# Mars Science Goals, Objectives, Investigations, and Priorities: 2006

MEPAG (Mars Exploration Program Analysis Group)

February 10, 2006

# Prepared by the MEPAG (Mars Exploration Program Analysis Group) Goals Committee:

John Grant, Chair, Smithsonian Institution (<grantj@si.edu>)

[Representing Goal I]{.underline}

Jan Amend, Washington University (<amend@levee.wustl.edu>)

Andrew Steele, Carnegie Institute of Washington (<steelie@mac.com>)

[Representing Goal II]{.underline}

Mark Richardson, Caltech (<mir@gps.caltech.edu>)

Steve Bougher, University of Michigan (<Bougher@engin.umich.edu>)

[Representing Goal III]{.underline}

Bruce Banerdt, Jet Propulsion Laboratory (<bruce.banerdt@jpl.nasa.gov>)

Lars Borg, University of New Mexico (<lborg@unm.edu>)

[Representing Goal IV]{.underline}

John Gruener, Johnson Space Center (<john.e.gruener@nasa.gov>)

Jennifer Heldmann, Ames Research Center (<jheldmann@mail.arc,nasa,gov>)

# Comments or concerns regarding this document should be addressed to Dr. John Grant, Chair, MEPAG Goals Committee (grantj@si.edu).

# This report has been approved for public release by JPL Document Review Services (CL#05-2215) and may be freely circulated. 

[Recommended bibliographic citation:]{.underline}

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.

PREAMBLE

In 2000, the Mars Exploration Program Analysis Group (MEPAG) was asked
by NASA to work with the science community to establish consensus
priorities for the future scientific exploration of Mars. Those
discussions and analyses resulted in a report entitled *Scientific
Goals, Objectives, Investigations, and Priorities*, which is informally
referred to as the "Goals Document" (MEPAG 2001[^1]). The initial report
proved to be very useful for guiding program implementation decisions.
It also has become clear over the past few years that the report
requires regular updating in light of dramatic new results from Mars and
evolving high-level strategic direction from NASA. For this reason,
MEPAG periodically revises the Goals Document (MEPAG, 2004[^2]; MEPAG,
2005^3^; MEPAG 2006-this document). As was the case with previous
versions, the Goals Document is presented as a statement of community
consensus positions.

The MEPAG Goals Document is organized into a four-tiered hierarchy:
goals, objectives, investigations, and measurements. The goals have a
very long-range character and are organized around major sectors of
scientific knowledge. Specific statements of these goals are found in
this report, but they are commonly referred to as Life, Climate,
Geology, and Preparation (for Human Exploration). Because developing an
understanding of Mars as a system requires making progress toward
meeting all four goals, MEPAG has not attempted to prioritize the goals,
but rather represents them equally.

The four goals each include 2-3 objectives that embody the strategies
and milestones needed to achieve them. Objectives are presented in
priority order, because there is often an order in which the scientific
questions can most logically be resolved, and/or some objectives are
perceived to be more important than others. In the present version of
the Goals Document, there are a total of 10 objectives, eight of which
are scientific in nature, and two of which relate to safe mission
operations.

A series of investigations that collectively would achieve each
objective is also identified. The investigation structure is
specifically intended to apply to the scientific objectives, but a
breakdown is also presented for the two engineering objectives. While
some investigations can be achieved with a single instrument, others
will require multiple instruments on multiple missions. Each set of
investigations is independently prioritized for each objective.

Measurements constitute the fourth tier of the MEPAG hierarchy.
Measurements are made by instruments, which are tangible objects that
can be built and flown to Mars. MEPAG has only considered scientific
objectives that can be traced down to measurements (i.e., theoretical
modeling was not considered). The Goals Document is presented as a
statement of community consensus positions and it is MEPAG's intent that
the descriptions of scientific objectives and investigations serve
simply as example targets for future instrument development and
measurements. As measurement capabilities and techniques evolve,
detailed requirements should to be defined by Principal Investigators,
Science Definition Teams, and Payload Science Integration Groups for
program missions and by the Principal Investigator and Science Teams for
Scout missions. These requirements can then contribute to forward
program planning. An important exception to this strategy, however, is
the measurement set associated with Goal IV Objective A, which relates
to environmental data sets necessary to reduce the risk of future human
missions to acceptable levels. In that case, a clear criterion exists
(degree of impact on risk reduction) that enables those measurements to
be listed in priority order.

Completion of all the cited investigations will require decades of
studying Mars and it is possible that many investigations may never be
truly completed (even if they have a high priority). Thus, evaluations
of prospective missions and instruments should be based on how well the
investigations are addressed. While priorities should influence which
investigations are conducted first, they should not necessarily be done
serially, except where it is noted that one investigation should be
completed first. In such cases, the investigation that should be done
first was given a higher priority, even in where it is believed that a
subsequent investigation will be more important.

Some types of Mars-related scientific research take place without flying
spacecraft to Mars. Most notably, these include meteorite studies,
telescopic observations, theoretical models, and fundamental research of
diverse character. The Goals Document does not consider these sectors of
research in its hierarchy, or in its prioritization system.

