^Xe/^132^Xe
ratios (where ^129^Xe and ^136^Xe derive from decay of ^129^I and U, Pu,
respectively) in igneous samples that formed in the crust or mantle can
and has yielded inferences about very early planetary processes. For
example, the ^40^Ar/^36^Ar and ^129^Xe/^132^Xe ratios in the martian
atmospheric are larger than apparent trapped noble gases in igneous
martain meteorites, just the opposite from the observation on Earth, and
this probably conveys information about mobility of the parent elements
during early planetary differentiation.

Comparison of isotopic compositions of elements like C, O, H, and S in
various chemical forms and in different phases of returned samples could
give a potential wealth of geochemical information about atmospheric and
volatile interactions and evolution. These light elements isotopically
fractionate, in generally predictable ways, between any two phases
(gas/liquid/solid) in chemical equilibrium. Thus, precise isotopic
measurements of these elements in returned samples could give
information on the kind of chemical process and possibly the temperature
that produced the analyzed phase. These data could provide information
about genetic relationships among sulfur and oxygen-bearing phases, the
oxidation pathways for compounds in the regolith that involve
atmospheric species with anomalous oxygen isotope compositions (speaks
to oxygen sinks), and the sources and mixing of martian sulfate.
Further, comparison of isotopic compositions of an element in two phases
having similar origins but different ages might give information on
changes in isotopic composition of the atmospheric inventory over time.
Because CO~2~ in the martian atmosphere is likely an important part of
carbonate formation in surface rocks, it would be important to
accurately measure its isotopic composition (see B-1). It also is highly
desirable to measure the C, O, and H compositions in condensed polar
deposits, as they act as chemical buffers on the atmospheric
composition. A related question is where most of the surface inventory
of CO~2~ (estimated at possibly \~20 meters of carbonate) is currently
located. Another possibility is determining to what extent non-linear
isotopic fractionation effects, produced in some atmospheric elements on
Earth (and detected in martian meteorites), could be measured in
returned samples and used as a further determinant of gas/solid phase
reactions.

In many of the above studies accurate age dating of some portion of the
returned samples would be desired (see Goal III). Although igneous
samples are more easily dated, age dating of chemically precipitated
phases has been performed on terrestrial samples and on one ancient
martian meteorite.

**Required Measurements**. Measurement of the isotopic composition of
the trapped noble gases, C, O, H, N, and S in various phases, including
trapped atmospheric gas, chemical precipitates, and igneous and
sedimentary rock.

**Sample types needed.** Ideally, it would be desirable to return a
diversity of sample types, including igneous and sedimentary rocks,
precipitates from chemical reactions as may occur in veins and voids
within samples, and impact melts that may contain ancient atmospheric
gases. Because concentrations of cosmogenic Ne, Kr, and Xe in samples
having long surface exposure times may approach trapped gas
concentrations, samples with shorter exposure times would be preferable
for these measurements. The sample size required for a measurement would
depend on the particular analysis and might vary from less than a
milligram to 100 mg. Most analyses would probably require samples some
10s of mg in size.

It might be desirable to analyze gases collected in the sample container
or released into the container during return, If so, this container
would have to be hermetically sealed (see B-1). Temperature excursions
to \<100^o^C for no more than a few minutes might release some
lightly-bound volatile species (e.g., water) but should not seriously
effect most volatiles. Higher temperatures or longer times should be
avoided.

\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_

**4. [Investigation:]{.underline} Find physical and chemical records of
past climates.**

This investigation centers on finding geomorphic and chemical evidence
of past climates or of prior environmental events or conditions that may
have perturbed the local or global climate in unexpected ways (e.g., the
former presence of an ocean or seas, large impacts, episodic volcanism
or outflow channel activity). These provide the basis for understanding
the extent, duration (e.g., gradual change or abrupt transition), and
timing of past climates on Mars. This investigation would require
determining sedimentary stratigraphy and the distribution of aqueous
weathering products.

**[Implications for sample return]{.underline}**.

**Discussion Leads**: Joel Hurowitz, Nicholas Tosca (Harvard
University), Sidney Hemming (Columbia University).

According to Cronin in *Principles of Paleoclimatology*, "...three
overriding principles govern most paleoclimatological studies. These are
the *climate system* itself and the dynamic interrelationships among its
component parts; *chronology*, the dimension of time that is the
prerequisite to trace changes in climate; and *climate proxies*, the
surrogates of climate related parameters..." The first principle is
addressed in large part through study of the current Martian climate
system, coupled to modeling studies that are capable of making
predictions about how the Martian climate system has evolved over
geologic time. This is the purview of Investigations in Goal IIA, as
well as IIB, Investigations 1-3 and 5. A note relevant to the issue of
understanding the climate system through time, however, is that
terrestrial paleoclimatologists use ice cores samples in order to
perform analyses of the stable isotope composition of the ice (as a
temperature proxy) and measure the composition of atmospheric gases
trapped in the ice. These ice core records are an invaluable tool for
directly sampling ancient atmospheric chemical compositions, and core
sampling of the Martian polar ice caps should be given some
consideration in the study of ancient Martian atmospheric compositions.

Further analysis of Investigation IIB-4 will concern itself with the
issues of chronology and climate proxies, and how one would sample the
Martian rock record in order to effectively capture variations in Mars'
climate.

Terrestrial paleoclimatologists often turn to layered sedimentary rocks
deposited in quiescent subaqueous environments in order to address the
issue of *chronology*. Because sediments deposited in such environments
are typically layered on relatively short geologic time scales (annual
to centennial), it is possible to obtain a high-resolution accounting of
climate variation occurring during deposition. Given a bedding layer
that could be dated using geochronological techniques (e.g., U-Th-Pb,
K-Ar), and some knowledge of the deposition rate of individual layered
beds, it is possible to approximate the length of time represented by a
given set of samples. Ideally, the "marker bed" used for
geochronological analysis would represent a snapshot in time (e.g., a
volcanic ash layer, or a chemical precipitate formed directly from an
aqueous phase). The isotopic compositions of such materials are
typically closed at the time of crystallization/deposition, and assuming
they remain closed to subsequent isotopic resetting (e.g., by
diagenesis), they form the chronometer against which underlying and
overlying layered samples could be compared.

In order to accurately reconstruct the chronology of a sampled section
for Mars sample return, one would need to identify cyclically deposited
sedimentary materials which are interbedded with layers of volcanic rock
and/or chemical sediments precipitated directly from solution. The most
practical way to go about identifying the section of interest would be
to first: identify the climate variability issue(s) that are of the
highest priority to address, and at what time (approximately) in Martian
geologic time they occurred. Second, using orbital remote sensing,
attempt to identify layered sedimentary rock deposits that appear to
have been deposited in a quiescent subaqueous environment. This layered
rock deposit should be bounded by geomorphic surfaces having crater
retention ages appropriate to an analysis of the climate variation
event(s) of interest.

The second issue relates to what *climate proxies* should be used in
order to reconstruct aspects of the climate system as recorded by the
rocks under investigation. On Earth, a great many climate proxies are
based on analysis of biogenic materials and the chemical and isotopic
composition of carbonate rocks (yielding information about the fluid
phase from which it was precipitated). Unfortunately, for Mars we cannot
assume that biogenic materials and/or carbonate rocks will be available,
and we must therefore turn to other potential proxies. One such
potentially useful climate proxy is the secondary mineral phases present
in a given stratigraphic sequence. Changes in the chemistry or
mineralogy of environmentally informative minerals across stratigraphy
could provide a useful record of a transition in climatic conditions.
For example, a transition from a sedimentary sequence dominated by clay
minerals and/or carbonates to one dominated by evaporative phases such
as halides or sulfates would provide constraints on how fluid chemistry
at the Martian surface has varied with time. Such locations in the
geologic record could first be identified with orbital spectrometers
(i.e., sedimentary contacts between sulfates/halides, or sulfates/clays,
carbonates/sulfates, etc.). A full analysis of the mineralogical,
chemical and textural characteristics of such materials would yield the
requisite information. Geochronologic analysis of key marker beds, and
or direct dating of sedimentary minerals would provide constraints on
the timing and duration of such an event. Finally, stable isotopic
analysis of chemical precipitates might yield further information
regarding issues such as fluid temperature, analogous to studies
performed on terrestrial samples.

This discussion of climate proxies brings up another potential sampling
strategy that differs from the high-resolution sedimentary stratigraphic
approach outlined above:

Obviously changes in climatic variables such as temperature, humidity,
atmospheric pressure, etc., will be reflected in the physical state of
rocks and soils at the Martian surface as they interact with the Martian
atmosphere-hydrosphere system. Therefore, in a broad sense, climatologic
conditions can be captured through an understanding of the conditions of
rock weathering. The rate and extent of rock (or soil) weathering are a
reflection of the predominant climate conditions during the time
weathering takes place. Thus, a cold and dry climate is likely to result
in conditions in which physical weathering predominates over chemical
weathering, and vice versa for wetter conditions. The study of
weathering profiles (be they weathering rinds on individual rock
samples, or meters thick weathering profiles developed on large scale
outcrop) would provide a low-resolution snapshot of the average
weathering conditions, and therefore climate conditions, which prevailed
during the time interval that the weathering occurred.

Using such an approach, the issue of *chronology* could be addressed via
isotopic dating of both the igneous rock protolith and the secondary
minerals formed as a result of the weathering process. Further analysis
of the types of secondary minerals formed during weathering would
provide the *climate proxy* necessary to interpret the conditions
prevailing while weathering was taking place. For example, a thin rock
weathering rind dominated by an assemblage of secondary minerals such as
Fe-sulfates, Fe-oxides, and amorphous silica would suggest a low-pH
weathering environment in which large volumes of water were not
available. Conversely, a thick soil profile developed on igneous bedrock
in which clay minerals, Fe-oxides, and (possibly) carbonates dominate
the secondary mineral assemblage would suggest a moderate pH weathering
environment in which larger quantities of water were available.

The constraints for a Mars sample return of this type of a
weathering-based approach would be to identify sample collection sites
from orbit that possess igneous rocks and their weathering products, and
which represent a large range in geologic age. In this manner, it might
be possible to sample different weathering regimes at distinctive
periods in Martian geologic history to see how the weathering
environment, and therefore the general climate system, has evolved
through time.

**Sampling strategy**: As far as specific sampling strategies are
concerned, the requirements for this investigation are probably very
similar to those of MEPAG Goal 3, Investigations 2 & 5, which also seek
to address issues relevant to water-rock interactions in the Martian
surface environment. The following list of sampling capabilities is
modified from the above referenced investigations:

1.  Clearly it would be desirable to collect multiple samples of
    autochthonous (in place) rock. For a stratigraphy sampling mission,
    one would need to analyze the site from orbit in order to ensure
    that multiple layers of stratigraphic section could be accessed. In
    other words, if the section is exposed in a cliff face, one would
    need to design a sample return spacecraft capable of accessing those
    layers.

2.  For rocks sampled from intact sedimentary sections, drill cores or
    sample chips should be collected with the size of the samples
    depending on the scale of bedding. For finely laminated units, it
    might be more realistic to collect chips or blocks of samples that
    cut across strike. It would be necessary to accurately document the
    original orientation of collected samples relative to each other in
    order to reconstruct the stratigraphy back on Earth. For more
    massively bedded units, sample collection might be somewhat easier,
    requiring a minimum of one drill core or sample chip per layer of
    interest.

3.  Experience from MER suggests that most rocks exposed to the current
    Martian environment possess weathering rinds that are on the order
    of a few millimeters thick, and so at a minimum, samples should be
    collected from a few millimeters beneath the rocks' exposed surface.
    It would also be desirable to collect that portion of the rock
    sample exposed to the surface environment so as to analyze the
    secondary phases present in rock weathering rinds formed in more
    recent geologic time.

4.  For the sampling of weathered igneous rocks (as opposed to a
    sedimentary stratigraphy sampling mission), sampling would
    ultimately be dictated by the thickness of the weathering profile of
    interest. As discussed in above, weathering rinds of a few
    millimeters thickness are to be expected on all rock samples exposed
    to the ambient Martian environment. Drill cores placed into igneous
    rock samples should attempt to collect both the weathering rind and
    the relatively pristine igneous rock below. For more extensively
    weathered igneous materials, the approach would be analogous to that
    of a stratigraphy sampling protocol. The desire would be to collect
    individual core, chip, or block samples from varying positions in
    the weathering profile that sample unaltered protolith, moderately
    weathered material, and extensively weathered igneous rock.

5.  Characterization of sampling context would also be desirable. This
    could vary over scales of \~1 m to several meters depending on the
    environment, and could include any or all of the following
    capabilities.

    a.  Context imaging on scales ranging from \<20 microns (scale of
        microtextures) to about 2 m (scale of bedforms). The intent here
        would be to get as much in situ textural information as possible
        so that if a sample changes, the original character of the
        sample could be reconstructed.

    b.  Use of a micro-analytical spectrometer (e.g., Raman microprobe)
        on samples to be collected could be valuable. In this manner, if
        the sample did undergo textural changes during transport as a
        result of changes in temperature or relative humidity,
        mineralogy could be tied directly to texture (e.g., size,
        morphology of sediment grains and/or crystals in a specific
        facies that are associated with a specific chemical or
        mineralogical signature) prior to sample disturbance.

    c.  If possible, remote mineralogic characterization might make a
        valuable complement if the resolution of the instrument is
        similar to the sampling scale of those materials to be returned
        to Earth. In this manner, understanding of the changes in
        mineralogy across stratigraphy could be extended above and below
        the sampled area.

6.  Preferred capabilities would be to monitor and, if possible, control
    relative humidity and temperatures. This might be particularly
    relevant if the stable isotope composition of hydrated minerals
    and/or trapped gas phases could be significantly altered by changing
    temperature and relative humidity during transport to Earth.
    Laboratory experience shows that sulfate minerals are particularly
    sensitive to temperature and relative humidity effects.

7.  Cross-contamination levels of \<1% (and preferably \<0.1%) would be
    required for chemical and isotopic analyses on Earth. Capability
    would be needed to evaluate potential contamination through imaging
    of the entire sampling stream (e.g., drill, scoop, inlet).

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**5. [Investigation:]{.underline} Characterize the stratigraphic record
of climate change preserved in polar layered deposits, residual ice
caps, other climate-modulated deposits of H~2~O, CO~2~, and dust found
elsewhere on the planet.**

The presence of extensive layered deposits suggests that the climate of
Mars has undergone frequent and geologically recent change. A key to
understanding the climatic and geologic record preserved in these
deposits is to determine (i) the relative and absolute ages of the
layers, (ii) their thickness, extent and continuity, (iii) their
petrologic/geochemical characteristics (including both isotopic and
chemical composition), and (iv) the environmental conditions and
processes that were necessary to produce them. Specific examples of the
type of information these deposits may preserve include a stratigraphic
record of volatile mass balance; insolation variations; atmospheric
composition; dust storm, volcanic and impact activity; cosmic dust;
catastrophic floods; solar luminosity (extracted by comparisons with
terrestrial ice cores); supernovae and perhaps even a record of
microbial life. Addressing this investigation would require
high-resolution imaging, *in situ* and remote sensing measurements of
stratigraphy and layer properties, and absolute ages determined either
*in situ* or from returned samples.

**[Implications for sample return]{.underline}**.

Discussion Leads: **Kathryn E. Fishbaugh,** Michael Hecht, David Fisher,
Shane Byrne, and Wendy Calvin, Oded Aharonson

**[[Retrieving a Polar Sample]{.underline}]{.smallcaps}**

In this short report, we briefly describe factors to consider if
retrieving a sample of polar material in the context of a Mars sample
return. We have decided to organize this report by sample type/location
since the technology considerations and, in part, the scientific
rational for each are different. However, the overall scientific benefit
of retrieving a polar sample would be shared by all sample types: of all
possible samples from all parts of Mars, polar samples potentially
provide the best insight into the water and climate history. The Polar
Layered Deposits represent a detailed record of recent Mars climate
history. The composition of material from approximately the top 100 m of
ice would reflect the influence of meteorology, depositional episodes
(volcanic, impact, dust storms), and planetary orbital/axial modulation
over the timescales during which these vary (of order 100 kyr -1 myr).
One or more samples from such depths, either in solid or liquid form,
would provide critical information on the atmospheric-surface water
cycle via hydrogen and oxygen isotopic composition, aeolian material via
incorporated impurities, and other particles delivered by volcanic or
impact processes. Returned samples would enable absolute age dating via
dissolved gas analysis, as well as searching for trace organics (e.g.,
methane). Samples smaller than a few g would typically be sufficient for
the analysis.

*[General Considerations]{.underline}*

For all samples, images of and spectroscopic data from the sampling site
would aid in placing the sample in the broader context of the relevant
polar region as a whole and in tying it to orbital data. Of low cost but
high scientific return for any polar landed mission would be a
meterology package, providing wind direction and speed and atmospheric
pressure and humidity; such measurements could be used as ground truth
for global climate models and to better constrain the local (volatile)
depositional environment. We mention minimum needed core lengths, but
longer cores would of course provide more stratigraphic information from
further back in time. Cores could be broken into smaller pieces as long
as their stratigraphic position is known. Of course, while it always
true that we could reap richer rewards from having several samples from
several locations, one sample would provide all of the scientific
results described below. As long as the location and geologic unit from
which the sample came is known and could be placed in the context of
orbital spectroscopic and image data, it would not be necessary to
obtain one sample from relatively clean ice and one from relatively
dusty ice nor would it be necessary to choose very specific sample sites
in order to obtain maximum scientific benefit. Any site within the
residual cap or layered deposits would be fine. Isotopic analysis of ice
and meltwater for dating purposes would require no larger of a sample
than what would be needed from a rock or rock powder sample (a few
cm^3^).

*[Short Ice Core Sample from the Southern Residual Polar
Cap:]{.underline}*

The southern residual polar cap is composed of CO~2~ ice. Deposition of
residual cap layers is highly sensitive to changes in the global
environment and is linked to dust storm activity, obliquity, season of
perihelion, elevation, and the effect of global topography on
atmospheric circulation patterns. It is thought that CO~2~ residual caps
may form and disappear relatively quickly, so that we may be witnessing
a special time in Mars' history, and it is yet unknown whether such a
deposit ever formed in the north. With a sample core 20-30 cm in length,
one could potentially determine the amount and composition of CO~2~ and
dust deposited over a full annual cycle (the most recent 2 years),
providing ground truth for climate models (which would in turn provide
better characterization of past martian climates). An advantage of
retrieving a sample of CO~2~ ice is that it could be absolutely dated
using carbon isotopes. Such a sample would need to remain frozen in
order to preserve stratigraphy.

*[Small Sample from the Northern Residual Polar Cap:]{.underline}*

A small (few cm^3^) sample of water ice from the surface of the northern
residual polar cap would provide carbon and oxygen isotope and D/H
ratios for the most recently deposited water ice. These isotope ratios
could be analyzed in the laboratory to determine changes in water ice
reservoirs, such as net flux into or out of the polar cap, atmosphere,
or planet as a whole. These ratios could also be used for absolute
dating by their link to known variations in solar activity. Analysis of
grain size and porosity would lead to a better understanding of exactly
how volatiles are deposited and accumulate at the poles, creating the
largest surface water reservoirs on the planet. Dust entrained within
the ice could also be characterized (volume percentage, composition,
grain size, etc.) to understand its role in the mass balance and
rheology of the polar deposits. Determination of composition would
provide ground truth to orbital spectroscopic observations. One could
also search for signs of alteration of dust grains (e.g., formation of
sulfates) and of ice grain metamorphism. Such a complete understanding
of even this small sample of polar ice would not only tell us a great
deal about the martian water cycle, but it would also provide
engineering constraints for future larger-scale drilling missions to the
poles. A sample that remains frozen would be ideal, but D/H and oxygen
isotope ratios, as well as volume percentages and grain sizes of dust,
could also be obtained from meltwater.

