# Scientific Goals, Objectives, Investigations, and Priorities: 2003

MEPAG (Mars Exploration Program Analysis Group)

March 15, 2004

This report was prepared by the MEPAG Goals Committee:

> G. Jeffrey Taylor, University of Hawai'i, Chair
>
> **Life:**
>
> Dawn Sumner, University of California, Davis
>
> Andy Steele, Carnegie Institution of Washington, Washington, DC
>
> **Climate:**
>
> Steve Bougher, University of Michigan
>
> Mark Richardson, California Institute of Technology
>
> Dave Paige, University of California, Los Angeles
>
> **Geology & Geophysics:**
>
> Glenn MacPherson, Smithsonian Institution
>
> Bruce Banerdt, Jet Propulsion Laboratory
>
> **Human Exploration:**
>
> John Connolly, Johnson Space Center
>
> Kelly Snook, Ames Research Center and Johnson Space Center

# 

# This report has been approved for public release by JPL Document Review Services (Reference \# CL#04-0387), and may be freely circulated. Suggested citation to refer to this document:

**MEPAG (2004), Scientific Goals, Objectives, Investigations, and
Priorities: 2003. Unpublished document,
http://mepag.jpl.nasa.gov/reports/index.html.**

# PREAMBLE

This document updates the goals for Mars exploration as reported in
*Scientific Goals, Objectives, Investigations, and Priorities*, edited
by R. Greeley under the auspices of the Mars Exploration Program
Analysis Group (MEPAG), which was based on discussions in 2000 and then
published in 2001. The original goals document has helped shape
priorities for the exploration of Mars. Recent successful missions and
analysis of data from them and previous missions have led to the need to
update the goals and objectives of Mars exploration. These revisions are
done in the context of the Mars program and its relationship to the
solar system exploration program as described in two recent
documents\--the Solar System Exploration Roadmap published by the NASA
Office of Space Sciences (Code S) and the report published by the NAS
National Research Council on New Frontiers in the Solar System: An
Integrated Exploration Strategy (the so-called Belton committee report).
The plan is that MEPAG will update the goals approximately every two
years, corresponding to each Mars launch opportunity. As with the 2001
version, the goals were revised with extensive participation from the
community of scientists and engineers active in Mars exploration.

The MEPAG Chair and steering committee appointed a subcommittee of the
Mars Exploration Program Analysis Group (MEPAG) to carry out the
revisions. The goals committee met through weekly teleconferences from
mid-January 2003 leading up to the MEPAG meeting held February 26-27,
2003, in Tempe, Arizona. The committee identified important potential
revisions during this time period and outlined a series of issues to
discuss at the Tempe MEPAG meeting. Over 100 Mars experts, in addition
to program managers, attended (see Appendix A). Participants discussed
goals revisions in four breakout groups, corresponding to the four major
goals for Mars exploration. A primary objective of the meeting was to
identify central issues and questions to discuss with the entire Mars
exploration community through an online survey that the Geophysical
Laboratory of the Carnegie Institution of Washington managed and
co-sponsored.. Over 300 individuals participated in the survey. A draft
report was then circulated via e-mail to the Mars Community and
discussed in detail during the September 10-11 MEPAG meeting in
Pasadena, California. Over 150 scientists attended the Pasadena meeting,
in addition to program managers. A revised document was circulated to
the community again in October 2004, which resulted in insightful
comments from about 40 individuals. Revised versions were circulated
among members of the Goals Committee and the MEPAG Executive Committee,
and approved by the MEPAG Executive Committee on 26 February 2004. Thus,
the updated goals outlined here represent the consensus view of a broad
cross section of the Mars exploration community.

[Prioritization]{.underline}

The four goals described below are ***not*** listed in priority order.
Each is important and they are interrelated. All must be pursued
aggressively to understand the entire complex Mars system and how it
operated through time, and to prepare for human exploration of Mars.
However, within each goal, the objectives and investigations ***are***
listed in priority order. Table 1 lists the prioritization criteria.
There is an enormous diversity of opinion among individual scientists
regarding these priorities, and this intellectual diversity is extremely
healthy for the Mars Exploration Program. However, to help guide
implementation and planning, we have put a major effort into
establishing consensus statements of priority within each goal area.

**Table 1.** Prioritization criteria

  ------- --------------------------------------------------------------------
  **1**   Degree of alignment with the high-level objectives of NASA and the
          Office of Space Science, such as the Solar System Exploration
          Roadmap (2003), as well as guidance from external groups, including
          the Solar System Decadal Survey (2002).

  **2**   Expected scientific value, if completed successfully

  **3**   The feasibility of implementing the necessary measurements (includes
          cost, risk, and technology readiness of missions and instruments)

  **4**   Any logic associated with the need to have investigations done
          sequentially
  ------- --------------------------------------------------------------------

The online survey was particularly useful in establishing these
priorities. No attempt was made to weight the priorities, but it is
clear that the highest priority objective or investigation is not ten
times more important than the lowest one.