*[Some general thoughts on mission technology planning]{.underline}*

Even a cursory reading of the goals, objectives, and investigations will
reveal several crucial technical capabilities that need development. The
most important of these are: (1) *Access to all of Mars*\--high and low
latitudes, rough and smooth surfaces, low and high elevations, plus
precision landing. (2) *Access to the subsurface*, from a meter to
hundreds of meters, through a combination of drilling and geophysical
sounding. (3) *Access to time varying phenomena* that requires the
capability to make some measurements over a long period of time (e.g.,
climate studies covering from one to several Martian years). (4) *Access
to microscopic scales* by instruments capable of measuring chemical and
isotopic compositions and determining mineralogy and the nature of
mineral intergrowths. Orbital and landed packages can make many of the
high priority measurements, but others require that samples be returned
from Mars. There is a strong consensus on the need for sample return
missions. As noted in other MEPAG and National Academy of Science
reports, study of samples collected from known locations on Mars and
from sites whose geological context has been determined from remote
sensing measurements has the potential to revolutionize our view of
Mars. A full discussion of these issues is beyond the scope of this
document, but we anticipate that they will be addressed by MEPAG and
other scientific advisory committees in the near future.

# Notes relating to this version of the Goals Document

The changes to this version of the Goals Document only involve
relatively minor revisions and additions to Goals I-III. It is
anticipated that a more extensive revision of the entire document will
be undertaken as data from the Mars Reconnaissance Orbiter becomes
available and is interpreted. Goal IV (Preparation for Human
Exploration) was revised in 2005 with the assistance of a MEPAG
chartered the Mars Human Precursor Science Steering Group (SSG) in order
to clarify text in the 2001 and 2004 versions of the Goals Document
regarding the time line and engineering implementation options for human
missions to Mars.

The present version of the Goals Document incorporates changes made by
the MEPAG Goals Committee and the broader science community. The Goals
Committee provided comments and suggested revisions in late 2005 that
were circulated to the MEPAG Executive Committee in December 2005. The
entire document was then made available for comment and additional
revisions by the science community in January 2006. All comments and
additional revisions were then approved by the Goals Committee in
January 2006 and the Executive Committee in February 2006.

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

Determining if life ever arose on Mars is a challenging goal. The focus
of this goal is to determine if life is or was present on Mars. If life
exists or existed, another focus is to understand the systems that
support or supported it. Finally, if life never existed and conditions
were suitable for formation and/or maintenance of life, a third focus
would be to understand why evidence of life was not found. A
comprehensive conclusion will necessitate understanding the planetary
evolution of Mars and whether Mars is or could have been habitable, and
will need to be based in multi-disciplinary scientific exploration at
scales ranging from planetary to microscopic. The strategy we have
adopted to pursue this goal has two sequential aspects: assess the
habitability of Mars (which needs to be undertaken environment by
environment); and, test for prebiotic processes, past life, or present
life in environments that can be shown to have high habitability
potential. These constitute two high-level scientific objectives. A
critical means to achieve both of these objectives is to characterize
Martian carbon chemistry and carbon cycling. Consequently, the science
associated with carbon chemistry is so fundamental to the overall *life*
goal that we have established it as a third primary science objective.
To some degree, these overarching scientific objectives can be addressed
simultaneously, as each requires basic knowledge of the distributions of
water and carbon on Mars and an understanding of the processes that
govern their interactions. Clearly, these objectives overlap, but are
considered separately here.

To spur development of flight technologies required to achieve these
objectives there must be an increase in the number of terrestrial ground
truth tests for instrumentation on samples of relevance to Mars
exploration. This aids the development of instrumentation directly while
maintaining pressure to improve detection limits. In support of such
tests, suites of highly characterized samples from relevant environments
should be identified and curated for laboratory studies.

In order to prioritize the objectives and investigations described here,
we need to be specific about the prioritization criteria. In broad
perspective, Objective C ("test for life") is a long-term goal.
Objectives A ("assess habitability") and B ("follow the carbon") are the
critical steps in narrowing the search space to allow Objective C to be
addressed. We need to know where to look for life before making a
serious attempt at testing for life. At the same time, Objectives A and
B are fundamentally important even without searching for life directly;
they help us understand the role planetary evolution plays in creating
conditions in which life might have arisen, whether it arose or not.
Thus, objectives A, B, and C, in this order, form a logical exploration
sequence. Note that research goals and technology development plans must
incorporate both short- and long-term scientific objectives.

## A. Objective: Assess the past and present habitability of Mars (investigations listed in priority order)

As used in this document, the term "habitability" refers to the
potential to support life of any form. Although Objective A is stated at
a planetary scale, we know from our experience on Earth that we should
expect that different environments on Mars will have different potential
for habitability. It will not be possible to make measurements of one
environment and assume that they apply to another. In order to address
the overall goal of determining if life ever arose on Mars, the most
relevant life detection investigations will be those carried out in
environments that have high potential for habitability. Thus,
understanding habitability in space and time is an important first order
objective.

