Appendix III

THE FIRST MARS SURFACE-SAMPLE RETURN MISSION: REVISED SCIENCE
CONSIDERATIONS IN LIGHT OF THE 2004 MER RESULTS

**Mars Sample Return Science Steering Group II (Glenn MacPherson,
Chair)**

*February 16, 2005*

This white paper is incorporated as an appendix within the following
larger document:

MEPAG ND-SAG (2008). Science Priorities for Mars Sample Return,
Unpublished white paper, 73 p, posted March 2008 by the Mars Exploration
Program Analysis Group (MEPAG) at
<http://mepag.jpl.nasa.gov/reports/ndsag.html>.

Recommended bibliographic citation:

MacPherson, Glenn, and the Mars Sample Return Science Steering Group II
(2005). The first Mars surface-sample return mission: Revised science
considerations in light of the 2004 MER results, Unpublished white
paper, 68 p, Appendix III of [Science Priorities for Mars Sample
Return]{.underline}; posted March 2008 by the Mars Exploration Program
Analysis Group (MEPAG) at
<http://mepag.jpl.nasa.gov/reports/ndsag.html>.

**TABLE OF CONTENTS**

[I. Executive Summary 3](#i.-executive-summary)

[II. Introduction 4](#ii.-introduction)

[III. Process 5](#iii.-process)

[IV. Philosophy of this Report 6](#iv.-philosophy-of-this-report)

[V. Scope and Structure of the Report
6](#v.-scope-and-structure-of-the-report)

[VI. Revised Science Considerations Pertaining to Mobility and
Accessibility
6](#vi.-revised-science-considerations-pertaining-to-mobility-and-accessibility)

[VII. Revised Science Considerations Pertaining to Sampling and Sample
handling
16](#vii.-revised-science-considerations-pertaining-to-sampling-and-sample-handling)

[VIII. Revised Science Considerations Pertaining to Forward Organic
Contamination
27](#viii.-revised-science-considerations-pertaining-to-forward-organic-contamination)

[Summary of Organic Contamination Issues and Findings
31](#summary-of-organic-contamination-issues-and-findings)

[IX. Revised Science Considerations Pertaining to Forward Inorganic
Contamination
32](#ix.-revised-science-considerations-pertaining-to-forward-inorganic-contamination)

[X. Site Dependency of Mobility and Sampling Requirements
37](#x.-site-dependency-of-mobility-and-sampling-requirements)

[XI. Summary Findings of MSR SSG II
41](#xi.-summary-findings-of-msr-ssg-ii)

REFERENCES 38

APPENDICES

[Appendix A 44](#__RefHeading___Toc187465122)

[Appendix B 47](#__RefHeading___Toc187465123)

[Appendix C 49](#__RefHeading___Toc187465124)

[Appendix D 55](#__RefHeading___Toc187465125)

# I. Executive Summary

The working concept for a first Mars surface-sample return mission, as
defined in 2002 and named Groundbreaker, envisioned a static lander with
simple sampling tools at the end of an extendable arm, and only an
imaging camera for on-board science instrumentation. The experience
during 2004 with the Opportunity Lander on Mars forced a rethinking of
the Groundbreaker concept: had Groundbreaking Mars Sample Return (MSR)
landed precisely where the Opportunity Lander did, the spectacular
layered deposits within Eagle Crater would have been out of reach by the
sampling arm and therefore inaccessible.

In order for the first MSR to be capable of taking maximum scientific
advantage of the evaporite stratigraphy such as that exposed at
Meridiani, the Groundbreaker MSR concept should be revised to
accommodate small "Fetch" rovers equipped with small coring devices for
sampling. On-board scientific instrumentation should still be kept to an
absolute minimum, such as a color imaging camera.

The potential for a previous mission (e.g., MSL 2009) to collect and
physically cache samples for retrieval by MSR is an option that should
be kept open and studied in more detail, but it should not be imposed as
a requirement on MSR.

Cores of layered samples should, if at all possible, be separately
stored and isolated. Active temperature control of the samples during
the return mission would not be required. However, the discovery by
Opportunity of abundant sulfur-bearing compounds on Mars makes it very
important that passive controls be employed to retain the samples at \<
20oC or below if at all possible, to prevent the dehydration of possible
magnesium sulfate species that might in turn lead to degradation or even
cross-contamination of samples.

# II. Introduction

In 2002, NASA's Mars Exploration Program chartered a group of scientists
to define the science floor for a Mars surface sample return mission:
one that would be relatively simple and low cost (in comparison with
industry proposals involving fully mobile rovers and robust on-board
science packages), but still achieve important Mars science goals. This
group, designated the Mars Sample Return Science Steering Group (MSR
SSG), was formally a subcommittee of the Mars Exploration Program
Analysis Group (MEPAG). The MSR SSG concluded that a static lander,
having very simple sampling tools at the end of an extendable arm and no
on-board science instrumentation other than an imaging camera, would
achieve important Mars science objectives (as defined by the MEPAG)
relating to both geology and astrobiology, provided that: (1) the lander
went to a location within a geologic unit believed (on the basis of
previous orbital or landed missions) to have biologic potential; and (2)
the lander collected small pebbles in addition to local regolith. This
concept, titled Groundbreaking MSR, served for two years as the
reference at JPL for planning and budgeting a possible Mars sample
return mission.

Early in 2004, the two Mars Exploration Rovers landed safely on the
surface of Mars. The second to land, Opportunity, ended up inside a
small impact crater. Exposed within the crater are finely laminated
sedimentary rocks whose chemistry indicates them to be evaporitic in
origin. This remarkable and unexpected finding was enabled by the
ability of the rover to travel to the outcrops and analyze them. Had
Opportunity instead been the Groundbreaker MSR mission, the layered
deposits would have been out of reach of the extendable arm.

![](media/image1.pct)

This event suggested that a rethinking of the Groundbreaker concept was
in order, and in July of 2004 a second MSR SSG was created with the task
of re-examining the science goals of a first Mars sample return mission.
Unlike the first MSR SSG, this second group was not tasked with costing
out a revised mission. The active components of the charter for MSR SSG
II are given below; the complete charter is given in Appendix B.

# III. Process 

The MSR SSG II met for the first time on August 25-26, 2004, at the Jet
Propulsion Lab in Pasadena CA. At that meeting, four separate subgroups
were established to consider the topics of (1) forward organic
contamination; (2) forward inorganic contamination; (3) mobility and
accessibility; and (4) sampling and sample handling. During September
and the first half of October, each of the four subgroups held
approximately weekly teleconferences to conduct their deliberations,
supplemented by extensive e-mail communication. The MSR SSG II met for
the second time on October 21-22, 2004, again at the Jet Propulsion Lab
in Pasadena CA, at which time the four subgroup leads presented their
preliminary findings. The subgroup leads delivered draft written reports
to SSG Chair MacPherson by Mid-November. The four sub-group reports were
bundled together and submitted to the MEPAG Executive Committee by the
end of November. A complete draft document containing the SSG findings
was be presented to the full MEPAG at its meeting on February 16-17,
2007 in Crystal City, Virginia. Comments received at that meeting will
be incorporated into a final report.

The membership of the MSR SSG II and of the 4 subgroups is given in
Appendix A.

# IV. Philosophy of this Report 

This report is intended to supplement rather than replace the original
Groundbreaking Sample Return Report. It is predicated on the assumption
that the results of the MER mission are so exciting and compelling that
the agency support for a sample return mission be enhanced to the extent
that the MSR concept itself would be financially enabled to allow for
mobility. Thus none of the recommendations herein should be construed as
requirements that financially threaten the very existence of a Mars
sample return mission. The original Groundbreaking concept remains
valid, but the MER experience indicates that taking
[maximum]{.underline} scientific advantage of anything like the
Meridiani site would entail adding limited mobility back into the
mission.

# V. Scope and Structure of the Report 

The diverse science issues taken up by the SSG were considered in far
more detail than was possible in the original Groundbreaking MSR report.
Therefore the tasks were divided into four parts and the committee
divided into four subgroups. Owing to the limited size of the overall
committee, most members belonged to two subgroups and thus there is
significant overlap of subcommittee membership (Appendix A).

The subgroup leads each were responsible for preparing written reports
resulting from their group deliberations. Those four reports are
presented individually herein, largely verbatim. An additional section
is added at the end that addresses the issue of how different potential
landing sites might affect the desired spacecraft configuration. As the
committee discussions evolved, it became very clear that desired mission
enhancements beyond the Groundbreaker concept would vary depending on
site location and other circumstances. One size will not fit all.

# VI. Revised Science Considerations Pertaining to Mobility and Accessibility

The task for the mobility/accessibility subgroup was to examine to what
degree of accessibility and mobility (range, rate, slopes handled), if
any, should now be considered desirable for the collection and return of
samples from the surface of Mars.

**General approach**

The subgroup proceeded in its examination by identifying sampling and
science criteria that potentially dictate the degree of accessibility
and mobility capabilities of MSR, defining accessibility and mobility
parameters, evaluating these parameters within the context of increasing
more complex MSR missions, and ranking these parameters within the
framework of missions to specific Martian terrains. Based on these
examinations and subsequent exercises the subgroup attempted to produce
findings that would be applicable to a wide range of possible science
goals defined by a future science definition team.

**Identification of Sampling and Scientific Criteria**

The subgroup identified numerous sampling criteria/tasks that influence
the mobility and accessibility capabilities of MSR. The relative
importance of these criteria is dependent on characteristics of landing
site terrain, MSR science goals, and complexity of the MSR. As such,
establishing these criteria was valuable for ranking of mobility
capabilities and evaluating potential trade offs among capabilities
within the framework of diverse missions with different degrees of
complexity, costs, and goals.

The criteria identified by the subgroup are

\(1\) The ability to traverse and perform sampling upon rocky terrain,
crater walls, and sloping hills at angles up to 30 degrees. This would
allow access to boulders and bedrock where sampling has the best chance
of avoiding surficial weathering products and finding organics.

\(2\) The ability to access samples that would be minimally contaminated
by exhaust from the MSR lander.

\(3\) The ability to sample lithologic diversity within a terrain or
across terrain boundaries.

\(4\) The ability to place samples within a well-defined geologic
context.

\(5\) The ability to return to a previously explored site or terrain
(i.e. MPF, MER A/B, MSL, V1,2).

\(6\) The degree of accessibility to different Martian terrains (i.e.
high percentage of the Martian surface, Martian highlands).

**Identification of Important Accessibility and Mobility Parameters**

Numerous accessibility and mobility parameters were identified by the
subgroup. These are listed in Table 1. These parameters are extremely
different in terms of overall metrics (distance, time, slope, degree of
autonomy). Their relative importance is dependent upon scientific goals
of MSR and characteristics of landing site (rough or flat terrain,
location). Many of these parameters are highly dependent upon one
another. For example, access to higher altitudes may effect precision
landing and distance capability of rover. Linkages between parameters
dictate the efficiency of sampling. This is illustrated by the
interaction between landing precision and roving capability that will
dictate duration on the Martian surface and the number of samples
collected. Trade off among these parameters will be eventually made
based on science goals, cost, and risk.

**Table 1. Range of Accessibility and Mobility Parameters relevant to
MSR.**

+-----------------------------------+-----------------------------------+
| **Landing Precision**             | **100 meters to 10s of km**       |
+-----------------------------------+-----------------------------------+
| **Distance capability of rover**  | **10s of meters to multiple kms** |
|                                   |                                   |
|                                   | **obstacle avoidance of 8 to 20   |
|                                   | cm**                              |
+-----------------------------------+-----------------------------------+
| **Time on Martian Surface**       | **\< 1 month to 4 months**        |
+-----------------------------------+-----------------------------------+
| **Ability to traverse slopes**    | **0 to 30** °                     |
+-----------------------------------+-----------------------------------+
| **Communications**                | **Line-of-sight of lander,        |
|                                   | direct-to-Earth, orbiter relay.   |
|                                   | In order of increasing            |
|                                   | bandwidth.**                      |
+-----------------------------------+-----------------------------------+
| **Degree of navigational          | **None to high**                  |
| autonomy**                        |                                   |
+-----------------------------------+-----------------------------------+
| **Altitude requirements**         | **\<-1.5 km accesses 39.5 % of    |
|                                   | Mars**                            |
|                                   |                                   |
|                                   | **\<+2 km accesses 83.1% of       |
|                                   | Mars**                            |
+-----------------------------------+-----------------------------------+
| **Latitude requirements**         | **Equator to +/- 60˚**            |
+-----------------------------------+-----------------------------------+

Parameters that dictate the distance capability of MSR includes landing
precision, distance capability of rover and time on the surface. The
overall distance capability of the rover is related to a variety of
other constraints such as radial distance from lander, traverse
distance, obstacle avoidance, and sols/sampling site. Parameters that
dictate the terrain capability of the MSR include the ability to
traverse slopes, communications, degree of navigational autonomy,
ability to navigate obstacles, and altitude and latitude of terrain.
Many of the mobility parameters listed in Table 1 are potentially
attainable with the rocker-bogie suspension system design that was
incorporated in both Mars Pathfinder (MPF) and MER.

Evaluating the ability for MSR to access Martian surfaces at variable
altitudes can be made using the topography derived from the Mars Orbiter
Laser Altimeter (Figure 1).

**Figure 1. Topography of Mars determined by the Mars Orbiter Laser
Altimeter illustrating location of previous Mars landing sites and
altitude of Mars highlands.**

> ![](media/image2.png){width="5.625196850393701in"
> height="3.2311023622047244in"}

The percentage of Martian terrains within select elevations constructed
from the laser altimeter data is illustrated in both Figure 2 and Table
2. Figure 1 illustrates that to return previous Mars landing sites or
similar terrains would require the access to terrains at altitudes of
\< - 1km relative to the Mars geoid. This altitude requirement would
provide access to approximately 45% of the Martian surface (Table 2) but
would give no access to the older highlands. Gaining access to a
substantial portion of the early Noachian environments in the highlands
(a potential target for the Mars Science Lab (MSL)) is much more
demanding and would require the ability to access Martian terrains
between 1.5 to 2.5 km above the Mars geoid. This altitude requirement
would provide access to approximately 89.5% of the Martian surface
(Table 2).

> **Figure 2. Mars hypsometric curve.**

![](media/image3.png){width="4.666666666666667in" height="3.59375in"}

**Table 2. Percentage of Martian terrains within select elevation ranges
from \<-1.5 to \>2.5 relative to geoid. Data derived from Figure 2.**

  ----------------------- ----------------------- -----------------------
  **Elevation Range**     **% of Mars surface**   **Cumulative % of
                                                  Mars**

  **\< -1.5**             **39.5**                **39.5**

  **-1.5 - 0**            **11.4**                **50.9**

  **0 - 0.5**             **4.7**                 **55.6**

  **0.5 - 1**             **7.6**                 **63.2**

  **1-1.5**               **10.4**                **73.6**

  **1.5-2**               **9.5**                 **83.1**

  **2-2.5**               **6.4**                 **89.5**

  **≥ 2.5**               **10.6**                **100.0**
  ----------------------- ----------------------- -----------------------

**Sampling Models, Mission Complexity and Science Value**

Five MSR sampling models were derived based on an increasing degree of
complexity and scientific payoff from the original GMSR proposed by the
MSRSSG #1 to a model that is essential MER plus sample return
capabilities (Table 3). Intermediate sampling models include original
GMSR with minor mobility capability (100 m roving capability), a highly
mobile MSR (1 km roving capability) returning to a previously visited
site to return a real or virtual sample cache, and a highly mobile MSR
(1 km roving capability) to an interesting, unvisited sampling a site
that was documented by orbital data. The cost, risk, and scientific
advantages and disadvantages of each sampling model are presented in
Table 3.