As noted in the first MEPAG goals report, completion of all the
investigations will require decades of studying Mars. Many
investigations may never be truly complete (even if they have a high
priority). Thus, evaluations of prospective missions 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, as many other factors come into play in
the overall Mars Program. On the other hand, we have tried to identify
cases where one investigation should be done before another. In such
cases, the investigation that should be done first was given a higher
priority, even if in the long run the second investigation will be more
important.

[Future Studies]{.underline}

[Technology development]{.underline}. Even a cursory reading of the
goals, objectives, and investigations outlined below will show that
several crucial technical capabilities need to developed. 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*; hence we need to be
able to make some measurements over a long period of time (at least a
Martian year). This applies particularly to climate studies. (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 absolutely 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.

# [Measurements]{.underline}. In the previous edition of this document (MEPAG, 2001), the measurements that could contribute to each investigation are listed. Within each investigation, MEPAG chose not to place the measurements in priority order, in large part because of the difficulty of establishing systematic and impersonal criteria for doing so. In planning for the current revision of the "Goals" document, at the Sept. 2003 MEPAG meeting MEPAG adopted the position that any listing of measurements related to an investigation would be as examples only. It is not MEPAG's intent to discourage the innovation of the science community in developing additional measurements that can contribute to these investigations as science and technology evolve in the future. Scientists and engineers working with this document are specifically ENCOURAGED to apply their creativity to improved measurement approaches. 

# In addition, an aspect of the measurements that will contribute heavily to forward program planning is the precision, accuracy, and detection limits required to achieve the stated objectives.

# These additions are planned for a future online addendum to this Scientific Goals, Objectives, Investigations, and Priorities: 2003 document. We anticipate that in the addendum the measurements will be listed as examples, not as specific requirements. The consensus view is that such detailed requirements ought to be defined by Science Definition Teams and Payload Science Integration Groups for program missions and by the Science Teams for Scout missions.

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

Determining if life ever arose on Mars is a challenging goal. The
essence of this goal is to establish that life is or was present on
Mars, ***or*** if life never was present to understand the reasons why
Mars did not ever support its own biology. 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 prioritzation 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. 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.

### **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
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} Oxidation chemistry of 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 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 space
craft 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.

### **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 micro-climates.**

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 distributions of key photochemical species
(O~3~, H~2~O~2~, CO, OH, 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 at both polar and
mid-latitude 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* measurements of 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, and
subaerial sedimentary processes and their evolution 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. Eolian sediments record
a combination of globally-averaged and locally-derived fine-grained
sediments and weathering products. Sedimentary layers are also likely
sites of past or present aquifers. Understanding sedimentary processes
requires knowledge of the age, sequence, lithology, and composition of
sedimentary rocks (including chemical deposits); 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.

**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,
geologic mapping, techniques for distinguishing igneous and sedimentary
rocks, evaluation of current activity.

**5. [Investigation:]{.underline} Characterize surface-atmosphere
interactions on Mars, including polar, eolian, chemical, weathering, and
mass-wasting 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 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
remote sensing of surface and subsurface, 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 subsurface sounding, 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 global topographic
data combined with high-resolution images, 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 soil. 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 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
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 (Objective A), and the demonstrations of critical technologies
that must be validated in the actual Martian environment (Objective B).

Note: As MEPAG was finalizing this document, discussion of the new
vision and direction for NASA was focusing much attention on
human-exploration goals and objectives, and on the technology necessary
to achieve them.  It is clear that such increased attention will allow
us to identify or clarify additional issues that enable human
exploration. Thus, we fully expect that the issues described in this
section will evolve considerably over the coming months and years, and
the present discussion should be taken as a snapshot perspective rather
than as a definitive discussion that holds far into the future.

A.  **Objective: Acquire Martian environmental data sets (investigations
    listed in priority order)**

Scientist-astronauts on the Martian surface will add a new dimension of
discovery and exploration to a Mars science program. The safety and
productivity of these human explorers requires an understanding of the
hazards present in the Martian environment, and the design of systems to
mitigate them. Quantitative models of the Martian atmosphere, surface,
and subsurface will increase the safety of human missions, and help to
identify resources that may greatly decrease the cost of human
exploration.

1.  **[Investigation]{.underline}**: **Determine the ionizing radiation
    environment at the Martian surface and the shielding properties of
    the Martian soil and atmosphere.**

The propagation of high energy particles through the Martian atmosphere
must be understood, and the measurement of secondary particles must be
made at the surface to determine the buffering (or amplifying) effects
of the Martian atmosphere, to understand the backscatter effects of the
regolith, and to validate radiation transport models for the Martian
atmosphere. Simultaneous monitoring of the ionizing radiation from
Mars\' orbit and at the surface to determine the shielding component of
the atmosphere is desirable. Soil and dust from the Martian surface
offer a readily available source of shielding material. The properties
of the soil that contribute to its shielding effectiveness must be
quantified to establish the transport of high-energy particles. UV is
also a source of ionizing radiation and knowledge of the UV spectrum at
the surface is required.