Arguably, until we discover an extant Martian life form and measure its
life processes, there is no way to know [definitively]{.underline} which
combination of factors must simultaneously be present to constitute a
Martian habitat. Until then, "habitability" will need to describe the
[potential]{.underline} of an environment to sustain life and will
therefore be based on our understandings of habitable niches on Earth or
plausible extrapolations. Current thinking is that at a minimum, the
following three conditions need to be satisfied in order for an
environment to have high potential for habitability:

-   The presence of liquid water. As we currently understand life, water
    is an essential requirement. Its identification and mapping
    (particularly in the subsurface, where most of Mars' water is
    thought to reside) can be pursued on a global, regional and local
    basis using established measurement techniques.

-   The presence of the key elements that provide the raw materials to
    build cells

-   A source of energy to support life.

Finally, environments with potential for habitability are assumed to
have unequal potential to preserve the evidence in geological samples.
There needs to be an understanding of these effects in order to
understand the significance of many types of life-related
investigations.

### **1. [Investigation:]{.underline} Establish the current distribution of water in all its forms on Mars.** 

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.

### **2. [Investigation:]{.underline} Determine the geological history of water on Mars, and model the processes that have caused water to move from one reservoir to another.** 

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 can 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.

### **3. [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**. 

Assessing the availability of biological important elements and the
phases in which they are contained, will 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.

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

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 is 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.

## B. Objective: Characterize Carbon Cycling in its Geochemical Context (investigations listed in priority order)

Carbon is the basic building block of life on Earth and is probably the
building block of life on Mars (if life exists/existed). Understanding
how carbon has been distributed on Mars through time, including now, is
critical for understanding where to look for life on Mars, how life
might have evolved on Mars, and how life might have originated on Mars.
In addition, there may be aspects of the carbon cycle that reveal the
existence of life (extant or extinct), and results are likely to
strongly influence approaches to searching for other biosignatures.
Thus, characterization of the carbon cycle is critical to determining if
life ever arose on Mars.

Understanding the origin of organic carbon is particularly important and
sources on Mars could be from several reservoirs that are summarized in
Table 2. Once organic carbon is discovered, a major challenge will be in
constraining the source of that organic carbon. Terrestrial
contamination is a significant concern, because of the need to avoid
false identification of organic carbon or specific organic molecules on
Mars. In addition, meteoritic delivery of organic carbon to the surface
of Mars and abiotic organic synthesis processes could produce measurable
organic carbon concentrations. Understanding the origin of organic
carbon is as important as identifying it.

We assume that extraterrestrial life would be based on carbon chemistry.
Although this assumption may subsequently need to be relaxed, we would
not know where else to begin in designing investigations of possible
extraterrestrial life. If anomalous measurements indicate the presence
of non-carbon based macromolecules associated with some form of
life-like processes then further experiments can be designed to address
this problem.

**Table 2**. Possible sources of organic carbon that need to be
distinguished in Martian samples.

  ----------------------- ---------------------------------------------------
  **Source of Carbon**    **Carbon compounds (examples/comments)**

  Prebiotic/protobiotic   Amino acids, purines and pyrimidines, polycyclic
  molecules from          aromatic hydrocarbons, chain hydrocarbons, fatty
  meteoritic / cometary   acids, sugars and sugar derivatives.
  influx                  

  Prebiotic/protobiotic   Amino acids, purines and pyrimidines, polycyclic
  molecules from abiotic  aromatic hydrocarbons, chain hydrocarbons, fatty
  process on Mars         acids, sugars and sugar derivatives.

  Terrestrial             Condensation products derived from rocket exhaust,
  contaminating organics  lubricants, plasticizers, atmospheric contaminants

  Terrestrial             Whole cells, cell components (LPS, DNA, proteins,
  contaminating organisms cytochromes)

  Terrestrial like        Organisms not present on the craft measuring them,
  organisms -- from Earth but had been previously transferred from Earth by
                          either meteorite impact or contamination of
                          previous spacecraft. Target molecules could include
                          individual genes, membrane constituents, specific
                          enzymes, and co-enzymes that would be expected to
                          be over expressed or adapted in Martian conditions.

  Terrestrial-like        Organisms that utilize terrestrial like
  organisms -- evolved on biochemistries and have evolved on Mars. Target
  Mars                    molecules could include individual genes, membrane
                          constituents, specific enzymes, and co-enzymes that
                          would be expected to be over expressed or adapted
                          in Martian conditions, or organisms using
                          metabolisms that would not be present on a space
                          craft contaminant such as methanogens,
                          psychrophiles endolithic survival mechanisms.

  Non-terrestrial-like    Utilizes an array of molecules for information
  organisms               storage, information transfer, compartmentalization
                          and enzymatic activity that differ from those used
                          by extant terrestrial life. Examples would be the
                          use of novel amino acids and nucleotides or the use
                          of novel nitrogen utilization strategies.

  Fossil biomarkers       Detection of established terrestrial fossil
                          biomarkers such as hopanes, archaeal lipids and
                          steranes, for the detection of the diagenetic
                          remains of terrestrial based life.
  ----------------------- ---------------------------------------------------

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

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 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.

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

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.

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

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 will substantially aid interpretations of the
carbon cycle and may provide indicators that can 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.

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

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[^3] and within weathered rocks is 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 will 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.