*[Short Ice Core Sample from the Northern Residual Polar
Cap:]{.underline}*

While not well-constrained, the average absolute accumulation rate of
north polar volatiles over the last several hundred thousand years is
estimated to be \~0.5 mm/yr. Thus, a very short core sample yields
stratigraphic information covering many years (e.g., a minimum of 5 cm
would span 100 years, allowing a link with Viking observations even if
the topmost layer is 70 yrs old). The same types of analyses described
above could be performed on a core sample containing many annual layers,
leading to an invaluable record of the changes in composition, grain
size, accumulation rate, etc., over time to annual or even seasonal
precision. No other type of sample from anywhere on Mars would provide
such a complete and accurate characterization of Mars' recent climate
history. One sample from the pole would tell us about the history of the
planet as whole, in terms of both surface and atmospheric water. Such a
sample would clearly need to remain frozen.

*[Short Ice Core Sample from the Northern or Southern Polar Layered
Deposits:]{.underline}*

If a Mars sample return includes a rover, then a core sample (10 cm
would cover \~200 years and would be of the layer thickness scale that
HiRISE could observe, providing context) could be retrieved from an
exposure of the polar layered deposits within a polar trough or scarp.
On the polar plateaus, the areas between scarps and troughs are wide and
flat, and the north polar troughs have walls whose maximum slopes are
\~10°, well within the capability of current rovers. The polar layered
deposits are older than the residual caps; thus, analyses similar to
those described above would allow us to characterize the martian climate
from hundreds of thousands of years into the past. A sample taken from
the base of the north or south polar deposits exposed in one of the
large chasmata would be composed of ice and other materials potentially
millions of years old.

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**C. Objective: Characterize the State and Processes of the Martian
Atmosphere of Critical Importance for the Safe Operation of Spacecraft**
(**no priority order).**

This objective focuses on atmospheric processes of importance for the
safe implementation of spacecraft missions. These investigations would
yield the critical information necessary to improve the likelihood of
successful execution of missions in the Martian environment.
Investigations would seek to characterize the atmosphere from the
surface to 400 km altitude to support spacecraft landing, flight,
aerocapture, aerobraking, long-term orbital stability, targeting of
observations from orbit, and mission planning. Every effort should be
made to accommodate instruments that address these investigations on
each spacecraft bound for Mars.

**[Implications for sample return]{.underline}**.

Discussion Leads: **Rob Manning** and **Walt Engelund**

Returned samples do not contribute to this objective. This statement
applies to all four investigations under this objective.

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**1. [Investigation:]{.underline} Understand the thermal and dynamical
behavior of the planetary boundary layer.**

**2. [Investigation:]{.underline} Understand and monitor the behavior of
the lower atmosphere (0-80km) on synoptic scales.**

**3. [Investigation:]{.underline}** **Determine the atmospheric mass
density and its variation over the 80 to 200 km altitude range.**

4.  **[Investigation:]{.underline} Determine the atmospheric mass
    density and its variations at altitudes above 200 km.**

**III. GOAL: DETERMINE THE EVOLUTION OF THE SURFACE AND INTERIOR OF
MARS**

Insight into the composition, structure, and history of Mars is
fundamental to understanding the solar system as a whole, as well as
providing insight into the history and processes of our own planet. Thus
there are compelling scientific motivations for the study of the surface
and interior of the planet in its own right. The recent heightened
interest in the possibility of life on Mars provides additional emphasis
for these investigations. Geology informs virtually every aspect of the
study of conditions conducive to the origin and persistence of life, and
the study of the interior would provide important clues about a wide
range of topics, including the early history of Mars, sources of
volatiles, and geothermal energy.

The unique aspect of Mars, that in many ways makes it appear more
Earth-like and sets it apart from the other planets, is evidence of the
presence and activity of liquid water at or near the surface. This has
enormous geological implications affecting, for example, erosion,
weathering, heat flow, and the possibility of life (which can, in turn,
have significant effects on geological processes). Thus, an emphasis on
water is a logical framework within which to explore the planet.

**A. Objective:** **Determine the nature and evolution of the geologic
processes that have created and modified the Martian crust and surface
(investigations in priority order)**

The Martian surface contains the record of all the processes that shaped
it, from initial differentiation to volcanism, to modification by
impact, wind, and water. Understanding that record would help us
understand the total inventory and role of water on Mars, regions likely
to have been habitable to life, the processes involved in
surface-atmosphere interactions, and the thermal history of the planet.

**1. [Investigation:]{.underline} Determine the present state,
3-dimensional distribution, and cycling of water on Mars.**

Water is an important geologic material on Mars, influencing most
geological processes including the formation of sedimentary, igneous and
metamorphic rocks, the weathering of geological materials, and
deformation of the lithosphere. Determining the distribution of water on
Mars would require global observations using subsurface sounding and
remote sensing, coupled with detailed local and regional sounding and
measurements.

Water on Mars today is present in several forms potentially accessible
by sample return: the atmosphere contains a trace amount of water that
varies with season and location; the polar regions and pole-ward
subsurface are inferred to contain water ice; and rocks and soils very
likely contain water trapped in both relatively high temperature
("igneous" or "primary") and low temperature ("sedimentary" or
"alteration") minerals. This would be a broad investigation intended to
capture a current "snapshot" of water in various Martian reservoirs and
to understand how these reservoirs interact. Quantitative analyses of
Martian atmosphere, ices, regolith, and a variety rocks would be
required to address this investigation. The present state and
information on the distribution of water could be determined through
simple abundance determinations in different minerals, ices and gas
samples, while isotopic ratios of hydrogen (D/H) and oxygen (^18^O/^16^O
and ^17^O/^16^O) would provide key insights into the cycling of water.

The location of the landing site would profoundly affect the types of
samples available to satisfy this goal. Latitude is the dominant
control, but other geologic factors would determine the abundance of
water in its various forms; ground ice is likely to be accessible
pole-wards of \~55°; water of hydration is found heterogeneously at the
MER landing sites; surface frost is found on pole-facing slopes;
atmospheric water vapor is geographically and seasonally variable.

Because of the wide variety of likely water-hosts and the paucity of
quantitative knowledge about the distribution and form of water on Mars,
almost any samples collected by a Mars sample return could be of use in
addressing this investigation. Specifically, samples collected to
address Goal III investigations A-2 thru 6 and A-8 and 9 would all be
very relevant to this investigation and the goals in these sections
overlap the ones here.

**Sample types needed.** Samples from the atmosphere, regolith grains,
and cores/small pebbles of sedimentary, altered, and igneous rocks would
be needed.

**Sample diversity needed.** The greater the variety of samples, the
more complete the "inventory" required for this investigation would be.
Ice samples also would be desired, but would probably be beyond the
scope of the first sample return mission.

**Physical condition (rock, pulverized rock, etc.).** Samples would
include atmospheric, grains, and rock cores or small pebbles.

**Contamination types and limits that affect this investigation.**
Samples should be separated to minimize reaction/interaction in the
sample container.

**Sample number and mass.** At a minimum, significant progress on this
investigation could be made with the following samples:

> \(1\) \~1 cc STP of atmosphere isolated from soil and rock samples
>
> \(2\) \~ 1 gram of regolith for mineralogical and isotopic studies of
> individual grains
>
> \(3\) Cores or small (several gram) pebbles of sedimentary/aqueously
> altered rocks for petrologic, geochemical and isotopic analysis
>
> \(4\) Cores or small (several gram) pebbles of igneous rocks for
> petrologic, geochemical and isotopic analysis

**Vulnerability of samples to degradation effects (T, volatile loss,
etc.).** Samples for this investigation should be collected in such a
way as to preserve their mineralogic integrity as much as possible so
that water could be attributed to specific minerals. In addition, the
samples should be preserved at relatively low temperatures so as to not
compromise their volatile content or form.

**Maximum sample temperatures for sample integrity.** Given the goal of
characterizing water content of these samples, they should be kept at
\<0° C.

**Impact of degradation on the investigation.** Loss of volatile
components in samples would diminish their value to this investigation.

**Required/preferred sampling hardware.** None identified.

**Data needed for sample choice and in situ characterization.** In order
to translate the microscopic analyses of the rock samples to the
"global" inventory sought in this investigation, some documentation that
would allow the samples to be placed in their local and global context
is highly desirable. Therefore, samples of units either characterized by
other missions (MER, MSL) or by in situ observations on a Mars sample
return itself would be much more valuable than random or poorly
documented samples.

**Estimate of required mobility range.** Not determined.

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**2. [Investigation:]{.underline} Evaluate fluvial, subaqueous,
pyroclastic, subaerial, and other sedimentary processes and their
evolution and distribution through time, up to and including the
present.**

Locations with fluvial and lacustrine sediments are likely sites to
detect traces of prebiotic compounds and evidence of life. Sediments
also record the history of water processes on Mars. Polar layered
terrains in particular may preserve a unique record of climate history.
Aeolian sediments record a combination of globally averaged and locally
derived fine-grained sediments and weathering products. Understanding
sedimentary processes requires knowledge of the age, sequence,
lithology, and composition of sedimentary rocks (including chemical
deposits, such as those observed at Meridiani); the rates, durations,
environmental conditions, and mechanics of weathering, cementation, and
transport processes; and the fluvial and lacustrine record preserved in
the morphology of the surface and shallow subsurface (e.g., beneath
surficial deposits).

Orbital and in-situ investigations of sedimentary materials ultimately
are limited by the scale and complexity of the desired measurements.
Returned samples would greatly expand our understanding of the
environments and processes that have led to the range of sedimentary
materials evident at the Martian surface. The types of measurements that
could be done on returned samples in the lab include:

-   Grain size distribution: would allow assessment of the physical
    parameters of transport currents and sedimentation type, i.e.,
    gravity vs. current driven processes, and different sedimentary
    environments from sorting characteristics

-   Grain morphometry: the shape of the grain is indicative of velocity,
    rheology and duration of the sedimentary flow (i.e., aeolian sands
    show very smooth shape with characteristic impact marks)

-   Microscopic studies of rock thin-sections: for clastic sediments
    this would help to understand the origin (provenance) of the grains
    as well as the composition of cements. For chemical sediments, it
    would aid in matrix vs. cement classification to understand the
    diagenetic processes of lithification including the environment
    conditions (e.g., arid vs. wet conditions, chemical characteristics,
    relative timing, selection of samples for dating sedimentary
    processes)

-   Geochemical and stable isotopic studies at high resolution, using
    microanalytical methods to characterize sources and processes in
    both clastic and chemical sediments

-   Isotopic dating of chemical precipitates, such as carbonate and
    sulfates, might also be accomplished if the correct samples are
    returned. This would provide the only direct and absolute temporal
    constraint on the timing of water-based chemical processes on the
    Martian surface. However, multiple isotopic systems yielding the
    same age would be required before the time of formation of the
    material could be known with confidence. Ar-Ar dating has been
    completed on terrestrial jarosite and might be a useful technique
    when applied to Martian materials. However, the presence of
    atmospheric Ar adds complexity to the interpretation of these data
    and likely necessitates the use of additional chronometric systems
    such as Rb-Sr, Sm-Nd, or U-Th-Pb. In order to apply these isotopic
    systems, several minerals would be required that are: (1) derived
    from a common fluid with the same initial isotopic composition
    and (2) have different parent/daughter ratios within their
    structures. Potential sample sets that could be dated include
    jarosite-gypsum and calcite-siderite-magnesite. Individual samples
    containing multiple mineral phases or multiple samples derived from
    single evaporation/precipitation sequences would be required for
    dating.

The large variety of sedimentary deposits identified from orbit requires
studies at the outcrop scale using high-resolution imaging and
topographic analysis to recognize sedimentary structures from
meter-scale to centimeter-scale. To select the appropriate samples for
terrestrial studies, a survey from the landing site should be supported
by high-resolution imaging (at mm scale) to identify any diagnostic
sedimentary structures that are indicative of particular flow dynamics.

Experience from MER has demonstrated that sedimentary materials can
include a complex mixture of siliciclastic components (derived from
basalt with varying degrees of alteration leading to varying amounts of
clays and amorphous secondary products) and chemical components
(sulfates, chlorides, silica - state of crystallization unknown and
likely variable, possibly carbonates, and no doubt some surprises). Such
rocks typically have a complex diagenetic history that is preserved in
the micro-textures and mineralogical compositions. Thus the challenge
would be to preserve these features to the greatest degree possible in
any returned samples.

Sedimentary materials, especially those that have experienced
interaction with water, would be the target of other investigations.
These include but are not limited to IA2, IB4, IC2, IC3, IIB4, and
IIIA6.

**Sample types needed.** Sedimentary material from outcrop would be the
ideal. Samples of float rocks that could be readily related to a
stratigraphic section would be permissible.

**Sample diversity needed.** Stratigraphy can vary over scales of \~1 m
to several meters depending on sedimentary environment. It would not be
necessary that degree of induration be a major factor in sample
selection, but it is recognized that there would be the need to cover
the major lithologies and the diagenetic history to the greatest degree
possible. As an example, we could take a section such as Meridiani and
plan how it should be sampled. At Endurance/Eagle craters, about 8
samples would be a minimum to properly characterize the stratigraphic
variability. This would include 3 samples of different facies and 2
extra samples to gauge the degree of stratigraphic variation in
chemistry, an extra from the upper unit that has high grind energy
(i.e., especially hard rock) and 2 samples from the diagenetic front at
Whatanga contact.  This emphasizes the importance of *in situ*
measurements in preparation for sampling. This is also just an example.
For a different depositional environment, the answer could be very
different.

**Physical condition (rock, pulverized rock, etc.).** It would be
advisable to collect a chunk of rock rather than small fragments to
allow the reconstruction of the stratigraphy at microscopic scale from
the thin-section. Core samples would be ideal.

**Contamination types and limits that affect this investigation.** For
rocks, intact drill cores or sample chips, cross-contamination would not
be a major problem for textural analysis if samples remain intact. For
unconsolidated sediments, cross contamination would be an issue for
textural analysis and should be \<2%. Cross-contamination levels of \<1%
(and preferably \<0.1%) would be required for chemical and isotopic
analyses on Earth. Capability would be needed to evaluate potential
contamination through imaging of the entire sampling stream (e.g.,
drill, scoop, inlet).

**Sample number and mass.** As indicated above, to investigate even a
few meters of stratigraphic section might require 5-10 samples. A rough
estimate of the sample mass, considering the need for 1 cm on a side for
the microscopic analysis, about 1 cm^3^ would be needed, if density \~3
g/cm3 then we should have \~3 g of sample. For unconsolidated sediments
at least 1 cubic centimeter, depending on scale of bedding, textures
anticipated and grain sizes. For age dating, because the abundances of
Rb, Sr, Sm, Nd, U, Th, Pb, and even K are unknown in these minerals the
amount of sample that would be required to complete these analyses is
poorly constrained. Nevertheless, it seems likely that ages could be
determined on samples of \~1-2 g mass.

**Vulnerability of samples to degradation effects (T, volatile loss,
etc.).** Many sulfates are highly unstable and are likely to undergo
phase transformations (e.g., dehydration) and mineralogical reactions
(e.g., Fe-sulfate to Fe-oxides) if the ambient environment is not
maintained.

**Maximum sample temperatures for sample integrity.** Given the
susceptibility to phase changes of various sulfates, temperatures less
than those experienced at the sampling site would be desired. This is
likely to be \~0° C or less.

**Impact of degradation on the investigation.** Some phase
transformations could result in major volume changes and thus could
seriously disrupt the textures of the samples during collection and
transport to Earth.

**Required/preferred sampling hardware.** Mineral structure and
composition must be preserved during collection and transport. Sample
storage in sealed containers to preserve any water released from
dehydration reactions would be desired. Capability to rapidly transfer
samples to storage containers, preferably autonomously within minutes
but no longer than one communication cycle, would help ensure
preservation of hydrated phases. Preferred capabilities would be to
monitor and, if possible, control relative humidity and temperatures.
The kinetics of sulfate dehydration and oxidation reactions should be
evaluated, but it is expected that they may show rapid changes. For
example diagenetically altered melanterite (in water) through the
sequence schwertmannite -- jarosite -- goethite (-starting to form
hematite) is known to form at room temperature in the space of a several
weeks. So keeping samples at as low a temperature as possible would be a
priority. However, if that is unrealistic, then the entire sample should
be encapsulated and "put the pieces back together" on Earth.

**Data needed for sample choice and in situ characterization.** Context
imaging on scales ranging from \<20 microns (scale of microtextures) to
about 2 m (scale of bedforms). The intent here would be to get as much
*in situ* textural information as possible so that if the sample
changes, its original character could be reconstructed. The preservation
of textures would be a very high priority. In diagenetic studies, the
textures provide the roadmap to the sequence of events that could then
be analyzed using micro-sampling techniques. 

**Estimate of required mobility range.** This would be landing site
dependent, but the need to reach outcrop would be the most significant
mobility requirement. Once at outcrop, mobility of \<10 m probably would
be sufficient.

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**3. [Investigation:]{.underline} Calibrate the cratering record and
absolute ages for Mars.**

The evolution of the surface and interior of Mars, as well as the
possible evolution of life, must be placed in an absolute timescale,
which is presently lacking for Mars. Developing this chronology requires
determining the absolute ages of geological units of known crater ages.

Returned samples of known geological context offer the only way to
characterize the absolute chronology of Martian surfaces. Once the
absolute age of a surface is known, then ideas of superposition and
crater density could be used to infer relative ages of units on a more
global scale (i.e., photogeologically). These sorts of calibrations
could feed into life questions, i.e., Could life have developed during a
heavy bombardment? Was there a heavy bombardment?

The choice of landing site would be of paramount importance to the
success of this investigation. At a minimum, the landing site must be
well characterized in terms of crater density. Given the abundant
evidence for burial and exhumation in various locations across Mars, the
geomorphic surface containing the landing site must have been
continuously exposed to impacts throughout Martian history.
Additionally, this surface must contain a rock unit exposed over a large
enough area and emplaced over a short enough time period that it
represents a distinct time horizon marking the zero age of the cratering
history. Large flood basalts are an example. The surface must contain
materials that could be dated by several radioactive age-dating methods
including Rb-Sr, Sm-Nd, U-Pb, and Ar-Ar. Basalts and/or other igneous
rocks could be dated using these techniques, and it would be important
to apply multiple chronometers to each sample, because concordant ages
are considered more robust. Among Martian meteorite studies, it is not
uncommon for a particular isotopic system to be disturbed while other
system(s) are not. These disturbances can often result from varying
degrees of thermal metamorphism associated with shock or are due to
alteration on Mars. By applying multiple chronometers it would be
possible to obtain absolute crystallization ages, metamorphic overprint
ages, and possibly the timing of any aqueous alteration present in the
igneous rocks.

The need for igneous rock samples overlaps with investigation IIIA4 and
the requirement that they come from large-scale crustal units would
satisfy one of the requirements from IIIA6. This investigation also is
closely linked to IIIA11 concerning the effect of impacts on the
evolution of the Martian crust.

**Sample types needed.** Individual samples must be relatable to
cratered surfaces in order to calibrate cratering rates. This could be
accomplished by directly sampling outcrop, or from float rocks by
identifying unique mineralogical/geochemical characteristics in the rock
and relating it to localized bedrock.

**Sample diversity needed.** Ideally, cratering rates would be best
determined if at least 3 surfaces representing young, medium, and old
terrain were sampled.

**Physical condition (rock, pulverized rock, etc.).** Rock, core, or
chips would be appropriate for this investigation.

**Contamination types and limits that affect this investigation.**
Samples for chronometry would not need to be isolated from other samples
nor packaged separately.

**Sample number and mass.** Two samples from any available time
stratigraphic surface would insure that the best dates could be obtained
and maximize the probability that ages could be determined on any given
surface. The basic petrography of the sample must be determined in order
to confirm that the sample is igneous, homogeneous, and likely to be in
isotopic equilibrium. This would require enough mass for a thin section
to be made. The absolute minimum sample requirements would be on the
order of \~300 mg/sample assuming a depleted composition; slightly less
sample could be used if samples are more enriched. However, more sample
would be required if the sample is dominated by one mineral or contains
large amounts of impact melt.