2.  **[Investigation:]{.underline} Determine the chemical and
    toxicological properties of Martian surface materials.**

Measurements related to toxicity and reactivity are needed to develop
hazard mitigation strategies to ensure the safety of human explorers on
the Martian surface. Surface materials include all soil, dust, ice,
water or atmospheric aerosols that human explorers may come in contact
with. Measurements require *in-situ* surface and subsurface sample
analysis or return of environmentally preserved samples if *in-situ*
measurement is not possible. Multiple sites should be sampled including
designated human missions sites.

3.  **[Investigation:]{.underline} Measure atmospheric parameters and
    variations that affect atmospheric flight and surface systems.**

Upper level atmospheric parameters play a critical role in planning safe
entry, descent, and landings for human missions. Knowledge of
near-surface (boundary layer) properties is needed for safe design and
operation of human surface systems.

4.  **[Investigation:]{.underline} Understand the characteristics,
    accessibility, and distribution of water resources in regolith, and
    Martian groundwater systems.**

Water is a principal resource to humans, and a critical element in
surface operations. Measurements require geophysical investigations and
*in-situ* sample analysis.

5.  **[Investigation:]{.underline} Measure the engineering properties of
    the Martian surface, and characterize topography, and other
    environment characteristics of candidate outpost sites.**

Soil and surface engineering data are needed to eliminate uncertainty in
the design of landers, mobile systems, EVA suits and tools, and power
and thermal systems. Also, site certification for human outposts
requires a set of data about the specific site that can best be
performed by surface investigations. Measurements require *in-situ*
analysis at individual, specific sites.

6.  **[Investigation:]{.underline} Determine electrical effects in the
    atmosphere**.

Mixing dust and sand of various compositions and sizes has the potential
to develop electric charge, and in "dust devils" and dust storms to
create large electric fields. Electrostatic charging and associated
electrical discharges pose possible hazards to surface operations
through unanticipated arcing, dust adhesion, and radio frequency (RF)
contamination (charge grain/antenna incidence). These effects become
particularly significant in a low pressure (low Paschen breakdown)
atmosphere.

**B. Objective: Conduct in-situ engineering science demonstrations
(investigations listed in priority order)**

Technology validation and engineering science demonstrations are needed
to reduce the risk inherent in new, unproven technologies. Demonstrating
the performance of these technologies in the Martian environment prior
to their use on human flights will reduce risk and improve confidence in
mission safety. The investigations listed in this section were chosen
because of their high degree of interaction with the Martian
environment, and because of the uncertainty of whether analog testing
would supply sufficient data to reduce risk and cost, or increase
performance of these systems.

4.  **[Investigation:]{.underline} Demonstrate terminal phase hazard
    avoidance and precision landing.**

System testing is necessary to decrease the risks associated with soft
landing, and to enable pinpoint landing. Validation requires flight
demonstration during terminal descent phase.

5.  **[Investigation:]{.underline} Demonstrate mid-range lift-to-drag
    (mid-L/D) aeroentry /aerocapture vehicle flight.**

Mid-L/D (0.4-0.8) aeroentry shapes will be required as payload masses
increase. Mid-L/D aeroassist increases landed vehicle payload
performance and landing precision. Validation requires flight
demonstration during aeroentry phase of the mission. Flight validation
must be performed with a vehicle size that yields test results scalable
to vehicle performance for a human mission.

6.  **[Investigation:]{.underline} Demonstrate high-Mach deployable
    aerodecelerator performance.**

Higher ballistic coefficient entry vehicles will result from flying more
massive landers. This will result in higher parachute deployment speeds,
which are beyond the qualification of current parachute systems.
Validation requires flight demonstration during Mars entry phase.

7.  **[Investigation:]{.underline} Demonstrate in-situ propellant
    (methane, oxygen) production (ISPP) and in-situ consumables
    production (ISCP) (fuel cell reagents, oxygen, water, buffer
    gasses).**

The potential for Martian resources to be converted to useable products
needs to be evaluated. Components that directly interact with the
Martian environment should be evaluated in a relevant environment to
determine their performance. End-to-end performance may be evaluated by
acquisition of local resources, processing, storage, and potential use
of end products. Validation requires process verification with
experiments performed *in-situ* to reduce both engineering design
uncertainties and the program risk of incorporating this technology into
future robotic/human missions.

8.  **[Investigation:]{.underline} Demonstrate in-situ water collection
    and conditioning using surface resources*.***

Water concentrations in the Mars surface regolith**,** and concepts to
collect and separate the water**,** should be evaluated in a relevant
environment to determine their performance. Hardware and investigation
objectives can be performed separately or combined and integrated with
other regolith characterization experiments. Validation requires process
verification with *in-situ* experiments to reduce both engineering
design uncertainties and the program risk of incorporating this
technology into future robotic/human missions**.**

9.  **[Investigation]{.underline}: Demonstrate access to subsurface
    resources.**

The Martian subsurface contains potential resources (e.g., water) as
well as potentially important scientific samples. Drilling or other
techniques for accessing the subsurface need to be developed. Validation
requires *in-situ* demonstration.

10. **[Investigation:]{.underline} Demonstrate plant growth in the
    Martian environment.**

Demonstrate the ability of the Martian environment (soil, solar flux,
radiation, etc.) to support life, such as plant growth, to support
future human missions. Validation requires *in-situ* measurements and
process verification.