## C. Objective: Assess whether life is or was present on Mars (investigations listed in priority order) 

This objective reflects several of NASA's chief exploration goals. As
mentioned earlier, the need to prevent false positives or negatives, and
develop technology and experimental protocols, makes Objective C ("test
for life") a long-term goal. Objectives A ("assess habitability") and B
("follow the carbon") are the critical steps in narrowing the search
space to allow Objective C to be addressed. Furthermore, the Objective
itself does not halt upon a positive or negative answer. In the
eventuality of a positive answer there would be the need to characterize
whatever life form is discovered, as well as its origins and reason for
surviving on Mars. In the case of a negative answer, then further
characterization of why life did not start on Mars would become a
priority and in itself help us to understand more about life on earth.

Determining whether life ever existed on Mars is a scientifically
exciting and challenging endeavor. The following investigations look for
biosignatures, which are defined as results that REQUIRE the presence or
past presence of life. Commonly, multiple observations in a context are
required to identify biosignatures, and multiple scales of observation
are very important. Four investigations of features currently recognized
as biosignatures are listed here.

Investigation 1 (Characterize complex organics) is considered to be the
highest priority. Investigation 1 and some measurements to address
Investigation 4 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. Investigations 2 and 3, which depend on the spatial
distribution of signatures, are less sensitive to contamination and may
be more practical to pursue first. Remote sensing techniques addressing
investigation 4 also have much lower to no contamination issues.
Investigations 1-4 are largely *in situ* investigations that are best
conducted in those habitable environments identified in A1.

A fifth investigation concept consists of suites of observations based
on correlations in biological indicators, which by themselves are only
suggestive for life and only in combination can provide a true
biosignature. It seems likely that many of the combinations of
measurements have yet to be identified, and it is expected that exciting
proposals for suites of observations will be seriously considered in
choosing investigations to evaluate the past or present presence of
life.

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

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 entails 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 may
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.*

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

The spatial distribution of chemical or isotopic variations can be a
biosignature, if the distribution is inconsistent with abiotic
processes. Example measurements may 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.

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

### Sedimentary and weathered rocks can preserve biosignatures in the distribution of grains and minerals or in the morphology of biologically produced minerals. Example measurements may 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.

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

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 may 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.

## 

# 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 will measure key
indicators of the past climate of Mars. Finally, Objective C highlights
mission critical atmospheric measurements that will 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 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.**

To understand the present climate system, from the surface to the
exosphere, requires long-term (multi-year) continuous global monitoring
from both landed and orbital platforms. Understanding the factors that
control the annual variations of volatiles and dust is necessary to
determine to what extent processes operating today have controlled
climate change in the past.

\(i\) Lower atmosphere climate and processes

Landed missions can provide direct *in situ* measurements and are the
best way to measure near-surface water vapor, winds, and other variables
that control the exchange of volatiles and dust between the surface and
atmosphere.

Orbital missions can provide information on the global and vertical
structure of the atmosphere, direct measurement of winds, and
information on the spatial distribution of aerosols, water vapor, and
potentially other important trace species. This information leads to the
elucidation of the local through global scale processes that operate to
maintain the climate and transport volatiles and dust. The global
meteorological, radiative, and mass balance observations gathered from
these platforms on daily- to decade-long timescales will establish the
magnitude of inter-annual variability, aid in the identification of the
responsible mechanisms, and demonstrate whether there are any long-term
trends in the present climate system. These observations will also
assist in identifying the causes of the north/south asymmetry in the
nature of the polar caps, and the physical characteristics of the
layered deposits. These data will serve as the foundation for the
development of more realistic models to assess the effects of various
external forcing-factors (such as obliquity and increased atmospheric
pressure) on the climate of Mars.

\(ii\) Upper atmosphere climate and processes

Orbiter missions are also needed to investigate the mean state and
variability of the neutral and plasma environment above \~80 km. These
data will improve our understanding of the coupling of the Martian lower
and upper atmospheres, and characterize the regions of the upper
atmosphere that interact with the solar wind. Also, the global
characterization of the present lower and upper atmosphere structure and
dynamics is required over various timescales (daily, seasonal, and solar
cycle) in order to properly interpret volatile escape measurements and
the subsequent volatile evolution model results. This reemphasizes the
need for a ground-to-exosphere approach to monitoring the Martian
atmospheric structure and dynamics.

**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.

**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.**

This investigation necessarily involves study of both the lower and
upper atmosphere. Surface sinks and sources and lower atmospheric
distributions are required to interpret atmospheric escape rates and
upper atmosphere aeronomic processes. Current multi-dimensional
photochemical models predict global distributions of these species. Such
models require validation to confirm key reactions and rates and the
role of dynamics in the transport of these constituents. There is,
however, considerable uncertainty over surface fluxes of major species.
This investigation requires global orbiter observations of neutral and
ion species, temperatures, and winds in the lower and upper atmospheres,
and the systematic monitoring of these atmospheric fields over multiple
Mars years to capture inter-annual variability induced by the solar
cycle, seasons, and dust storms.

**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 focus on quantitative measurements
(concentrations and isotopic compositions) of important atmospheric
gases in the atmosphere and trapped in surface materials. It also
requires 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 requires high-precision
isotopic measurements of the atmosphere.