**Vulnerability of samples to degradation effects (T, volatile loss,
etc.).** None identified.

**Maximum sample temperatures for sample integrity.** Temperature
excursions to \~50ºC (during Earth re-entry if return canister is not
refrigerated) would not be a concern for these studies.

**Impact of degradation on the investigation.** None identified.

**Required/preferred sampling hardware.** No specific requirements.

**Data needed for sample choice and in situ characterization.**
Sufficient information to demonstrate igneous origin.

**Estimate of required mobility range.** With the proper landing site,
it might be possible to find surfaces of significantly different ages
within a few kilometers of each other or perhaps less. A single age
probably could be sampled with little to no mobility at the right site.

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**4. [Investigation:]{.underline} Evaluate igneous processes and their
evolution through time, including the present**.

This investigation covers the broad range of igneous processes
including, for example, volcanic outgassing and volatile evolution. In
addition to dramatically molding the surface of the planet, volcanic
processes are the primary mechanism for release of water and atmospheric
gasses that support potential past and present life and human
exploration. Sites of present day volcanism, if any, might be prime
sites to investigate for life. This investigation would require global
imaging at a range of wavelengths, geologic mapping, in-situ and remote
techniques for distinguishing igneous and sedimentary rocks, evaluation
of current activity.

Igneous samples returned from the surface of Mars could be used to
address various aspects of Martian magmatism including magmatic
differentiation, volatile outgassing, composition and evolution.
Knowledge gained from the analysis of these samples potentially could be
extended to other parts of Mars via orbital remote sensing.

Sample diversity would be critical in allowing interpretation of
magmatic differentiation. Specifically, if a differentiation sequence is
collected, knowledge of temperature, pressure, and oxygen fugacity could
be derived from detailed geochemical studies of samples. The Mars
Exploration Rover Spirit has identified a set of rocks that appear to be
part of an alkaline differentiation trend. But the limited analytical
capability of its payload leaves many unanswered questions. Returned
samples would allow a more robust and complete understanding of such
trends. In addition, many volcanic rocks may contain xenoliths from
other parts of the magmatic complex, or from the mantle source from
which they were derived. Identification and collection of such materials
would greatly enhance our understanding of magmatic processes operating
at a given site.

Collection of regolith would offer a diversity of clast types from
different localities, some potentially hundreds of kilometers away. The
utility of this approach is shown by detailed studies of Apollo 16
clasts from a breccia that have lead to a greater understanding of the
magmatic and volcanic processes in a large region of the Moon. Shock
pressure could of course transform the original igneous mineralogy of
some exogenous samples, as it has in some Martian meteorites (e,g,,
plagioclase has transformed to maskelynite glass), but igneous
petrogenesis could be unraveled despite this effect.

Volatile composition could be addressed with a multitude of approaches
using returned samples of primary unaltered igneous rocks. Small melt
inclusions in volcanic phenocrysts contain trapped magmatic volatiles
that could be measured using a variety of micro-techniques such as SIMS
and FTIR. The amount and nature of C, S, O and H associated with any
magmatic system could be evaluated using these inclusions, which are
also common in Martian meteorites. Any preserved volcanic glass could
lead to information about S and O (microprobe and Mössbauer
measurements), and H measurements in minerals such as olivine or
pyroxene (FTIR measurement) could provide information about OH or H~2~O
in Martian magma chambers or source regions (mantle).

Outgassing processes could be understood with studies of vesicle size
and distribution, which could be studied using non-destructive 3D
imaging techniques such as micro-tomography at a synchrotron facility.
Such approaches have yielded much useful data about basaltic volcanism
on asteroids and the Moon. In addition, minerals formed by sublimation
at volcanic areas could give insight into nature of fluids (chlorides,
sulfates, oxides), just as they do on Earth, and could be studied using
a wide variety of analytical techniques including x-ray diffraction,
raman and infrared spectroscopy, SEM, SIMS, and electron microprobe
analysis.

The evolution of volatiles in the Martian crust and mantle could be
known from isotopic and trace element studies of all samples collected:
classic Ar-Ar, Rb-Sr, Sm-Nd, and Lu-Hf would all possible with standard
mass spectrometry techniques, and many key trace elements (rare earth
elements or REE, siderophile elements, volatile elements, and
chalcophile elements) could provide information about the Martian
interior, while providing links to volatiles. For small samples, where
not enough material is present to use a classical approach, ion
microprobe dating and characterization would be possible (albeit with
lower precision, but yielding nonetheless useful ages) on very small
igneous rocks, and could even broaden the number of systems possible to
include systems such as Re-Os (normally more mass intensive).

The collection of igneous rock samples for this investigation overlaps
with investigation IIIA3 and IIIA6.

**Sample types needed.** Martian magmatism could be studied, with an
emphasis on evolution through time, using several different kinds of
returned samples -- large samples collected in place (5 to 10 g of
igneous rock), would allow application of several different isotope
chronometers, but even relatively small regolith samples (0.5 to 1 g)
could include some exogenous rocks that would provide information about
regional magmatism.

**Sample diversity needed.** In order to document possible magmatic
trends, at least three samples of different composition are desired.

**Physical condition (rock, pulverized rock, etc.).** Cores, rocks, or
chips, either from outcrop or exogenous materials would constitute good
samples for this investigation.

**Contamination types and limits that affect this investigation.** Cross
contamination levels of \< 1% (and preferably \< 0.1%) would be required
for chemical and isotopic analyses in Earth labs).

**Sample number and mass.** At least three samples are desired. Mass
estimates for magmatism studies could draw on the experience of studying
a small Martian meteorite, such as QUE 94201. Allocation of \~ 2 g of
material to various investigators allowed a determination of its age,
and bulk elemental and isotopic composition. Utilization of a 1 g chip
of this meteorite to make 5 thin sections allowed a great diversity of
scientific problems to be addressed by 14 investigators. This experience
has guided us in making mass estimates for this investigation in Table
1.

**Vulnerability of samples to degradation effects (T, volatile loss,
etc.).** Not identified.

**Maximum sample temperatures for sample integrity.** The momentary
heating to 50 °C upon entry into Earth's atmosphere would not pose a
problem unless volcanic sublimates breakdown and release water or other
volatiles into the sample chamber affecting other samples. However,
heating above 500 °C (as per possible planetary protection requirements)
could cause the breakdown of volcanic sublimates and/or compromise the
integrity of volatiles trapped in melt inclusions; a less invasive
sterilization technique would be preferred.

**Impact of degradation on the investigation.** Not identified.

**Required/preferred sampling hardware.** A coring device would provide
ideal samples.

**Data needed for sample choice and in situ characterization.** Context
imaging on scales ranging from 1 mm to about 2 m in order to sample
vertically on lava or pyroclastic flows to maximize diversity.
Capability would be needed to evaluate potential contamination through
imaging of the entire sampling stream (e.g., scoop, drill, inlet, etc.).

**Estimate of required mobility range.** With the likelihood of
encountering exogenous rocks over relatively short distances, a range of
a few km's would be sufficient.

**Additional comments.**

Table 1: Summary of processes, samples, mass required, and techniques
(thin section uses 1 g)

  ----------------- ---------- ---------------- -------- ----------------------
  *Process*         *Sample    *technique*      *Min.    *Element, isotope, or
                    type*                       mass     mineral*
                                                (g)*     

  1\) Magmatic      Rock       Mass             0.5      Major elements, REE,
  differentiation              spectrometry              MSE, HSE, lithophile,
                               (TIMS, ICP)               chalcophile elements

                    Thin       Laser ablation,  \-       Major and trace,
                    section    SIMS, XANES               oxidation state

  2\) Volatile      Rock       Mossbauer, TEM   0.2      oxidation state,
  composition                                            ferromagnesian
                                                         minerals

                    Thin       SIMS, FTIR, EMPA \-       S, C, O, H, N, F, Cl,
                    section                              Br

  3\) Outgassing    Rock       Raman, xrd, SEM, 0.5      Sulfates, sulfides,
                               tomography                phosphates,
                                                         hydroxides, oxides,
                                                         carbonates

                    Thin       SEM, SIMS, FTIR, \-       S, C, O, H, N, F, Cl,
                    section    EMPA, crystal             Br
                               size                      
                               distribution              
                               (CSD)                     

  4\) Evolution     Rock       TIMS             1.0      Ar-Ar, Rb-Sr, Sm-Nd,
                                                         Lu-Hf

                    Thin       SIMS             \-       Rb-Sr, Sm-Nd, Lu-Hf,
                    section                              Re-Os
  ----------------- ---------- ---------------- -------- ----------------------

\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_

**5. [Investigation:]{.underline} Characterize surface-atmosphere
interactions on Mars, including polar, Aeolian, chemical, weathering,
mass-wasting and other processes.**

The focus of this investigation is on processes that have operated for
the last million years as recorded in the upper 1 m to 1 km of Mars.
Understanding present geologic, hydrologic, and atmospheric processes is
the key to understanding past environments and possible locations for
near-surface water. Knowing the morphology**,** chemistry and mineralogy
of both near surface rocks and alteration products is essential for
calibrating remote sensing data. This study also has strong implications
for resources and hazards for future human exploration. It would require
orbital and surface-based remote sensing of the surface and shallow
subsurface (meters to 10s of meters), and direct measurements of
sediments and atmospheric boundary layer processes.

Physical processes related to surface-atmosphere interaction that have
operated on time scales of \~10^6^ years will be dominated by aeolian
transport, with deposits resulting from recent mass-wasting and impact
processes being potential but unlikely features observable at landing
sites. Aeolian dust (suspension load) would be sampled for a variety of
purposes but there is also potential for sampling active or inactive
dunes and ripples (saltation, rolling loads). Both MER locations contain
aeolian bedforms of interest to this investigation. Ripples were
observed with a single-layer, coarse-grained lag that appears to armor
the underlying finer-grained sand/silt particles. Samples obtained from
such bedforms might offer clues to recent climate change on Mars.

Obliquity variation on timescales of \~10^6^ years could result in
transport of water from polar regions to mid- to low-latitudes via
sublimation and precipitation and thus to a potential landing site. This
in turn, could play a role in recent aqueous alteration or
chemical/mineralogical remobilization on rock and grain surfaces.
Chemical processes that have affected the Martian surface on time scales
of \~10^6^ years will influence samples to very shallow depths and would
be difficult to distinguish from processes operating over much longer
time scales (up to \~10^9^ years). The best examples to draw from with
the MER experience are the mm-scale alteration profiles found on all
rock surfaces and mm-scale cemented zones at the surfaces of ripples and
dunes. Such materials would include a variety of highly labile secondary
minerals (clays, sulfates, chlorides). Interpreting such materials would
require both chemical and textural information. The likely presence of
highly reactive sulfate and chloride minerals may also result in
hydration state profiles on surfaces of rocks, soils and aeolian
features that, in turn, would reflect recent surface-atmosphere
interaction. Finally, the identification of possible superoxides in the
Martian soil would be an important objective of this investigation,
although difficult to preserve in a returned sample.

Accordingly, the challenge for sampling would be to preserve primary
mineralogy, chemistry, and textural relationships during sampling,
storage and transport to Earth. If sample integrity could not be
guaranteed, it would be necessary to characterize samples on the Martian
surface to the greatest degree possible so that changes could be
evaluated and to preserve all components of the original sample.

Many of the goals of addressing this investigation would also be
relevant to addressing Goal III investigations A1, A2, A9 and perhaps A8
(and no doubt others). These sections should be coordinated to ensure
that mutually exclusive requirements are not mandated. Any liquid water
or ice that might be encountered would also play a role in interpreting
recent surface-atmosphere interaction and sampling approaches designed
for other purposes (i.e., A1) should be adequate to address this
investigation.

**Sample types needed.** The types of samples that would be needed
include grains of various sizes and rock cores.

**Sample diversity needed.**. An ideal set of samples would include
dust, grains from aeolian bedforms, rock cores/chips with alteration
rinds, and regolith.

**Physical condition (rock, pulverized rock, etc.).** For rock surfaces,
one intact drill core sample to at least 1 cm depth for each surface
profile studied. For cemented surfaces of unconsolidated deposits,
ability to sample top 1 cm of deposit is desired. Preferred capability
would be to keep profile intact, otherwise, it would require two samples
(one surface, one interior) to characterize profile.

**Contamination types and limits that affect this investigation.**
Cross-contamination levels of \<1% (and preferably \<0.1%) would be
required for chemical and isotopic analyses on Earth. Capability would
be needed to evaluate potential contamination through imaging of the
entire sampling stream (e.g., drill, scoop, inlet).

**Sample number and mass.** In order to characterize and interpret the
physical processes of young aeolian ripples and dunes (e.g., grain size
distribution, grain shape) the requirements would be as follows:

1.  For grain size analysis, minimum sample sizes of \~1 g (equivalent
    to several hundred sand grains 1mm in diameter) and perhaps greater
    (up to \~10 g) depending on grain size;

2.  Three samples would be preferred to characterize a single ripple
    (dune) consisting of leeward, windward and interior.

For regolith material, a sample from the surface and one or more within
a trench would be ideal. For weathered rocks, one core that includes the
outer surface would be a minimum requirement. A single sample of dust
would be sufficient.

**Vulnerability of samples to degradation effects (T, volatile loss,
etc.).** There is a range of vulnerability to degradation among the
different sample types. For the most vulnerable samples, we recommend:

1.  Sample storage in sealed containers to preserve any water released
    from dehydration reactions.

2.  Preferred capabilities would be to monitor and, if possible, control
    relative humidity and temperatures.

**Maximum sample temperatures for sample integrity.** The key
requirement for preserving the chemical nature of the soil surfaces to
the extent possible would be to keep the sample at low temperature,
i.e., at Mars-ambient temperature or ideally colder.

**Impact of degradation on the investigation.** The impact ranges from
severe for the investigation of superoxides to modest for characterizing
aeolian sediments.

**Required/preferred sampling hardware.**

1.  Coring would be required for sampling of rocks.

2.  Capability to rapidly transfer samples to storage containers;
    preferably autonomously within minutes but no longer than one
    communication cycle.

3.  Preferred capability would be for trenching to depths of \>10 cm to
    access subsurface material with the ability to preserve the trench
    wall undisrupted.

**Data needed for sample choice and in situ characterization.** Context
imaging on scales of \~100 μm (intact sample prior to storage) to \~2 m
(size of rock/outcrop). Similar context imaging would be required for
aeolian samples

**Estimate of required mobility range.** Based on MER experience,
probably \<1 km for all materials of interest.

\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_

**6. [Investigation:]{.underline} Determine the large-scale vertical
structure and chemical and mineralogical composition of the crust and
its regional variations. This includes, for example, the structure and
origin of hemispheric dichotomy.**

The vertical and global variation of rock properties and composition
record formative events in the planet's early history, constrain the
distribution of subsurface aquifers, and aid interpretation of past
igneous and sedimentary processes. Determining these structures requires
global and local remote sensing and deeper subsurface sounding (100s of
meters to kilometers), detailed geologic mapping, and determination of
mineralogy and composition of surface material.

The large-scale crustal units of Mars have been identified based on
information obtained from orbital and in some cases, telescopic data
sets. The hemispheric dichotomy and other more regional-scale variations
of the crust are recognized by a combination of topographic,
morphologic, spectral, magnetic, and gravity attributes. Vertical
variations of the crust are poorly constrained but are evident in the
layering visible in the walls of the Valles Marineris and suggested by
the presence of lateral heterogeneities of surface attributes. The best
way to ensure that returned samples serve as "ground truth" for
large-scale crustal units would be to collect samples that could be
related to observations made from orbit. At a minimum, samples must be
understood within the geologic context of the landing site from which
they are collected. Although a diverse set of samples is desirable, with
respect to the investigation of regional/global-scale features of the
crust, samples with no clear provenance would be best avoided.

On the surface, identifying samples representative of large-scale
crustal units would in some cases be straightforward and in others, more
challenging. At a given landing site, the potential exists to encounter
rocks that represent both local and regional geologic units. For
example, the sedimentary rocks of the Home Plate feature in Gusev Crater
appear highly localized, while the olivine-rich basalts of the plains
are more regionally significant. The former supply information about a
small-scale addition to the crust, while the latter are probably
representative of large-scale contributions found elsewhere across the
planet. Both rock units are readily distinguishable on the ground and
from orbit. This is not the case with other rocks encountered by the
Spirit rover. In the Columbia Hills at least three varieties of basalts
were discovered, including plains basalt, based on their spectral
characteristics. All three are visually similar yet only the plains
basalt appears to represent a major component of Gusev Crater. Had the
rover only traversed the Columbia Hills, it would have been unclear
which of the three basalt types was regionally significant. This example
demonstrates the need for a carefully chosen landing site, mobility, and
some means of characterizing rocks prior to selection in order for
returned samples to be placed into a larger context.

Samples collected for this investigation would most likely to be
volcanic igneous rocks but sedimentary rocks that encompass large-scale
regional deposits are desirable. This set of samples overlaps with those
from investigations IIIA2-4.

**Sample types needed.** Orbital instruments have revealed a range of
spectrally distinct crustal units that are the result of mineralogic
diversity. Rock samples representative of the various spectral "types"
and igneous minerals observed from orbit would be most appropriate for
this investigation.

**Sample diversity needed.** Because of the emphasis in this
investigation on large-scale crustal units, it is unlikely that a given
landing site would contain more than one or two rock types that fit the
criteria. However, there exists the possibility of exogenous samples
representing other crustal units that have been lofted into place by
impact processes that might be available at a given landing site.

**Physical condition (rock, pulverized rock, etc.).** Because they would
serve as ground truth for orbital spectral measurements, consideration
must be given to what constitutes an ideal sample for laboratory
spectral measurements. Cores or chips that preserve some of the natural
surface of the original rock would be required.

**Contamination types and limits that affect this investigation.** Bulk
mineral and chemical measurements would be the first priority for these
samples. Consequently, the main science goal (ground truth) would not be
significantly impacted by minor contamination.

**Sample number and mass.** Two samples from each representative crustal
unit, each with a mass of at least 1g would be ideal.

**Vulnerability of samples to degradation effects (T, volatile loss,
etc.).** Igneous samples would be less susceptible to degradation than
possible sedimentary samples.

**Maximum sample temperatures for sample integrity.** The possibility of
hydrated alteration minerals to be present on/in the samples would
require maintaining temperatures to \<50° C.

**Impact of degradation on the investigation.** Probably low.

**Required/preferred sampling hardware.** To achieve the objectives of
this investigation, some form of instrumentation would be required that
can characterize 10s to 100s of rocks along a traverse. The analytic
capability would need to be at the scale of the samples to be collected.
Not only would such instrumentation ensure a diversity of samples, but
it would also form the basis for establishing the provenance of a given
sample. Once identified, coring of outcrop or large float rocks would be
ideal.

**Data needed for sample choice and in situ characterization.** VNIR
and/or TIR spectra would best serve the objective of identifying samples
that are representative of large-scale crustal units.

**Estimate of required mobility range.** Both Gusev crater and Meridiani
Planum sites demonstrate that rocks representing large-scale units were
readily available within several meters of the lander. Accessing a
greater diversity of samples might require several km of driving.

\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_

**7. [Investigation:]{.underline} Document the tectonic history of the
Martian crust, including present activity.**

Understanding the tectonic record is crucial for understanding the
geologic history as well as the temporal evolution of internal
processes. This, in turn, places constraints on release of volatiles
from differentiation and volcanic activity and the effect of tectonic
structures (faults and fractures in particular) on subsurface hydrology.
This investigation requires geologic mapping using high resolution
topographic data combined with high-resolution images at a range of
wavelengths, magnetic and gravity data, and seismic monitoring.

No perceived relevance to sample return.

\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_

**8. [Investigation:]{.underline}** **Evaluate the distribution and
intensity of hydrothermal processes through time, up to and including
the present.**

Hydrothermal systems are thought to be connected with the earliest
evolution of life on the Earth. Hydrothermal systems may also play an
important role in the chemical and isotopic evolution of the atmosphere,
and the formation of the Martian regolith. Deposits from hydrothermal
systems have the potential to record the history of the biosphere and
crust-atmosphere interactions throughout Martian history. Assessing
hydrothermal processes requires knowledge of the age and duration of the
hydrothermal system, the heat source, and the isotopic and trace element
chemistry and mineralogy of the materials deposited.