**Table 3. Sampling Models and Scientific Value.**

+-----------------------------------------------------------------------+
| **Original GMSR**                                                     |
+-----------------------------------------------------------------------+
| **[Description of capabilities:]{.underline}**                        |
|                                                                       |
| -   The first MSR need not "follow" MSL or any other prior mission,   |
|     but land in a scientifically interesting area, as determined by   |
|     previous *in situ* or orbital missions.                           |
|                                                                       |
| -   Mobility not required.                                            |
|                                                                       |
| -   Limited sample characterization package. Context camera for       |
|     sample selection and collection.                                  |
|                                                                       |
| -   Grab samples of regolith and clasts adjacent to lander.           |
+-----------------------------------------------------------------------+
| **[Advantages:]{.underline}**                                         |
|                                                                       |
| -   Lowest cost MSR.                                                  |
|                                                                       |
| -   Least complex of the MSR missions and therefore it has a higher   |
|     probability of success.                                           |
|                                                                       |
| ```{=html}                                                            |
| <!-- -->                                                              |
| ```                                                                   |
| -   Duration of surface operations is short.                          |
|                                                                       |
| -   Samples are put into a geologic context based on by previous *in  |
|     situ* or orbital missions.                                        |
|                                                                       |
| -   Will return rock fragments, regolith, and atmosphere within reach |
|     of the lander.                                                    |
+-----------------------------------------------------------------------+
| **[Disadvantages:]{.underline}**                                      |
|                                                                       |
| -   Cannot directly sample outcrops.                                  |
|                                                                       |
| -   Cannot reach samples out of reach of arm/scoop.                   |
|                                                                       |
| -   No mobility to explore and sample local geology.                  |
|                                                                       |
| -   Collection of only regolith and rock fragments has a lower        |
|     probability of returning organic compounds.                       |
|                                                                       |
| -   Higher likelihood of returning altered samples.                   |
+-----------------------------------------------------------------------+
| **Original GMSR with minor mobility capability**                      |
+-----------------------------------------------------------------------+
| **[Description of capabilities:]{.underline}**                        |
|                                                                       |
| -   Land in a scientifically interesting area, as determined by       |
|     previous *in situ* or orbital missions.                           |
|                                                                       |
| -   Mobility less than MER.                                           |
|                                                                       |
| -   Core large rocks.                                                 |
|                                                                       |
| -   Limited sample characterization package. Context camera for       |
|     sample selection and collection.                                  |
+-----------------------------------------------------------------------+
| **[Advantages:]{.underline}**                                         |
|                                                                       |
| -   Possibility of sampling unaltered lithologies.                    |
|                                                                       |
| -   Lessen the possibility of sample contamination from lander.       |
|                                                                       |
| -   Duration of surface operations shorter than sampling models 2, 3  |
|     and MER.                                                          |
+-----------------------------------------------------------------------+
| **[Disadvantages:]{.underline}**                                      |
|                                                                       |
| -   Cannot sample outcrops in crater walls.                           |
|                                                                       |
| -   Limited mobility to explore and sample local geology significant  |
|     distances from lander.                                            |
|                                                                       |
| -   Regolith samples will have a lower probability of sampling        |
|     organic compounds                                                 |
|                                                                       |
| -   Samples are put into a limited geologic context.                  |
+-----------------------------------------------------------------------+
| **Mobil MSR to previous visited and documented site**                 |
+-----------------------------------------------------------------------+
| **[Description of capabilities:]{.underline}**                        |
|                                                                       |
| -   Return to previously documented site.                             |
|                                                                       |
| -   Access to outcrops in crater walls.                               |
|                                                                       |
| -   Core large rocks and outcrops                                     |
|                                                                       |
| -   Limited sample characterization package. Context camera for       |
|     sample selection and collection.                                  |
|                                                                       |
| -   Mobility equivalent to MER.                                       |
+-----------------------------------------------------------------------+
| **[Advantages:]{.underline}**                                         |
|                                                                       |
| -   Samples put into context of local geology defined by previous     |
|     missions (i.e. MER, MSL).                                         |
|                                                                       |
| -   Return to previous site lowers cost resulting from smaller sample |
|     characterization package and known site specific engineering      |
|     requirements.                                                     |
|                                                                       |
| -   Cored outcrop samples may be unaltered.                           |
|                                                                       |
| -   Duration of surface operations shorter than sampling models 3 and |
|     MER.                                                              |
|                                                                       |
| -   Sample outcrops in crater walls.                                  |
+-----------------------------------------------------------------------+
| **[Disadvantages:]{.underline}**                                      |
|                                                                       |
| -   First sample return mission will not be a mission of exploration  |
|     to a new Martian terrain.                                         |
|                                                                       |
| -   Contamination from previous mission.                              |
|                                                                       |
| -   Return sites are limited in number and interest if MSL fails or   |
|     does not provide adequate characterization of the surface.        |
+-----------------------------------------------------------------------+
| **Mobil MSR to interesting site documented by orbital data**          |
+-----------------------------------------------------------------------+
| **[Description of capabilities:]{.underline}**                        |
|                                                                       |
| -   Explore site unexplored by previously *in situ* missions.         |
|                                                                       |
| -   Access to outcrops in crater walls.                               |
|                                                                       |
| -   Core large rocks and outcrops.                                    |
|                                                                       |
| -   Limited sample characterization package. Context camera for       |
|     sample selection and collection.                                  |
|                                                                       |
| -   Mobility equivalent to MER.                                       |
+-----------------------------------------------------------------------+
| **[Advantages:]{.underline}**                                         |
|                                                                       |
| -   Sample outcrops in crater walls.                                  |
|                                                                       |
| -   Cored outcrop samples may be unaltered.                           |
|                                                                       |
| -   Has the flexibility to explore new sites.                         |
+-----------------------------------------------------------------------+
| **[Disadvantages:]{.underline}**                                      |
|                                                                       |
| -   Samples are placed within the context of orbital geology and not  |
|     local geology.                                                    |
|                                                                       |
| -   With a limited sample characterization package, samples are not   |
|     well documented on surface.                                       |
|                                                                       |
| -   Higher costs resulting from unknown site specific engineering     |
|     requirements.                                                     |
|                                                                       |
| -   Duration of surface operations longer than sampling models 1 and  |
|     2.                                                                |
+-----------------------------------------------------------------------+
| **MER with sampling capabilities**                                    |
+-----------------------------------------------------------------------+
| **[Description of capabilities:]{.underline}**                        |
|                                                                       |
| -   Sample characterization package similar to MER with the           |
|     capability to document sampling site prior to sampling.           |
|                                                                       |
| -   Explore site unexplored by previously *in situ* missions.         |
|                                                                       |
| -   Access to outcrops in crater walls.                               |
|                                                                       |
| -   Core large rocks and outcrops.                                    |
|                                                                       |
| -   Mobility equivalent to MER.                                       |
+-----------------------------------------------------------------------+
| **[Advantages:]{.underline}**                                         |
|                                                                       |
| -   Sample outcrops.                                                  |
|                                                                       |
| -   Has the flexibility to return to documented sites or document new |
|     sites.                                                            |
|                                                                       |
| -   In situ documentation of samples prior to collection.             |
|                                                                       |
| -   Further exploration could continue after sample collection and    |
|     launch of MAV.                                                    |
+-----------------------------------------------------------------------+
| **[Disadvantages:]{.underline}**                                      |
|                                                                       |
| -   Estimated costs greater than \$3 billion.                         |
|                                                                       |
| -   Duration of surface operations longer than sampling models 1-3 if |
|     sample collection-documentation-exploration occurs                |
|     simultaneously.                                                   |
|                                                                       |
| -   Most complex of all the MSR missions.                             |
+-----------------------------------------------------------------------+

**Analysis of Mobility-Accessibility Requirements of Different Martian
Terrains**

Lacking a science definition team report establishing specific science
goals for the first MSR we evaluated mobility and accessibility
requirements necessary to sample both real and hypothetical sampling
sites: (1) Meridiani-like site, (2) a Gusev-like site, (3) a high
altitude MSL site, and (4) a previously unvisited site with a geologic
contact. Each site would require some differences in mobility and
accessibility requirements and necessitate some trade offs between
requirements (Table 4).

Table 4. Accessibility and mobility requirements for example sites.

  ----------------- ------------------ --------------- --------------- -----------------
                    **Meridiani site** **Gusev         **MSL site**    **Unvisited site
                                       crater**                        with geologic
                                                                       contact**

  **accessibility   Go to outcrop;     Go to boulders  Go to boulders  Go to boulders
  to rock           rover mass         and outcrops;   and outcrops;   and outcrops;
  interiors**       sufficient for     rover mass      rover mass      rover mass
                    coring             sufficient for  sufficient for  sufficient for
                                       coring          coring          coring

  **accessibility   Mobility           Mobility        Mobility        Mobility
  to uncontaminated sufficient to      sufficient to   sufficient to   sufficient to
  samples**         escape exhaust     escape exhaust  escape exhaust  escape exhaust
                    pattern (\> 1/2    pattern (\> 1/2 pattern (\> 1/2 pattern (\> 1/2
                    km?), lander       km?), lander    km?), lander    km?), lander
                    debris, organic    debris, organic debris, organic debris, organic
                    contam.;           contam.;        contam.;        contam.;
                    subsurface         subsurface      subsurface      subsurface
                    sampling ability   sampling        sampling        sampling ability
                    (e.g., coring)     ability (e.g.,  ability (e.g.,  (e.g., coring)
                                       coring)         coring)         

  **altitude**      -1.3 km            -1.9 km         CRITICAL to     Higher altitude
                                                       match MSL\'s    range (+0.5 or +1
                                                       altitude        km) would be
                                                       capability      desirable because
                                                       (+2.5 km)       it would provide
                                                                       access to
                                                                       high-quality
                                                                       science sites in
                                                                       the ancient
                                                                       Southern
                                                                       Highlands
                                                                       (possibly
                                                                       recording a
                                                                       warmer wetter
                                                                       climate on Mars)

  **landing         Accessibility to   Within 500 m of Within 500 m of Within 500 m of
  precision**       \>20 m diam        the contact     any contact.    any contact. You
                    crater; \~ 200m    between the     You would want  would want
                    precision? Note:   hills and the   accessibility   accessibility to
                    Landing precision  plains; closer  to the terrain  the terrain
                    and roving         is better. You  boundary        boundary between
                    distance are       would want      between the two the two geologic
                    intertwined. It\'s accessibility   geologic units, units, to sample
                    probably more      to the terrain  to sample both  both units away
                    important to       boundary        units away from from the landing
                    minimize the time  between the     the landing     contamination
                    the rover spends   plains and the  contamination   
                    on the surface     hills, to                       
                    collecting         sample both                     
                    samples. The       terrains away                   
                    terrain at         from the                        
                    Meridiani between  landing                         
                    craters is smooth, contamination                   
                    flat and barren of                                 
                    rocks, so it would                                 
                    take less time to                                  
                    drive.                                             

  **minimum roving  1 km               1 km            1 km            1 km
  distance**                                                           

  **time on         Time sufficient to Time sufficient Time sufficient Time sufficient
  surface, autonomy sample             to sample       to sample the   to sample the
  to lessen the     stratigraphy by    plains          diversity of    diversity of rock
  time**            coring within      regolith,       rock types by   types and
                    single crater, and plains rocks, a coring, and to  regolith in both
                    to also sample     diversity of    also sample     geologic units;
                    regolith, dust,    rock types in   regolith, dust, as well as dust
                    and atmosphere     the hills,      and atmosphere  and atmosphere
                                       regolith in the                 samples
                                       hills, dust,                    
                                       and atmosphere                  

  **slopes/         Must be able to    Must be able to The more MSR    Need flexibility
  terrain**         enter and exit     drive up and    matches its     to respond to
                    crater             down the side   slope/terrain   unknown terrain
                                       of the Columbia capability to   characteristics
                                       Hills and the   that of MSL,    to maximize the
                                       rugged rocky    the better able diversity of rock
                                       plains          we would be to  types collected
                                                       follow MSL      

  **rover           Rover must be able Orbiter and/or  Rover must be   Orbiter and/or
  communication**   to communicate     direct to Earth able to         direct to Earth
                    w/orbiter and/or   com is          communicate     com would be
                    directly to Earth. advantageous,   w/orbiter       advantageous, but
                    Rationale: rover   but we could    and/or directly we could design a
                    entering/exiting   design a        to Earth        mission that
                    craters may be out mission that                    would not require
                    of range of direct would not                       it.
                    lander com.        require it.                     

  **latitude**      2 degrees S        15 degrees S    CRITICAL: MSL   Opening the
                                                       latitude range  latitude range as
                                                       (+/- 60         far south as
                                                       degrees?)       possible would
                                                                       improve the
                                                                       science by
                                                                       allowing access
                                                                       to more possible
                                                                       ancient highlands
                                                                       landing sites
  ----------------- ------------------ --------------- --------------- -----------------

**Findings**

These examinations by the M&A subgroup indicate that several of the
mobility and access parameters will vary depending upon the scientific
goals and surface terrain to be sampled. The most site sensitive
mobility and accessibility parameters are latitude, altitude, and
communications. In addition, changes in these MSR parameters may affect
less sensitive parameters (i.e. a site at high latitudes and altitudes
may affect roving capability, landing precision, and duration on Martian
surface).

Access to uncontaminated samples would require rover mobility sufficient
to escape exhaust pattern, lander debris, and organic contamination.
Lander contamination which may extend 200-400 meters requires rover
mobility of at least 1 km. With pinpoint landing the exhaust pattern may
be more extensive and should be monitored. A potential trade off for
requiring extensive mobility to escape lander contamination would be to
sample the uncontaminated subsurface via coring of rock boulders and
outcrop interiors and trenching regolith. It is important to better
understand the dispersion of exhaust during landing and the extent
exhaust permeates the subsurface. This is particularly important for the
regolith.

Sampling that would be the least demanding on MSR would be coring large
boulders or near-horizontal relatively smooth expanses of bedrock.
Slopes that need to be navigated under this sampling scenario would not
be substantial (\<10˚). Direct communication to lander would likely be
sufficient in this case. Much more demanding on MSR would be gaining
access to outcrops that may be exposed along walls of a crater (i.e.
Meridiani site) or inclined slope of hills (i.e. Columbia Hills). This
more demanding sampling strategy would fulfill the desire to sample
stratigraphy that may be exposed in outcrop and increases sample
diversity. In addition, sampling of outcrops would allow the samples to
be placed within a regional and perhaps planetary-scale context. To
fulfill this more challenging sampling agenda, the rover would need to
navigate and sample from slopes up to 30˚. The rocker-bogie suspension
system of MPF and MER rovers has demonstrated some of these
capabilities. It would also be advantageous to be able to communicate to
an orbiter and/or directly to Earth. A rover that is entering and
exiting a crater or hilly terrain may be out of range of direct lander
communications. Navigating over rough and inclined terrain for the
purpose of coring outcrop may require substantial residence time on the
Martian surface (1-3 months). Some degree of rover autonomy and pinpoint
landing may assist in lessening the time on the surface. There may be
trade offs between time on the Martian surface and accessibility to
higher latitudes since the solar power available to the rover is
strongly coupled to latitude.

Reducing surface time, placing samples with a well-defined geologic
context, collecting a diverse set of lithologies, and returning to a
previously visited site (retrieving a sample cache) are closely coupled
to the linkage between roving distance capability and precision of
landing. Generally, the most efficient manner to use surface time to
explore and sample would be to use precision landing to land close to
the scientific target. In the simplest situation in which previously
documented (orbit or in situ) geologic units having a lateral extents of
\> 10 to 100s km are targeted landing precision of up to 10 km would be
adequate. In the scenario in which a geologic terrain boundary between
two distinct lithologies is targeted (*i.e.* Gusev crater), so that both
could be sampled, a landing precision of better than 500 meters is
recommended. In the more demanding scenario in which accessibility to
outcrops in a \>20m diameter crater is required (i.e. Meridiani) an even
greater landing precision may be required to minimize roving time. In
all these sampling scenarios, roving capabilities still need to be at
least 1 km.

Returning to a previously explored site that has a real or virtual
sample cache would have several advantages. Duration on Martian surface
would be less due to the retrieval of cached samples or sampling more
efficiently due to the previous documentation of outcrops. Decreasing
the time on the Martian surface may mitigate risk. Sending MSR to a
documented terrain would increase sample diversity and better place
samples within the context of local and regional geology. A documented
terrain presents a more predictable environment for engineers. There are
trade offs with returning to a site. These include eliminating
exploration to a new Martian terrain, adding cost to preceding mission,
and sampling a site contaminated by a previous mission.

Returning to sites previously explored by VL1,2, MPF, and MER would
necessitate landing elevation requirements of less than -1.3 km relative
to the Mars geoid. Returning to a previously explored site at high
elevation and high latitude (i.e. possibly MSL) or gaining access to a
substantial portion of the early Noachian environments in the highlands
would be much more demanding and require the ability to access Martian
terrains between 1.5 to 2.5 km above the Mars geoid. This was considered
problematic and potentially costly by the MSR SSG#1. Therefore, the MSR
SSG #1 eliminated latitude and elevation requirements. In that early
Noachian terrains may have preserved remnants of a possible warm and wet
environment conducive for life and the possibility of real or virtual
sample caching by MSL having the ability for MSR to sample terrains at
elevations up to +1.5 km above the geoid would provide access to
approximately 74% of the Martian surface and a portion of the early
Noachian terrains. The capability to access this terrain for sample
return will be demonstrated by the design (and possibly landing) of 2009
MSL. MSR SSG#2 does realize expanding the Martian surface available to
sample return (by both latitude and altitude) does have its trade offs
with regards to cost, the size and roving distance of the rover, the
precision of landing and time on the Martian surface. We consider access
to more of the Martian surface, especially the early Noachian terrains,
more important than extensive roving distance (\> 1 km). Returning to a
MSL site at high altitudes may limit the effects of rover capability
(size, roving distance, time on surface, limited sample documentation
package) on the MSR science goals. Returning to such a site still
requires pinpoint landing

**Summary Findings on Mobility and Accessibility**

-   Terrain navigability is site dependent. Gaining access to outcrops
    that may be exposed along crater walls (i.e. Meridiani site) or
    inclined hillslopes (i.e. Columbia Hills) would require the ability
    to negotiate slopes of \~ 30o

-   Landing Precision is site dependent; but the requirement would
    always be within 500 m

-   Access to uncontaminated samples would require rover mobility
    sufficient to (1) escape exhaust pattern, lander debris, and organic
    contamination; (2) travel to and return from target. Round trip
    distance \~ 1 km regardless of landing precision.

-   Access to elevations \> 1.5 km is highly desirable but is recognized
    as possibly prohibitive.

# VII. Revised Science Considerations Pertaining to Sampling and Sample handling

The Sampling Subgroup of the Mars Sample Return Science Steering Group
(MSR SSG II) was convened to revisit sampling needs based on an
evolution from the previous capability of "Groundbreaking Mars Sample
Return". The sampling goal of GMSR was to return regolith and rock
fragments from a site that was hypothesized to have relevance to
following the water on Mars. The conceptual GMSR consisted of a
stationary lander with a simple scoop-rake sampling system, and a single
bin into which all samples would be placed. This mission also had the
requirement to maintain the temperature of the samples below 50°C. The
MSR SSG I concluded that the first samples to be returned from Mars
probably wouldn't contain evidence of past or present life, because at
the time that the previous MSR SSG report was written, we had little
confidence that we could find the type of rocks capable of preserving
this evidence. MER discoveries, especially at Meridiani, but possibly
also at the Columbia Hills, have revealed likely outcrops of sedimentary
rocks and low-temperature aqueous precipitates and alteration products,
rendering this previous conclusion incorrect. It appears now that rocks
that could preserve evidence of complex aqueous processes, organic
geochemistry, and even life are accessible at the Martian surface. The
SSG sampling subgroup was tasked to address the clear desire and
scientific need to sample adequately these types of units. In short, we
were asked: how do the MER results affect how we select, collect, store,
and return samples?

In detail, the MSR SSG Sampling Subgroup Charter addressed the following
questions for the *first* MSR:

1.  *Sampling approach:* What are the science priorities for the
    functionality of the MSR sampling system?

2.  *Sample packaging:* What are the science priorities for the
    functionality of the MSR handling and storage system?

3.  *Assay techniques & Caching:* In order to select samples, what
    measurements must MSR conduct? Would MSR benefit if samples were
    cached for it by a prior mission, e.g. MSL?

4.  *Sample Preservation:* What are the science community's priorities
    for controlling the environment of returned samples?

Note that the *italicized* titles for each question were added by the
group -- these are shorthand for the topics we discussed, and will be
repeated throughout this document.

**General approach and comments**

Our approach to addressing these questions initially involved combining
them into a holistic sample-related discussion, where the
characteristics of a realistic but optimized first sample return were
considered. This was followed by a "science value exercise" to consider
the science value of increased capabilities more "quantitatively." We
held discussions in person at our two SSG meetings, in four
teleconferences, and via email.

Lacking an SDT report laying out the specific science goals of the first
MSR, for most of our discussions, it was assumed that a site with
exposed sedimentary rocks, preferably with accessible igneous rocks,
would be a very likely target of the first MSR. Objectives would be
related to (1) seeking the preservation and history of organics
(possibly life), water, and other volatiles, (2) understanding the
depositional history and environment of the samples and (3) determining
their age if possible. The larger SSG considered application to other
sites of the priorities we derived from this site and found virtually no
differences in sampling needs if MSR visits a (1) Meridiani-like site,
(2) a Gusev-like site, (3) the MSL site, or (4) a previously unvisited
site with a geologic contact. Thus the results of this subgroup's
discussion are considered to be fairly resilient to site selection
details.