**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.**

These measurements will provide crucial constraints to atmospheric
evolution models that extrapolate these rates to determine past
climates. This investigation requires global orbiter observations of
neutral and plasma species, crustal magnetic fields, temperatures, and
winds in the extended upper atmosphere. The systematic monitoring of
these fields over multiple Mars years is needed to capture the
inter-annual variability induced by the solar cycle, seasons, and dust
storms. This investigation also requires more thorough and
higher-resolution measurements of crustal magnetic fields.

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).

**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 requires determining
sedimentary stratigraphy and the distribution of aqueous weathering
products.

**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 requires 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.

**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 will
yield the critical information necessary to improve the likelihood of
successful execution of missions in the Martian environment.
Investigations 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.

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

The lowest portion (\<5km) of the atmosphere can be highly turbulent.
Horizontal and vertical winds in this region represent a significant
risk to spacecraft Entry, Descent, and Landing (EDL) and the operation
of aerial platforms (balloons and aeroplanes). The turbulence also
transports heat, so is a concern for thermal design. The turbulence is
driven by thermal contrasts between the surface and the atmosphere, and
mechanical interactions between the mean wind and the rough planetary
surface. This investigation is designed to probe the connections between
surface temperature, the modification of surface and air temperatures by
aerosol radiative heating, and the dynamical and thermal state of the
lower atmosphere.

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

Mars exhibits significant seasonal and dramatic, episodic changes in the
state of the atmosphere. Of great concern to the operation of surface
and near-surface spacecraft, and for aerobraking, aerocapture, or
aeropass maneuvers, is the onset of regional and global dust storms. The
mechanisms of storm development are unknown at this time, and thus
current models cannot predict them. Prediction will require much further
study of these events, while early observation will greatly mitigate
them. It is critical for support of Mars missions that
continuously-operational, meteorological assets be maintained in Martian
orbit to improve our understanding of the processes so that we can
better predict atmospheric conditions at the time a spacecraft arrives
and to make observations near the time of entry.

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

Aerobraking, aerocapture, and aeropass operations use the atmosphere as
a brake. These operations are safest when the drag imparted by the
atmosphere can be accurately estimated ahead of time. Unfortunately, the
Martian atmosphere exhibits substantial variations in density at a given
geometric height due to the influence of the diurnal cycle, seasonal
cycle, large-scale atmospheric circulation, and the propagation of
waves. Mapping and understanding the processes responsible for the
density variations in the upper atmosphere is critical to high-precision
spacecraft trajectory planning. For example, techniques for measuring
and predicting the mass density on time scales of hours to days are key
requirements for aerobraking. This information is also important for
mission planning (e.g., estimating the amount of fuel needed throughout
mission life).

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

The constraint of mass density variations at high altitudes is important
for precision targeting of orbital observations and for long-term
orbital stability required to meet planetary protection mandates.

**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 provides 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, which in many ways make it appear more
Earth-like and sets it apart from the other planet, 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 will 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 requires global observations using subsurface sounding and remote
sensing, coupled with detailed local and regional sounding and
measurements.

**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.**

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).

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

The evolution of the surface, interior, and surface 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.

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

This investigation includes 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, may be prime sites
to investigate for life. This investigation requires global imaging at a
range of wavelengths, geologic mapping, in-situ and remote techniques
for distinguishing igneous and sedimentary rocks, evaluation of current
activity.

**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 requires
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.

**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.

**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.

**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 the 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.

**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.

**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.

**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.

**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 for 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.

**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.

**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.

**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.

GOAL IV: PREPARE FOR HUMAN EXPLORATION

Robotic missions serve as logical precursors to eventual human
exploration of space. In the same way that the Lunar Orbiters, Ranger
and Surveyor landers paved the way for the Apollo moon landings, a
series of robotic Mars Exploration Program missions is charting the
course for future human exploration of Mars. Goal IV of the MEPAG
document differs from the previous Goals in that it addresses science
and engineering questions specific to increasing the safety, decreasing
the cost, and increasing the productivity of human crews on Mars. To
address these issues this section 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).

The 2004 National Vision for Space Exploration provides guidance for a
broad range of human and robotic missions to the moon, Mars and
destinations beyond. Robotic missions serve as one component of a
"system of systems", the sum of which work together to accomplish the
goals of implementing a safe, sustained, and affordable robotic and
human program to explore and extend human presence across the solar
system and beyond. One of the Vision's main points is to conduct robotic
exploration of Mars to prepare for human exploration, and NASA has
adopted a "level zero" requirement to "conduct robotic exploration of
Mars to search for evidence of life, to understand the history of the
solar system, and to support future human exploration activities."
Specifically, robotic precursor missions will be used in part to acquire
and analyze data for the purpose of reducing cost and risk of future
human exploration missions, to perform technology and flight system
demonstrations for the purpose of reducing cost and risk of future human
exploration missions, and to deploy infrastructure to support future
human exploration activities.

As part of the momentum associated with the 2004 National Vision for
Space Exploration, in 2004-2005 MEPAG undertook a major reassessment of
the issues associated with preparing for the human exploration of Mars.
This work is summarized in the following two documents, which represent
analyses of Goal IV Objective A, and Goal IV Objective B, respectively.
The logic associated with the investigations and measurements is
described in these reports.