Beginning with the identification of aqueously derived mineral phases in
Martian meteorites and now extending to identifications made by orbiting
and rover-based instruments, the concept of aqueous alteration on Mars
is well supported. However, in the case of the various sulfate,
phyllosilicate, hematite, and goethite phases identified at Mars, the
potential role of hydrothermal processes in their formation must be
further investigated. Returned samples would allow detailed analyses
that could not be done by landed missions alone. Fluid chemistry,
temperature and atmospheric pCO~2~ or pSO~2~ conditions could be
established. Radiometric age dating on secondary assemblages (e.g.,
Rb-Sr and K-Ar have been used successfully) would determine the age of
hydrothermal alteration events and aqueous precipitation in the Mars
geological history. Stable isotope analysis (e.g., C, N, O) would be
necessary in order to constrain fluid temperatures associated with the
secondary mineral formation. It would also help to reveal the isotopic
composition of the atmosphere and crustal isotopic reservoirs at the
time at which they formed. This, in turn, would provide constraints on
past atmospheric thickness, composition and loss. For instance, heavy
stable isotope compositions (e.g., ^13^C, D/H) in Martian meteorites are
probably a result of impact induced atmospheric loss and sputtering from
the early Mars atmosphere.

The discovery of an opaline silica deposit by the *Spirit* rover at Home
Plate appears consistent with an ancient hydrothermal system probably
arising from the interaction of magma with near-surface water or ice.
This may represent the first intact hydrothermal system discovered on
Mars and perhaps demonstrates what can be expected for the surface
expression of some forms of hydrothermal alteration. No obvious
indication of clay minerals or carbonates has been observed in the
silica deposits. However, at least three of the 4-7 localities on Mars
from which the Martian meteorites were derived contain carbonate at up
to 1 vol. %. This carbonate -- together with co-existing smectite clay
and salts -- has been used to constrain the temperature, composition and
duration of fluids from which these secondary mineral assemblages
formed. There is a general consensus that they were precipitated
relatively rapidly at \<150^o^C from CO~2~-charged, brine-like fluids.
The volume of carbonate could be used to constrain the partial pressure
of CO~2~ that the fluid equilibrated with in a near-surface setting.
Heat sources for the fluids may include impact or local volcanism.
However their origin is clearly decoupled from the igneous
crystallization of the rocks from which the meteorites were ultimately
formed. Returning carbonate, salt, clay-bearing or silica samples would
be the best way to establish the environment in which these deposits
formed.

The samples collected for this investigation most directly overlap with
investigations outlined in Goal I. Martian materials that have
experienced hydrothermal alteration, or more importantly, formed in a
hydrothermal environment, would be good candidates for any investigation
focused on addressing questions about habitability and life on Mars.

**Sample types needed.** Aqueous alteration is likely to be present in
variety of different rock types on Mars. The igneous rocks in the
Martian meteorites and the basalts of the *Spirit* site show significant
secondary alteration. The sedimentary rocks at *Opportunity* show higher
volumes of sulfate and hematite in some of their outcrops. Thus soil and
igneous or sedimentary rocks may all contain secondary minerals formed
in different ways: hydrothermal veins of silica, weathering of igneous
minerals, evaporation of brines, deposition from standing water.

**Sample diversity needed.** See previous description.

**Physical condition (rock, pulverized rock, etc.).** Chips or cores
that preserve original rock surfaces and possible veins would be
important for investigating alteration.

**Sample number and mass.** The number of samples would be dependent on
what is available at the landing site. Preparation of polished surfaces
for compositional and textural analyses would require less than
half-gram sized pieces

**Vulnerability of samples to degradation effects (T, volatile loss,
etc.).** Some of the hydrated sulfate minerals identified by the MER
landers are only stable at \<0° C. For example, MgSO~4~.11H~2~O (soon to
be officially called meridianiite) can change to the more common mineral
epsomite at only 2° C. This phase change also results in the release of
\~30% water by volume which could alter other water analyses. Silica
materials also may be hydrated, although probably are less sensitive to
dehydration than the sulfates. Release of water from some minerals could
cause efflorescence and recrystallization of a variety of salt minerals
particularly the highly soluble sulfate minerals. Clay minerals
obviously are also sensitive to environmental conditions and ideally
would be encapsulated in a way that preserves their hydration state:
this means ensuring that smectite-like clays such as those identified at
Marwth Vallis would be kept below 100^o^C, at which temperature they
irreversibly dehydrate. Temperature control would be necessary if we
wish to preserve the original mineralogy of the Mars samples.

**Maximum sample temperatures for sample integrity.** See previous
description.

**Impact of degradation on the investigation.** See Vulnerability
description.

**Required/preferred sampling hardware.** Coring would produce ideal
samples in which exterior surfaces and interior textures are preserved.

**Data needed for sample choice and in situ characterization.** Some
means of establishing whether a given rock or soil contains candidate
hydrothermal phases would be needed.

**Estimate of required mobility range.** As shown by the *Spirit*
example in Gusev crater, several km of traverse might be required to
encounter clear examples of hydrothermal alteration.

\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_

**9. [Investigation:]{.underline} Determine the processes of regolith
formation and subsequent modification, including weathering and
diagenetic processes.**

The regolith is a filter through which we view most of the Martian
surface by remote sensing. In addition, it may provide a valuable record
of the history of surface conditions and processes. Understanding
regolith formation and modification requires quantitative measurement of
mineralogy, chemistry, and physical parameters of the surface and
shallow subsurface.

The regolith has proven to be among the most mineralogically, chemically
and physically complex geological units encountered on Mars. Physical
processes are likely dominated by aeolian transport and impact, but in
places could also involve other mechanisms such fluvial and glacial
transport. Soil samples, from the uppermost part of the regolith, would
provide a mixture of dust, sand and gravel-sized material. Coarse
materials would provide access to locally derived components while the
finer materials would be expected to be more representative of a global
sampling.

The regolith at the visited landing sites appears to contain components
that are broadly homogeneous but most sites also possess distinctive
characteristics suggesting multiple sources. Thus the Meridiani regolith
contains hematite spherules from the underlying bedrock, Pathfinder
regolith contains components of the local K-rich rocks, and in places
Columbia Hills regolith exhibits the P-rich characteristics of
surrounding rocks. There is likely a meteoritic component averaging on
the order of 2%. The regolith is enriched in S and Cl and in some places
highly enriched in these elements. Sulfate mineralogy is complex and may
involve a variety of post-depositional mineral transformations (e.g.,
involving ferric sulfates), constraining atmosphere-surface
interactions. High silica deposits (most likely opaline silica) have
also been found. Accordingly, sampling regolith must preserve material
that could be used to address questions relating primary depositional
processes, primary mineralogy, and complex post-depositional aqueous
processes that likely range from low-temperature (i.e., cryogenic)
through to hydrothermal conditions (see also A8). The oxidation state,
water content and pH of the current uppermost regolith or soil could
also be determined, constraining mineral stability.

Although regoliths are complex, sampling issues are not dissimilar to a
number of other investigations. Sufficient sample must be collected and
preserved in a manner that would allow an evaluation of a variety of
physical processes (e.g., grain size distributions) as well as the
identification and characterization (chemically and isotopically) of
complex mineralogy. Important textural information would likely be
present on scales larger than sampling scales (centimeter to meter) and
so sample sites would need to be characterized to the greatest degree
possible.

**Sample types needed.** Regolith grain samples would be needed for this
investigation.

**Sample diversity needed.** Regolith samples from any compositionally
distinct units would be desired.

**Physical condition (rock, pulverized rock, etc.).** Regolith samples
would be needed at various grain sizes.

**Contamination types and limits that affect this investigation.**
Cross-contamination levels of \<1% (and preferably \<0.1%) would be
required for chemical and isotopic analyses on Earth. Capability would
be needed to evaluate potential contamination through imaging of the
entire sampling stream (e.g., drill, scoop, inlet).

**Sample number and mass.**

1.  Using the Columbia Hills as an example, it would be necessary to
    examine at least 2 regolith profiles in the vicinity of the landing
    site. For homogeneous regolith, at least 2 samples would be required
    (surface and at depth); for complex soils at least 3 samples and
    perhaps as many as 4-5 would be required to characterize regolith
    (e.g., surface, each visually distinctive zone within profile).

2.  Scale of distinctive zones may be as fine as cm-scale requiring
    comparable scale for sampling. Sample sizes should be at least 1
    cm^3^ in size.

**Vulnerability of samples to degradation effects (T, volatile loss,
etc.).**

1.  Sample storage in sealed containers to preserve any water released
    from dehydration reactions.

2.  Preferred capabilities would be to monitor and, if possible, control
    relative humidity and temperatures. For instance, preservation of
    sulfates during sample return for subsequent mineralogical study
    would require temperature control \<2° C and low humidity to inhibit
    efflorescence of the most soluble minerals.

**Maximum sample temperatures for sample integrity.** See above.

**Impact of degradation on the investigation.** See above.

**Required/preferred sampling hardware.**

1.  Ability to carry out trenching on a scale comparable to MER would be
    required in order to expose soil profiles to scales on the order of
    decimeter. Deeper penetration of trenches is desirable.

2.  Capability to rapidly transfer samples to storage containers;
    preferably autonomously within minutes but no longer than one
    communication cycle.

**Data needed for sample choice and in situ characterization.** Context
imaging would be needed on scales of \~100 μm (grain to grain
relationships of soils) to \~50 cm (upper limit on depth of trench).

**Estimate of required mobility range.** Based on all previous landed
missions, regolith material would be readily available surrounding the
lander.

**Additional comments.** Determination of the volatile and ice content
of the regolith sample would be used to calculate a global inventory of
CO~2~ and H~2~O that is currently trapped as ice or clathrate in the
regolith. If the samples' temperature and humidity could be preserved
during sample return then the identification of clathrates and ice could
be attempted. These, together with hydrated minerals, are the two types
of structure that are likely to currently trap volatiles in the Mars
regolith (see also A5).

\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_

**10. I[nvestigation:]{.underline} Determine the nature of crustal
magnetization and its origin.**

The magnetization of the Martian crust is poorly understood, but is
intimately related to the igneous, thermal, tectonic and hydrologic
history of the crust. Addressing this problem requires high-resolution
mapping of the magnetic field and knowledge of the mineralogy and
magnetization of the surface.

When magnetic minerals form or deposit in presence of a magnetic field,
they tend to align themselves in the direction of the magnetic north
pole and become magnetized with a magnitude that scales with the field
intensity \[1\]. Therefore paleomagnetic studies of rocks yield two main
pieces of information: the *direction* and the *intensity* of ancient
fields. Paleo-directional data could be used for at least three very
important investigations: 1) determining if ancient magnetic fields were
due to impact processes or a core dynamo, 2) characterizing the temporal
behavior of the Martian paleofield (reversal frequency and secular
variation) and 3) chronicling local and planetary tectonic evolution
(motion of the crust and/or mantle with respect to the background
field). Paleo-intensity studies of returned samples could provide a
wealth of information concerning the cooling history of the planet by
monitoring the strength of the Martian dynamo versus time. This
information could be used to determine when the planet had a dynamo and
when it decayed, which would give information about the mechanism
generating the dynamo and thermal evolution of the planet. A strong
ancient dynamo may have also provided protection from solar wind
destruction of the Martian atmosphere and radiation protection for any
primitive forms of life.

Because the original orientations of Martian meteorites on Mars are
unknown, all paleomagnetic studies to date have only been able to
measure the paleo-intensity of the Martian field. *In situ paleomagnetic
studies of Mars bedrock and analysis of returned Martian samples would
afford the advantage of knowing the geologic context of the samples but
just as importantly, would provide the first opportunity to get
paleo-directional information on Martian fields.*

As measured from Mars orbit, the current Martian magnetic field is
rather weak, but the discovery of intense magnetic anomalies in the
ancient southern cratered terrain and weaker anomalies even underlying
the North Polar Basin by the Mars Global Surveyor mission provides
strong evidence for an internal Martian dynamo acting during Noachian
time \[2\]. These Martian magnetic anomalies are easily an order of
magnitude stronger than their terrestrial counterparts; downward
continuation of the spacecraft observations implies that local magnetic
fields in many places on the surface of Mars are of comparable magnitude
to that on Earth. These magnetic anomalies are intense enough to deflect
and focus incoming radiation, so knowledge of their distribution and
pattern would be extraordinarily important for locating possible future
human settlements.

This investigation is strongly connected to investigations in Goal III,
Objective B: Characterize the structure, composition dynamics and
evolution of Mars' interior.

**Sample types needed.** The ideal samples for paleomagnetic
investigations would be basalts from outcrops because of their high
magnetization intensity, excellent fidelity for recording
paleodirectional and paleointensity information, and the simple process
by which they become magnetized. Sediments (both siliclastic and
chemical) would also be useful for paleomagnetic studies, but they are
less ideal because of their relatively weaker magnetization, tendency to
record a magnetization direction shallower than the true direction
(particularly for claystones), and the lack of robust absolute
paleointensity techniques for sediments. For either rock type, the
samples should be collected from units with identifiable stratigraphy,
layering, or other paleo-direction indicators, if possible. This would
greatly facilitate determining how the orientation of the unit has
changed since the time of magnetization.

**Sample diversity needed.** The choice of the landing site would be
critical. Impact melts and regions heated by impacts should be avoided
because they would likely have been demagnetized or remagnetized by
impact processes (which may generate strong fields \[4\]). The samples
ideally should be unshocked and unweathered. Potentially interesting
sites would be the high crustal magnetic anomaly localities and bedrock
outcrops at Meridiani and Gusev.

**Physical condition (rock, pulverized rock, etc.).** Core samples would
be ideal.

**Contamination types and limits that affect this investigation.** See
Vulnerability.

**Sample number and mass.** It would be advisable to collect multiple
samples from each stratigraphic level with a coring device, or a long
core that samples across stratigraphic sequences. This is done so that
the samples could be averaged together and statistical analysis could be
used. Using a coring unit ensures that orientation could be
reconstructed in the laboratory. Assuming the samples are basalt, a
minimum mass of 0.03 cm^3^ per sample would be measurable with modern
superconducting rock magnetometers. Sedimentary samples might require
one or more orders of magnitude more sample mass (depending on the
lithology).

**Vulnerability of samples to degradation effects (T, volatile loss,
etc.).** Samples should not be exposed to magnetic fields greater \~100
and ideally no greater than \~ 1 G. The latter requirement could be
easily fulfilled if the samples are shielded inside of a high magnetic
permeability container for the return trip to Earth.

**Maximum sample temperatures for sample integrity.** Samples ideally
should not be heated above ambient Martian temperatures.

**Required/preferred sampling hardware.** The drill used to collect the
cores ideally should be made from nonmagnetic materials to avoid
contaminating weakly magnetized rocks. To determine the direction of the
paleomagnetic field the samples should be orientated with respect to
present true north and vertical before they are removed from the
outcrop. This was done on the Apollo missions by photographing the
sample in the same field of view as a gnomon. A gnomon is a tripod and
sun compass with a freely rotating gimbaled vertical bar that always
points toward true vertical (such that sample inclination can be
inferred) and whose shadow can be used for obtaining geographic
declination \[5\]. This could also probably be done with a combination
of imagery and orientation data from a rover arm.

**Data needed for sample choice and in situ characterization.** See
previous description.

**Estimate of required mobility range.** Given the need for samples from
outcrop, the MER experience demonstrates that depending on landing site,
outcrops would be within several meters to several km of the lander.

**Additional comments. References:**

\[1\] R.F. Butler, Paleomagnetism: magnetic domains to geologic
terranes, Blackwell Scientific Publications, Boston, 1992, 319 pp.

\[2\] M. Acuna, J. Connerney, P. Wasilewski, C. Mazelle, J. Sauvaud, D.
Vignes, C. d\'Uston, H. Reme, R. Lin, D. Mitchell, J. McFadden, D.
Curtis, P. Cloutier, S. Bauer, MGS magnetic fields and electron
reflectometer investigation: Discovery of paleomagnetic fields due to
crustal remanence, Moon and Mars 23(1999) 1879-1886.

\[3\] J.H. Allton, Catalog of Apollo Lunar Surface Geological Sampling
Tools and Containers, National Aeronautics and Space Administration,
Houston, 1989, 97 pp.

\[4\] D.A. Crawford, P.H. Schultz, The production and evolution of
impact-generated magnetic fields, Int. J. Impact. Eng. 14(1993) 205-216.

\[5\] J.H. Allton, Catalog of Apollo Lunar Surface Geological Sampling
Tools and Containers, National Aeronautics and Space Administration,
Houston, 1989, 97 pp.

\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_

**11. [Investigation:]{.underline} Evaluate the effect of impacts on the
evolution of the Martian crust.**

Impact is arguably the most important of the processes shaping the crust
and surface of Mars. A firm understanding of effects of impacts on the
structural, topographic and thermal history is a prerequisite for any
broad understanding of the Martian crust and surface. Understanding
impact effects requires geologic mapping using global topographic data
combined with high-resolution images and remote sensing.

Remote sensing observations of the Martian surface have revealed the
dominant role played by impacts in the geologic evolution of the planet.
Although other geologic processes contribute, impact cratering with its
associated ejecta blanketing and target fracturing is a dominant
contributor to regolith formation. Sample return from both the original
bedrock as well as from craters exhibiting a range in apparent formation
ages would provide constraints on the crater production rate (see
III.A.3) that in turn would provide insights into the rate of regolith
production. A regolith sample would be important to understanding how
quickly the regolith is overturned by other processes. On the Moon,
impacts of micrometeorites churn the regolith and provide a mechanism
for its overturn ("impact gardening"). A similar regolith sample,
preferably a core that extends 2 to 3 centimeters into the regolith,
could provide insights into the relative roles of small impacts,
aeolian, and other geologic processes in overturning the Martian
regolith. Compositional analysis of such a sample would be important to
understanding how well the regolith can trap volatiles near the surface
for extended periods of time.

Analysis of a sample retrieved from a layered ejecta blanket could be
used to test the hypothesis that subsurface volatiles are primarily
responsible for formation of this ejecta morphology. Theoretical
considerations suggest that impacts into volatile-rich crust produce
more impact melt than impacts into drier materials. Investigations at
Haughton Crater on Devon Island, Canada, provide observational support
for this idea. The proportion of impact melt in a small sample from a
Martian layered ejecta blanket could be compared with impact melt from
lunar samples to determine if there is support for this hypothesis.

Impact crater formation deposits a substantial amount of heat into the
crust adjacent to the crater. If the crust is volatile-rich, this can
create hydrothermal systems (see III.A.8). The temporal extent of such
systems depends on the size of the crater, amount of volatiles in the
crust, and external climate conditions. Long-lived impact-induced
hydrothermal systems have been proposed for craters larger than
\~25-km-diameter during early Mars history based on numerical modeling,
but the lifetime of hydrothermal systems associated with recent large
impacts is unconstrained. Retrieval of samples from the crater rim or
central peak/pit could be analyzed for the presence of hydrothermal
minerals. Retrieval of such samples from several craters of various
sizes and ages could be used in numerical models to better constrain the
conditions under which impact-induced hydrothermal systems form.

**Sample types needed.** A core sample of the regolith that extends 2-3
cm would be desired. Other core samples or chips of impact target rock
as well as impact ejecta/melt would be required.

**Sample diversity needed.** Samples representing a range of locations
within a crater as well as from craters of various sizes and ages would
be desired.

**Physical condition (rock, pulverized rock, etc.).** The core sample of
regolith ideally would maintain its original layering and some
indication of its original orientation relative to the surface.

**Contamination types and limits that affect this investigation.** None
specified.

**Sample number and mass.** A regolith core would be the minimum
requirement. Sample sizes of 300 mg to 1 g should be sufficient for this
investigation.