It is important to note that part of the reason for undertaking this
evolution of MSR capabilities was the realization that the GMSR concept
would likely not have fulfilled its goals at Meridiani (i.e., there
would have been no small rocks within the reach of a stationary lander).
Thus the simplest evolution to GMSR would be a "mobile GMSR", capable of
"fetching" the rock fragments. *[Such a mission would have increased
cost and complexity, but no real increase in science value over
GMSR.]{.underline}* Increased science value comes from enhancing the
stated goals and capabilities beyond those of a mobile GMSR mission.

**Science Value Exercise**

***Introduction.*** In order to evaluate the *relative science value* of
various types and levels of increased sampling and sample handling
capabilities to the first MSR mission, we undertook a "science value
exercise" to determine where the most science value would be gained by
increasing capability. The exercise in its entirety is given in Appendix
C, and is summarized only briefly here. Basically, the exercise
consisted of defining the range of mission elements related to sampling
approach possibilities, sample packaging options, assay techniques and
caching, and sample preservation, then combining variations of each of
these four elements into example missions, and finally having each panel
member subjectively rate the science value of each mission on a scale of
1 --- 1000 (where GMSR is defined = 1, and a MER-scale and capable MSR
is defined = 1000). The entire purpose of this exercise was to find out
which capabilities give the most "bang for the buck" in the minds of the
committee. Of course, missions of higher capability will always have
higher science value, but some components provide especially large gains
in science value. This was not and did not pretend to be a quantitative
exercise, but rather a qualitative way to articulate the more and less
valued characteristics of the first MSR mission.

The conclusion from this exercise is that enhanced capabilities in the
sampling system (specifically, a coring device for bedrock sampling) and
sample isolation (to isolate regolith, windblown fines, and individual
cores from each other) are strongly viewed as most important to greatly
increasing the science value of the mission.

**Each of the four major element categories -- sampling approach
possibilities, sample packaging options, assay techniques and caching,
and sample preservation -- are discussed individually below.**

*Element #1: Sampling Approach*

As stated above, the group strongly prioritizes the ability to sample
bedrock (either igneous or sedimentary), in stratigraphic context
preserving weathering gradients into unaltered rock. We believe the most
straightforward way to do this would be through coring. Sampling bedrock
would provide the most direct record of geologic processes on Mars, and
would provide the highest likelihood of being able to place the small
amount of MSR samples in local, regional and even global context on
Mars, thus maximizing the knowledge gained from MSR. Although rock
fragments and soil would be extremely valuable, sampling a stratigraphic
sequence would clearly be the priority if such a sequence is available.
MER showed us that such sequences exist, and contain extraordinarily
interesting rocks!

Obtaining a suite of samples from a single "site" where outcrop is
available (e.g., Eagle or Endurance crater) is considered sufficient for
the first MSR. Sampling strategy for a sedimentary site would need to
optimize a mix of sample diversity (determined with whatever means
available) and documentation of a stratigraphic time series by
collecting samples along a defined rock sequence. This sampling strategy
must integrate on-site knowledge and thus cannot be pre-determined
before landing and viewing the site.

Coring into rocks would allow important textures as well as chemical and
physical gradients to be preserved. These signatures would provide clues
to evolving conditions as the rocks were deposited. Preserving the
exposed surface on at least some of the samples would be critical to
understanding atmospheric weathering effects (such as oxidation) after
the rocks were deposited. Some of these effects may erase the
biosignatures that we seek -- recognizing them is therefore critically
important.

Although rocks are the highest science priority samples for the First
MSR, locally-derived regolith and windblown fines are also considered
extremely important samples to understand the role of water both locally
and globally on Mars. Because of the fine-grained nature of these
materials, they are extremely difficult to analyze remotely, and
therefore they are uniquely suited for returned sample analysis on
Earth.

A *separate* atmosphere sample on the first MSR is also considered very
important. Returning an atmosphere sample, uncontaminated by degassing
of or interaction with soil (in other words, in a separate container
from soil) has been a high priority of Mars science for many years. The
chemical composition and isotopic ratios in the atmosphere provide a
unique snapshot of the current state of volatiles on Mars, as well as
windows into volatile loss through time. If forced to prioritize among
the sample types (rock, regolith, windblown fines, and atmosphere), a
*separate* atmosphere sample would be considered less important than the
other four sample types. However if a separate atmosphere sample could
not be accommodated on the first sample return, every effort must be
made to recover the "headspace gases" that would inevitably be returned
in the rock, regolith, windblown fines containers.

The group discussed the nature of a contingency sample. A scoop/rake
sample from the lander, below the effect of surface contamination, is
considered an acceptable contingency sample.

The group did not close on most of the *sample size* issues -- these
need to be revisited FOR ALL SAMPLE TYPES (rocks of different types,
regolith, windblown fines and atmosphere). For example, the group
recognized that most prior constraints on rock sample sizes (\~10-20 g
per "sample" -- where a sample is from a single outcrop location or
subsample of a rock -- equivalent to a "RAT hole" on MER) were driven by
knowledge of analysis protocols on meteorites and/or lunar samples. This
needs to be revisited for sedimentary rocks. To do so would require
development of analysis protocols for such samples. These protocols are
likely to differ from those for igneous rocks mainly in (1) the number
of analyses that are performed in sequence on the same sample rather
than splits of the sample and (2) the sub-sampling of fine-scale layers
that might be necessary. In spite of these uncertainties, a preliminary
finding is that 10-20 g per rock sample should be approximately
sufficient and could be used as a placeholder until this matter can be
taken up by a sample handling protocol group.

Regolith and wind-blown fines samples would be analyzed both in bulk and
essentially grain-by-grain to investigate their components in more
detail. Regolith samples of 20 - 50 g in size should be sufficient for
replicate diverse analysis types and sample curation. It would be ideal
to obtain a sample of regolith right at the surface (away from the
lander to minimize contamination from descent), and from at least one
depth below the surface as far as would be feasible without seriously
driving requirements. Similarly, a 10 g sample of windblown fines should
be sufficient for science purposes, but more sample than this may be
desired for human spaceflight preparation purposes (this needs to be
addressed through coordination with the other MEPAG SSG).

Atmospheric sampling is still very much an open issue, especially
whether a small (say, 20-30 cc) ambient atmosphere sample would be
sufficient to meet the science objectives of MSR. It is possible that a
30 cc sample at ambient Mars conditions would allow most all types of
analysis to be done, but this needs to be revisited. In any case,
leakage of gases from the container would result in some alteration of
the abundances and isotopic compositions of gases during transport, and
such changes need to be well understood. Monitoring leak rates, or
having good constraints on them would be desired in an atmosphere
sample. The container material needs to be considered carefully, as most
materials will interact with the gas in some way over time.

*Element #2: Sample Packaging*

The highest priority in sample packaging would be to keep individual
cores separate from one another and from regolith/fines contamination.
Separate containers are also strongly desired for regolith and windblown
fines samples. Each rock, regolith and fines sample records a unique
history and set of processes by which it formed and evolved. Unraveling
these processes is at the heart of the goals for sample return. A broad
science community would apply the most sensitive analytical capabilities
achievable toward deciphering the record in these materials. Mixing the
samples would cause the records of these critical processes to be
jumbled, and make them very difficult to interpret. Such an approach
would significantly compromise the great promise of MSR to reveal a
detailed history of rocks and soils on Mars. The prospects of making a
great discovery and (more importantly) of properly interpreting it,
would be maximized by isolating individual samples from one another.

The potential for migration of volatiles from one sample to another is a
matter of some concern. Beyond simple cross-contamination of sample
chemistries, there is the potential for release of substantial amounts
of water from some samples (e.g., samples rich in hydrated magnesium
sulfate salts). This water could significantly alter samples to which it
migrates, whether it migrates as vapor or liquid. Container design
elements that could potentially mitigate volatile migration include
gas-tight seals, desiccants, and cryotemperature stabilization.

*Element #3: Assay Techniques and Caching*

The group discussed the idea of requiring MSR to visit only sites that
have been previously explored by another landed mission (virtual
caching)[^1]. We discussed strengths and weaknesses of this approach.
Because samples at the site will have been previously characterized,
fewer on-board tools (and possibly less mobility) would be needed,
decreasing cost and complexity of MSR -- this would clearly be a
strength. Also, if the terrain is well understood from a previous
mission, spacecraft constraints perhaps could be more targeted to this
site, simplifying the design. Clearly the main weakness of this approach
would be the inability of MSR to explore new sites. This would be
especially limiting if MSR has improved landing capabilities (e.g.,
pinpoint landing) over previous missions. Imagine that MRO discovers
some very interesting units or features that are inaccessible except by
pinpoint landing. Would we want to turn our back on such a site simply
because we hadn't visited it before? It could be argued that such sites
present more science risk, because their make up has not been confirmed
or studied by an in situ mission. However, by the time of the first MSR
we will have increasingly sophisticated orbital measurements and we will
have visited at least 7 sites on the Martian surface. Surely our
predicative capabilities will be reasonable enough to allow us to choose
a compelling site even if it has not been visited previously. The group
concluded that although returning to a previously visited site may be
desirable in some cases, we believe it is not wise to commit exclusively
to this strategy. In other words, in order to allow MSR to be as
discovery driven as possible, we should not commit to sending the first
MSR to a previously explored site.

The above discussion was useful because it forced us to consider how
much we value on board instrumentation for sample "assaying" even in the
event that a previous lander had not surveyed a site. Given the MER
experience in Eagle and Endurance craters, the group concluded that
simple on-board instrumentation (i.e., a reasonable quality imager
capable of seeing layering and crude color differences) would probably
be sufficient for this mission. Assuming we are capable of choosing a
compelling landing location, this instrumentation would allow us to
design a sampling strategy that would have a high probability of
maximizing the diversity of samples from the site. For example, such a
camera was the primary tool used to decide where to "sample" (with the
RAT and the IDD tools) along the outcrop in Endurance Crater, and it
could easily observe differences between the igneous rocks on the floor
of Gusev Crater and the different rocks in the Columbia Hills. For the
first MSR, sample documentation with imaging at the outcrop scale
(resolution comparable to Pancam on MER) and the hand sample scale
(resolution comparable to Microscopic Imager on MER) is considered
important.

The group also discussed having MSR pick up a physical cache from MSL.
The group felt that this idea has merit and should be studied, but we
are (1) content with the conceptual MSR constraints we have laid out
with or without the added capability MSL would provide, and (2)
concerned that pursuit of MSL caching may divert attention and resources
from MSR issues, and therefore could threaten mission success. This
ambivalence was reflected in the Science Value Exercise in which the
addition of the MSL cache to mission capabilities resulted only in a
very slight increase in science value (see missions 14 and 18 in Table
2). *A critical point is that MSR must not be designed to be completely
dependent on a cache; MSR must have independent sampling and storage
systems in the case that the caching system fails or if another site is
deemed of higher value for MSR than that visited and cached by MSL.*

*Element #4: Sample Preservation*

The group considered four types of sample preservation issues: packaging
(discussed above), physical integrity, sterilization issues on Mars, and
sample temperature history after leaving the Martian surface.

*Physical integrity.* Every effort must be made to preserve the physical
integrity of the samples during all phases of the mission. Minor
fracturing of cores would not significantly impair scientific study if
the core pieces remain in their original orientation and only small
amounts of powder are produced along the fracture planes. Preserving
physical and chemical gradients in the samples is of high scientific
value. Such information would be lost if the samples are pulverized. Put
simply, the main value of coring would be lost if the samples are
powdered. The group was satisfied that this constraint could be met
without driving design significantly, and thus did not focus much
attention on it after initial discussions. However, it is a high
priority that rock samples be returned as close to intact as possible,
and certainly without powdering.

*Sterilization*: Mechanisms for collecting "clean" samples, including
sterilizing the surface chemically, or physically scraping surfaces off
of rocks/soils were NOT considered acceptable. As discussed above, much
important science would be lost if the surface materials are removed or
chemically altered through sterilization. In addition, the science
community represented on the SSG is skeptical of chemical or other
sterilization approaches being reliable to the point of being acceptable
for use. For example, a porous and permeable regolith could easily
permit the penetration (to several mm depth) of terrestrial spores
and/or microbes shed from a rover or lander. If an approach to
sterilizing the surface were absolutely required to meet Planetary
Protection requirements, physically scraping surface materials off is
considered better than alteration of the samples by some in situ
chemical sterilization method. From the perspective of *science* (not
planetary protection), a slightly contaminated sample could still have
value as long as the contaminants are well understood. These topics are
taken up in more detail by the contamination subgroup.

*Temperatures.* The subgroup explored in great detail the ramifications
of heating of the samples once they leave the Martian surface, primarily
during Earth atmospheric entry and especially after landing on Earth.
The original GMSR concept did not require active refrigeration, but did
recommend sufficient insulation to ensure that the samples would not
experience temperatures in excess of 50 °C; simple temperature
monitoring during Earth landing would be required.

The present subgroup looked at the temperature effects on specific
classes of compounds, organic and inorganic. The results at Meridiani
seem to support the possibility that hydrated salts exist in abundance
at interesting sites on Mars, and some of these salts (especially
magnesium sulfates) could release water upon mild heating, possibly
accelerating other breakdown reactions. Therefore, it is prudent to
study the possibility of including some desiccant materials in the
return capsule to trap any released water. Clearly, such material would
need to be accessible to any gases being released, but physically
isolated from the Martian samples.

Our study of temperature effects is given in complete form in Appendix
D; excerpts from that study are given here.

From a science perspective, therefore, it is desired that sample
temperatures should be kept below 50 °C; ideally, they should remain at
or below Mars surface ambient temperatures (\<0 oC). However, the group
recognized that requirements for active refrigeration were unrealistic
for the first MSR, and so this should be pursued through design
optimization of the sample capsule and Earth entry vehicle (EEV) to the
best extent possible, as well as mission plans to recover and cool the
EEV as soon as possible after impact.

The potential alteration of inorganic phases centers on the fate of
water: structural in certain minerals, interlayer in clays, brine ice or
liquid brines in fractures and interstices, and chemisorbed and
physisorbed on mineral surfaces. The main concern would be preventing
hydrated magnesium sulfate salts from melting. Data from Viking 1 and 2
and from Pathfinder suggest that MgSO4 is present at roughly 10 wt %
(anhydrous equiv.) in Martian soils (Vaniman et al., 2004; Wänke et al.,
2001), and data from Spirit at Gusev crater are not inconsistent with
this finding (Gellert et al., 204). These salts are likely to be present
on Mars, in the minerals kieserite (MgSO4 · 1 H2O), epsomite (MgSO4 · 7
H2O), and MgSO4 · 12 H2O, as well as in amorphous phases with variable
water contents (e.g., Vaniman et al., 2004). Hexahydrite (MgSO4 · 6 H2O)
could be formed by hydration or dehydration reactions of these other
phases if the sample storage temperature climbs above about 280K.

At temperatures above 270K, these phases are all near the point of
partially dehydrating or melting to form a Mg++, SO4­\-- rich brine
(Appendix D, Figures 2, 3). The phase changes appear to be rapid, for
example the dehydration of hexihydrite at 298K, 580 torr, and relative
humidity of 0.3-0.4% takes on the order of several hours (Appendix D,
Figure 4). However, the kinetics of most of the phase changes have not
been studied sufficiently well to understand what would happen in a
sample return container as temperature and relative humidity rise in
concert.

***Table 5. Thermal Effects on Inorganic Phases During Storage and
Return of Mars Surface Sample.** Worst case scenario: heating a Mars
surface sample to 50°C for several hours.*

**[Possible major effects:]{.underline}**

1)  Dehydration and/or melting of hydrated magnesium sulfate salts
    (e.g., epsomite, hexahydrite).

**[Major issues if ice and/or hydrated magnesium sulfate salts are
present in sample]{.underline}**

1)  Melting of ice or hydrated magnesium sulfate.

2)  Minor dissolution of evaporitic minerals in the resultant aqueous
    solution.

3)  Enhanced redistribution and reaction of organics if present.

4)  Loss/exchange of some interlayer cations in clays minerals (if
    present).

**[Probable minor effects:]{.underline}**

1)  Volatilization of chemisorbed and physisorbed water (especially from
    clays & zeolites if present).

2)  Slow dehydration of hydrated clay minerals (if present).

3)  Loss (dehydration/decomposition) of minor abundance, delicate
    evaporitic minerals.

4)  Reversible changes in fluid inclusion chemistry due to
    temp-dependent salt solubilities.

5)  Reactivity and catalytic properties of mineral surfaces towards
    volatile/soluble organics.

**[Possible minor effects:]{.underline}**

1)  Recrystallization/hydration/oxidation of reactive iron minerals.

**[Probable non-issues for this scale of temperature/time
history:]{.underline}**

1)  Decrepitation of fluid inclusions.

2)  Thermal sensitivity of hydroxylation/dehydroxylation reactions.

Table 5 summarizes the expected effects of heating on inorganic phases
in Martian surface samples. This summary assesses a worst case scenario
in which samples would be kept below 0˚C from collection time until
reentry into Earth's atmosphere; then following reentry and prior to
retrieval the samples reach 50˚C for a maximum of a few hours due to
heat soakback from the reentry vehicle's heat shield. This table takes
into account the phases likely to be encountered in Martian regolith and
in weathered and unweathered outcrops.

If these salts serve as a cement in regolith materials or sedimentary
rocks, then dehydration or melting could result in physical
disaggregation of samples and concomitant loss of structural features
and chemical gradients. Phase stability fields are a function of
relative humidity, and thus, desiccant functionality in the sample
return capsule may prevent melting of these salts (Figure 2). Hydration
and dehydration reactions appear to proceed more slowly than melting, so
a rapid recovery of the returned sample would help significantly in
minimizing disaggregation problems.

**Temperature Effects on Organic Phases**

Few published organic geochemical studies report molecular or stable
isotopic data for fine-grained sediments or sedimentary rocks on Earth
containing trace (\< 0.05 wt%) amounts of organic carbon for two
reasons. First, samples containing trace concentrations of organic
carbon are almost always contaminated during sampling to a level where
extraneous organic compounds pervasively overprint indigenous organic
compounds. Second, organic compounds are tightly bound to mineral
surfaces in fine-grained siliciclastic, calcareous, and evaporitic
sedimentary materials containing trace amounts of organic matter.
Increasing sample size is ineffective because extraction yields from
these types of samples are proportionally lower than yields for similar
sediments containing higher contents of organic carbon. For all of these
reasons, it is difficult to predict the fate of organic molecules in a
Mars return samples that are anticipated to contain only trace level
organic carbon. In Table 6, we described the fate of organic molecules
using generalized terms because most of the compound classes contain a
wide range of structural configurations and molecular weights combined
with substantial uncertainties regarding mineral composition and
hydration state for near-surface Mars regolith and rocks. The term
*mobilized* refers to molecules that are unaffected chemically but are
capable of physical migration between absorbed or complexed phases.
*Volatilized* refers to molecular classes that will be present primarily
in a vapor state. Volatilization at the chosen temperatures is estimated
based on standard laboratory evaporation procedures at controlled
temperature using vacuum aspiration to about 20 millibars (Rotavap or
equivalent apparatus). *Partial decomposition* refers to initial stages
of chemical transformation including isotope exchange, dehydration, and
isomerization. *Decomposition* refers to chemical transformations more
severe than those listed for partial decomposition, typically involving
structural breakdown and/or molecular reorganization.