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.

Hinners, N.W., Braun, R.D., Joosten, K.B., Kohlhase, C.E., and Powell,
R.W., (2005), Report of the MEPAG Mars Human Precursor Science Steering
Group Technology Demonstration and Infrastructure Emplacement (TI)
Sub-Group, 24 p. document posted July, 2005 by the Mars Exploration
Program Analysis Group (MEPAG) at
<http://mepag.jpl.nasa.gov/reports/index.html>.

**Objective A. Obtain knowledge of Mars sufficient to design and
implement a human mission with acceptable cost, risk and
performance.**[^4]

*[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 terrane:

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 select high latitude polar deposits for a
human landing site, geotechnical data will 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 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 is 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 will 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 is required.*

**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
requires sample return and analyses in terrestrial laboratories. *

*[Note #8]{.underline}: The samples can 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 is 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 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.

*[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.  (May require Mars Sample Return (MSR)).

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 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

c.  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 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 can survive and reproduce on
    the martian surface.

**[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 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.**

[Measurements:]{.underline}

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.

b\. Determine variation in in-situ internal angle of friction of
regolith for dust dunes and dust pockets to within 1 degree.

c\. Determine regolith cohesion for rocky areas, dust dunes and in dust
pockets to within 0.1 kN m-2.

d.  Precision imaging to Mars Reconnaissance Orbiter High Resolution
    Imaging Science Experiment (MRO HiRISE) standards (30 cm/pxl) for
    selected potential landing sites

For basic design of mobility systems, the following measurements are
needed (not just at the dust pockets and dunes, but also on the
consolidated regolith surfaces where we may do most of the driving): (i)
rolling resistance (the torque that regolith applies to a rolling wheel
while driving), (ii) traction test (torque required to spin a wheel
while the rover is held stationary), and (iii) shape/size of the
resulting wheel ruts while driving normally.

*Note #11: These three things will probably be measured routinely on all
Mars rovers.*

*Note #12: ISRU excavation could require hauling larger loads
(regolith/ice payload) than what we have ever hauled in the past.
Therefore they will need these data to properly design wheels and chases
(e.g., rover and large structure mobility systems), avoiding
energy-wasteful designs or risk of getting bogged down.*

**[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:

```{=html}
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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

```{=html}
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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.

Table 1. Summary of Location Considerations for high-priority human
Precursor Investigations.

+---------------------+-------+------------+-----------+--------------+
| Investigation       | Carry | Me         | Mea       | Precursor    |
|                     | out   | asurements | surements | measurement  |
|                     | once  | needed at  | needed    | needed at    |
|                     | at    | multiple   | over time | the human    |
|                     | Mars  | sites      |           | landing site |
+---------------------+-------+------------+-----------+--------------+
| 1Aa-b. Basic        | ### X | **?**      |           |              |
| dust/regolith       |       |            |           |              |
| properties          |       |            |           |              |
+---------------------+-------+------------+-----------+--------------+
| 1Ac. Airborne dust  | ### X | ###        |           |              |
| in dust storms      |       |            |           |              |
+---------------------+-------+------------+-----------+--------------+
| 1B. Atmospheric     | ###   | ### X      | ### X     |              |
| variations          |       |            |           |              |
+---------------------+-------+------------+-----------+--------------+
| 1Ca.                | ### X | ###        | ###       | ###          |
| Biohazard\--dust    |       |            |           |              |
+---------------------+-------+------------+-----------+--------------+
| 1Cb.                | ###   | ###        | ###       | ### X        |
| Biohazard---site    |       |            |           |              |
| spec.               |       |            |           |              |
+---------------------+-------+------------+-----------+--------------+
| 1D. Water for ISRU  | ###   | ### X      | ###       | ### X        |
+---------------------+-------+------------+-----------+--------------+
| 2\. Toxicology of   | ### X | ###        | ###       | ###          |
| dust                |       |            |           |              |
+---------------------+-------+------------+-----------+--------------+
| 3\. Atmospheric     | ###   | ### X      | ### X     | ###          |
| electricity         |       |            |           |              |
+---------------------+-------+------------+-----------+--------------+
| 4\. Forward PP      | ### X | ###        | ### X     | ### ?        |
+---------------------+-------+------------+-----------+--------------+
| 5\. Ionizing        | ### X | ###        | ### X     | ###          |
| radiation           |       |            |           |              |
+---------------------+-------+------------+-----------+--------------+
| 6\. Terrain         | ### X | ### ?      | ###       | ### ?        |
| trafficability      |       |            |           |              |
+---------------------+-------+------------+-----------+--------------+
| 7\. Dust storms     | ### X | ###        | ### X     | ###          |
+---------------------+-------+------------+-----------+--------------+

**[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.

#### [Prioritization Criteria]{.underline}

The following criteria were used, assuming a series of robotic flight
missions preceding the first human mission, to establish the priority of
importance, when the validation should be done and whether or not the
validation must be done on a Mars mission[:]{.underline}

1.  Priority: The anticipated magnitude of the risk and/or cost
    reduction of human missions to Mars.

2.  Timing: The likely timing of the technology flight mission needed
    relative to the first human mission:

    -   Early: to influence architecture decisions (14 to 20 years
        prior)