**Vulnerability of samples to degradation effects (T, volatile loss,
etc.).** Not specified.

**Maximum sample temperatures for sample integrity.** Not specified.

**Impact of degradation on the investigation.** Not specified.

**Required/preferred sampling hardware.** A rock corer and sample
container that could be sealed to prevent loss of any volatiles
contained within it.

**Data needed for sample choice and in situ characterization.** Not
specified.

**Estimate of required mobility range.** Impact regolith is ubiquitous
and could be expected to be accessible with minimal driving (\<1 km).
Other targets of interest like crater rims or peaks may require a few to
10s of km driving.

\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_

**B. Objective: Characterize the structure, composition, dynamics, and
evolution of Mars' interior (investigations in priority order)**

Investigating the internal dynamics and structure of Mars contributes to
understanding the bulk chemical composition of Mars, the evolution of
its crust and mantle, and the origin of its magnetic field and the
nature and origin of the minerals that record the field. These are
fundamental aspects of Mars that form the basis of comparative
planetology.

**1. [Investigation:]{.underline} Characterize the structure and
dynamics of Mars' interior.**

Understanding the structure and dynamical processes of the deep interior
is fundamental for understanding the origin and evolution of Mars in
general, and its surface evolution and the release of water and
atmospheric gasses in particular. For example, the thickness of the
crust and the size of the core provide strong constraints on the bulk
composition of the planet and the manner in which it differentiated.
This investigation requires mineralogic, isotopic, seismic, magnetic,
gravity and heat flow data bearing directly and indirectly on interior
structure and processes.

The most profound advances in understanding the interior structure and
dynamics of the Earth have been derived from seismology, supplemented by
measurements of heat flow, magnetism, gravity, and electromagnetics.
Without a Mars geophysical network, essential progress on this
investigation would be limited. Nonetheless, the petrologic,
mineralogic, elemental, and isotopic signatures recorded in returned
Mars samples could provide useful information on how thermal and
differentiation history affected planetary structure and dynamics

Basaltic lithologies from known locations would provide insights into
the rate of basalt produced from the Martian mantle when combined with
orbital spectroscopy and age dating. Further, basalts would provide
insights into the array of potential mantle reservoirs, mantle redox
state, estimates of the bulk composition of the Martian mantle and
initial estimates of the size of the Martian core. Distinctly different
measurements such as magnetic properties of basalts combined with
crystallization ages and siderophile element abundances may yield a wide
range of information about the composition and dynamics of the Martian
core. Experimental studies of basalts that approach liquid compositions
would yield information concerning the minimum depth of mantle melting.
The basalt lithologies may also yield information on the volatile
content of Martian basaltic magmas that have profound implications for
mantle degassing and the role of volatiles in a variety of mantle
processes (i.e. magma transport, early differentiation). Finally,
laboratory measurements of density and seismic velocity of returned
samples could help constrain deep petrology inferred from future
geophysical measurements at Mars.

With the need for basaltic rocks to be used in compositional, magnetic,
and geochronologic studies, the samples for this investigation overlap
with those of IIIA3,4,6,10; B2,3.

**Sample types needed.** Basaltic lithologies from known locations. The
optimum samples for geochronology would be unshocked igneous rocks from
the beginning of the Hesperian epoch, in order to provide an absolute
age for this major transition in Martian geology.

**Sample diversity needed.** The collection of a series of deep crustal
lithologies would allow the reconstruction of crustal structure, crustal
temperatures, and history of crustal extraction from the Martian mantle.
A wide range of possible deep crustal lithologies may be accessible.
They may include igneous complexes, metamorphic terrains, and
hydrothermal systems. Such samples could be used to determine whether
there are relationships between crustal structures as indicated by these
lithologies and orbital geophysical observations

**Physical condition (rock, pulverized rock, etc.).** Intact cores or
whole rocks known to be derived from bedrock would be the best samples,
but chips would be acceptable. Powders would not provide textural and
mineralogical context for other sets of geochemical data. Further,
powders would be contaminated far too easily. Samples should have
limited degrees of shock and alteration.

**Contamination types and limits that affect this investigation.** It
would be somewhat detrimental to have the basalts interacting with
volatiles derived from volatile-bearing phases (sulfates, clays) in the
same sample containment vessel.

**Sample number and mass.** The number would be site dependent. Total
mass that would be required for analytic studies is 0.1-1g per
lithology; petrophysical measurements could drive this requirement
higher.

**Vulnerability of samples to degradation effects (T, volatile loss,
etc.).** Basaltic samples for this investigation would be relatively
insensitive to degradation. There would be no stringent storage
requirements.

**Maximum sample temperatures for sample integrity.** Not specified.

**Impact of degradation on the investigation.** Not specified.

**Required/preferred sampling hardware.** Coring would be desirable but
not required.

**Data needed for sample choice and in situ characterization.** The
ability to identify and distinguish among various basaltic lithologies
would be needed.

**Estimate of required mobility range.** This would be entirely site
dependent. For example, at the Meridiani Planum site no basalts have
been observed that are locally derived, unlike at the Gusev crater site,
where locally derived basalts are ubiquitous. However, several
kilometers of driving was required to encounter basalts of different
composition.

\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_

**2. [Investigation:]{.underline} Determine the origin and history of
the magnetic field.**

Evidence that Mars had a magnetic field early in its history has
important implications for its formation and early evolution, as well as
for the retention of its early atmosphere and for the shielding of the
surface from incoming radiation and the possible evolution of life.
Requires high-precision, high-resolution global, regional, and local
magnetic measurements, as well as mineralogic, isotopic, seismic,
gravity and heat flow data bearing on interior structure and processes.

See III.A.10.

\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_

**3. [Investigation:]{.underline} Determine the chemical and thermal
evolution of the planet.**

Knowledge of the chemical and thermal evolution places constraints on
the composition, quantity, and rate of release of volatiles (water and
atmospheric gasses) to the surface. This investigation requires
measurements of the internal structure, thermal state, surface
composition and mineralogy, and geologic relationships.

There are numerous contributions to the investigation of Mars' chemical
and thermal evolution that could be made by a Mars sample return. The
return of basaltic lithologies from known locations would provide
insights into the rate of basalt produced through the melting of the
Martian mantle. Placing these data within the context of orbital
observations would more firmly establish this rate on a planetary scale.
Further, basalts would provide insights into the array of potential
mantle compositions, estimates of the bulk composition of the Martian
mantle, initial estimates of the size of the Martian core, and the
chemical-thermal regimes during initial planetary differentiation.
Experimental studies of true liquid compositions would yield information
concerning depth of melting.

The collection of a series of deep crustal lithologies would allow the
reconstruction of magmatic and thermal evolution of the early Martian
crust. This would include finding and sampling both metamorphic rocks,
rocks that represent igneous complexes emplaced into these types of deep
crustal environments, and crustal remnants of initial Martian
differentiation.

Sampling fossil hydrothermal systems would provide evidence for heat and
fluid transfer through the Martian crust, the thermal and compositional
history of these systems, and allow the identification of different
types of crust, mantle, and atmospheric components contributing to these
systems. Radiogenic and stable isotopic measurements of phases deposited
in these systems would provide age, temperature, redox conditions and
fluid composition. Stable isotopic compositions may also yield
fingerprints of biologic activity. Fluid inclusions in mineral phases
would also provide insights into evolving fluid composition and
temperature.

Finding and sampling differentiated magmatic rocks (andesites, silicic
rocks such as rhyolites and granites) in the Martian crust would yield
important information concerning growth of the crust and lithosphere. If
such rocks exist, their magmatic petrogenesis and relationship to
tectonic processes on Mars could be investigated.

Samples acquired for this investigation would serve other Goal III
investigations including A3,4,6,10 and B1 and B2. Sample requirements
essentially are identical to those of B1.

**Sample types needed.** Basaltic lithologies from known locations.

**Sample diversity needed.** The collection of a series of deep crustal
lithologies would allow the reconstruction of crustal structure, crustal
temperatures, and history of crustal extraction from the Martian mantle.
A wide range of possible deep crustal lithologies may be accessible.
They may include igneous complexes, metamorphic terrains, and
hydrothermal systems. Such samples could be used to determine whether
there are relationships between crustal structures as indicated by these
lithologies and orbital geophysical observations

**Physical condition (rock, pulverized rock, etc.).** Intact cores or
whole rocks known to be derived from bedrock would be the best samples,
but chips would be acceptable. Powders would not provide textural and
mineralogical context for other sets of geochemical data. Further,
powders would be contaminated far too easily. Samples should have
limited degrees of shock and alteration.

**Contamination types and limits that affect this investigation.** It
would be somewhat detrimental to have the basalts interacting with
volatiles derived from volatile-bearing phases (sulfates, clays) in the
same sample containment vessel.

**Sample number and mass.** The number would be site dependent. The
total mass that would be required for analytic studies is 0.1-1g per
lithology; petrophysical measurements could drive this requirement
higher.

**Vulnerability of samples to degradation effects (T, volatile loss,
etc.).** Basaltic samples for this investigation are relatively
insensitive to degradation. There would be no stringent storage
requirements.

**Maximum sample temperatures for sample integrity.** Not specified.

**Impact of degradation on the investigation.** Not specified.

**Required/preferred sampling hardware.** Coring is desirable but would
not be required.

**Data needed for sample choice and in situ characterization.** The
ability to identify and distinguish among various basaltic lithologies
would be needed.

**Estimate of required mobility range.** This would be entirely site
dependent. For example, at the Meridiani Planum site no basalts have
been observed that are locally derived, unlike at the Gusev crater site,
where locally derived basalts are ubiquitous. However, several
kilometers of driving was required to encounter basalts of different
composition.

\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_

**4. [Investigation:]{.underline} Study the structure, dynamics and
composition of Phobos and Deimos as indicators of the formation and
early evolution of Mars.**

Dynamical arguments suggest that the origin of Phobos and Deimos are
intimately connected with that of Mars itself. The dynamics of their
orbits may provide constraints on the structure of Mars' interior and
their composition may provide further clues to its evolution. This
investigation is not aimed at detailed studies of Phobos and Deimos, but
rather at using their properties to constrain the composition and
evolution of Mars.

No perceived relevance to sample return (from Mars proper).

**GOAL IV**

**[Introduction and Synthesis]{.underline}**

Martian robotic missions could serve an essential function as precursors
to the eventual human exploration of Mars. This is analogous to the role
Ranger, Surveyor and Lunar Orbiters played in paving the way for Apollo
and that the Lunar Reconnaissance Orbiter would do for the next phase of
human lunar exploration. Recognizing that potential, MEPAG included Goal
IV - Prepare for Eventual Human Exploration - to its Mars Science Goals,
Objectives, Investigations, and Priorities document. Goal IV addresses
science and engineering questions specific to increasing the safety,
decreasing the cost, and increasing the productivity of human crews on
Mars. Goal IV describes both the data sets that are to be collected and
analyzed (Objective A), and the demonstrations of critical technologies
that must be validated in the actual Martian environment (Objective B).
Although robotic science missions have science as their prime goal, it
is prudent and sensible to examine them to see how they might contribute
to Goal IV. In that regard, we herein look specifically at how Mars
sample return missions could help accomplish Goal IV objectives.

Each investigation of the Goal IV Objectives was examined to see what
requirements might be imposed on the acquisition of martian samples in
order to satisfy the investigation. A general conclusion is that a Mars
sample return could contribute uniquely to many of the Goal IV
investigations with priorities ranging from high to low. For example,
gaining a comprehensive understanding of the toxicity, electrostatic and
biohazard potential of martian particulates, whether airborne dust or
regolith, is high priority in that it could best be determined by
analyzing returned sample. At the other end of the spectrum, at low
priority, determining the engineering properties of martian regolith for
trafficability purposes and developing simulants benefits markedly from
laboratory analysis of soil particles (chemical and mineralogical
composition, shape, size distribution, hardness, etc.) but would demand
dedicated in-situ soil mechanics measurements, at sites where humans
would actually land, to provide the bulk of needed data. The same holds
for investigating the potential for using martian water (bound or
otherwise) as an ISRU feedstock. At the extreme, sample return would do
relatively little for understanding atmospheric and meteorological
properties pertaining to EDL and surface operations.

Fortuitously, the high priority Goal IV requirements could be largely
satisfied with samples collected primarily for science investigations;
e.g., Goal IV dust and regolith sample needs would be redundant to first
order with science needs regarding diversity, context, acquisition and
packaging; it is important, however, to consider that engineering
measurements may require slightly more sample mass. Some Goal IV
investigations could lead to special sample acquisition or handling such
as the desire to obtain sample downwind from the lander to aid in
determining the potential for forward planetary contamination. A special
opportunity has been identified for studies of materials degradation
that envisions the application of coupons of different materials to some
of the sample return containers. This would apply mostly to Mars sample
return scenarios that utilize a dedicated sample caching mission that
would be on Mars for several years prior to sample return.

There are two aspects of Mars sample return missions that would not be
investigation dependent yet could contribute materially to human
exploration aspirations. First is the "fact of" demonstration of the
ability to conduct a round-trip mission to Mars. Mars sample return
would demonstrate for the first time the ascent of a vehicle off the
surface of Mars and the subsequent entry at Earth. Second, the greatly
improved science understanding of Mars would inevitably provide a
sounder, more productive basis for designing the scientific research to
be conducted by human missions. Proof-of-concept for this feed-forward
is 30 years old, coming from studying how analyses of the returned
samples from early Apollo missions significantly enhanced the science
accomplished on later missions.

In summary, Mars sample return missions would have a significant
low-cost contribution to make to preparing for human exploration of
Mars. NASA's human exploration and science communities should work
closely together to gain the reality of the potential.

\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_

**Objective A. Obtain knowledge of Mars sufficient to design and
implement a human mission with acceptable cost, risk and
performance.**[^2]

*[Investigations #1A-1D are judged to be of indistinguishable high
priority.]{.underline}*

**[Investigation 1A.]{.underline} Characterize the particulates that
could be transported to hardware and infrastructure through the air
(including both natural Aeolian dust and other materials that could be
raised from the martian regolith by ground operations), and that could
affect engineering performance and in situ lifetime. Analytic fidelity
sufficient to establish credible engineering simulation labs and/or
performance prediction/design codes on Earth is required.**

[Measurements]{.underline}

a\. A complete analysis, consisting of shape and size distribution,
mineralogy, electrical and thermal conductivity, triboelectric and
photoemission properties, and chemistry (especially chemistry of
relevance to predicting corrosion effects), of samples of regolith from
a depth as large as might be affected by human surface operations.

> *Note #1: For sites where air-borne dust naturally settles, a bulk
> regolith sample is sufficient---analysis of a separate sample of dust
> filtered from the atmosphere is desirable, but not required.*
>
> *Note #2: Obtaining a broad range of measurements on the same sample
> is considerably more valuable than a few measurements on each of
> several samples (this naturally lends itself to sample return).*
>
> *Note #3: There is not consensus on adding magnetic properties to the
> list of measurements.*

b\. Characterize at least one regolith deposit with fidelity sufficient
to establish credible engineering simulation labs and/or software codes
on Earth to solve engineering problems related to differential
settlement of the regolith, and plume/regolith interactions (see Note
#4).

> 1\. For one site on Mars (see Note #5), measure the following
> properties of the regolith as a function of depth to 1 meter:

(i) Particle shape and size distribution

(ii) Ice content and composition to within 5% by mass

(iii) Regolith density to within 0.1 g/cm^3^

(iv) Gas permeability in the range 1 to 300 Darcy with a factor of three
     accuracy.

(v) Presence of significant heterogeneities or subsurface features of
    layering

(vi) An index of shear strength

(vii) Flow Rate Index test or other standard flow index measurement

> 2\. Repeat the above measurements at a second site in different
> geologic terrain:

c\. The same measurements as in a) on a sample of air-borne dust
collected during a major dust storm.

d\. Subsets of the complete analysis described in a), and measured at
different locations on Mars (see Note #2).  For individual measurements,
priorities are:

> i.      shape and size distribution and mineralogy\
> ii.     electrical\
> iii.    Chemistry

*[Note #4]{.underline}. Because there is a large engineering lead-time
required to solve the geotechnical problems, these data must be obtained
early in the precursor program.*

*[Note #5]{.underline}. These measurements should be made in a competent
regolith deposit as opposed to loose drift material (cohesionless sand
dunes), as landing is expected to attempt to avoid the looser material. 
Also, if mission planners were to select high latitude polar
deposits for a human landing site, geotechnical data would be required
from a representative location of those deposits. These measurements
should include polarity and magnitude of charge on individual dust
particles suspended in the atmosphere and concentration of free
atmospheric ions with positive and negative polarities. Measurement
should be taken during the day in calm conditions representative of
nominal Extra Vehicular Activity (EVA) excursions.*

**[Investigation IVA-1: Implications for sample return]{.underline}**.

Analysis Leader: Phil Metzger, Paul Carpenter, and Brad Joliff.

> Two sub-topics are comprehended in this investigation, and they shall
> be addressed in this order: (1) bulk mechanical properties of the soil
> component of the regolith plus its ice content, and (2) physical and
> chemical properties of the regolith particles including soil and dust
> fractions.
>
> *[Bulk Mechanical Properties]{.underline}*
>
> \(1\) It is hard to justify sample return on the basis of soil
> mechanics. The general consensus among soil mechanics experts is that
> *in situ* measurements are more valuable than sample return for
> understanding the bulk mechanical properties of the soil. That is
> because soil mechanics is highly dependent upon the environment and
> the undisturbed properties of the soil, such as the compaction,
> fabric, and stress pre-loading of the soil before it is excavated. As
> a result, the first priority for soil mechanics would be to make
> high-fidelity measurements *in situ* at a suitable number of
> locations, and there are divergent opinions among soil mechanics
> experts whether a sample return for the purposes of soil mechanics is
> justifiable or necessary. This is consistent with knowledge gained
> about bulk mechanical properties of lunar soil from Apollo surface EVA
> experience.
>
> Nevertheless, certain aspects of the soil mechanics could not be fully
> understood unless measurements are made in a laboratory environment.
> These would include measurements of the soil\'s dilatancy, strength,
> and stiffness, which are ordinarily measured with a suite of
> specialized laboratory instruments. If samples are not returned from
> Mars, then the soil mechanics modeling would not achieve the highest
> fidelity prior to the arrival of humans unless special instruments are
> developed to enable making these measurements *in situ.* Significant
> technology advances would be required to make these instruments
> lightweight, accurate, and reliably autonomous for implementation on a
> spacecraft, and it is likely that a practical set of spacecraft
> instrumentation would still leave questions unanswered about the
> mechanical behavior of the soil. Therefore, at least some soil
> mechanics experts believe that it would be prudent to return
> sufficient soil from one or two representative sites in order to
> develop a higher fidelity basis for soil mechanics models. But this is
> not a conclusion of the consensus. Certainly something like 90% of the
> needed knowledge of the soil mechanics could be obtained using a
> reasonable set of instruments on a robotic spacecraft, and this
> probably would be sufficient to achieve program objectives.
>
> Another argument that limits the value of sample return for soil
> mechanics is that different soil deposits have vastly different
> mechanical properties, and so returning one or two samples would not
> provide sufficient data for most of the places that may be visited in
> the exploration program, anyway.
>
> The particular measurements described in the 2006 MEPAG Goals
> document, Goal IV, Objective A, Investigation 1a, were designed to be
> able to perform them *in situ*, and hence by definition no sample
> return would be required to measure these parameters. However, in some
> cases, sample return would provide some benefit. These are:

(i) Particle shape and size distribution

> Could be measured by microscopy using a vibrational or compressed-gas
> particle delivery method (to effect particle separation) to the
> microscope

(ii) Ice content and composition to within 5% by mass

> Volatiles could be measured by gravimetrics and by mass spectrometry
> as they are thermally driven from a sample. However, sample return
> would provide for a more complete chemical assay of the ice content

(iii) Regolith density to within 0.1 g/cm^3^

> Could only be measured *in situ.* All returned samples should have the
> relative density measured or estimated (by volume measurement, e.g.,
> photographic analysis of the removal site) prior to return to aid the
> subsequent analysis.