**It is clear from the table that at 50oC a significant number of
compounds experience decomposition, and even at 20oC some compounds are
decomposed. At -5oC some compounds are mobilized or even volatilized.**

<table style="width:100%;">
<colgroup>
<col style="width: 5%" />
<col style="width: 8%" />
<col style="width: 5%" />
<col style="width: 8%" />
<col style="width: 5%" />
<col style="width: 1%" />
<col style="width: 6%" />
<col style="width: 6%" />
<col style="width: 3%" />
<col style="width: 13%" />
<col style="width: 6%" />
<col style="width: 10%" />
<col style="width: 17%" />
</colgroup>
<tbody>
<tr class="odd">
<td colspan="13"><em><strong>Table 6</strong></em></td>
</tr>
<tr class="even">
<td colspan="13"><em><strong>Fate Of Indigenous Martian Organic
Molecules During Sample Return<br />
</strong>Information Compiled in 2004 by Lisa Pratt, Simon Brassell,
Arndt Schimmelmann, Bernd Simoneit</em></td>
</tr>
<tr class="odd">
<td colspan="2" rowspan="2"><strong>Molecular Class</strong></td>
<td colspan="2" rowspan="2"><strong>Examples</strong></td>
<td colspan="2" rowspan="2"><blockquote>
<p><strong>Scientific Interest</strong></p>
</blockquote></td>
<td rowspan="2"><blockquote>
<p><strong>Susceptible to Photo -Decomposition</strong></p>
</blockquote></td>
<td rowspan="2"><blockquote>
<p><strong>Susceptible to Hydrolysis or Water Solvation</strong></p>
</blockquote></td>
<td colspan="5"><strong>organic matter sampled in an intact sedimentary
matrix, sample canister sealed under oxidizing atmosphere at 6-10
millibars pressure, maximum temperature during re-entry not
exceeding:</strong></td>
</tr>
<tr class="even">
<td colspan="2"><strong>-5<sup>"</sup>C</strong></td>
<td colspan="2"><strong>20<sup>"</sup>C</strong></td>
<td><strong>50<sup>"</sup>C</strong></td>
</tr>
<tr class="odd">
<td colspan="2"><strong>Aromatic Hydrocarbons</strong></td>
<td colspan="2">benzene</td>
<td colspan="2">M</td>
<td></td>
<td></td>
<td colspan="2">Unm</td>
<td colspan="2">Mob</td>
<td>Vol</td>
</tr>
<tr class="even">
<td colspan="2"><strong>Polyaromatic Hydrocarbons</strong></td>
<td colspan="2">anthracene, phenanthrene</td>
<td colspan="2">H</td>
<td>√</td>
<td></td>
<td colspan="2"><p>LMW - Mob</p>
<p>HMW-Unm</p></td>
<td colspan="2"><p>LMW - Vol</p>
<p>HMW - Vol</p></td>
<td><p>LMW - Vol</p>
<p>HMW - Vol</p></td>
</tr>
<tr class="odd">
<td colspan="2"><strong>S, N, O Heteroatomic Aromatics</strong></td>
<td colspan="2">pyrimidine, furan, pyridine, purines,
benzothiophene</td>
<td colspan="2">M</td>
<td></td>
<td></td>
<td colspan="2"><p>LMW - Mob</p>
<p>HMW-Unm</p></td>
<td colspan="2"><p>LMW - Vol</p>
<p>HMW - Mob</p></td>
<td><p>LMW - Vol /PDec</p>
<p>HMW - Vol /PDec</p></td>
</tr>
<tr class="even">
<td colspan="2"><strong>Aliphatic Hydrocarbons</strong></td>
<td colspan="2">alkanes, alkenes, pristane, phytane</td>
<td colspan="2">H</td>
<td></td>
<td></td>
<td colspan="2">Unm</td>
<td colspan="2"><p>LMW - Vol</p>
<p>HMW -Unm/ Mob</p></td>
<td><p>LMW - Vol /PDec</p>
<p>HMW - Vol /PDec</p></td>
</tr>
<tr class="odd">
<td colspan="2"></td>
<td colspan="2">Methane</td>
<td colspan="2">VH</td>
<td></td>
<td></td>
<td colspan="2">Vol</td>
<td colspan="2">Vol</td>
<td>Vol</td>
</tr>
<tr class="even">
<td colspan="2"></td>
<td colspan="2">ethane, propane, butane</td>
<td colspan="2">VH</td>
<td></td>
<td></td>
<td colspan="2">Vol</td>
<td colspan="2">Vol</td>
<td>Vol</td>
</tr>
<tr class="odd">
<td colspan="2"></td>
<td colspan="2">hopanes, steranes</td>
<td colspan="2">H</td>
<td></td>
<td></td>
<td colspan="2">Unm</td>
<td colspan="2">Unm</td>
<td>Mob</td>
</tr>
<tr class="even">
<td colspan="2"><strong>Saccharides</strong></td>
<td colspan="2">tetrose, glucose, cellulose</td>
<td colspan="2">VH</td>
<td></td>
<td>√</td>
<td colspan="2">Unm</td>
<td colspan="2">Unm</td>
<td>Unm</td>
</tr>
<tr class="odd">
<td colspan="2"><strong>Carboxylic Acids and their Salts</strong></td>
<td colspan="2">alkyl and aromatic acids, fatty acids</td>
<td colspan="2">H</td>
<td></td>
<td>√</td>
<td colspan="2"><p>LMW- Mob</p>
<p>HMW-Unm<br />
salt-Unm</p></td>
<td colspan="2"><p>LMW - Vol</p>
<p>HMW - Mob<br />
salt-Unm</p></td>
<td><p>LMW - Vol</p>
<p>HMW - Mob/Vol<br />
salt-Unm</p></td>
</tr>
<tr class="even">
<td colspan="2"><strong>Amino Acids</strong></td>
<td colspan="2">basic, neutral, acidic</td>
<td colspan="2">VH</td>
<td></td>
<td>√</td>
<td colspan="2">Unm</td>
<td colspan="2">Unm</td>
<td><p>LMW - Unm</p>
<p>HMW - Unm</p></td>
</tr>
<tr class="odd">
<td colspan="2"><strong>Nitrogen-Containing Compounds</strong></td>
<td colspan="2">amines, amides</td>
<td colspan="2">H</td>
<td></td>
<td></td>
<td colspan="2"><p>LMW- Vol</p>
<p>HMW-Unm</p></td>
<td colspan="2"><p>LMW - Vol /PDec</p>
<p>HMW -Unm/ Mob</p></td>
<td><p>LMW – Vol /PDec</p>
<p>HMW – Vol /PDec</p></td>
</tr>
<tr class="even">
<td colspan="2"></td>
<td colspan="2">tetrapyrroles, porphines, siderophores</td>
<td colspan="2">VH</td>
<td>√</td>
<td>√</td>
<td colspan="2">Unm</td>
<td colspan="2">Unm</td>
<td>PDec</td>
</tr>
<tr class="odd">
<td colspan="2"><strong>Peptides</strong></td>
<td colspan="2">polar and non-polar</td>
<td colspan="2">H</td>
<td></td>
<td>√</td>
<td colspan="2">Unm</td>
<td colspan="2">Unm</td>
<td>Mob /PDec</td>
</tr>
<tr class="even">
<td colspan="2"><strong>Functionalized Lipids</strong></td>
<td colspan="2">glycerides, fats</td>
<td colspan="2">VH</td>
<td></td>
<td>√</td>
<td colspan="2">Unm</td>
<td colspan="2">Unm- Mob /PDec</td>
<td>PDec</td>
</tr>
<tr class="odd">
<td colspan="2"></td>
<td colspan="2">ether lipids</td>
<td colspan="2">VH</td>
<td></td>
<td></td>
<td colspan="2">Unm</td>
<td colspan="2">Unm</td>
<td>Unm</td>
</tr>
<tr class="even">
<td colspan="2"></td>
<td colspan="2">esters, ketones, aldehydes</td>
<td colspan="2">H</td>
<td>√</td>
<td>√</td>
<td colspan="2">Unm</td>
<td colspan="2"><p>LMW - Mob</p>
<p>HMW -Unm</p></td>
<td><p>LMW -PDec</p>
<p>HMW -PDec</p></td>
</tr>
<tr class="odd">
<td colspan="2"></td>
<td colspan="2">alcohols</td>
<td colspan="2">H</td>
<td></td>
<td>√</td>
<td colspan="2"><p>LMW- Mob</p>
<p>HMW-Unm</p></td>
<td colspan="2"><p>LMW - Mob</p>
<p>HMW - Mob</p></td>
<td><p>LMW -PDec</p>
<p>HMW -PDec</p></td>
</tr>
<tr class="even">
<td colspan="2"><strong>Humic and Fulvic Acids</strong></td>
<td colspan="2"></td>
<td colspan="2">M</td>
<td>√</td>
<td>√</td>
<td colspan="2">Unm</td>
<td colspan="2">Mob /PDec</td>
<td>PDec/Dec</td>
</tr>
<tr class="odd">
<td colspan="2"><strong>Unresolved Complex Molecules</strong></td>
<td colspan="2"></td>
<td colspan="2">H</td>
<td></td>
<td></td>
<td colspan="2">Unm</td>
<td colspan="2">Mob</td>
<td>Mob /PDec</td>
</tr>
<tr class="even">
<td colspan="2"><strong>Phospholipids</strong></td>
<td colspan="2"></td>
<td colspan="2">VH</td>
<td></td>
<td>√</td>
<td colspan="2">Unm</td>
<td colspan="2">Mob/PDec</td>
<td>Mob /PDec</td>
</tr>
<tr class="odd">
<td colspan="2"><strong>Nucleic Acids, Nucleotides</strong></td>
<td colspan="2">DNA, RNA, TNA</td>
<td colspan="2">VH</td>
<td>√</td>
<td>√</td>
<td colspan="2">Unm</td>
<td colspan="2">Unm</td>
<td>DNA -Unm<br />
RNA -PDec</td>
</tr>
<tr class="even">
<td colspan="2"><strong>Nitrogen-Containing Gases</strong></td>
<td colspan="2">NH<sub>3</sub>, HCN, NO<sub>2</sub>, N<sub>2</sub>O,
NO</td>
<td colspan="2">H</td>
<td></td>
<td></td>
<td colspan="2">Mob</td>
<td colspan="2">Vol</td>
<td>Vol</td>
</tr>
<tr class="odd">
<td colspan="2"><strong>Sulfur-Containing Gases</strong></td>
<td colspan="2">H<sub>2</sub>S, (CH<sub>3</sub>)<sub>2</sub>S</td>
<td colspan="2">H</td>
<td></td>
<td></td>
<td colspan="2">Mob / Vol</td>
<td colspan="2">Vol</td>
<td>Vol /PDec</td>
</tr>
<tr class="even">
<td colspan="13"><em><strong>Abbreviations and
acronyms</strong></em></td>
</tr>
<tr class="odd">
<td></td>
<td colspan="2">VH = very high<br />
H = high</td>
<td colspan="2">M = moderate<br />
L = low</td>
<td colspan="4">Unm = unmobilized<br />
Mob = mobilized<br />
Vol = volatilized</td>
<td colspan="2">PDec = partially decomposed<br />
Dec = decomposed</td>
<td colspan="2">LMW = low molecular weight<br />
HMW = high molecular weight</td>
</tr>
</tbody>
</table>

# VIII. Revised Science Considerations Pertaining to Forward Organic Contamination

**Terrestrial Organic Contamination in Returned Samples:**

**Background:** Identification and characterization of organic compounds
on Mars is given high priority by the recent Mars Exploration Program
Analysis Group (MEPAG) update (Taylor et al., 2004). This investigation
of carbon compound sources and processing is considered to be an
essential step to advance the understanding of the possibility of past
or present life on Mars. The carbon investigation is intended to proceed
in parallel with studies that lead to an increased understanding of the
history of liquid water on the planet and the availability of other
elements and energy sources necessary to sustain life. The ability
demonstrated by the Mars Exploration Rover Opportunity to reach surface
sites that show direct evidence of substantial aqueous alteration
further motivates the search for organic compounds and the locations
that might best preserve such compounds.

Although examination of patterns in complexity, oxidation state, and
isotopic composition is expected to point toward sources and processing
of organic compounds found on Mars, predictions regarding the abundances
of organic compounds that might be found in near surface samples are
presently highly uncertain. The most easily quantifiable source of
organic compounds is exogenous delivery of meteoritic material that
could, in principle lead to parts per million (ppm) of organics in the
near surface (Benner et al., 1999). The degree of gardening of these
materials into the regolith and the extent of subsequent chemical
oxidation are highly uncertain. The recent reports of up to 30 ppb of
methane in the Martian atmosphere (Formisano et al., 2004, Krasnopolsky,
2004) or even higher localized mixing ratios (Mumma et al., 2004) also
has implications for the organic compounds present in the near surface
of Mars. Methane that diffuses from the regolith into the atmosphere
forms ethane and higher hydrocarbons by UV photolysis (Wong et al.,
2003) and the subsequent condensation of these phases in surface ice and
sorption on to mineral surfaces (for diffusion to the atmosphere at a
rate of \~2-6x10^5^ cm^-2^s^-1^) should occur at a rate of \~7 ppb C
byr^-1^ for a 10 cm thick layer. The degree of gardening of these
materials into the regolith and the extent of subsequent chemical
oxidation are highly uncertain. Other sources of organic compounds such
as those that might be produced by abiotic synthesis are not quantified
even to first order. Upper limits to the amount of biologically produced
organic matter can be inferred from the austere environment in the
Antarctica dry valleys (Wynn-Williams, 1990) where organic carbon
concentrations are \<200 ppm and the density of living bacteria are
\~10^5^ gm^-1^ (Cowan et al., 2002). Thus, a sensitive search for a wide
range of organic compounds in returned samples by a variety of
techniques would be of high priority. To avoid ambiguity in the
interpretation of these measurements that seek to find and characterize
organics it would be essential that terrestrial contamination introduced
to the returned samples be limited and well characterized.

**Organic Compounds of Interest in a Returned Sample:** A wide range of
possible organic compounds is of interest from the point of view of
understanding the habitability of Mars -- its potential for past or
present life. Although distributions of organic compounds in classes
directly participating in terrestrial biology such as amino acids,
nucleobases, sugars, carboxylic acids, and more complex molecules such
as proteins, enzymes, lipids or their fragments may provide the most
direct potential biomarkers, a broad survey of organic molecules and
molecular types would be necessary to develop an understanding of how a
particular Martian chemical environment might transform exogenous or
endogenous organic species. Thus, limits on total molecular carbon would
be important as well as limits on individual species or classes of
compounds.

**Sources of Terrestrial Contamination in a Returned Mars Sample:**
Likely terrestrial contamination sources that might interfere with in
situ measurements have been recently identified by the Report of the
Organic Contamination Science Steering Group (OCSSG) (Mahaffy et al.,
2003). These include materials used in spacecraft fabrication such as
conformal coatings that outgas volatile organics, lubricants for moving
parts, propulsion fluids and solids, and organics contained in
particulate matter. Contaminants may accumulate during spacecraft
assembly even in a typical clean room environment and are more rapidly
distributed during events such as launch or entry, descent, and landing
(EDL) where substantial levels of terrestrial material is both
redistributed within the spacecraft and released into the Martian
environment.

Many of the likely contaminants consist of or contain biologically
produced or processed organic molecules of the type that would be of the
highest interest if their Martian origin could clearly be established.
These contaminants may migrate to the tools and surfaces that contact
the sample at Mars or residual contamination on the landed system may
migrate to the Mars surface prior to sample collection. While for an in
situ experiment, it may be possible to make a measurement shortly after
sample collection to minimize the amount of contamination transferred
from the lander system, the extended time required to return a sample to
Earth would provide an additional opportunity for contamination to mix
with the collected sample prior to analysis.

The sample temperature history between collection and analysis in
laboratories on Earth may be a critical parameter in determining the
extent of mixing of both terrestrial organic contaminants and indigenous
organics. The worst-case thermal environment may be during and shortly
after Earth entry. Thermal transformation of the collected sample
constitutes another type of sample contamination. Of particular concern
is the chemical effect of thermally released water or water vapor on
molecules of interest.

Storage and processing of the samples and their containers in the return
sample facility again introduces an additional path for contamination.
Subsequently, each analysis technique with the associated sample
manipulation and physical and chemical processing, such as the use of
solvents for organic extraction, has the potential to introduce
additional contamination. The design of the sample curation facility
must be an integral element of planning for the sample return mission.

**Relationship to Planetary Protection Requirements:** Agency planetary
protection requirements for the first Mars sample return mission are
expected to minimize the probability that a viable terrestrial organism
that could be cultured with standard protocols would be returned with
the collected sample. These mission requirements would not, however,
address the contamination issues of non-viable terrestrial organisms and
their molecular byproducts that might be contained in the return sample.
Thresholds for these contaminants must be separately set during the
mission science definition process.

**Lessons from the Apollo experience:** Considerable attention was paid
to contamination issues during the Apollo program to maintain the
integrity of returned lunar samples. Critical sample processing surfaces
were cleaned to \~ 1 nano-gram/cm^2^ of molecular material. The total
organic content of the returned lunar samples was typically in the 0.1
to 100 ppb range. Several amino acids were present (Brinton and Bada,
1996) and in the worst case at an abundance of 70 parts per billion
(ppb) by mass (ppbw). Amino acids such as free alanine and aspartic acid
were identified as terrestrial contaminants. The lesson learned from the
lunar organic contamination may be that additional measures beyond
rigorous pre-launch cleaning of surfaces that contact samples may be
necessary to obtain samples with terrestrial contamination below the
several ppbw level.

**Contamination Threshold Goals:** The OCSSG report proposed thresholds
of 1-10 ppbw for the maximum amount of terrestrial contamination that
could be contained in a Mars sample on delivery to an instrument in a
landed payload package for proxy compound classes of high scientific
interest such as benzene or aromatic hydrocarbons, carbonyl and hydroxyl
containing compounds, amino acids, amines, amides, or non-aromatic
hydrocarbons. The OCSSG proposed a threshold for total reduced carbon
contamination at 40 nanograms per gram sample delivered to an analytical
instrument. In light of the great variety of state of the art analytical
techniques that could be applied to organics analysis of returned
samples, it would be desirable to realize even lower thresholds in a
returned sample than these proposed thresholds for in situ analysis. For
example, thresholds of less than 10 ppbw in total organic contamination
and ppbw or below in the proxy compound classes listed above could
enable robust conclusions to be drawn regarding the origin and
processing of indigenous Martian organics found in the ppbw or higher
abundances.