    -   Mid: to influence mission and flight system design decisions (8
        to 12 years prior)

    -   Late: to influence operability decisions (4 to 6 years prior)

3.  Venue: Some technology validations can be accomplished less
    expensively and more comprehensively on other than Mars missions.
    Required technologies were therefore grouped according to whether
    they can best be performed (in decreasing order of cost) :

> a, At or in transit to/from Mars
>
> b\. On the Moon
>
> c\. In Earth orbit
>
> d\. On Earth

Only those technology and infrastructure items requiring demonstration
at Mars, 3a, are listed below as candidates for Mars human precursor
missions. Those not requiring development and demonstration on Mars
missions, 3b,c and d, are prioritized and described in the associated
white paper. Additionally, a set of suggested near-term systems studies
has been defined which will, when completed, enable refined definition
and prioritization.

The following is a prioritized grouping 1 through 3; there is no
sub-prioritization within the groups.

**[T/I Demonstration 1A.]{.underline} Conduct a series of three
aerocapture flight demonstrations:**

1.  70 deg sphere cone shape (robotic scale) to demonstrate aerocapture
    at Mars (Early).

2.  New entry vehicle configuration suitable for human exploration
    (robotic scale) aerocapture at Mars (Mid).

3.  New entry vehicle configuration suitable for human exploration
    (larger scale, end-to-end mission sequence) aerocapture at Mars
    (Late).

> A primary challenge of flight missions to Mars is decelerating the
> incoming spacecraft. There are four primary options:

1.  Chemical propulsion

2.  Aerobraking

3.  Direct entry

4.  Aerocapture

Given the expected mass of human missions, the required mass of
propellant to use Option #1 is large---this could lead to severe cost
and operational problems. Aerobraking (Option #2) is the approach in
which multiple orbits are used, extending over months, to gradually
lower the apoapsis as was done on the Mars Global Surveyor (MGS) and
Odyssey missions. The disadvantage of using this for human missions is
that it takes considerable time, which is likely to be incompatible with
other constraints on the human mission. Direct entry (Option #3), as
used by Pathfinder and Mars Exploration Rover (MER) missions, is at the
extreme variation of aeroassist in which entry capsules are decelerated
to the point of parachute deployment. However, the \"g\" forces involved
in direct entry are excessive relative to human tolerance. Aerocapture
(Option #4) is an intermediate form of aeroassist in which the vehicle
is captured into low Mars orbit on the first atmospheric pass.
Aerocapture requires accurate navigation, attitude control, and an
effective aeroshape design. It is thought that it will take three flight
missions to develop this technology to a level of confidence that one
would be prepared to use it on a human mission.

**[T/I Demonstration 1B.]{.underline} Conduct a series of three in-situ
resource utilization technology demonstrations:**

> \(1\) ISRU Atmospheric Processing (Early)
>
> 1\. Demonstrate acquisition and separation of atmospheric resources
> for life support & propulsion/fuel cell power systems. Demonstrate
> production and storage of critical mission consumables (oxygen, fuel,
> life support gases, etc.).
>
> 2\. Preliminary Experiment Requirements: Mass \<25 kg; Power \<50 W;
> Production rate \> 20 gm/day O2 or O2/fuel;
>
> 3\. Duration \> 30 sols
>
> \(2\) ISRU Regolith-Water Processing (Early)
>
> 1\. Perform excavation of Mars regolith down to 2 meters, and
> demonstrate regolith handling and transport capabilities to regolith
> processing unit. Perform in-situ measurements to support design of
> robotic and human scale excavation systems. Perform regolith
> processing to extract and separate water from the regolith in multiple
> batches to obtain TBD ml of water. Perform in-situ measurements of the
> water & volatiles released during processing. Perform processing on
> the water to produce oxygen, hydrogen, and methane.
>
> 2\. Requirement for mobility is dependant on results from '07 Phoenix
> and '09 Mars Science Laboratory (MSL) missions
>
> 3\. Preliminary Experiment Requirements: Mass \<30 kg; Power \<50 W;
> Production rate \> 10 cm3/day of water;
>
> 4\. Duration \> 15 sols
>
> \(3\) ISRU Human-Scale Application Dress Rehearsal (Late)
>
> 1\. The primary purpose of this demonstration is to "buy down" risk by
> operating a complete end-to-end ISRU system (1/20 scale, duration 80
> sols) culminating in a significant application such as producing
> propellants for a Mars Hopper, and the subsequent operation of the
> Hopper. An additional goal is to make a first attempt to gather and
> utilize regolith for construction purposes, e.g., radiation shielding,
> at a small scale. This will be closely coupled to excavation, material
> transport, and beneficiation techniques derived from Regolith-Water
> Processing demonstration.
>
> 2\. Perform in conjunction with other human mission subsystems if
> possible, e.g.., RTG power system, fuel cell power system,
> oxygen/methane propulsion, landing hazard avoidance.
>
> 3\. Preliminary Requirements: 0.25 to 0.05 kg of O2-fuel/hr, Power 200
> to 400 W, Duration 80 sols min.