(iv) Gas permeability in the range 1 to 300 Darcy with a factor of three
     accuracy.

> Would be best measured *in situ* since extraction changes the porosity
> of the sample. However, samples that are epoxy-stabilized prior to
> return would also support estimation of the gas permeability through
> computer analysis of thin sections.

(v) Presence of significant heterogeneities or subsurface features of
    layering

> Could be assessed only *in situ.*

(vi) An index of shear strength

> It is generally agreed that the index tests are difficult to
> extrapolate or interpret apart from an existing base of experience,
> which does not yet exist for Martian soil. Yet, a measurement of this
> sort is so basic that it must be done. Also, index tests would be the
> easiest for an astronaut to perform, or for a rover spacecraft to
> perform robotically on multiple sites, and so a more careful set of
> index measurements should be performed with higher-fidelity
> instruments first in order to provide the beginnings of the base of
> experience. This would be best measured in a terrestrial laboratory
> since the higher-fidelity index testers would be difficult to adapt
> and operate on Mars without significant uncertainty as to the meaning
> of the measurements. However, an *in situ* test on undisturbed soil
> with a vane shear tester at the point of sample extraction would
> supplement the laboratory measurement, providing a comparison between
> undisturbed soil and the more careful laboratory measurements on the
> same sample.

(vii) Flow Rate Index test or other standard flow index measurement

> These could be performed in situ, but the discussion is very similar
> to the item above for index tests of shear strength. Laboratory tests
> in combination with in situ tests would be ideal. However, there is no
> consensus for either case whether or not the sample return would be
> justified or necessary for these purposes.
>
> *[Physical and chemical properties of the regolith]{.underline}*
>
> \(2\) Detailed knowledge of the physical and chemical properties of
> martian dust and soil particles are needed to fully understand health
> risks to astronauts, behavior of mechanical processes in the martian
> dust and regolith environment, and processing methods and approaches
> to development of martian regolith-based resources. Martian regolith,
> like lunar regolith, represents a mixture of materials that have
> different sources. Broad compositional variations across the surface
> of Mars exist, but differ in detail from the compositional variations
> seen across, for example, the Moon, and the processes leading to
> compositional variations also differ. Despite such variations,
> however, much could and would be learned about physical and chemical
> properties by the first return of martian regolith from a single
> location. They would indicate surface processes that can be
> extrapolated to other regions of Mars of differing bedrock and
> regolith compositional characteristics. For comparison, the first
> return of regolith from the Moon revealed the presence of glassy
> agglutinates or fused-soil aggregates formed by solar wind
> implantation and micrometeorite bombardment. Although agglutinates are
> not expected to form in martian regolith because of the presence of an
> atmosphere, other unanticipated but important particles may be found.
>
> The makeup and characteristics of the grains that constitute dust and
> regolith are difficult to study in-situ because of very fine grain
> sizes of the chemical and mineral constituents. MER results show the
> fine soil to be composed of composite or multimineralic grains with
> constituent or sub-grain sizes of less than 30 μm and the
> characteristics of the dust suggest that much of it probably exists in
> the sub-micron size range. Martian dust is very well mixed and
> homogeneous on a global scale because of frequent and giant regional
> dust storms that, at times, coalesce into global dust clouds. To the
> extent that it has been studied in-situ and sensed remotely, the
> martian regolith is more variable than martian dust. For the most
> part, it is basaltic to andesitic in composition, but with a strong
> sulfate component, generally 5-7 wt.% S as SO3. Locally, soils can be
> quite variable, such as in parts of Gusev crater explored by Spirit
> where silica and sulfate concentrations are locally very high. As
> coarser regolith grains are considered, they reflect more and more the
> character of local bedrock, and the bedrock has been shown by surface
> exploration to be quite variable, although strongly basaltic in many
> places.
>
> Despite the significant knowledge gained about dust and regolith
> materials by surface exploration, especially that of the MERs, much
> remains unknown about the physical properties and details of
> mineralogy and chemistry of the grains that make up martian regolith.
>
> Physical properties of grains include grain size and size
> distribution, shape, hardness, fracture and strain, crystallinity,
> compaction and cohesion characteristics, magnetic susceptibility,
> mineral assemblage, and chemical reactivity in different environments
> that may cause mineralogical or other physical phase changes.
>
> Chemistry and mineralogy properties include bulk chemistry, mineral
> speciation, mineral chemistry, oxidation state, and volatile contents,
> especially OH and H2O. Chemical reactivity and variations as a
> function of exposure to martian or terrestrial (in the case of sample
> return) environments is not yet well known.
>
> *[Investigation Summary: Sample needs/priorities]{.underline}*
>
> Priority for first sample return: HIGH
>
> Sample types required:

1.  Dust sample. Because martian dust is globally homogeneous, the first
    sample would be extremely important. Much has been learned about the
    magnetic properties and mineralogy of martian dust through the MER
    mission; however, the dust needs to be understood on the size scale
    of individual mineral and grain constituents. As mentioned above,
    these are extremely fine-grained, extending into the sub-micrometer
    range. To fully understand processes that generate the dust and its
    full range of physical properties including those related to
    reactivity and potential health concerns, dust particulates and
    adhering or adsorbed components must be studied by
    high-magnification methods such as scanning electron microscopy,
    transmission-electron microscopy, electron-probe microanalysis,
    secondary-ion mass spectrometry, laser-desorption mass-spectroscopy,
    and others.

2.  Regolith sample(s) beneath surficial dust deposits. The dust layer
    as experienced by landed missions on Mars is generally very thin.
    Beneath dust coatings is regolith that may consist of wind-blown
    sediments and admixed materials from weathering of underlying or
    nearby bedrock and materials excavated by nearby impact craters.
    Aeolian processes can very effectively sort materials locally, thus
    care must be taken to obtain multiple samples that would provide a
    representation of the local variability and not a single well-sorted
    grain type or size. In general, regolith samples derived from
    missions subsequent to the first sample return that represent
    significantly different source or local geology would be highly
    valuable, especially with respect to characteristics such as
    volatile content, mineralogy, and considerations related to resource
    potential.

[Simulants]{.underline}

We have a significant body of knowledge based on studies of lunar
samples that motivates the development of lunar regolith simulant
materials. A minimum set of simulants for lunar technology development
is a basaltic mare simulant, a gabbroic anorthosite highland simulant,
and additive materials such as ilmenite, glass, and specific components
like nanophase iron. These simulants are being developed sequentially
according to budget restrictions and priorities. To date, the approach
has been to make use of material that is readily available with only
milling and sieving in order to produce the necessary lunar grain size
distribution. Lunar mare simulant JSC-1 and JSC-1A are obtained from
basaltic ash from the Meriam crater in Arizona, and a lunar highland
simulant is under development using gabbroic and anorthositic materials
obtained from the Stillwater intrusion in Montana. These materials are
milled, homogenized, and then sieved with no other processing. High
fidelity simulants can be produced by mixing mineral, glass, and rock
fractions obtained from multiple sources, but this will be a complex and
costly approach which will only make sense for reduced quantities of
material. One can anticipate planning for hundred ton quantities of
final simulant for physical purposes, and tens of tons for chemical
processes. Experience with usage demands to date indicates a desire to
work with simulant very early in technology development when perhaps
simplified materials should be used, and also that users desire to
consume large quantities of simulant before developing efficient usage
schedules for material. Distribution of simulant to NASA centers has
been in quantities no smaller than 1 ton lots. An understanding of the
lunar simulant program and the perspective gained from that experience
should be applied to discussions concerning the development of martian
simulants.

For all discussions of simulant development, it is important to discern
between processes and activities that are primarily physical as compared
to those that are chemical in scope. Simulants that have high fidelity
in matching the planetary regolith become more important as the process
transitions from physical to chemical. For example, it is likely that
excavation and drilling depend more on physical simulant properties, and
oxygen extraction depends more on chemical and mineralogical properties.
The analysis of process and activities leads to a prioritization of
material properties of candidate simulant materials for further
development.

The martian regolith has not been characterized as intensively in
comparison to the lunar regolith. However, martian materials are
predominantly basaltic in composition, with a significant proportion of
wind-blown dust. Compositional analysis by the MER rovers indicates the
presence of sulfate as SO~3~ and chloride in addition to compositions
that are nominally basaltic. From our knowledge of the martian soils the
likely set simulant materials should include:

1.  Martian basaltic regolith simulant. This simulant should have a
    grain size distribution of a typical martian soil, with a size
    cutoff at both coarse and fine grain sizes that are appropriately
    chosen. The material properties of the simulant should be present in
    the source material to the greatest extent possible, with only
    milling and sieving required for use as a simulant. The simulant
    should be either an average composition requiring no addition of
    components, or alternatively, a root composition which could be used
    as a compositional end-member and modified by addition of components
    to bring it in line with specific martian regolith compositions.
    This simulant would be comparable to lunar mare basalt simulant
    JSC-1A.

2.  Martian dust simulant. This simulant should be a dust-sized simulant
    that duplicates the average martian dust, and has a grain size
    distribution that terminates at a coarse size of, for example, 20
    microns. This simulant would be comparable to lunar mare basalt
    simulant JSC-1AF which is the dust size fraction of JSC-1A and is
    compositionally equivalent.

There is clearly no substitute for a sample return with respect to
complete characterization of mineralogy, texture, and chemistry. On
Mars, it is possible that dust and fine soil samples are globally
homogenized, so that a relatively few sample locations would be expected
to return similar material properties. However, it is likely that
significant variations in rock mineralogy and chemistry exist, and have
not yet been mapped or otherwise identified by remote sensing, so that
more sampling localities would be required in order to document the
variation.

The need for sample return would be primarily for analysis of
mineralogy, texture, and chemistry, both as precious scientific samples
of a planetary body, but also for engineering studies in support of
exploration. The necessarily small sample size dictated by a sample
return mission could not reasonably be seen as directly supporting
geotechnical measurements such as load bearing capacity. However, the
properties of samples could be used to model these parameters by scaling
up in size. Many geotechnical measurements result in consumption or
modification of materials and are therefore unsuited to preserving the
nature of a returned sample.

\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_

**[Investigation 1B.]{.underline} Determine the atmospheric fluid
variations from ground to \>90 km that affect EDL and TAO including both
ambient conditions and dust storms.**

[Measurements:]{.underline}

a.  Measure v, P, T and  in the upper, middle and lower atmosphere
    during EDL. Obtain as many profiles at various times and locations
    as possible (requested for ALL landed missions). Sample rate should
    be high enough (\~ 100 Hz) to quantify turbulent layers. Specific
    direct or derived measurements include:

-   Density from 120 km to surface ranging from high altitude values of
    10^-9^ to near-surface values of 10^-1^ kg/m^3^, d = 1% of local
    ambient, rate= 100 Hz

-   Pressure from 120 km to surface ranging from high altitude values of
    10^-7^ to near-surface values of 15 mb, dP= 1% of local ambient,
    rate =100 Hz

-   Temperature 60-300 K, dT = 0.5K, rate= 100 Hz (direct measurement
    may be slower)

-   Directional Wind Velocity, 1-50 m/sec, dv = 1 m/s, rate= 100 Hz

> Particular emphasis on measurements between 0-20 km to quantify
> boundary layer wind and turbulence and 30-60 km where vehicle dynamic
> pressure is large.

a.  Monitor surface/near-surface v(z), P, T(z), and  as a function of
    time. Quantify the nature of the surface heating driver and
    associated boundary layer turbulence at altitudes above station.
    Data defines the initial conditions for high altitude modeling.
    Obtain data from as many locations as possible (requested for all
    landed missions). Surface/near surface packages should measure
    directly:

-   Pressure, at surface, 0.005 mb to 15 mb, dP = 2 microb, full diurnal
    sampling, rate= \>10 Hz

-   Velocity, at surface, 0.05-50 m/sec, dv = 0.05 m/s, horizontal and
    vertical, full diurnal sampling, rate= 10 Hz

-   Air temperature, at surface, 150-300 K, dt = 0.04K, full diurnal
    sampling, rate= 10 Hz

-   Ground temperature 150-300 K, dt = 1K, full diurnal sampling, rate=
    1 Hz

-   Air temperature profile, 0-5km, \<1km resolution, 150-300K, dt=2K,
    full diurnal sampling, rate=1 Hz

-   Velocity profile, 0-5km, \<1km resolution, 1-50 m/sec, dv=1 ms/,
    horizontal and vertical, full diurnal sampling, rate=1 Hz

    -   Opacity, visible, depth 0.2-10, dtau = 0.1, once every 10 min

c.  Make long-term (\>\> 1 martian year) remote sensing observations of
    the weather (atmospheric state and variations) from orbit, including
    a direct or derived measurement of:

-   Aeolian, cloud, and fog event frequency, size, distribution as a
    function of time, over multi-year baseline.

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-   Vertical temperature profiles from 0-120 km with better than 1 km
    resolution between 0-20 km, 1-3 km resolution between 20-60 km, 3 km
    resolution \> 60 km and with global coverage over the course of a
    sol, all local times *\[Development work required for T from surface
    to 20 km\].*

-   Vertical density/pressure profiles from 0-120 km with better than 1
    km resolution between 0-20 km, 1-3 km resolution between 20-60 km, 3
    km resolution \> 60 km and with global coverage over the course of a
    sol, all local times *\[Development work required for  from surface
    to 20 km\].*

-   3-D winds as a function of altitude, from 0-60 km with better than 1
    km resolution below 20 km, and 1-3 km resolution between 20-60 km,
    and with global coverage over the course of a sol, all local times

-   *\[Development work required at all altitudes for an independent
    means to derive V, with special emphasis from surface to 20 km\].*

> Note particular emphasis on measurements between 0-20 km to quantify
> boundary layer wind and turbulence and 30-60 km where vehicle dynamic
> pressure would be large.

d.  At time of human EDL and TAO, deploy ascent/descent probes into
    atmosphere to measure P, V, and T just prior to human descent at
    scales listed in 1Ba.

*[Note #6]{.underline}: We have not reached agreement on the minimum
number of atmospheric measurements described above, but it would be
prudent to instrument all Mars atmospheric flight missions to extract
required vehicle design and environment information. Our current
understanding of the atmosphere comes primarily from orbital
measurements, a small number of surface meteorology stations and a few
entry profiles. Each landed mission to Mars has the potential to gather
data that would significantly improve our models of the martian
atmosphere and its variability. It is thus desired that each opportunity
be used to its fullest potential to gather atmospheric data.
Reconstructing atmospheric dynamics from tracking data is useful but
insufficient. Properly instrumenting entry vehicles would be required.*

**[Investigation IVA-2: Implications for sample return]{.underline}**.

Analysis Leader: Vicky Hipkin.

Investigations IVA-2, IVA-6 and IVA-10 describe **transient atmospheric
phenomena** and hence could not be addressed directly by sample return.
Current MEPAG recommendations **do not include sample return** to
address these specific risks. Highest priority for all three
investigations are in situ studies (**every** landed Mars mission to
carry a surface meteorology package given importance of risk reduction,
and at least one landed mission to carry surface electricity package),
coupled with multi-year orbital survey to capture statistics on
transient events on a global scale. However the understanding of these
transient phenomena, especially on the small spatial scales of dust
devils, arcing and electrical discharge, depends on the continued
refinement of atmospheric models, and could benefit from laboratory
studies.

A sample of mars atmospheric dust could support the validation of these
models and provide parameters needed to produce improved mars dust
stimulant for laboratory studies of electrical processes.

A sample of Mars dust acquired from the atmosphere using a filter could
be thought to be representative of global Mars dust in terms of **shape
and composition** due to the well-mixed state of the Mars atmosphere
after a global dust storm (cite).

For GCM\'s, dust is parameterized for radiative transfer usually by
assuming composition (optical properties), a simple single or bimodal
size distribution, and shape represented by single scattering albedo and
asymmetry factor (e.g., Basu et al., 2006).

For electrical properties studies, differences in particle composition
(conductivity) and shape are important parameters that influence the
distribution and type of charge. Mars soil simulant JSC-Mars-1 in
laboratory triboelectric experiments shows a broad charge distribution
which may be related to particle heterogeneity (Sickafoose et al, 2001).

Knowledge of particle composition and shape can be improved from sample
return.

**Particle size distribution** is a useful parameter for both electric
and meteorology studies and is influenced by current atmospheric state.
A particle size distribution would be measured in a sample collected on
a filter. For ease of interpretability thought should go into the
atmospheric conditions under which this sample would be collected. Wind
speed influences saltation (dust lifting); temperature/radiation
influence buoyancy; together these would result in a time dependent
particle size distribution with height.  Electrical effects may produce
a mass-dependent levitation of dust grains from an induced electric
field once dust is moving.  

> *[Investigation Summary: Sample needs/priorities]{.underline}*
>
> Priority for first sample return: LOW
>
> Sample types required:

1.  dust sample

> Priority of samples from a second landing site: LOW

\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_

**1C. Determine if each martian site to be visited by humans is free, to
within acceptable risk standards, of biohazards that may have adverse
effects on humans and other terrestrial species.  Sampling into the
subsurface for this investigation must extend to the maximum depth to
which the human mission may come into contact with uncontained martian
material.**

[Measurements:]{.underline}

a.  Determine if extant life is widely present in the martian
    near-surface regolith, and if the air-borne dust is a vector for its
    transport.  If life is present, assess whether it is a biohazard. 
    For both assessments, the required measurements are the tests
    described in the Draft Test Protocol.

*[Note #7]{.underline}: To achieve the necessary confidence, this would
require sample return and analyses in terrestrial laboratories. *

*[Note #8]{.underline}: The samples could be collected from any site on
Mars that is subjected to wind-blown dust. *

*[Note #9]{.underline}: At any site where dust from the atmosphere is
deposited on the surface, a regolith sample collected from the upper
surface would be sufficient\--it is not necessary to filter dust from
the atmosphere.*

b.  At the site of the planned first human landing, conduct biologic
    assays using in-situ methods, with measurements and instruments
    designed using the results of all prior investigations.  All of the
    geological materials with which the humans and/or the flight
    elements that will be returning to Earth come into contact need to
    be sampled and analyzed.

*[Note #10]{.underline}: It is recommended that a decision on whether
human landing sites after the first one require a lander with biological
screening abilities be deferred until after Measurement a) has been
completed.*

**[Investigation IVA-3: (Biohazards) Implications for Sample
Return]{.underline}**.

**Analysis Leader:** Carl Allen.

The Mars Exploration Program Analysis Group (MEPAG) defined four overall
Goals that continue to guide future mission planning. Goal IV is to
"Prepare for Human Exploration." The MEPAG-chartered Human Precursor
Science Steering Group recently assessed the implementation of this
Goal, and specifically Objective IV-A "Obtain knowledge of Mars
sufficient to design and implement a human mission with acceptable cost,
risk and performance." (Beaty et al., 2005). This study recommended four
high-priority investigations, including "Determine if each martian site
to be visited by humans is free, to within acceptable risk standards, of
replicating biohazards which may have adverse effects on humans and
other terrestrial species."

This question can be addressed at two levels -- global and human landing
site-specific. The global question is particularly appropriate for a
first sample return mission. The investigation proposed for this
question by the Science Steering Group is "Determine if extant life is
widely present in the martian near-surface regolith, and if the airborne
dust is a vector for its transport. If life is present, assess whether
it is a biohazard. . . . To achieve the necessary confidence, this
requires sample return and analyses in terrestrial laboratories." (Beaty
et al. (2005).

The samples and analyses required for such assessment were carefully
addressed by a diverse group of experts in five dedicated workshops
organized by the NASA Planetary Protection Officer. The resulting "Draft
Test Protocol for Detecting Possible Biohazards in Martian Samples
Returned to Earth" (**Rummel et al., 2002**) describes the
currently-accepted "minimum set" of analyses acceptable for this
assessment.

The following considerations apply to requirements for biohazard
assessment on a first sample return mission.