Significant scientific work in terrestrial organic geochemistry is
carried out using sub parts per billion of certain species as
discriminators. For example, phospholipid fatty acid analyses (PLFA) of
deep subsurface rock cores provide the principle method of determining
biomass and discriminating between contaminant and indigenous
microorganisms (Onstott et al., 1998). In some cases the total PLFA is
\< 0.1 ppb C (Colwell et al., 1997) corresponding to \~10^4^ cells
gm^-1^.  The presence of 10me16:0 (a 16 carbon saturated hydrocarbon
chain with a methyl group branching off a the C10 position) at \< 0.01
ppb C was used to identify indigenous sulfate reducing bacteria existing
in a rock sample collected at 3.3 km depth in which 95% of the bacterial
biomass was contaminants (Onstott et al. 2004).

Sedimentary units on Earth contain widely varying contents of organic
matter. Coal and oils shale are examples of sedimentary rocks containing
more than 50 wt% organic carbon (C~org~). At the other end the
concentrations range, red sandstones, mudstones, and shales
(collectively termed redbeds) are generally in the range 0.1 to 0.01 wt%
C~org~. Sedimentary units on Mars are anticipated to contain relatively
small amounts of organic matter and, therefore, acceptable thresholds
for contamination of Mars return samples logically are based on reported
yields for specific classes of organic molecules in the lowest C~org~
sediments from Earth such as redbeds. The most widely studied classes of
organic molecules in sedimentary rocks on Earth are aliphatic and
aromatic hydrocarbons (see Table X). Hydrocarbons in ancient sediments
are extracted using nano-pure chlorinated organic solvents and are
isolated using chromatographic separation preferably under clean-room
conditions. Identification of individual molecules is performed using
molecular mass spectrometers with sub-picogram sensitivity. The
solvent-soluble fraction of a rock is called bitumen and the residual
organic fraction is called kerogen. Bitumen yields from redbeds are
generally less than 10 µg/g (weight bitumen/weight rock) and are often
less than 1µg/g. Samples containing less than 1µg/g bitumen are
challenging to study because substantial contamination occurs during
sample collection and sample handling. For this reason, there are few
published organic geochemical studies on any type of sedimentary rocks
containing less than about 0.2 wt% C~org~ (Pratt, 1984). The major
compound classes recovered from redbed samples are S-N-O-heteroatomic
organic compounds, aliphatic hydrocarbons, aromatic hydrocarbons, and
unresolved mixtures of high-molecular-weight organic compounds
(asphaltenes). The proportion of aliphatic plus aromatic hydrocarbons
can represent less than 1% of total bitumen. If we assume a yield of 1
µg/g bitumen and 0.01µg/g aliphatic plus aromatic hydrocarbons then the
concentration of individual n-alkanes and hopanes (compounds of high
scientific interest) would be in the range of 1 to 0.1 ng/g. Thus,
contamination at a level of 1 ppb (ng/g) for an individual compound of
interest would be equivalent to anticipated concentrations of indigenous
Martian organic compounds and greater by a factor of 10^5^ than current
detection levels for mass spectrometers.

However, it is important to note that not all samples distributed for
analysis would have organic measurements as a prime focus. If subsets of
the returned sample that would be analyzed for organics are effectively
isolated from transport of organic molecules contained in other samples,
then the average contamination level in the returned sample could be
larger than that in the isolated samples of interest without impacting
the primary organics studies.

The OCSSG report also specified a 1 ppbw threshold for DNA as a proxy
for very complex molecules that could only have a biological source. It
is desirable for a returned sample to have the threshold for such
complex molecules far below the thresholds desired for in situ
exploration where the techniques for analysis of such materials are not
present. A contamination threshold for DNA or complex molecules such as
proteins could usefully be set at an abundance that would make any
detection with current analytical technologies in analyses of a returned
sample unlikely. Achieving this goal might require cleaning of the
sampling containers and tools while on the surface of Mars, prior to
sample collection and sealing.

**Contamination mitigation:** The OCSSG report describes a range of
possible contamination mitigation steps including selection of low
outgassing materials, cleaning of all spacecraft elements, and
maintaining a clean environment during assembly and test operations. The
microbial community in the assembly area and on the spacecraft would
need to be fully and quantitatively characterized. Particular attention
should be focused upon the removal of spore forming, phototrophic and
autotrophic microorganisms (e.g. methane oxidizers) that have the
ability to survive on Mars within the protective environment of the
rover. In addition, a clear understanding of contamination pathways
within the spacecraft systems must be developed. Special attention must
be paid to sample processing and storage equipment both with regard to
its cleaning and its effective molecular isolation from more
contaminated areas of the spacecraft. In addition to these design and
fabrication and assembly mitigation methods, surface operational
sequences should be designed to minimize the amount of terrestrial
contamination that would be mixed with the returned sample. For example,
a landed system with mobility could remove itself sufficiently far from
the landing site to minimize the collection of chemicals vented and
released during the landing process. An approach to a sample of interest
by a mobile collection system could be designed to minimize the time in
close proximity to the sample to reduce accumulation of contamination
from the collection platform. Monitoring of winds by the mobile landed
system and approaching samples of interest from the down-wind side could
minimize the amount terrestrial contamination transferred to the sample
of interest.

Heat, UV, or plasma treatment of sample storage volumes and sampling
tools shortly before sample collection could eliminate or minimize the
contamination from large molecules that are effectively destroyed by
high heat, plasma, or radiation. For example, even a short 500^o^C
treatment of sampling tools and containers is expected to rapidly
destroy complex molecular species associated with dead organisms.
Effective isolation of a sample immediately after collection could
prevent contamination from either the landed system or other samples
from migrating into the collected sample. In a subset of the sample
containers, it might be useful to study the use of adsorbant traps such
as synthetic zeolites that would remove water vapor as it was out gassed
during the return to Earth in order to minimize its subsequent chemical
interaction with the sample and retain it for analyses.

**Blanks and Controls:** Controls in the form of passive monitors that
would collect contamination from the environment during the various
mission phases from early in the assembly process to sample return are
essential to build up a library that would enable the nature of the
terrestrial contamination to be understood. Likewise, blanks, such as
empty sample containers, that mimic sample processing operations and
exposure could be valuable in validating organic measurements on
returned samples. Use of organic free terrestrial blanks that would be
exposed to the Martian environment and sealed for return might be
useful, but should be approached with great caution to avoid any
possibility of contamination of Martian samples with inorganic
terrestrial materials. Post collection organic migration potentially
could be studied by exposure of a small subset of Martian samples to the
mobile lander environment for a variable time period prior to sealing.
This would help to evaluate contamination transfer rates or heat
devolitalization of a Mars sample prior to storage and isolation for
return to Earth. Contamination monitors should not only be used in clean
rooms and fabrication sites prior to launch, but could also be
incorporated into the return system to collect contamination in the
later mission phases. In spacecraft locations where contamination
monitors cannot be collected for return, the use of active sensors such
as quartz crystal microbalances should be considered to monitor the
buildup of contamination.

# Summary of Organic Contamination Issues and Findings

\(1\) **While OCSSG specified contamination levels for organic molecules
would be adequate for a subset of the samples where organics analysis is
not the primary objective, lower thresholds by a factor of 4 or more are
desired for an isolated subset of the samples such as cores from
sedimentary deposits or selected rocks where organics analysis would be
a primary investigation.** Although modern instrumentation may be able
to detect much lower levels of organics, achieving a significantly lower
threshold may be impractical as may the realization of lower organic
levels in blanks used during the sample analysis. The Apollo experience
suggests that these thresholds can be realized.

\(2\) For large biomolecules that are the residue from terrestrial
organisms (e.g. DNA, RNA, and large or medium sized proteins) the
contamination threshold in returned samples should be sufficiently low
that analyses of test samples have a high probability to produce a
negative result. Technologies such as in situ heat, UV, or plasma
treatment of sample containers and tools prior to collection activities
should be explored as a means of breaking down these large biomolecules.

\(3\) Isolation of sample subsets after collection to prevent diffusion
of organic contamination is recommended. Sample collection methods that
lend themselves to effective sample isolation, such as leaving the
sample contained in its coring device until return to Earth, should
continue to be explored.

\(4\) Rigorous end-to-end contamination control and monitoring of
contamination is required through use of witness plates. A library of
spacecraft produced molecular contamination should be developed and
maintained for use during the returned sample analysis period. A similar
library should be developed for microbial contaminants where ever
spacecraft instruments are assembled and in the final assembly area.

\(5\) Judicious use of blanks and controls is necessary to establish
confidence in selected sample collection and processing protocols.

\(6\) Thermal perturbations of the sample to temperatures above its
natural diurnal maximum for surface samples and mean annual temperature
for cores from below the thermal skin depth have the potential to
chemically transform organic species of interest. The possible release
of water is of particular concern. Sample container designs that remove
water vapor and other volatile species as they are produced after
collection deserve study.

\(7\) Definition of the curation facility requirements and the
protection of samples from contamination during analysis within this
facility and during subsequent transport to and analysis in distributed
laboratories should be carried out in parallel with definition of the
space systems.

# IX. Revised Science Considerations Pertaining to Forward Inorganic Contamination

***General Considerations***

Any spacecraft includes a semi-infinite multitude of components.
Contaminants can be found in elemental form, alloys, and compounds and
can have a variety of physical forms, including coatings, sealants and
greases. While the distinction between organic and inorganic components
may appear simple, it definitely gets blurred in practice. For this
report we will emphasize inorganic contaminants.

The identification of contaminants is an ongoing process as mission
design progresses. Since contaminants cannot be avoided for many mission
components, emphasis must be placed on components that come into direct
contact with samples or which can become attached or admixed with the
samples of interest. For a sample return mission, the sensitivity of
analytical techniques in laboratories on Earth, where the analyses would
be performed provides stringent limits on contamination. However, there
are also mechanical design considerations which may prevent elimination
of certain contaminants. Of paramount importance is the recognition that
space is a hostile environment and that experience with past successful
missions is a key parameter for selecting materials for new missions.
Heritage of use as well as technology developments and demonstrations
are key considerations.

In considering components that may come into contact with samples,
properties under use of these materials are important, such as:

a)  components subject to wear and tear (drilling, abrasion, sliding,
    seals);

b)  engine exhaust, including abraded particles coated with catalysts
    (e. g., Al~2~O~3~ spheres coated with Ir);

c)  contributions pyro explosions, especially in tight spaces and near
    samples;

d)  brazing/welding components;

e)  lubricants and sealants

To minimize contamination, one needs to consider first-order design
constraints:

a)  prevention of contamination should be an intrinsic aspect of
    equipment design, from the start of the design;

b)  the need to use tested materials, for reliability, with "heritage";
    and

c)  developments from identified technology tasks, which may allow use
    of alternative materials.

Relevant technology tasks may also address, the degree of abrasion and
of release of contaminants; methods to clean surfaces, e.g., by
processing duplicate (or multiple) identical samples through a sample
collection and processing equipment (potentially removing or diluting
surface contamination); and the degree of mobility of fine-grained
contaminants, during sample collection for avoiding contamination. A
specific example is provided by technology development needed on the
design of drills. Materials used previously on the Moon and in the Lunar
Curatorial Facility include: a) tungsten carbide cutters, brazed to
stainless steel drill bits; b) diamonds imbedded in nickel or
copper-based materials. Furthermore, the choice of cutting tool on Earth
may depend on the specific scientific investigation. For example, a
non-stainless steel chisel may be used if the study of platinum group
elements is of interest. New potential materials may be identified by
new technology developments, such as low-wear diamond bits for drilling,
advanced diamond coating methods (e.g., chemical & physical vapor
deposition). Drilling on Mars may also trade power level and drilling
time, in order to reduce wear and contamination.

Of equal importance is record keeping for all materials used and for all
cleaning components. This is especially important if we expect that
contamination levels in the laboratory woulf improve during the many
years it takes for a sample return mission to be designed, flown and to
return to Earth. In particular, record keeping needs to include:

a)  archive samples of all materials used (and identify all specific
    batches used);

b)  tests of solutions used for chemical processing, such as for electro
    polishing, electroplating; anodizing

c)  archiving of these solutions, used for plating, anodizing, etc.

d)  archival materials processed through plating, anodizing etc.

e)  keep sets of witness plates of materials ready to be flown.

In addition, it is important to require that new (not previously used)
reagents and solvents be used for any chemical processing and cleaning,
in order to prevent memory effects and contaminants introduced from
previously processed items. It is recommended that reagent grade
chemicals be used and that the processing tanks and equipment be made of
acceptable materials (such as polypropylene, stainless steel cathodes
for electro polishing, etc.).

Archiving of these many materials would require the existence or
construction of a storage facility, with clean sections for archiving
witness plates and provisions for venting from the materials being
stored. Provisions need to be made for separate storage of inorganic and
organic materials (e. g., solvents) in such a facility.

***Acceptable Contamination Levels***

It is important to emphasize that returned samples need to be subject to
much less contamination than would be acceptable for in situ analyses on
Mars because of the greater sensitivity of laboratory instrumentation as
compared to instrumentation used in situ. **This suggests strongly that
designs for sample handling and materials used for MSL [may
not]{.underline} be directly applicable to MSR.** In particular, an MSL
corer and abrader may not be usable for MSR without modifications.

In addressing acceptable contamination levels, it is important to
recognize that controls of inorganic and organic contamination are
inexorably linked. In particular, competing and potentially
contradictory requirements for prevention of inorganic and organic
contamination need to be identified early and resolved. Contamination
levels dictated for planetary protection may also present a challenge
for inorganic and organic contamination. Examples include a) special
surface coatings could compromise a suite of similar elements (e.g., Au
and Platinum Group Elements, PGE); b) special cleaning procedures may
adversely affect materials (e .g., excessive oxidation of Al); c)
special cleaning procedures may introduce inorganic contamination. All
these areas need to be addressed by a vigorous and detailed technology
development program.

In addressing acceptable contamination levels it is important to
consider the natural abundance of elements. It is harder to contaminate
major elements in nature and easier to contaminate trace elements. By
contrast, specific materials used as components for spacecraft and in
specific areas of spacecraft may concentrate large amounts of minor and
trace elements, due to specific chemical and physical processes. Generic
categories of inorganic compounds which contribute major contaminants
include:

a)  Greases, lubricants;

b)  Pyrotechnic devices;

c)  Abrasives, as for drilling;

Specific compounds that are a potential serious source of contamination
include: Mo and W disulfides, sulfates, nitrates and chlorates and
perchlorates (from pyrotechnic devices); phosphates.

Significant attention must be exercised for any proposed use of
separated isotope tracers. An integral part of control of inorganic
contamination is the total avoidance of the use of separated isotope
tracers for labeling of contaminants. Isotope tracers directly interfere
with all key isotope geochemistry measurements, including those used for
age determinations. Extensive experience shows that isotope tracers
include cross-contamination for many elements with [non normal isotopic
compositions]{.underline} (in the tracers). An example helps clarify
this issue. A ^42^Ca tracer includes unacceptable levels of ^84^Sr
(collected in magnetic separators as ^84^Sr^2+^).

The use of isotope tracers is based on the isotope dilution technique.
However, for the case of determining contamination in a complex process
of construction and assembly the technique yields potentially
uninterpretable results, because the calculations of contamination
levels depend on when and how frequently contamination is introduced in
time, relative to the introduction of the isotope tracer(s). In
particular, contamination introduced after introduction of the tracer is
not measurable, if no isotope exchange occurs with the tracer.

In deciding acceptable contamination levels we may consider that the
chemical composition of Mars samples can be correlated to the chemical
composition of SNC meteorites.

**To first order, we may then accept contamination levels for major and
minor elements at 0.1 percent of the contents of SNC meteorites.**

For trace elements it is more reasonable to consider Shergottites and
Nakhlites (at the exclusion of Chassigny, in which trace elements are
highly deficient, due to the unique mineralogy of Chassigny). For trace
elements at the ppm (parts per million, by weight) level, we may
consider acceptable contamination at the ppb (parts per billion, by
weight) level. For trace elements at the ppb level we may consider
acceptable contamination levels at the ppb and sub-ppb level, on a best
effort basis.

This general approach is not satisfactory because specific minor and
trace elements have unique significance in geochemistry, in isotope
geochemistry, and for dating techniques. Therefore, attention needs to
be paid to specific elements. We attach a table of selected key minor
and trace elements of interest to cosmochemistry and for the purpose of
age dating. As a simplifying approach we have set acceptable levels by
comparison with the abundances for SNC meteorites (the SN part) shown in
the Table, down to sub-ppb levels of contamination. It is inevitable
that some individual elements would be compromised by specific materials
choices, so that careful choices would be needed, throughout the mission
design and implementation. For halogens, we consider that low
contamination for Cl and Br are desirable, but with due consideration of
the apparent presence of evaporites on Mars, which contain substantial
amounts of halogens. In any case it is recognized that control of
halogen contamination may need to exclude restrictions on key lubricants
and greases based on fluorocarbons and other chlorinated compounds, with
strong heritage, unless alternates are identified through technology and
research.

**The Inorganic Contamination Subgroup has reached the following overall
conclusions:**

a)  **It is necessary to identify early, materials with sufficient
    heritage, expected to be used on *in situ* and sample return
    missions;**

b)  **Sample return missions require much stricter constraints than *in
    situ* missions;**

c)  **It is necessary to identify all materials in contact with the
    samples (sample acquisition and storage)**

d)  **Technology development is needed for identifying alternates;**

e)  **The cross-contamination between organic, inorganic and biologic
    materials needs to be identified;**

f)  **Containment materials (e. g., for gaskets) need to exclude
    objectionable materials, as much as possible; and**

g)  **The use of separated isotope tracers needs to be prevented.**

![](media/image4.pct)

Table 7. Recommended Limits on Inorganic Contaminants

# X. Site Dependency of Mobility and Sampling Requirements

During the deliberations of both the mobility and sampling subgroups, it
quickly became obvious that most of the parameters under consideration
would be highly site dependent: e.g., what would be needed on the
Meridiani plane would not necessarily work if the decision were made to
follow MSL to pick up a cache, or to go to a previously unexplored site
containing a major geologic contact.