It is not yet known when, if at all, ISRU will be a part of human
missions to Mars. However, ***if** ISRU is to be fully assessed,* the
demonstrations are considered to be required, e.g., they are necessary
to reach a decision to proceed or not with ISRU, and constitute yes/no
gates. These demonstrations would need to be carried out in parallel
with Goal IVA Investigation #1D, which relates to discovery and
characterization of the water deposits.

Currently there are no criteria for where human exploration will occur
on Mars. If ISRU is a potentially enabling factor in affordability or
safety, then resource location and feasibility will be a driver in site
selection. Alternatively, if a negative decision regarding ISRU were to
be made on the basis of relative cost or risk alternatives, then these
demonstrations become moot.

In addition to the exploration-related questions in Goal IVA-1D, the
practicalities of implementing ISRU are serially dependent upon two
fundamental factors: 1). Is the potential resource \"economically\"
accessible, meaning can enough be procured at acceptable cost, to more
than offset the cost of bringing it from Earth? 2). Can sufficient
supplies of the end-product be produced, stored and transferred with low
risk? The most obvious uses of in situ resources are those that focus on
obtaining resources that, if they have to be launched from Earth, are
large mass, thus cost, drivers. Typically water, oxygen and fuels are
leading candidates for ISRU. Water has immediate use as such for crew
life support and hygiene. It also serves as a source for hydrogen and
oxygen. The atmosphere of Mars contains carbon dioxide, traces of water
vapor, and inert gases (useful for diluting atmospheric oxygen). The
carbon dioxide can be a source of oxygen and can be reacted with
hydrogen to make fuel.

**[T/I Demonstration 1C.]{.underline} Demonstrate an end-to-end system
for soft, pinpoint Mars landing with 10m to 100m accuracy using systems
characteristics that are representative of Mars human exploration
systems. (Mid)**

Pinpoint landing systems for human exploration vehicles are required for
two reasons. First, safety and risk mitigation. It is likely that
pre-positioned supplies and emergency abort systems will be located on
Mars prior to arrival of humans. Landing near such assets increases the
likelihood of successfully accessing such in an emergency and enhances
mission efficiency in non-emergency situations. Second, it is likely
that a site selected for human exploration will be selected because
there is a specific science objective to be accomplished. Such could be
sufficiently localized that landing in proximity increases the
probability of successful science accomplishment.

**[T/I Demonstration 2A.]{.underline} Demonstrate continuous and
redundant in-situ communications/navigation infrastructure (Early).
Deploy in full-up Precursor Test Mission (Late).**

Mission safety and effectiveness will require the development of high
band-width continuous and redundant communications. This support for
human mission can be met, e.g., by a pair of longitudinally-offset
areostationary relay satellites

**[T/I Demonstration 2B.]{.underline} Investigate long-term material
degradation over times comparable to human mission needs. (Mid)**

Our current state of knowledge of the Mars environment is inadequate to
confidently design essential space systems to be used on the martian
surface. These include EVA suits, habitats and ancillary systems,
including mobility.

It is essential to verify the capability of materials under
consideration for Mars surface operations to tolerate long term exposure
(years) to Mars environmental phenomena using coupon, component,
subsystem and system level tests on Mars. Phenomena include: radiation;
temperature extremes and cycles; wind; atmosphere chemical and
electromagnetic properties; regolith and dust chemical, mechanical, and
electromagnetic properties; and Mars biology (if any). An LDEF (Long
Duration Exposure Facility) should be considered (implied return of test
samples).

**[T/I Demonstration 3.]{.underline} Develop and demonstrate accurate,
robust and autonomous Mars approach navigation. (Mid)**

This is a mission safety item. It would provide a backup/replacement to
Deep Space Network (DSN)-based terminal navigation for a mission
time-critical event (e.g., Mars Orbit Insertion (MOI) or aerocapture).

[^1]: MEPAG (2001), Scientific Goals, Objectives, Investigations, and
    Priorities, in [Science Planning for Exploring Mars]{.underline},
    JPL Publication 01-7, p. 9-38. Available on the web at
    http://mepag.jpl.nasa.gov/reports/index.html.

    ^2^ MEPAG (2004), Scientific Goals, Objectives, Investigations, and
    Priorities: 2003, G. J. Taylor, ed., 23 p. white paper posted
    07-16-04 by the Mars Exploration Program Analysis Group (MEPAG) at
    http://mepag.jpl.nasa.gov/reports/index.html.

[^2]: ^3^ MEPAG (2005), Mars Scientific Goals, Objectives,
    Investigations, and Priorities: 2005, 31 p. white paper posted
    August, 2005 by the Mars Exploration Program Analysis Group (MEPAG)
    at http://mepag.jpl.nasa.gov/reports/index.html.

[^3]: Regolith. As used in this document, a general term referring to
    the mantle of fragmental, unconsolidated to partially cohesive
    material, of any origin (in-situ, residual, or transported) that
    nearly everywhere underlies the surface of Mars (after Glossary of
    Geology).

[^4]: [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.*

    *[Assumptions]{.underline}:*

    *The first human mission includes a landed human element.*

    *The possibilities of "short-stay" (\~30 sols) and "long-stay"
    (\~300 sols) are both under consideration, so the precursor program
    needs to support both.*