The minimum sample required for global biohazard analysis would be the
airborne dust. This material, carried planet-wide by frequent
windstorms, integrates fines from across Mars. The major and minor
element compositions and reflectance spectra of dust deposits at five
widely-separated landing sites are indistinguishable, indicating a
well-mixed airborne component.

The sample could be collected from any site on Mars that is subjected to
wind-blown dust. At any site where dust from the atmosphere is deposited
on the surface, a regolith sample collected from the upper surface would
be sufficient.

The sample for return to Earth for biohazard assessment must be
minimally altered by the acts of collection and storage. Biological
contamination must be kept below sampling hardware sterilization limits
required by Planetary Protection (currently Viking-level sterilization).
Organic contamination must be kept below Viking-level detection limits
(1 ppb).

A single sample of dust would be sufficient to conduct this
investigation. The Draft Test Protocol (Rummel et al., 2002) states that
15 -- 25 g would be sufficient to carry out all required biohazard
testing. The actual protocols to be used for biohazard testing a decade
from now may well be more sensitive than those recommended during the
2002 study, resulting in a somewhat lower sample mass requirement.

The environmental tolerance of martian organisms (if any) is unknown, so
the sample should be preserved and transported in an environment as
little altered as possible. Specifically, it should be kept at or near
ambient pressure in a Mars-like atmosphere and at a temperature within
the annual temperature range at the sampling site. The effects of
exposure to environmental conditions outside of this range are unknown
but could include death of viable organisms, alteration of organism
remains, and alteration of chemical biosignatures.

The biohazard sample should be collected using sterilized, precision
cleaned sampling hardware. If more than one sample is collected, a
separate implement to contact each sample preferred is preferred to
prevent cross-contamination. Each sample should be placed in a
sterilized, precision cleaned, sealable container.

The biohazard sample must be representative of the planet-wide windblown
dust. This material could be identified based on its small particle
size, elemental composition, and reflectance spectrum.

The lateral mobility range that would be required for collecting a dust
sample from a surface deposit is site-specific. Dust coverage on Mars
ranges from total to essentially nil. However, the dust cover can be
reliably determined from current orbital data, so the range to suitable
dust deposits would be known prior to landing. The sample of surface
dust would not require vertical mobility beyond that of an arm-mounted
scoop.

The biohazard sample would be one of the key materials to be collected,
and would be subjected to detailed analysis at the sub-micron scale. It
must therefore be stringently protected from contamination from the
sample handling equipment and from cross-contamination by other samples.
The biohazard sample must be stored in a dedicated container designed to
remain intact and sealed until secured in the Sample Receiving Facility
(SRF) on Earth. Additional martian samples must also be maintained in
one or more sealed containers until secured in the SRF, but requirements
for separate packaging of these samples would be determined by other
research criteria.

All material from the first Mars sample return mission must be treated
as a high-level biohazard until the actual level of biohazard is
determined by analyses on Earth. These analyses must, at a minimum, meet
the requirements of the Draft Test Protocol (Rummel et al., 2002) or its
updated equivalent.

> *[Investigation Summary: Sample needs/priorities]{.underline}*
>
> Priority for first sample return: HIGH
>
> Sample types required:

1.  dust sample (scoop acquisition is OK)

> Priority of samples from a second landing site: LOW

\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_

**[Investigation 1D.]{.underline} Characterize potential sources of
water to support In Situ Resource Utilization (ISRU) for eventual human
missions. At this time it is not known where human exploration of Mars
may occur. However, if ISRU is determined to be required for reasons of
mission affordability and/or safety, then the following measurements for
water with respect to ISRU become necessary (these options cannot be
prioritized without applying constraints from mission system
engineering, ISRU process engineering, and geological potential):**

[Measurement Options:]{.underline}

a.  Perform measurements within the top few meters of the regolith in a
    location within the near-equatorial region (approximately ±30°) that
    the Mars Odyssey mission indicates is a local maximum in hydrogen
    content, to determine: (i) concentration of water released upon
    regolith heating, (ii) composition and concentration of other
    associated volatiles released with water, and (iii)
    three-dimensional distribution of measurements i & ii within a 100
    meter x 100 meter local region. This option would include water
    contained in hydrous minerals, as adsorbed water, and in any other
    form it might be present in the regolith. Either unconsolidated or
    loosely consolidated regolith is a focus of current attention
    because of the need to minimize mining engineering, but outcrops of
    rock containing hydrous minerals may also be a valuable possibility
    if they are sufficiently friable.

b.  Perform measurements to (i) identify and determine the depth,
    thickness, and concentration of water in subsurface ice deposits to
    a few meters depth at approximately 40° to 55° latitude, (ii)
    determine the demarcation profile/latitude where near-surface
    subsurface ice formation does and does not occur.

c.  Perform measurements in the polar region (70º to 90º) to determine
    the depth, thickness, and concentration of near-surface water/ice.

d.  Measurements for water at other locations and depths are not
    precluded but require further scientific measurements and/or
    analysis to warrant consideration. This option would specifically
    include accessing a deep aquifer.

**[Investigation IVA-4: Implications for sample return]{.underline}**.

Analysis Leader: Ben Clark.

For In Situ Resources, the most valuable potential constituent would be
H~2~O, and this could exist in loosely bound, tightly bound, and/or
chemically incorporated forms. For minimum energy cost, the loosely
bound H~2~O would be the most valuable, but also the most difficult to
contain during sample acquisition when digging into the regolith. 
Although it could be captured if the acquisition system works fast, it
would require many separately sealed containers to properly characterize
the depth distribution of H~2~O. Sealing an entire deep core of material
as one item would allow subsequent vertical re-distribution during
return to Earth.  Thus, an in situ experiment probably would be far more
appropriate, informative and precise for H~2~O determination. An example
instrument would be the Thermal Evolved Gas Analyzer (TEGA) on the
Phoenix Mars Scout mission.

Tightly bound H~2~O may actually survive the return trip, although
sealing still might be desired. Chemically incorporated H~2~O, such as
in clay mineral structures (as hydroxyl) should fully survive return
without the necessity of sealed containers and could be analyzed on
Earth. Various maximum permissible temperature limits to maintain sample
preservation have been proposed for various putative hydrous minerals.
However, ISRU would be most particularly interested in the quantitative
relationship between energy expenditure and release of H~2~O, mapped as
a function of quantities versus depth and possible horizontal
heterogeneities in the regolith, which could be done more accurately,
comprehensively and exhaustively on site at Mars.

> *[Investigation Summary: Sample needs/priorities]{.underline}*
>
> Priority for first sample return: MEDIUM
>
> Sample types required:

1.  regolith sample (sample must be encapsulated with air-tight seal)

> Priority of samples from a second landing site: HIGH if second landing
> site has different attributes related to water content.

\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_

*[The following investigations are listed in descending priority
order.]{.underline}*

**[Investigation 2.]{.underline}  Determine the possible toxic effects
of martian dust on humans. \
**[Measurements:]{.underline}

a\. For at least one site, assay for chemicals with known toxic effect
on humans.  Of particular importance are oxidizing species such as
CrVI.  (Might require a Mars sample return).

b\. Fully characterize soluble ion distributions, reactions that occur
upon humidification and released volatiles from a surface sample and
sample of regolith from a depth as large as might be affected by human
surface operations.

c\. Analyze the shapes of martian dust grains sufficient to assess their
possible impact on human soft tissue (especially eyes and lungs).

d\. Determine if martian regolith elicits a toxic response in an animal
species that are surrogates for humans. 

**Investigation IVA-5: (Toxicity) Implications for sample return**.

**Analysis Leader: Jeff Jones** with John James, Russ Kerschman, David
McKay, Mark Ott

[Context]{.underline}

Potential toxicity of returned martian soil and dust can be conveniently
grouped into two categories:

1.  Toxicity from chemical and mineralogical properties (CM- Toxicity).

2.  Toxicity from biological properties. (B-Toxicity)

While not mutually exclusive, this grouping into two major sub
categories helps systemize the issues and approaches.

**CM-Toxicity of dust**

For lunar dust, only CM- Toxicity is relevant^1,2^. No biological
activity of any kind has been found on the moon and none is expected^3^;
B-Toxicity does not exist in lunar dust^3^. We have addressed the
CM-Toxicity issues for lunar dust (defined as \<20 μm soil).

We have evidence from Apollo samples, that short term exposures to lunar
regolith are irritating to the mucous membranes and respiratory
epithelium in some humans, with varying sensitivity, however, there is
no current evidence of permanent sequelae from the Apollo very short
duration exposures. It must be considered, that most terrestrial
diseases associated with dust exposure (e.g. anthracosis, silicosis,
etc., the exception being for freshly fractured quartz) occur after
longer duration of contact with the dust.

We are doing toxicologic studies now with lunar simulant and a limited
quantity of Apollo dust in rodents and human volunteers. Tests include
intratracheal, corneal, dermal and ingestion studies that would allow
validation of toxic effects. After the lunar dust toxicological studies
are complete (estimated by end of 2008), we will have a much better idea
of the minimum amount of martian sample needed for reliable testing.
However, at this point, we estimate that 100 grams of actual martian
dust will be the maximum requirement, and we can only accurately
determine the minimum requirement after our test program, but we
currently estimate that 20 grams would be necessary. In parallel with
lunar dust simulant testing and Apollo soil dust testing, we would
prefer to conduct toxicity testing on appropriate martian dust simulants
now available. Results will provide better mass requirements for
returned martian soil and dust.

**[Sample priorities]{.underline}**

1\) Returned amount should be in the range of 20 to 100 gm (subject to
review at the end of testing in 2008). This would enable microbiological
activity assessment, chemical and morphological assessment focusing on
biological correlates, and mechanical, chemical and biological toxicity
assessment. The morphological (surface area, shape, size distribution,
adhesion properties) and chemical (compositional and reactivity)
studies to allow biological understanding may significantly overlap with
geological science analyses, and the data would be shared by both
scientific communities. The size of interest for toxicity is in the \<20
μm size fraction, esp. \<5 μm range.

The most essential tests could be carried out using much smaller
samples: a minimal quantity from which meaningful toxicological studies
alone, with adequate \"n\" size, could be conducted with as little as 3
g.

The preference is to obtain multiple small samples of regolith (e.g.
five 5-gram samples) than one larger 25-gram sample.  Obviously, if
there are multiple samples, they would need to be encapsulated. While
global dust storms may tend to homogenize dust over the martian surface,
local rock types, chemistry, and present and past processes may add a
distinctive character to dust from each collection site, and such
heterogeneity should be anticipated.

2\) The minimum sample set would be at least two regolith samples.  Q: 
If these are collected 1 km apart, would that be sufficient, or would
they need to be separated on a planetary scale?  Q: Could you justify
more samples than 2, or would two be sufficient?

A: The regolith samples would need to be kept distinct, so as to be able
to interpret heterogeneity. The samples could be a km apart if we only
needed to assess toxicity of a specific destination; however if we want
to determine regolith toxicity planetary wide, then we would need
samples from multiple regions. We know the lunar mare regions have
regolith with significance compositional differences than the highlands,
etc. Data from Spirit and Opportunity show that surface soils can have
significantly different variations in albedo and chemistry and that
these variations can occur over short distances \<1 meter). Whether
these differences would influences potential toxicity studies cannot be
predicted in advance. Therefore it would be necessary to return samples
of each major distinctive soil type based on albedo, spectral
properties, and chemistry. This requirement would likely parallel the
requirement of the chemical/mineralogical team, so the same set of
samples could be split between this team and the toxicology team.

We would also require a minimum of two depth samples from the deepest
part of the martian regolith sampled by the lander/rover. The purpose of
these samples would be to assess whether potential toxic properties vary
with depth. Such properties may include the surface reactivity of dust
grains, the possible presence and abundance of particularly toxic
species such as hexavalent chromium, and the variation of oxidation
potential, pH, and toxic metals with depth.

3\) Samples should be preserved in a vacuum-sealed container; however if
a vacuum is not achievable, then the samples should be in a container
sealed in Martian atmosphere. We need them sealed (not exposed to Earth
atmosphere) to truly characterize their reactivity and toxicity. The
regolith samples need to be kept distinct, so as to be able to interpret
heterogeneity.

Both airborne and ground samples should be taken. Airborne dust may be
quite different in overall properties from local martian soil. It may be
more strongly activated by UV and radiation, and it may have a
significantly different oxidation potential. As wind-blown dust is
likely to be directly encountered by future human explorers, its toxic
properties must be understood. You should get one airborne sample during
a raging dust storm, one in nominal conditions, one superficially,
"skimming" the surface, and at least 2 from different depths into the
soil. The more samples, the less uncertainty in human health effects of
the dust. We recommend pushing for at least 2 sites, 3 if possible to
assess heterogeneity, and to improve confidence that the composition and
reactivity issues have been bounded.

The grain size distribution of airborne dust would be of great interest
for toxicology studies. Data on terrestrial dust shows that nano-size
particles may have the highest toxicology potential. It is therefore
important to determine the abundance of nanoparticles in airborne
martian dust. This material may be higher risk to enter the habitat. Of
note, the airborne sample would not tell much about the size
distribution of the regoltih as a whole, since that which is wind-swept
would be skewed, although wind borne samples might be reasonable to
evaluate for shape/angularity/surface area and composition. Having a
small quantity of both windborne and scoop samples to compare would be
informative.

A filtered sample of dust, as proposed, would be quite valuable, and
probably quite adequate because it could be analyzed on a grain-by-grain
basis \-\-- a few ten thousands of grains would provide a lot of data. 
One problem is how to disconnect the filter from the pump or vacuum
plenum, so it is a somewhat non-trivial task.  The simplest engineering
solution would be something like collecting dust on a passive filter via
fallout, but if the mission is short, you may not get adequate sample.
(The actual sampling strategy could be evaluated by the assigned project
design engineers, and the most practical hardware recommended.)

***B-Toxicity of martian dust***

Unfortunately the evidence base for establishing the hazard associated
with biological toxicity of Martian soil and dust is scant. The
information currently available about putative life on Mars, either
current or historically, is derived from preliminary *in situ*
experiments conducted by the Viking lander, and from analysis of a
Martian meteorite found in the Allan Hills region of the Antarctic ice
fields ^3,4^. If life does exist on Mars currently, it is likely
microbial, and is comprised of organism(s) somewhat adapted to extreme
environments. The organism is likely not dwelling on the surface, but
instead at a depth which is protected from surface radiation, has
access, at least episodically, to liquid water, and under pressure \>8
mbar. Whether more complex life once existed on Mars is a matter of
intense scientific interest, which is a principle driver for exploration
of the planet. Life more complex than terrestrial prokaryotes is
improbable on Mars currently, however remnant organics from any
historical life may be present in the soil/dust. These putative
organics, in general, would pose low toxicity risk, however are
molecules that scientists would want to be preserved for terrestrial
analysis. Without complex lifeforms on Mars currently, the existence of
martian microbial pathogens is very unlikely, as there would be no hosts
for the microbes to adapt infectiously.

Biological toxicity of potential microbes on Mars can be broken into 3
categories: 1) irritative/allergic, 2) infectious, and 3) pathogenic:

[Irritative]{.underline}- this is a minor form of toxicity, that would
most likely to result in cutaneous or mucous membrane reaction
(erythema, edema, pruritis, urticaria) from contact with the microbial
surface antigens. A potentially serious, although rare reaction to
microbial antigens could be anaphylaxis- from either inhaled, ingested,
or hematogenous exposure of the human to the organism. Anaphylaxis, if
not properly treated, can be fatal, due to laryngospasm. Irritative or
allergic manifestations are expected to be the highest probability of
human reaction to martian microbes.

[Infectious]{.underline}- it is possible putative martian microbes could
be infectious to humans, that is could survive and propagate inside the
human body. If the organisms are motile, the likelihood of systemic
distribution would be greater, however the human immune response to
these putative organisms is at this point only speculative. It is
possible, that should a martian microbe be able to avoid immune
surveillance and survive inside a human body compartment, it may not
produce any adverse affect on the host. They could co-exist with the
host or less likely, be symbiotic.

[Pathogenicity]{.underline}- even if martian organisms are infectious,
it does not mean they would be pathogenic, i.e.- produce human disease.
The number of highly evolved terrestrial microbes which can produce
disease in humans, is quite small %-wise, and many of those are due to
contact with elaborated (exo-) or inherent (endo-) toxins (e.g.
botulinum, tetanus, etc.) and not due to the actual infection/invasion
of the human body. Pathogenicity is extremely rare among extremophiles
(authotrophs, lithotrophs, chemotrophs)^3^ as we suspect the martian
microbes to be.

A very small dust sample should be set aside for use in assessing crude
biologic toxicity, in both cell culture and a whole rodent models.

[Planetary Protection]{.underline}- The prospect of Martian surface or
subsurface life, together with the existence of a diversity of routes by
which microbial pathogenicity has emerged on Earth, suggests that the
possibility of human pathogens on Mars, while low, is not zero. In 1997
the National Research Council (NRC) Space Studies Board assessed the
biohazard risk of putative Martian microorganisms as it relates to the
issue of back contamination from a Mars sample return mission^3^. The
report concluded that it is unlikely that putative Martian organisms
would be capable of out-competing Earth organisms for nutrients, since
Earth's microorganisms are optimally adapted to their environments as a
result of billions of years of intense competition. Contamination of
Earth by putative Martian microorganisms is thus unlikely to pose a risk
of significant ecological impact or other harmful effects according to
the study. The risk was not felt to be zero, however. Therefore, the
board recommended that samples returned from Mars by spacecraft be
contained and treated as though potentially hazardous unless and until
sufficient knowledge of Mars and its environment becomes available.
Since the discovery and study of Martian life can have long-term
benefits for humanity, the risk that Martian life might include
pathogens should not be an obstacle to human exploration; however,
planetary protection must be considered. Both an agency planetary
protection officer concurred biosafety protocol and appropriate
laboratory BSL certification must be employed for the returned martian
soil/dust sample^3^.

[Discussion\
]{.underline}No one on this medical/toxicity team is putting a Mars
sample return in the critical path for human missions to Mars. However,
sample return may significantly improve the hazard knowledge and thereby
reduce uncertainty about the risk of human exposure. Characterization of
the dust also would allow better design of systems for Mars surface
operation, and human protection.

Issue- *amount of regolith*

It would be wise to exert some caution regarding the requirement for the
amount of sample required for medical/toxicity assessment.  A single
sample return might not answer all the questions that a human mission
might like to have under their belts.  On the other hand, Safe on Mars
and some NASA studies have concluded that sample return might not be
necessary at all.

If we levy too many requirements on sample return, and SMD opts to go
for a single attempt at such a mission rather than the series of 3 to 10
missions that have been recommended by scientists, then it would not be
good to invent requirements that such a mission simply could not
achieve. For example, obtaining regolith samples 1 km apart may be a
completely arbitrary requirement, as MER, Pathfinder, and Viking all
found what appears to be a very similar soil, planet-wide. Yet just
meters apart, occasionally a significant signature from nearby rocks
(e.g., high K-content at Pathfinder, and high P-Ti content for a couple
of soils at Gusev) has been found, and the S and Cl contents can vary
somewhat. 

Likewise, the use of samples for biological testing in lieu of physical
and chemical testing may be ill advised, since the returned samples
could be analyzed for every conceivable hazardous element and compound-
and thereby the hazard characterized significantly, without any
biological tests.  In a previous workshop held at Ames Research Center
approximately 10 years ago, the conclusion was that it might be
necessary to expose tiny amounts of soil to cell cultures, and perhaps
even to rodents.

Perhaps another way we should look at this is that our first Mars sample
return mission would be the pioneer that could provide the capability to
screen a future human landing site.  If the human program decides that
it needs large quantities of material to further characterize the risks,
then the challenge would be to fund a dedicated mission for toxicity
evaluation purposes, but the scientific rationale for large quantities
of Martian soil cannot be defended if approached with the knowledge that
we managed to go to a putatively hazardous moon with not a single grain
of lunar regolith in hand, prior to the mission.