In order to convey to NASA the need for flexibility in this regard, an
exercise was set up in which each of the two subgroups was asked to
consider the science needs for mobility and sampling under four very
different landing site circumstances: (1) MSR returns to Meridiani; (2)
MSR returns to Gusev Crater; (3) MSR follows MSL; (4) MSR goes to a
previously unvisited site that contains a major geologic contact of
interest.

The following table (Table 8) contains the results of this exercise. It
must be emphasized: this table is for example only, and is intended to
show in principle the kinds of flexibility that the SSG believes ought
to be maintained in the program to the extent possible.

**Table 8. Accessibility and mobility requirements for example sites.**

  ------------------- ------------------ ------------------ -------------------------- --------------------------
  **Critereon**       **Meridiani site** **Gusev crater**   **Go to MSL site**         **Previously unvisited
                                                                                       site with geologic
                                                                                       contact**

  **MOBILITY AND                                                                       
  LANDING                                                                              
  REQUIREMENTS**                                                                       

  **Accessibility to  Go to outcrop;     Go to boulders and Go to boulders and         Go to boulders and
  rock interiors**    rover mass         outcrops; rover    outcrops; rover mass       outcrops; rover mass
                      sufficient for     mass sufficient    sufficient for coring      sufficient for coring
                      coring             for coring                                    

  **Accessibility to  Mobility           Mobility           Mobility sufficient to     Mobility sufficient to
  uncontaminated      sufficient to      sufficient to      escape exhaust pattern (\> escape exhaust pattern (\>
  samples**           escape exhaust     escape exhaust     1/2 km?), lander debris,   1/2 km?), lander debris,
                      pattern (\> 1/2    pattern (\> 1/2    organic contam.;           organic contam.;
                      km?), lander       km?), lander       subsurface sampling        subsurface sampling
                      debris, organic    debris, organic    ability (e.g. coring)      ability (e.g. coring)
                      contam.;           contam.;                                      
                      subsurface         subsurface                                    
                      sampling ability   sampling ability                              
                      (e.g. coring)      (e.g. coring)                                 

  **Altitude**        -1.3 km            -1.9 km            CRITICAL to match MSL\'s   Higher altitude range
                                                            altitude capability (+2.5  (+0.5 or or +1 km) would
                                                            km)                        be desirable because it
                                                                                       would provide access to
                                                                                       high-quality science sites
                                                                                       in the ancient Southern
                                                                                       Highlands (possibly
                                                                                       recording a warmer wetter
                                                                                       climate on Mars)

  **Landing           Accessibility to   It would be good   If there is a geologic     If there is a geologic
  precision**         \>20 m diam        to land within 500 contact, it would be good  contact, it would be good
                      crater; \~ 200m    m of the contact   to land within 500 m of    to land within 500 m of
                      precision? Note:   between the hills  the contact. You would     the contact. You would
                      Landing precision  and the plains,    want accessibility to the  want accessibility to the
                      and roving         and closer would   terrain boundary between   terrain boundary between
                      distance are       be better. You     the two geologic units, to the two geologic units, to
                      intertwined. It\'s would want         sample both units away     sample both units away
                      probably more      accessibility to   from the landing           from the landing
                      important to       the terrain        contamination              contamination
                      minimize the time  boundary between                              
                      the rover spends   the plains and the                            
                      on the surface     hills, to sample                              
                      collecting         both terrains away                            
                      samples. The       from the landing                              
                      terrain at         contamination                                 
                      Meridiani between                                                
                      craters is smooth,                                               
                      flat and barren of                                               
                      rocks, so it would                                               
                      take less time to                                                
                      drive.                                                           

  **Minimum roving    1 km               1 km               1 km                       1 km
  distance**                                                                           

  **Time on surface,  Time sufficient to Time sufficient to Time sufficient to sample  Time sufficient to sample
  autonomy to lessen  sample             sample plains      the diversity of rock      the diversity of rock
  the time**          stratigraphy by    regolith, plains   types by coring, and to    types and regolith in both
                      coring within      rocks, a diversity also sample regolith,      geologic units; as well as
                      single crater, and of rock types in   dust, and atmosphere       dust and atmosphere
                      to also sample     the hills,                                    samples
                      regolith, dust,    regolith in the                               
                      and atmosphere     hills, dust, and                              
                                         atmosphere                                    

  **Slopes /          Must be able to    Must be able to    The more MSR matches its   Need flexibility to
  terrain**           enter and exit     drive up and down  slope/terrain capability   respond to unknown terrain
                      crater             the side of the    to that of MSL, the better characteristics to
                                         Columbia Hills and able we will be to follow  maximize the diversity of
                                         the rugged rocky   MSL                        rock types collected
                                         plains                                        

  **Rover             Rover must be able Orbiter and/or     Rover must be able to      Orbiter and/or direct to
  communication**     to communicate     direct to Earth    communicate w/orbiter      Earth com is advantageous,
                      w/orbiter and/or   com is             and/or directly to Earth   but we could design a
                      directly to Earth. advantageous, but                             mission that would not
                      Rationale: rover   we could design a                             require it.
                      entering/exiting   mission that would                            
                      craters may be out not require it.                               
                      of range of direct                                               
                      lander com.                                                      

  **Latitude**        2 degrees S        15 degrees S       CRITICAL: MSL latitude     Opening the latitude range
                                                            range (+/- 60 degrees?)    as far south as possible
                                                                                       would improve the science
                                                                                       by allowing access to more
                                                                                       possible ancient highlands
                                                                                       landing sites (if altitude
                                                                                       is also increased).

  **SAMPLING                                                                           
  REQUIREMENTS**                                                                       

  **Sample            Sample identified  Samples of plains  Rock types as diverse as   Rock types as diverse as
  diversity**         units within       basalt lava, rocks possible.                  possible.
                      single crater,     in the hills that                             
                      based on imaging;  show variations in                            
                      regolith; dust;    texture and degree                            
                      atmosphere. No req of oxidation                                  
                      for finding        (red/blue                                     
                      non-sedimentary    reflectance                                   
                      rocks. That means  ratio), regolith                              
                      that the coring    (from plains and                              
                      device could be    from hills), dust,                            
                      designed for       and atmosphere                                
                      evaporite rock.                                                  

  **Rover sampling    Desirable; much of Highly desirable.  Highly desirable. Could    Highly desirable. Could
  arm (as opposed to  the outcrop in the Could not          not guarantee that some    not guarantee that some
  body-mounted,       walls of Eagle &   guarantee that     key diversity would be     key diversity would be
  \'under-rover\'     Endurance Crater   some key diversity available as rocks under   available as rocks under
  coring)**           could be driven on would be available the body of the rover.     the body of the rover.
                      top of and sampled as rocks under the This would help ensure     This would help ensure
                      using a            body of the rover. maximum diversity.         maximum diversity.
                      body-mounted       This would help                               
                      corer. It would    ensure maximum                                
                      provide more       diversity.                                    
                      flexibility to be                                                
                      able to sample                                                   
                      diversity, e.g. if                                               
                      there were some                                                  
                      impact ejecta                                                    
                      blocks of a                                                      
                      different rock                                                   
                      type, sitting on                                                 
                      the surface, that                                                
                      could not be                                                     
                      driven over by the                                               
                      rover.                                                           

  **Sample collection Corer with         Corer with         Corer with flexible        Corer with flexible
  tool orientation**  flexible           flexible           orientation to respond to  orientation to respond to
                      orientation to     orientation to     the possible geometry of   the possible geometry of
                      respond to         respond to         sedimentary rock fabric.   sedimentary rock fabric.
                      layering geometry  geometry of layers                            
                                         (or foliation)                                
                                         seen in the hills                             

  **Capability to do  Desirable, but not Desirable, but not If the rocks are highly    If the rocks are highly
  close-up imaging of critical, because  critical, because  dust covered or you cannot dust covered or you cannot
  rock interiors (1   we know that we    the rock interiors distinguish the diversity  distinguish the diversity
  possibility would   could sample the   are not diagnostic based on color camera      based on color camera
  be to spit out      stratigraphic      of diversity of    images, then this would be images, then this would be
  cores onto the      section without    rocks in the       desirable.                 desirable.
  ground that you     having to expose   hills. Imaging of                             
  would not return to rock interiors     outer rock                                    
  earth)**                               surfaces could                                
                                         discern the plains                            
                                         basalt lava rock                              
                                         from altered rocks                            
                                         in the hills.                                 

  **Sample            Sample isolation   Sample isolation   Sample isolation critical. Sample isolation critical.
  containers**        critical. First in critical. First in First in importance would  First in importance would
                      importance would   importance would   be separation of regolith  be separation of regolith
                      be separation of   be separation of   from rock from dust.       from rock from dust.
                      regolith from rock regolith from rock Second would be isolation  Second would be isolation
                      from dust. Second  from dust. Second  of individual rock cores   of individual rock cores
                      would be isolation would be isolation from each other. This      from each other. This
                      of individual rock of individual rock sample isolation would be  sample isolation would be
                      cores from each    cores from each    especially important to    especially important to
                      other. This sample other. This sample prevent the migration of   prevent the migration of
                      isolation would be isolation would be water vapor and organic    water vapor and organic
                      especially         especially         volatiles in the event     volatiles in the event
                      important to       important to       that hydrous minerals      that hydrous minerals
                      prevent the        prevent the        and/or organic             and/or organic
                      migration of water migration of water volatile-rich samples are  volatile-rich samples are
                      vapor and organic  vapor and organic  collected.                 collected.
                      volatiles in the   volatiles in the                              
                      event that hydrous event that hydrous                            
                      minerals and/or    minerals and/or                               
                      organic            organic                                       
                      volatile-rich      volatile-rich                                 
                      samples are        samples are                                   
                      collected.         collected.                                    

  **Sample            Lower is better;   Lower is better;   Lower is better; desire    Lower is better; desire
  temperature reqs**  desire Mars        desire Mars        Mars ambient T.; not       Mars ambient T.; not
                      ambient T.; not    ambient T.; not    active refrig.             active refrig.
                      active refrig.     active refrig.                                

  **On-board          Color imager to    Color imager to    Color imager to see the    Color imager to see the
  instrumentation**   see the outcrop    see the outcrop    outcrop would be CRITICAL. outcrop would be CRITICAL.
                      would be CRITICAL. would be CRITICAL. Desirable to see the hand  Desirable to also see the
                      Desirable to see   Desirable to see   samples at sub mm          hand samples at sub mm
                      the hand samples   the hand samples   resolution. Could partly   resolution. Lower down in
                      at sub mm          at sub mm          rely on MSL to provide a   priority would be a remote
                      resolution.        resolution.        correlation between sample sensing instrument on the
                                                            diversity and              lander (to cross-correlate
                                                            textures/colors/features   orbital remote sensing
                                                            seen in images             textures/colors/features
                                                                                       seen in color camera
                                                                                       images) or on the rover, a
                                                                                       brush or grinding tool on
                                                                                       the rover to expose rock
                                                                                       interiors to the close-up
                                                                                       imager (if rock dust &
                                                                                       coatings hide the
                                                                                       diversity). For a site
                                                                                       that has never been
                                                                                       previously visited, some
                                                                                       kind of diagnostic mineral
                                                                                       analyzer would be helpful.

  **Sample surface    Desirable          Desirable          Desirable                  Desirable
  layer**                                                                              

  **A \"reasonable    Important at any   Ability to core    Important at any site      Important at any site
  coring workvolume\" site. A t this     into basalt                                   
  (access to a large  site, it would be  boulders on the                               
  % of rock faces)    less important,    plains would be                               
  for rocks as hard   because the rover  CRITICAL                                      
  as dense basalt**   might not                                                        
                      encounter any                                                    
                      rocks as hard as                                                 
                      dense basalt.                                                    

  **TRADE-OFF                                                                          
  POSSIBILITIES**                                                                      

                                                            Access to higher altitude  Access to higher altitude
                                                            would more important than  would more important than
                                                            large roving distances     large roving distances

                      Outcrop            Outcrop            Outcrop accessibility and  Outcrop accessibility and
                      accessibility and  accessibility and  core sampling, and sample  core sampling, and sample
                      core sampling, and core sampling, and isolation, would be most   isolation, would be most
                      sample isolation,  sample isolation,  important                  important
                      would be most      would be most                                 
                      important          important                                     

                      A smaller number   A smaller number   A smaller number of        A smaller number of
                      of carefully       of carefully       carefully collected and    carefully collected and
                      collected and      collected and      stored samples would be    stored samples would be
                      stored samples     stored samples     more valuable than larger  more valuable than larger
                      would be more      would be more      number of less carefully   number of less carefully
                      valuable than      valuable than      collected and stored       collected and stored
                      larger number of   larger number of   samples                    samples
                      less carefully     less carefully                                
                      collected and      collected and                                 
                      stored samples     stored samples                                

                      If samples are     If samples are     If samples are             If samples are
                      \"hermetically\"   \"hermetically\"   \"hermetically\" separated \"hermetically\" separated
                      separated from one separated from one from one another to        from one another to
                      another to prevent another to prevent prevent water movement     prevent water movement
                      water movement     water movement     between samples, the       between samples, the
                      between samples,   between samples,   stringent temperature      stringent temperature
                      the stringent      the stringent      desirements (as low as     desirements (as low as
                      temperature        temperature        possible) could be relaxed possible) could be relaxed
                      desirements (as    desirements (as    somewhat.                  somewhat.
                      low as possible)   low as possible)                              
                      could be relaxed   could be relaxed                              
                      somewhat.          somewhat.                                     
  ------------------- ------------------ ------------------ -------------------------- --------------------------

# XI. Summary Findings of MSR SSG II

The finding by the 2004 Opportunity rover of layered evaporite deposits
on the surface of Mars during 2004 necessitated a reexamination of the
science priorities for a first Mars surface sample return mission. If
additional resources would be made available relative to the ongoing
planning for a static Groundbreaking MSR, it is highly desirable to add
limited mobility back into that mission. Other science findings by the
MSR SSG II, again contingent on necessary resources being available,
include:

-   Access to uncontaminated samples requires rover mobility should be
    sufficient to (1) escape exhaust pattern, lander debris, and organic
    contamination; and, (2) travel to and return from target. Round trip
    distance \~ 1 km regardless of landing precision.

-   Desired landing precision is site dependent; but would always be
    within 500 m

-   Rover navigability is site dependent, but the Opportunity experience
    suggests that gaining access to outcrops that may be exposed along
    crater walls or inclined hillslopes would require ability to
    negotiate slopes of \~ 30o

-   Access to elevations \> 1.5 km is highly desirable but is recognized
    as possibly prohibitive.

-   The ability to sample bedrock, preferably with a coring device, is
    very important

-   Particularly for cores, it is highly desirable to store individual
    rock samples separately from one another

-   Samples should be kept as far below 50°C as possible during Earth
    atmosphere entry and sample retrieval; ≤ 20oC is highly recommended

-   Complex in situ instrumentation would not be considered important
    for the first MSR mission \-- high quality and high-resolution
    imaging would be considered sufficient to select and document
    interesting samples

-   Caching by MSL is an interesting and potentially beneficial option
    that should be kept open, but it should not be a requirement for MSL
    or MSR.

-   While OCSSG specified contamination levels for organic molecules
    would be adequate for a subset of the samples where organics
    analysis would not be the primary objective, lower thresholds by a
    factor of 4 or more are desired for an isolated subset of the
    samples such as cores from sedimentary deposits or selected rocks
    where organics analysis would be a primary investigation.

-   To first order, the acceptable inorganic contamination levels for
    major and minor elements would be 0.1 percent of the contents of SNC
    meteorites.

REFERENCES

[Benner, S.A., K.G. Devine, L.N. Matveeva, and D.H. Powell]{.smallcaps}
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[]{#__RefHeading___Toc187465122 .anchor}Appendix A

**MARS SAMPLE RETURN SCIENCE STEERING GROUP II**

**Committee Members**

Don Bogard

NASA / JSC

Donald.D.Bogard@jsc.nasa.gov

Max Coleman

NASA / JPL

Max.Coleman@jpl.nasa.gov

Albert Colman

Carnegie Inst. Of Washington

A.Colman@gl.ciw.edu

Joy Crisp

NASA / JPL

Joy.Crisp@jpl.nasa.gov

John Eiler

Caltech

Eiler@gps.caltech.edu

Matt Golombek

NASA / JPL

Mgolombek@jpl.nasa.gov

Albert Haldemann

NASA / JPL

Albert.Haldeman@jpl.nasa.gov

Bruce Jakosky

Univ. Colorado / Boulder

Bruce.Jakosky@lasp.colorado.edu

Laurie Leshin

Arizona State University

Laurie.Leshin@asu.edu

Tim Lowenstein

SUNY / Binghamton

Lowenst@binghamton.edu

Glenn MacPherson \[Chair\]

Smithsonian Institution

Glenn@volcano.si.edu

Paul Mahaffy

NASA / Goddard SFC

Paul.R.Mahaffy@gsfc.nasa.gov

Suparna Mukherjee

NASA / JPL

Tullis Onstott

Princeton Univ.

Tullis@Princeton.edu

Dimitri Papanastassiou

NASA / JPL

DAP@mail1.jpl.nasa.gov

Lisa Pratt

Indiana Univ.

Prattl@indiana.edu

Charles (Chip) Shearer

Univ. New Mexico

cshearer@unm.edu

Dawn Sumner

University of California, Davis

Sumner@geology.ucdavis.edu

Ashwin Vasavada

NASA / JPL

Ashwin.R.Vasavada@jpl.nasa.gov

Aaron Zent

NASA / Ames

Azent@mail.arc.nasa.gov

**JPL**

Dave Beaty

David.Beaty@jpl.nasa.gov

Carol Hansen

Carol.A.Hanson@jpl.nasa.gov

Frank Jordan

Jjordan@mail1.jpl.nasa.gov

Richard Mattingly

Richard.L.Mattingly@jpl.nasa.gov

Dan McCleese

Daniel.J.McCleese@jpl.nasa.gov

Andy Morrison

Andrew.D.Morrison@jpl.nasa.gov

Marguerite Syvertson

Marguerite.Syvertson \@jpl.nasa.gov

**NASA HQ**

Dave Lindstrom

David.Lindstrom@nasa.gov

John Rummell

Jrummel@hq.nasa.gov

**Subgroup Memberships**

***Accessibility / Mobility***

J. Bibring

M. Coleman

J. Crisp

M. Golombek

A. Haldemann

B. Jakosky

F. Jordan

T. Lowenstein

D. McKay

D. Papanastssiou

C. Shearer *\[group lead\]*

A. Vasavada

***On-Board Sampling and Analytical Instruments***

J. Bibring

D. Bogard

A. Colman

J. Crisp

J. Eiler

M. Golombek

J. Jones

L. Leshin *\[Group Lead\]*

T. Lowenstein

P. Mahaffy

R. Mattingly

T. Onstott

L. Pratt

D. Sumner

A. Zent

***Forward Organic Contamination***

D. Beaty

A. Colman

B. Jakosky

P. Mahaffy *\[Group Lead\]*

R. Mattingly

D. McKay

T. Onstott

L. Pratt

D. Sumner

A. Zent

***Forward Inorganic Contamination***

D. Bogard

M. Coleman

J. Eiler

A. Haldemann

J. Jones

F. Jordan

L. Leshin

D. Papanastassiou *\[Group Lead\]*

C. Shearer

A. Vasavada

***"Floaters"***

D. McCleese G. MacPherson Suparna Mukherjee

[]{#__RefHeading___Toc187465123 .anchor}Appendix B

Mars Sample Return Science Steering Group II

**Charter**

Early results from the Mars Exploration Rovers have revealed several
discoveries that will influence strongly the future exploration of Mars.
MER has also clearly established that access to distributed targets can
be essential to surface science. In light of these findings, we believe
that it is appropriate for the Mars science community to take a fresh
look at the surface functionality required for the first Mars Sample
Return mission.

Current planning for a future MSR is based, in large part, upon the
report of the MSR Science Steering Group, "Groundbreaking Mars
Surface-Sample Return: Science Requirements and Cost Estimates for a
First Mission\" (MacPherson et al., 2002). We wish to form a MSR SSG II,
chartered to re-examine aspects of the 2002 report in light of new
discoveries and operations experience from MER. This new SSG will amend
the earlier work by preparing an addendum to the 2002 report. The
addendum will be reported back to MEPAG and, after acceptance, be
delivered to the Mars Exploration Program no later than November 19,
2004. The terms of reference for the MSR SSG II follow.

The report of MSR SSG I included the following Executive Summary:

Final Report of the Mars Sample Return Science Steering Group

> *EXECUTIVE SUMMARY*

The first surface-sample return mission from Mars, termed Groundbreaking
Mars Surface-sample Return, should consist of a simple lander whose only
tools are an extendable arm with very simple sampling devices (e.g.
combination of scoop + sieve), and a context camera (in addition to the
navigation camera). Given that the mission will visit a site that has
been previously characterized as interesting by other landed or orbital
missions, the samples collected (minimum of 500g of fines + rock
fragments + atmosphere) will provide critical fundamental knowledge
about the evolution of Mars' crust and climate and thereby enable the
selective targeting of more sophisticated sample return missions in the
future.

We request that the MSR SSG II identify changes to these findings by
answering the following questions:

-   What degree of mobility (range, rate, slopes handled), if any, is
    now considered essential for the collection of returned samples?

-   What are the science priorities for the functionality of the MSR
    sampling system?

-   What does the science community consider the maximum acceptable
    levels of contamination in the returned samples? Please incorporate
    into your deliberations the findings of the 2003 MEPAG Organic
    Contaminants SSG, and consider the following potential contaminating
    materials:

    -   Live Earth-sourced organisms (including viable microbial spores)

    -   Dead Earth-sourced organisms and fragments of organisms

    -   Earth-sourced molecular organic contaminants

    -   Non-organic contaminants

-   In order to select samples, what measurements must MSR conduct?

    -   The MSR SSG I determined only a camera will be required.

-   What are the science community's priorities for controlling the
    environment of returned samples?

-   Would MSR benefit if samples cached for it by a prior mission, e.g.
    MSL?

    -   Identify implications, both positive and negative, if MSR is
        designed to retrieve samples cached in a single container by
        MSL? It would be useful for the SSG to consider various issues,
        including:

        -   Samples cached by MSL will have been collected from more
            widely distributed sites and with more extensive *in situ*
            measurements and context information than is likely to be
            possible from MSR alone.

        -   MSR would likely be required to fund development and
            accommodation of a cache-container carried by MSL.

        -   MSR will need to pinpoint land if it is to retrieve cached
            samples utilizing modest mobility.

    -   What sampling capability must MSR have, as a backup, if a
        previously a sample cached previously is irretrievable?

    -   The SSG need not delve into the issues of planetary protection
        requirements that may be imposed upon MSL if it caches samples
        for MSR.

It is our desire that the MSR SSG II interact closely with the mission
development team at JPL. Like the MSR SSG I, which worked extremely well
with JPL, the current group will be the source of detailed preliminary
requirements for MSR while receiving feedback from engineering.

Jim Garvin, the Lead Scientist for MEP NASA, and Dan McCleese, Chief
Scientist for MEP JPL, are available to address questions from the SSG.
MEP JPL will facilitate the work of the MSR SSG II by assisting its
Chairperson with logistical support and through coordination with JPL's
mission development team. We look forward to your report.

July 24, 2004

[]{#__RefHeading___Toc187465124 .anchor}Appendix C

**An Exercise To Determine The Relative Science Payoff Of Different
Sampling And Storage Options On An Enhanced MSR**

**Science Value Exercise (Sampling Subgroup)**

***Introduction.*** As stated above, our initial approach to reaching
consensus was to examine in a holistic way the various components of the
sampling approach. During these discussions, it became clear that we
were trying to anticipate what would be difficult to implement and avoid
concluding such capabilities were "required" for fear that the suggested
mission would be too risky or expensive. However, this distracted us
from our task, which was to provide well-considered science advice to
NASA on the *relative science value* of various types and levels of
increased capability to the first MSR mission. Thus, after general
discussions about possible evolutionary paths for the various components
of MSR, we undertook a "science value exercise" to determine where the
most science value was gained by increasing capability. The Chair of the
Subgroup created example missions with different characteristics. She
took the capabilities of GMSR and assigned them a science value of 1,
and a super-capable MSR was arbitrarily given a science value of 1000
(there is no implication that the super-capable mission has 1000 times
better science value than GMSR). Missions with different levels of
capability between these two end-members were then rated by individual
members of the subgroup. The mission capabilities were broken down along
the lines of the four questions in the subgroup charter, taking into
consideration the priorities for deliberation that emerged from group
discussions (e.g., only sample temperature was considered, rather than
other "environmental controls" as this was considered the most important
part of question 3).

***Example Missions.*** What follows are the descriptions of the
**mission elements** (Table 1) and the **example missions** (Table 2)
that were rated by the group. Note that these 18 missions do not
represent every conceivable combination of the various mission
capabilities, but they were chosen to be reasonable combinations of
these and spanning a reasonable range in overall MSR sampling
capability. Specifically, some of the higher-end missions, which would
clearly be "out of the box" for the first MSR were not included, thus
there is a large jump in science value from the highest rated
combination (#16) and the super-capable MSR, worth 1000 points on the
science value scale.

Table 1. Mission Elements in the Science Value Exercise

  -------------------- ----------------- ---------------- -----------------
  **A: Sampling        **B: Sample       **C: Assay       **D: Peak
  Approach**           Packaging**       Techniques**     Temperature of
                                                          samples (assume
                                                          this is for some
                                                          time like an
                                                          hour...)**

  A1: ***Scoop/rake in B1: ***One        C1: ***Color     D1: ***50 deg
  a single location*** container***: All Imaging*** (some C***
  \-- this does NOT    samples (dust,    reasonable       
  mean 1               regolith, rocks,  number of        
  scoop/rake-full \--  atm) would be put filters, like 3  
  it means we would    into a single     or more)         
  sit in one place and \"bucket\", which                  
  scoop/ rake anything is sealed                          
  in reach \-- capable                                    
  of collecting dust,                                     
  regolith and small                                      
  rocks of varying                                        
  shapes and sizes                                        

  A2: ***Multi-site    B2: ***Multiple   C2: ***C1 +      D2: ***20 deg
  scoop/rake*** \--    containers***,    \"remote         C***
  samples of           probably separate sensing\"***     
  dust/soil/rock       ones for dust and like raman or IR 
  collected from a     soil and atm, but spectroscopy     
  mobile platform but, all rocks in a                     
  rocks must be loose  single \"bucket\"                  
  fragments in order   perhaps packed in                  
  to be able to        soil, OR multiple                  
  collect them         containers with                    
                       rocks and                          
                       soil/dust from                     
                       different                          
                       sampling sites                     
                       (e.g., at                          
                       surface, slightly                  
                       below surface,                     
                       etc.), including                   
                       a separate atm                     
                       sample                             

  A3: ***Bedrock       B3: ***Separate   C3: ***C2 +      D3: ***-5 deg
  sampling:*** in situ containers*** for MER-like contact C***
  sampling of bedrock, atm, dust,        instruments***   
  for example by use   regolith (perhaps                  
  of a small coring    2 containers                       
  device (say \~1 cm   \--one surface                     
  diam, 2-5 cm in      sample one                         
  length)              subsurface) and                    
                       rocks, with the                    
                       ***rocks                           
                       individually                       
                       packaged*** to                     
                       prevent cross                      
                       contamination and                  
                       minimize damage                    
                       from Earth return                  
                       forces                             

  A4: ***Super         B4: ***B3 +       C4: ***C3 + in   
  drilling:*** in situ multiple          situ lab         
  sampling of bedrock  containers for    instruments***   
  through substantial  different         like MSL         
  continuous coring    regolith                           
  into both bedrocks   samples***                         
  and regolith                                            
  -------------------- ----------------- ---------------- -----------------

Table 2. Example Missions and ratings in the Science Value Exercise

  -------------- -------------- ----------- ----------- ----------- --------------
  **Mission      **Mission                                          **Sci. Value
  Number**       Capability**                                       Rating\*\***

  1              A1             B1          C1          D1          1

  2              A4             B4          C4          D3          1000

  3              A2             B1          C1          D1          139

  4              A2             B2          C1          D1          202

  5              A2             B2          C1          D3          292

  6              A2             B2          C2          D3          353

  7              A2             B2          C3          D3          392

  8              A3             B2          C1          D1          382

  9              A3             B2          C1          D3          495

  10             A3             B2          C2          D3          569

  11             A3             B2          C3          D3          615

  12             A3             B3          C1          D1          584

  13             A3             B3          C1          D2          643

  14             A3             B3          C1          D3          701

  15             A3             B3          C2          D2          710

  16             A3             B3          C3          D2          750

  17             A3             B3          C3          D3          776

  18             A3             B3          C1 (plus    D3          735
                                            MSL Cache)              
  -------------- -------------- ----------- ----------- ----------- --------------

\*\* the science value for the first two missions were assigned, the
values below these are the averages of the 9 individual respondents

***Results.*** The results of the Science Value Exercise are given in
the right-hand column of Table 2, in Figs. 1-3, and Table 3. Nine people
on the team responded to the Science Value Exercise. Although these
numbers are small, the group is broadly representative of the science
community at large, so the qualitative results of the exercise are
probably reasonable. In addition, the priorities expressed numerically
in this exercise are in agreement with those obtained in general
discussions with this subgroup, and the larger MSR SSG.

Figure 1 shows the raw "data" -- the Science Value responses of the SSG
subgroup members plotted against mission number. The black lines are
individual responses, and the large dots connect the average values for
each example mission. It is easy to see that there were a wide range of
values for each mission within the group, but the trends are similar
within each set of ratings, with missions generally increasing in
science value from left to right across the diagram. From here forward
we will use the average science value for each example mission.

![](media/image5.pct){width="5.993055555555555in"
height="3.8368055555555554in"}

***Fig. 1.*** Results of the Science Value Exercise. Lines are
individual responses and large dots connect the average of the group.
Recall that missions 1 (GMSR) and 2 (a super-capable MSR) had values of
1 and 1000, respectively, assigned to them.

Figures 2 and 3 show the average science values for each mission, this
time arranged from left to right in increasing order of science value.
These two figures are exactly the same, except Fig. 3 shows some
superimposed trend lines demonstrating a break in slope in the science
value as capability increases. The entire purpose of this exercise is to
seek out such changes in slope, as they represent natural points where
more "bang for the buck" can be achieved. In other words, it is not
surprising that missions of higher capability would always have higher
science value, the point is to see where especially large gains in
science value could be achieved. The science value ratings level out
significantly once the two highest priorities of the SSG subgroup,
bedrock sampling capability and multiple bins/individual sample storage
are included in the mission capabilities.

![](media/image5.pct){width="5.996527777777778in"
height="3.553472222222222in"}

***Fig. 2.*** Science Value of Example Missions in order of increasing
Value. Each mission number is shown.

![](media/image5.pct){width="5.997916666666667in"
height="3.557638888888889in"}

***Fig. 3.*** Same as Fig. 2, but with trend-lines indicating a change
in slope in the Science Value curve..

Another way to examine these results is to take the mission ratings and
deconvolve the science value of each mission element. The results of
this are shown in Table 3, and they confirm the conclusions of the
science value exercise. Specifically, they show that increasing
capability in the sampling approach, preferably with a coring device,
and that providing the capability to isolate regolith, windblown fines,
and individual cores from each other are of the highest science value.

***Table 3. Science Value of MSR Sampling Mission Capabilities.***

***Refer to Table 1 for definitions of A1, B2, etc.***

  ------------- --------- -------------- --------- --------------- --------- ---------------- ---------
  ***A:                   ***B: Sample             ***C: Assay               ***D: Peak       
  Sampling                Packaging***             Techniques***             Temperature***   
  Approach***                                                                                 

  element \#    value     element \#     value     element \#      value     element \#       value

  A1A2         138       B1B2          63        C1C2           67        D1D2            59

  A2A3         206       B2B3          170       C2C3           43        D2D3            48

  **A1A3**     **344**   **B1B3**      **233**   **C1C3**       **110**   **D1D3**        **107**
  ------------- --------- -------------- --------- --------------- --------- ---------------- ---------

Finally, it is important to caution that this is NOT a quantitative
exercise, but rather a qualitative way to articulate the more and less
valued characteristics of the first MSR mission. Clearly improvements to
the sample acquisition system and the sample storage system are most
highly valued.

[]{#__RefHeading___Toc187465125 .anchor}Appendix D

**Temperature Effects on Samples**

**from Collection through Return**

**[Introduction]{.underline}**

The Martian surface is a thermally dynamic environment, which makes it
difficult to define optimal temperature conditions for cached and
returned samples. The surface temperature of Mars can fluctuate
diurnally by roughly 100°C at the equator and may reach daily highs
close to or slightly in excess of 0°C. These temperature fluctuations
are damped with depth in the regolith and in exposed bedrock. In the
context of cored, scooped, or grappled sample return, a single sample
will have experienced within itself a range of temperature histories (in
terms of the fluctuations and mean temperatures on daily and seasonal
timescales). Multiple collected samples, even within a small radius at a
single landing site, will differ from one another in temperature
histories as a function of sun exposure, albedo, thermal conductivity,
permeability (i.e., ventilation by Martian atmosphere), etc.

Deviations from in situ temperatures would begin once a sample has been
removed from the Martian surface and placed in a sample return
container. This would likely result in minor scale redistribution and
alteration of hydrous, aqueous, and soluble inorganic phases as well as
soluble or volatile organic phases. Keeping sample temperature low would
slow the kinetics of these transformations. Temperature control (passive
or active) of the samples would require balancing financial/technical
constraints against sample quality degradation.

For the purposes of MSR planning, we are primarily concerned with
transient temperature excursions during a return vehicles reentry to
Earth's atmosphere and resultant soakback of heat from the vehicle's
heatshield after "landing" and prior to transfer of the samples into a
temperature controlled environment on Earth. We assume that sample
temperatures would remain below the daily maximum summertime atmospheric
surface temperature at the Mars sampling site from collection through
transit from Mars to Earth. We assume this would be technically feasible
using passive temperature controls, and that it would impart minimal
changes in the chemical integrity of the samples relative to the period
of brief heating during reentry. We have not addressed explicitly the
effects of peripheral sample heating during coring. However, the
concerns expressed below apply equally to such heating to the extent
that it would be similar in magnitude and duration..

Here we have divided our scientific assessment of the potential for
thermally induced sample degradation into two parts: (a) inorganic
phases and (b) organic phases. These two are linked; many of the issues
that arise with organics result from changes in the quantity and
chemical activity of thin films and/or interstitial water and brine.

**Temperature Effects on Inorganic Phases**

**[Water on Mars]{.underline}**

Table 1 summarizes the expected effects of heating on inorganic phases
in Martian surface samples. This summary assesses a worst case scenario
in which samples are kept below 0˚C from collection time until reentry
into Earth's atmosphere; then following reentry and prior to retrieval
the samples reach 50˚C for a maximum of a few hours due to heat soakback
from the reentry vehicle's heat shield. This table takes into account
the phases likely to be encountered in Martian regolith and in weathered
and unweathered outcrops.

The potential alteration of inorganic phases centers on the fate of
water: structural in certain minerals, interlayer in clays, brine ice or
liquid brines in fractures and interstices, and chemisorbed and
physisorbed on mineral surfaces. Figure 1 shows the concentration of
water-equivalent hydrogen in near surface Martian regolith. These data
correspond to 2-10 wt % water over the latitudes within 60˚ of the
equator. However, these data represent areal averages over the 300km
radius footprint of the Mars Odyssey Neutron Spectrometer. In all
likelihood, heterogeneities exist in water content of the Martian
regolith such that returned samples could be richer in hydrogen than
these maps suggest. On the other hand, the temperature cycling of the
surficial regolith likely promotes sublimation of water from ice, brine,
mineral surfaces, and possibly interlayer positions in clay minerals and
much of the adsorbed water in microporous zeolite minerals such that 2%
appears to be a reasonable limit on the water-equivalent hydrogen
content in the top few cm of the Martian regolith (Feldman, 2004).

**[MgSO~4~ · n H~2~O salts]{.underline}**

If we assume that we could avoid ice and brine solutions in collected
samples, then the main concern would be preventing hydrated magnesium
sulfate salts from melting. Data from Viking 1 and 2 and from Pathfinder
suggest that MgSO~4~ is present at roughly 10 wt % (anhydrous equiv.) in
Martian soils (Vaniman *et al.*, 2004; Wänke *et al.*, 2001), and data
from Spirit at Gusev crater are not inconsistent with this finding
(Gellert *et al.*, 204). These salts are likely to be present on Mars,
in the minerals kieserite (MgSO~4~ · 1 H~2~O), epsomite (MgSO~4~ · 7
H~2~O), and MgSO~4~ · 12 H~2~O, as well as in amorphous phases with
variable water contents (*e.g.*, Vaniman *et al.*, 2004). Hexahydrite
(MgSO~4~ · 6 H~2~O) could be formed by hydration or dehydration
reactions of these other phases if the sample storage temperature climbs
above about 280K.

At temperatures above 270K, these phases are all near the point of
partially dehydrating or melting to form a Mg^++^, SO~4~^­\--^ rich brine
(Figure 2, Figure 3). The phase changes appear to be rapid, for example
the dehydration of hexihydrite at 298K, 580 torr, and relative humidity
of 0.3-0.4% takes on the order of several hours (Figure 4). However, the
kinetics of most of the phase changes have not been studied sufficiently
well to understand what would happen in a sample return container as
temperature and relative humidity rise in concert.