Issue- *sample return vs stimulant*

The team does not have confidence in our ability to develop a credible
Martian regolith/dust simulant for toxicity testing purposes.  The most
compelling reason for this thinking is that we have been unable to do so
for the lunar regolith.  Part of the problem is that the natural lunar
material begins to react with the Earth\'s atmosphere and particularly
the moisture very quickly.  This changes the essential properties.  Even
manufacturing grains of the right shape/mineralogy is very hard under
Earth\'s conditions.  Thus, this strategy might not be viable for IVA-5.

The challenge will be to find methods for both biohazard testing and
toxicity testing to with smaller amounts of material.  It is probably
realistic on the latter to get down to 3 grams or less. The challenge
should be equal for the laboratory analysis. Recommend developing a set
of \"requirements\" for up-grading/improving our laboratory ability to
analyze small samples. There was such a program in the 60s to prepare
for the Apollo samples. The cosmic dust/Stardust sample analyzers are
doing some of this (and keeping current with instrumentation) but there
is likely a deficiency in many of the labs to obtain reliable data with
small sample quantities.

***[Investigation Summary: Sample needs/priorities]{.underline}***

Priority for first sample return: HIGH

Sample types required:

Pristine (preserved) dust sample

Regolith sample(s) beneath superficial deposits

Size fraction priority: \<20 μm

Priority of samples from a second landing site: HIGH

[References]{.underline}:

### **1) Lunar In Situ regolith study justification white paper:** 

### **"Crew Health & Performance Requirements for RLEP2 mission lander" Anthony Colaprete; Jeff Jones; John James; Tom Sullivan; Noreen Khan; David McKay; Antony Jeervajan; John Lindsay; Lawrence Taylor; Keith Manuel; Richard McCluskey; Russell Kerschman 2006**

2\) "Safe On Mars: Precursor Measurements Necessary to Support Human
Operations on the Martian Surface" National Research Council, National
Academy of Sciences, National Academy Press, Wash. D.C. 2002

3\) Warmflash, D, Larios-Sanz, M., Jones, JA, Fox, GE, Mckay, DA.
Assessing the biohazard potential of putative martian organisms for
exploration class human space missions. ASEM 78(4) Section II suppl. A79

4\) McKay DS GE, Thomas-Keprta KL, Vali LH, Romanek CS, Clemett SJ,
Chillier ZD, Maechling CR, and Zare, RN. Search for past life on Mars:
Possible relic biogenic activity in Martian meteorite ALH84001. Science
1996;273:924.

\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_

**[Investigation 3.]{.underline} Assess atmospheric electricity
conditions that may affect TAO and human occupation.**

[Measurements:]{.underline}

a.  Basic measurements:

    i.  DC E-fields 0-80 kV/m, dV=1 V, bandwidth 0-10 Hz, rate = 20 Hz

    ii. AC E-fields 10 uV/m -- 10 V/m, Frequency Coverage 10 Hz-200 MHz,
        rate = 20 Hz, with time domain sampling capability

    iii. Atmospheric Conductivity 10^-15^ to 10^-10^ S/m, ds= 10% of
         local ambient value

    iv. Ground Conductivity \> 10^-13^ S/m, ds= 10% of local ambient
        value

    v.  Grain charge \>10^-17^ C

    vi. Grain radius 1-100 um

b.  Combine with surface meteorological package to correlate electric
    forces and their causative meteorological source \> 1 martian year,
    both in dust devils and large dust storms. Combine requirements for
    1Bb with 3a above.

**[Investigation IVA-6: Implications for sample return]{.underline}**.

Analysis Leader: Vicky Hipkin.

See discussion under IVA-2.

> *[Investigation Summary: Sample needs/priorities]{.underline}*
>
> Priority for first sample return: LOW
>
> Sample types required:

1.  dust sample

> Priority of samples from a second landing site: LOW

\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_

**[Investigation 4.]{.underline} Determine the processes by which
terrestrial microbial life, or its remains, is dispersed and/or
destroyed on Mars (including within ISRU-related water deposits), the
rates and scale of these processes, and the potential impact on future
scientific investigations.**

[Measurements:]{.underline}

a.  Determine the rate of destruction of organic material by the martian
    surface environment.

b.  Determine the mechanisms and rates of martian surface Aeolian
    processes that disperse organic contaminants. 

c.  Determine the adhesion characteristics of organic contaminants on
    landed mission elements, and the conditions and rates under which
    these contaminants are transferred to the martian environment.

d.  Determine the mechanisms to transport surface organic contaminants
    into the martian subsurface, and in particular, into a martian
    aquifer.

e.  Determine if terrestrial microbial life could survive and reproduce
    on the martian surface.

**[Investigation IVA-7: (Forward Planetary Protection) Implications for
sample return]{.underline}**.

Analysis Leader: Carl Allen.

The MEPAG-chartered Human Precursor Science Steering Group recently
assessed the implementation of this Goal, and specifically Objective
IV-A "Obtain knowledge of Mars sufficient to design and implement a
human mission with acceptable cost, risk and performance." (Beaty et
al., 2005). This study recommended five medium-priority investigations,
including "Determine the processes by which terrestrial microbial life,
or its remains, is dispersed and/or destroyed on Mars (including within
ISRU-related water deposits), the rates and scale of these processes,
and the potential impact on future scientific investigations."

This proposed investigation is associated with "Forward Planetary
Protection" -- the risk of terrestrial life transported to Mars. The
concern focuses on local or widespread contamination of the martian
surface, leading to possible false positive indications of martian life.
The major questions concern (1) the survival and reproduction of
terrestrial life on the martian surface and (2) the dispersal of
terrestrial life or its remains on Mars (Beaty et al., 2005).

[Can terrestrial life survive and reproduce on the martian
surface?]{.underline}

Important questions for a human mission involve the survival and
reproduction of terrestrial microorganisms on the martian surface. A key
corollary is to determine the rate of destruction of organic material by
the martian surface environment. Many details of these questions can,
and should, be addressed in terrestrial simulation laboratories, rather
than by deliberately placing terrestrial organisms on the martian
surface.

[Can terrestrial life, or its remains, be dispersed on Mars
?]{.underline}

This question addresses a wide variety of dispersal mechanisms, many of
which are being investigated in the existing Mars science program and in
recommendations from other groups. For instance, it would be important
to determine the mechanisms and rates of martian surface aeolian
processes which disburse organic contaminants. It would also be
important to determine the mechanisms of transport of surface organic
contaminants into the martian subsurface, and in particular, into a
martian aquifer. A parallel study, currently being addressed by the Mars
Technology Program Planetary Protection effort, seeks to determine the
adhesion characteristics of organic contaminants on landed mission
elements, and the conditions and rates under which these contaminants
are transferred to the martian environment.

The level of forward contamination from a robotic lander could possibly
be addressed by means of samples collected on Mars and returned to
Earth. Specifically, the surface material in the vicinity of a lander
could be sampled and assayed for evidence of biological contamination
from the spacecraft. This assay could be conducted in the vicinity of
the Sample Return lander, or in the vicinity of a previous lander that
might be visited to retrieve a sample cache. The following
considerations apply to requirements for forward contamination
assessment on a first sample return mission.

The minimum sample required for forward contamination analysis would be
the soil and dust immediately downwind of the lander.

The sample for return to Earth must be minimally altered by the acts of
collection and storage. Biological contamination must be kept below
sampling hardware sterilization limits required by Planetary Protection
(currently Viking-level sterilization). Organic contamination must be
kept below Viking-level detection limits (1 ppb).

A single sample of soil and dust from close to the lander would be
sufficient to conduct this investigation on a first sample return
mission. The Draft Test Protocol (Rummel et al., 2002) states that 15 --
25 g would be sufficient to carry out all required biohazard testing.
However, advances in the field of biohazard testing combined with
targeted high-sensitivity testing for specific terrestrial organisms or
their remains, might result in a requirement for considerably less
material.

The environmental tolerance of many terrestrial organisms are unknown,
so the sample should be preserved and transported in an environment as
little altered as possible. Specifically, it should be kept at or near
ambient pressure in a Mars-like atmosphere and at a temperature within
the annual temperature range at the sampling site. The effects of
exposure to environmental conditions outside of this range are unknown
but could include death of viable organisms, alteration of organism
remains, and alteration of chemical biosignatures.

The forward contamination sample should be collected using sterilized,
precision cleaned sampling hardware. If more than one sample is
collected, a separate implement to contact each sample preferred is
preferred to prevent cross-contamination. Each sample should be placed
in a sterilized, precision cleaned, sealable container.

The forward contamination sample should be selected based on its
location adjacent to the lander. The spacecraft imaging system should be
sufficient for sample selection.

The forward contamination sample should be collected in the immediate
vicinity of the spacecraft. Lateral mobility on the order of 1 meter
should be sufficient. The sample of surface material would not require
vertical mobility beyond that of an arm-mounted scoop.

The forward contamination sample would be subjected to detailed analysis
at the sub-micron scale. It must therefore be stringently protected from
contamination from the sample handling equipment and from
cross-contamination by other samples. The forward contamination sample
must be stored in a dedicated container designed to remain intact and
sealed until secured in the Sample Receiving Facility on Earth.

> *[Investigation Summary: Sample needs/priorities]{.underline}*
>
> Priority for first sample return: LOW
>
> Sample types required:

1.  dust sample

> Priority of samples from a second landing site: LOW

\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_

**[Investigation 5.]{.underline} Characterize in detail the ionizing
radiation environment at the martian surface, distinguishing
contributions from the energetic charged particles that penetrate the
atmosphere, secondary neutrons produced in the atmosphere, and secondary
charged particles and neutrons produced in the regolith.**

[Measurements:]{.underline}

a\. Measurement of charged particles with directionality. Identify
particles by species and energy from protons to iron nuclei in the
energy range 20-1000 MeV/nuc.

b\. Measurement of neutrons with directionality. Energy range from 1 keV
(or lower) to 100 MeV (or higher).

c\. Simultaneous with surface measurements, a detector should be placed
in orbit to measure energy spectra in Solar Energetic Particle events.

**[Investigation IVA-8: Implications for sample return]{.underline}**.

> Sample return would not significantly contribute to this
> investigation.

\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_

**[Investigation 6.]{.underline} Determine traction/cohesion in martian
regolith (with emphasis on trafficability hazards, such as dust pockets
and dunes) throughout planned landing sites; where possible, feed
findings into surface asset design requirements.**

**[Investigation IVA-9: Implications for sample return]{.underline}**.

*Overview:* Most of the measurements called for in this investigation
are properly conducted in situ and would require no sample return.
Additionally, the requirement for this investigation is that the
regolith properties are to be characterized "throughout planned landing
sites" (referring to the future human landing sites). Without a concrete
plan to send humans to the same landing site as a Mars sample return
mission, it is not possible to accomplish this investigation with Mars
sample return because the properties in question are known to be highly
variable from one site to another. The only components of the human site
we can hope to characterize with a Mars sample return are those that are
globally ubiquitous -- i.e., surface dust. 

*Mars sample return as it relates to the specific measurement
requirements of this investigation:*

a)     Determine vertical variation in in-situ regolith density within
the upper 30 cm for rocky areas, on dust dunes, and in dust pockets to
within 0.1 g cm-3. The vertical variation in in-situ regolith density in
the upper 30 cm is likely to be strongly dependent on landing site
location, thus there would be no value for sample return for this
measurement unless we send humans to the same site. Even if humans were
sent to the same site, the measurement would be of greater value if made
in situ. Packing of the regolith from the sampling and return process
could change its density as a function of depth. Also, a 30-cm long
sample would likely not be feasible for Mars sample return.

b)     Determine variation in in-situ internal angle of friction of
regolith for dust dunes and dust pockets to within 1 degree. This
measurement would be best made under martian ambient environmental
conditions (gravity, atmospheric pressure, and humidity) and in its
original (natural) packing condition. It is usually inferred from
looking at the sides of trenches made by rover wheels or scoops. There
would be no advantage in attempting to make this measurement on a sample
returned to Earth.

c)      Determine regolith cohesion for rocky areas, dust dunes and in
dust pockets to within 0.1 kN m-2. This measurement also must be made in
situ. For rocky areas, it would not be possible to bring back enough
rocks to make this measurement on Earth because of mass limitations on
returned sample. Even for dusty surfaces, the utility of the measurement
would be much greater if it is made under martian ambient environmental
conditions, with the regolith in its original packing condition.

d)     Precision imaging to Mars Reconnaissance Orbiter High Resolution
Imaging Science Experiment (MRO HiRISE) standards (30 cm/pxl) for
selected potential landing sites: Sample return would not be relevant to
this measurement.

*Mars sample return as it relates to measurement required for mobility
systems:*

The MEPAG goals also describe the following measurement requirements
related to basic design of mobility systems: i) rolling resistance on
wheels, ii) traction measurements for wheels, and iii) measurement of
the shape and size of the wheel ruts that result from normal driving.
All of these measurements are related to rovers traversing the martian
surface, so measurements with returned samples on Earth would not be as
useful as measurements made with robotic rovers on the Martian surface. 
It is possible that some utility could come from using the physical
properties (e.g., distributions of regolith grain size and shape) of a
small, representative sample of regolith to select a mechanical analog
material from terrestrial sources to help in the design of mobility
systems. However, such an investigation could easily "piggyback" on
other investigations that require samples of the regolith.

> *[Investigation Summary: Sample needs/priorities]{.underline}*
>
> Priority for first sample return: LOW
>
> Sample types required:

1.  regolith sample(s)

> Priority of samples from a second landing site: LOW

\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_

**[Investigation 7.]{.underline} Determine the meteorological properties
of dust storms at ground level that affect human occupation and EVA.**

[Measurements:]{.underline}

a.  P, V, T, n, and dust density (opacity) as a function of time at the
    surface, for at least a Martian year, to obtain an understanding of
    the possible meteorological hazards inside dust storms. Surface
    Package measure directly:

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i.  Same as requirement for 1Bb with added

ii. Dust size 1-100 um

iii. Dust density 2-2000 grains/cc

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b.  Orbiting weather station: optical and IR measurements to monitor the
    dust storm frequency, size and occurrence over a year, & measure
    terrain roughness and thermal inertia. Climate sounder would enable
    middle atmosphere temperature measurements. In situ density or
    spacecraft drag sensors could monitor the dust storm atmosphere
    inflation at high altitudes. Same as requirement 1Bc.

**[Investigation IVA-10: Implications for sample return]{.underline}**.

Analysis Leader: Vicky Hipkin.

See discussion under IVA-2.

> *[Investigation Summary: Sample needs/priorities]{.underline}*
>
> Priority for first sample return: LOW
>
> Sample types required:

1.  dust sample

> Priority of samples from a second landing site: LOW

\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_

**[Objective B.]{.underline} Conduct risk and/or cost reduction
technology and infrastructure demonstrations in transit to, at, or on
the surface of Mars.**

Technology validation on Mars flight missions and infrastructure
emplacements are needed to reduce the risk and associated uncertainty
inherent in new, unproven technologies and to reduce the cost of human
Mars exploration. These demonstrations were chosen for Mars robotic
flight missions based upon: (a) their high degree of interaction with
the Mars environment, (b) their anticipated large leverage on human Mars
mission architecture feasibility, and (c) uncertainty of whether Earth,
Earth-orbit or lunar testing would supply sufficient data to reduce risk
and cost, or increase performance of these systems.

Analysis Leader: Noel Hinners.

Materials degradation. The concern is how materials emplaced and/or used
on the martian surface may degrade due to 1. radiation; 2. thermal
cycling; 3. erosion and physical abrasion; and 4. chemical reaction with
the atmosphere or surface material. Materials degradation is a strong
function of the specific material, its use and conditions of exposure
(e.g., time, orientation). The radiation (UV, visible, proton, cosmic
ray) could be well simulated based on what we now know about the
radiation environment and what could be obtained from future in-situ
radiation experiments. Thermal cycling could be adequately simulated
based on our existing knowledge of the martian near-surface
temperatures. Erosion and physical abrasion is a result of exposure to
airborne dust ("sand blasting"), movement of materials on or over
martian regolith (e.g., wheel coverings, boots and gloves) and grinding
on moving surfaces (e.g., gears, motors). Analysis of the physical
properties of returned martian regolith (e.g., angularity, hardness,
size distribution) could provide much of the information needed to
evaluate the potential for erosion and physical abrasion. This
information could be used to develop a martian regolith stimulant that
could be used in large scale engineering tests. There would be no need
for a special "degradation" sample as long as representative regolith is
obtained (i.e., not all pebbles). This argues for multiple (minimum 2)
different regolith samples. The last factor, chemical reactivity, is a
concern that could be addressed in part by analysis of the chemistry and
chemical reactivity of returned samples, especially fines. This would
require that the sample be acquired in its native environment and that
it be preserved and thus represents pristine martian conditions.

The above indicates that analyses of returned sample could be of useful
in understanding the potential for materials degradation in the martian
environment. It is, however, not likely to be as definitive as desired
by human exploration mission planners. This results from two factors: 1.
returned samples would not indicate what short-lived, reactive chemical
species created by photochemistry, for example, might exist in the
atmosphere or that might be labile on soil particulate surfaces. 2.
materials degradation may be a synergistic effect of multiple
environmental factors acting in concert and which cannot be adequately
simulated. For these reasons it was suggested in Goal IVB that coupons
of materials be emplaced on the martian surface with the possibility of
eventual return to earth. This would be analogous to the Long Duration
Exposure Facility flown in earth orbit and retrieved by a Shuttle
flight. An "all-up" Mars-LDEF would likely be a major robotic mission
element in terms of size, mass, manipulation and packaging. It might
also be possible to instrument a Mars-LDEF to determine degradation
properties without return of the materials. Such would be an ESMD
mission and not a goal for an SMD sample return mission. Given that,
however, we should consider that it may be feasible to attach small
material coupons to sampling equipment (e.g., containers) sent on a
sample return caching mission with an inherent multi-year exposure on
the martian surface. Similarly, it might be plausible to include
material coupons on other robotic missions (e.g., rovers) placed where
they could be examined by instrumentation on the vehicles.

> *[Investigation Summary: Sample needs/priorities]{.underline}*
>
> Priority for first sample return: LOW
>
> Sample types required:

1.  manufactured materials that have been exposed to the martian
    environment for known lengths of time.

> Priority of samples from a second landing site: LOW

**[REFERENCES]{.underline}**

Beaty, D.W., Snook, K., Allen, C.C., Eppler, D., Farrell, W.M.,
Heldmann, J., Metzger, P., Peach, L., Wagner, S.A., and Zeitlin, C.,
(2005). An Analysis of the Precursor Measurements of Mars Needed to
Reduce the Risk of the First Human Missions to Mars. Unpublished white
paper, 77 p, posted June, 2005 by the Mars Exploration Program Analysis
Group (MEPAG) at http://mepag.jpl.nasa.gov/reports/index.html.

MEPAG (2006), Mars Scientific Goals, Objectives, Investigations, and
Priorities: 2006, J. Grant, ed., 31 p. white paper posted February, 2006
by the Mars Exploration Program Analysis Group (MEPAG) at
<http://mepag.jpl.nasa.gov/reports/index.html>.

National Research Council, Space Studies Board, 2002, Safe On Mars:
Precursor Measurements Necessary to Support Human Operations on the
Martian Surface. National Academy Press, Washington, D.C., www.nap.edu.

Rummel, J.D., M.S. Race, D.L. DeVincenzi, P.J. Schad, P.D. Stabekis, M.
Viso and S. E. Acevedo (eds.), 2002, A Draft Test Protocol for Detecting
Possible Biohazards in Martian Samples Returned to Earth,
NASA/CP-2002-211842, Washington, D.C. online at:
planetaryprotection.nasa.gov

[^1]:

[^2]: [General Notes]{.underline}:

    *Except as noted, investigations are listed in priority order.
    Within each investigation, measurements are listed in priority
    order.*

    *[Prioritization Criteria]{.underline}:*

    *Magnitude of effect of precursor information on reduction of risk
    and/or cost of a human mission to Mars.*

    *Perceived degree of viability and cost of available mitigation
    options.*

    *Potential to obtain minimum necessary information in a less
    expensive way than by flying a mission to Mars.*