***Table 1. Thermal Effects on Inorganic Phases During Storage and
Return of Mars Surface Sample.** Worst case scenario: heating a Mars
surface sample to 50°C for several hours.*

**[Possible major effects:]{.underline}**

1.  Dehydration and/or melting of hydrated magnesium sulfate salts
    (e.g., epsomite, hexahydrite).

**[Major issues if ice and/or hydrated magnesium sulfate salts are
present in sample]{.underline}**

2.  Melting of ice or hydrated magnesium sulfate.

3.  Minor dissolution of evaporitic minerals in the resultant aqueous
    solution.

4.  Enhanced redistribution and reaction of organics if present.

5.  Loss/exchange of some interlayer cations in clays minerals (if
    present).

**[Probable minor effects:]{.underline}**

6.  Volatilization of chemisorbed and physisorbed water (especially from
    clays & zeolites if present).

7.  Slow dehydration of hydrated clay minerals (if present).

8.  Loss (dehydration/decomposition) of minor abundance, delicate
    evaporitic minerals.

9.  Reversible changes in fluid inclusion chemistry due to
    temp-dependent salt solubilities.

10. Reactivity and catalytic properties of mineral surfaces towards
    volatile/soluble organics.

**[Possible minor effects:]{.underline}**

11. Recrystallization/hydration/oxidation of reactive iron minerals.

**[Probable non-issues for this scale of temperature/time
history:]{.underline}**

12. Decrepitation of fluid inclusions.

13. Thermal sensitivity of hydroxylation/dehydroxylation reactions.

If these salts serve as a cement in regolith materials or sedimentary
rocks, then dehydration or melting could result in physical
disaggregation of samples and concomitant loss of structural features
and chemical gradients. Phase stability fields are a function of
relative humidity, and thus, desiccant functionality in the sample
return capsule may prevent melting of these salts (Figure 2). Hydration
and dehydration reactions appear to proceed more slowly than melting, so
a rapid recovery of the returned sample would help significantly in
minimizing disaggregation problems.

Table 2 illustrates more vividly the potential for water release that we
face from hydrated magnesium sulfate salts. It is difficult to predict
which MgSO~4~ · n H~2~O salts would be encountered in Martian soils
given the wide diurnal and seasonal fluctuations in temperature and
relative humidity. Nevertheless, at present we could not rule out the
release of on the order of 1 g of H~2~O (as an MgSO~4~ rich brine) if
temperatures are permitted to rise significantly above 0˚C and/or sample
container relative humidity approaches 100%.

***Table 2. Water release due to dehydration or melting of hydrated
MgSO~4~ salt.** This example considers water released in a 10g sample
core that is 10% MgSO~4~ by mass on an anhydrous basis. The table
considers different initial and final salt compositions. Currently
available experimental data suggest that at least some of these phase
transitions are possible outcomes of taking near surface samples from
Mars and heating them to 50˚C. Other transitions may or may not be
possible depending on the reaction kinetics and persistence of
metastable minerals.*

![](media/image6.pct){width="4.095138888888889in" height="1.75in"}

Clearly the potential for sample degradation caused by dehydration
and/or melting of hydrated magnesium sulfate salts merits further
experimental study. The presence of an aqueous solution bathing a sample
would certainly compromise a wide range of organic and inorganic
chemical measurements and could lead to the physical disaggregation of
samples that are cemented by soluble salts.

**[Clays and Zeolites]{.underline}**

Clay and zeolite minerals have both been invoked as possible hydrous
phases in the Martian regolith. Clays have stacked sheet-like layers of
silica tetrahedra and alumina octahedra; interlayer sites possess
various cations to balance layer charges. The interlayer regions also
can retain significant amounts of structurally bound water. Zeolites
have high adsorption enthalpies for water and high specific surface
areas. Both mineral classes are likely to be present in the Martian
regolith, however, specific mineral identification awaits future lander
missions and/or sample return. Nevertheless, the water carrying capacity
and the kinetics of hydration and dehydration reactions have been
examined experimentally and theoretically for a few candidate minerals.

These studies suggest that zeolites and possibly clays, if present in
Mars soil samples, may contain 10-20 wt % water. Figure 5 illustrates
the capacity for Na-clinoptilolite, a common zeolite on Earth, to
release significant quantities of water as temperature is increased from
representative Mars subsurface temperatures to 50˚C. This release is a
continuum process; the warmer the temperature, the more water will be
expelled from the clinoptilolite crystal structure if relative humidity
is kept low.

Clay minerals probably have a reduced potential to release water because
they would be likely less hydrated under Mars surface conditions than
zeolite minerals (Bish *et al.* 2003, Zent *et al.* 2001). However,
Mg-smectites retain water more strongly than do Ca- and Na- smectites
and have not been studied as thoroughly under Mars-like conditions (Bish
*et al.* 2003). Thus, it is still possible that Mg-smectites might
retain water at Mars surface conditions and release it upon heating in
the range proposed for the reentry and recovery phase of MSR. The
kinetics of smectite hydration-dehydration reactions have an e-folding
time on the order of an hour to a few hours (Figure 6; also Zent *et
al.* 2001, Bish *et al.* 2003) \-- rapid enough to redistribute water
within a sample during even transient heating associated with soakback
of heat from the heat shield following sample return to Earth.

**[Other Inorganic Phases Susceptible to Indirect Effects from
Heating]{.underline}**

Most minerals at Mars surface temperatures will adsorb one to a few
mono-layer thicknesses of water (*e.g.*, Möhlmann, 2004). This water
behaves like a 2-D liquid. The thickness of this water layer is a
function of mineral, temperature, and relative humidity. The activity of
the water and organic and inorganic species that are "dissolved" in this
layer will be a function of temperature. Therefore, the catalytic
properties of mineral surfaces even in an essentially dry sample will
change as samples experience heating during sample return. It is unclear
if this will have a significant impact on, for example, the composition
and concentrations of trace organic species. It is possible that thin
films of water, replenished by minerals undergoing dehydration upon
heating, could result in alteration of mineral assemblages. One such
example given in Vaniman *et al.* (2004) is the oxidation of lawrencite
\[FeCl~2~\] to goethite \[FeO(OH)\] in lunar samples despite short
transit times and dry nitrogen storage. Some other possible minor
effects of transient heating on inorganic phases are listed in Table 1.

**Figure 1**. *(Figure 4 from Feldman et al., 2004)*

***A Robinson projection of the water-equivalent hydrogen content of the
semi-infinite layer of water-bearing soils derived from
epithermal-neutron counting rates measured by the Neutron Spectrometer
on the 2001 Mars Odyssey.*** Hydrogen content data are draped over a
global elevation map from the Mars Orbiter Laser Altimeter. The
semi-infinite layer comprises the regolith below the relatively
desiccated surface layer. The existence of a desiccated surface layer
with roughly 2 wt % water content is supported by both theoretical and
observational constraints. This surface layer is likely of variable
thickness, however, it is considered to be 10g/cm^2^ for the modeling of
the neutron data to produce this map. Assuming the regolith has an
average porosity of 30-70% and density of 2.5-3.5g/cm^3^, then this
surface layer is on the order of 4-14cm thick.

![](media/image7.png){width="7.0in" height="4.511111111111111in"}

**Figure 2.** (*Figure 3 from Vaniman et al., 2004)*

***Results of controlled-humidity XRD experiments at 298 K plotted
against stability fields for epsomite, hexahydrite and kieserite,
modified from Chou and Seal (2003).*** Their study provides accurate
constraints on the epsomite to hexahydrite transition (curve 1); their
estimate of the hexahydrite to kieserite transition (curve 2) is based
on thermodynamic data extrapolated from the experimentally determined
solution equilibrium; an alternative estimate of this transition is
based solely on thermodynamic data (curve 3). Estimated stability of
hexahydrite under Martian conditions depends on extrapolation of curves
2 or 3. Stability of the MgSO4·12H2O phase is poorly constrained. Our
experiments show that at RH of 0.5%, hexahydrite forms from solution but
becomes amorphous. Hexahydrite forms and persists at RH values from 55%
down to at least 7%. Amorphous MgSO4·nH2O formed at RH of 0.5%, and
subsequently exposed to RH of 7--55% crystallizes to various hydrates (n
= 1.25 to 6) dependent on RH; ongoing long-term experiments suggest that
crystalline end products vary with RH within the upper shaded region.
Above RH of 55%, both amorphous MgSO4·nH2O and kieserite transform to
hexahydrite and then epsomite. At Martian conditions below 280 K, the
rates and ranges for comparable reactions are not yet determined. The
diurnal temperature--RH range shown (lower shaded region) for the Mars
surface in summer at the Viking 1 site is from Savijarvi (1995, *Icarus,
117*, 120). The average diurnal surface temperature of 220 K near the
equator varies little despite changes in obliquity (Mellon & Jakosky,
1995, *JGR, 100*, 11781).

![](media/image8.png){width="6.0in" height="5.105555555555555in"}

**Figure 3.** *(Figure 6 from Hogenboom et al., 1995)*

***Phase diagram of the system H~2~O • MgSO~4~ at 0.1 MPa.*** MS1, MS6,
MS7, and MS12 stand for, respectively, MgSO~4~ • 1 H~2~O, MgSO~4~ • 6
H~2~O, MgSO~4~ • 7 H~2~O, and MgSO~4~ • 12 H~2~O. **E** is the eutectic;
**P1, P2,** and **P3** are peritectics. Also shown are the metastable
extensions of the liquidus branches of water ice and MgSO~4~ • 7 H~2~O
and the intersection of these branches (representing the metastable
eutectic, **E'**).

![](media/image9.png){width="6.0in" height="4.135416666666667in"}

**Figure 4.** *(Figure 1 from Vaniman et al., 2004)*

***Dehydration experiment in an environmental cell.*** Ten sequential
X-ray

diffraction (XRD) patterns of hexahydrite desiccated at 298 K and
0.3--0.4% RH to

produce amorphous MgSO4·nH2O. The ten XRD patterns represent desiccation
over a

period of 40 h. b, The XRD pattern of the hexahydrite starting material.
In Figs 1 and 2,

XRD was performed using CuKa radiation.

![](media/image10.png){width="6.875196850393701in"
height="3.604724409448819in"}

**Figure 5.** *(Figure 4 from Bish et al., 2003)*

**Thermodynamic modeling of hydration state of smectites (example clay
minerals) and clinoptilolite (an example zeolite).** The modeled
equilibrium water content as a function of temperature is plotted for
Na- and Ca-smectites on the left axis and for Na-clinoptilolite on the
right axis. *P*(H~2~O) is set to 1.5 x 10^-6^ bars in the model as an
approximation of the average vapor pressure of H~2~O at the surface of
Mars.

![](media/image11.png){width="6.875in" height="4.870833333333334in"}

**Figure 6.** *(Plate 1 in Zent et al., 2001)*

**The uptake curve of H~2~O on SWy-1, a sodium-rich montmorillonite.**
The adsorbate is substantially loaded in only a few hours. The clay
samples were preconditioned by baking under vacuum at 110°C to remove
essentially all water while avoiding disruption of interlayer cations.
The experimental temperature and
*P*(H~2~![](media/image12.png){width="6.875in"
height="4.342361111111111in"}O) conditions are listed in the inset
legend.

**Temperature Effects on Organic Phases**

Few published organic geochemical studies report molecular or stable
isotopic data for fine-grained sediments or sedimentary rocks on Earth
containing trace (\< 0.05 wt%) amounts of organic carbon for two
reasons. First, samples containing trace concentrations of organic
carbon are almost always contaminated during sampling to a to a level
where extraneous organic compounds pervasively overprint indigenous
organic compounds. Second, organic compounds are tightly bound to
mineral surfaces in fine-grained siliciclastic, calcareous, and
evaporitic sedimentary materials containing trace amounts of organic
matter. Increasing sample size is ineffective because extraction yields
from these types of samples are proportionally lower than yields for
similar sediments containing higher contents of organic carbon. For all
of these reasons, it is difficult to predict the fate of organic
molecules in a Mars return samples that are anticipated to contain only
trace level organic carbon. Above we described the fate of organic
molecules using generalized terms because most of the compound classes
contain a wide range of structural configurations and molecular weights
combined with substantial uncertainties regarding mineral composition
and hydration state for near-surface Mars regolith and rocks. The term
*mobilized* refers to molecules that are unaffected chemically but are
capable of physical migration between absorbed or complexed phases.
*Volatilized* refers to molecular classes that will be present primarily
in a vapor state. Volatilization at the chosen temperatures is estimated
based on standard laboratory evaporation procedures at controlled
temperature using vacuum aspiration to about 20 millibars (Rotavap or
equivalent apparatus). *Partial decomposition* refers to initial stages
of chemical transformation including isotope exchange, dehydration, and
isomerization. *Decomposition* refers to chemical transformations more
severe than those listed for partial decomposition, typically involving
structural breakdown and/or molecular reorganization.

**It is clear from the table that at 50oC a significant number of
compounds experience decomposition, and even at 20oC some compounds are
decomposed. At -5oC some compounds are mobilized or even volatilized.**

<table style="width:100%;">
<colgroup>
<col style="width: 5%" />
<col style="width: 8%" />
<col style="width: 5%" />
<col style="width: 8%" />
<col style="width: 5%" />
<col style="width: 1%" />
<col style="width: 6%" />
<col style="width: 6%" />
<col style="width: 3%" />
<col style="width: 13%" />
<col style="width: 6%" />
<col style="width: 10%" />
<col style="width: 17%" />
</colgroup>
<tbody>
<tr class="odd">
<td colspan="13"><em><strong>DRAFT November 13, 2023</strong></em></td>
</tr>
<tr class="even">
<td colspan="13"><em><strong>Fate Of Indigenous Martian Organic
Molecules During Sample Return<br />
</strong>Information Compiled in 2004 by Lisa Pratt, Simon Brassell,
Arndt Schimmelmann, Bernd Simoneit</em></td>
</tr>
<tr class="odd">
<td colspan="2" rowspan="2"><strong>Molecular Class</strong></td>
<td colspan="2" rowspan="2"><strong>Examples</strong></td>
<td colspan="2" rowspan="2"><blockquote>
<p><strong>Scientific Interest</strong></p>
</blockquote></td>
<td rowspan="2"><blockquote>
<p><strong>Susceptible to Photo -Decomposition</strong></p>
</blockquote></td>
<td rowspan="2"><blockquote>
<p><strong>Susceptible to Hydrolysis or Water Solvation</strong></p>
</blockquote></td>
<td colspan="5"><strong>organic matter sampled in an intact sedimentary
matrix, sample canister sealed under oxidizing atmosphere at 6-10
millibars pressure, maximum temperature during re-entry not
exceeding:</strong></td>
</tr>
<tr class="even">
<td colspan="2"><strong>-5<sup>"</sup>C</strong></td>
<td colspan="2"><strong>20<sup>"</sup>C</strong></td>
<td><strong>50<sup>"</sup>C</strong></td>
</tr>
<tr class="odd">
<td colspan="2"><strong>Aromatic Hydrocarbons</strong></td>
<td colspan="2">benzene</td>
<td colspan="2">M</td>
<td></td>
<td></td>
<td colspan="2">Unm</td>
<td colspan="2">Mob</td>
<td>Vol</td>
</tr>
<tr class="even">
<td colspan="2"><strong>Polyaromatic Hydrocarbons</strong></td>
<td colspan="2">anthracene, phenanthrene</td>
<td colspan="2">H</td>
<td>√</td>
<td></td>
<td colspan="2"><p>LMW - Mob</p>
<p>HMW-Unm</p></td>
<td colspan="2"><p>LMW - Vol</p>
<p>HMW - Vol</p></td>
<td><p>LMW - Vol</p>
<p>HMW - Vol</p></td>
</tr>
<tr class="odd">
<td colspan="2"><strong>S, N, O Heteroatomic Aromatics</strong></td>
<td colspan="2">pyrimidine, furan, pyridine, purines,
benzothiophene</td>
<td colspan="2">M</td>
<td></td>
<td></td>
<td colspan="2"><p>LMW - Mob</p>
<p>HMW-Unm</p></td>
<td colspan="2"><p>LMW - Vol</p>
<p>HMW - Mob</p></td>
<td><p>LMW - Vol /PDec</p>
<p>HMW - Vol /PDec</p></td>
</tr>
<tr class="even">
<td colspan="2"><strong>Aliphatic Hydrocarbons</strong></td>
<td colspan="2">alkanes, alkenes, pristane, phytane</td>
<td colspan="2">H</td>
<td></td>
<td></td>
<td colspan="2">Unm</td>
<td colspan="2"><p>LMW - Vol</p>
<p>HMW -Unm/ Mob</p></td>
<td><p>LMW - Vol /PDec</p>
<p>HMW - Vol /PDec</p></td>
</tr>
<tr class="odd">
<td colspan="2"></td>
<td colspan="2">Methane</td>
<td colspan="2">VH</td>
<td></td>
<td></td>
<td colspan="2">Vol</td>
<td colspan="2">Vol</td>
<td>Vol</td>
</tr>
<tr class="even">
<td colspan="2"></td>
<td colspan="2">ethane, propane, butane</td>
<td colspan="2">VH</td>
<td></td>
<td></td>
<td colspan="2">Vol</td>
<td colspan="2">Vol</td>
<td>Vol</td>
</tr>
<tr class="odd">
<td colspan="2"></td>
<td colspan="2">hopanes, steranes</td>
<td colspan="2">H</td>
<td></td>
<td></td>
<td colspan="2">Unm</td>
<td colspan="2">Unm</td>
<td>Mob</td>
</tr>
<tr class="even">
<td colspan="2"><strong>Saccharides</strong></td>
<td colspan="2">tetrose, glucose, cellulose</td>
<td colspan="2">VH</td>
<td></td>
<td>√</td>
<td colspan="2">Unm</td>
<td colspan="2">Unm</td>
<td>Unm</td>
</tr>
<tr class="odd">
<td colspan="2"><strong>Carboxylic Acids and their Salts</strong></td>
<td colspan="2">alkyl and aromatic acids, fatty acids</td>
<td colspan="2">H</td>
<td></td>
<td>√</td>
<td colspan="2"><p>LMW- Mob</p>
<p>HMW-Unm<br />
salt-Unm</p></td>
<td colspan="2"><p>LMW - Vol</p>
<p>HMW - Mob<br />
salt-Unm</p></td>
<td><p>LMW - Vol</p>
<p>HMW - Mob/Vol<br />
salt-Unm</p></td>
</tr>
<tr class="even">
<td colspan="2"><strong>Amino Acids</strong></td>
<td colspan="2">basic, neutral, acidic</td>
<td colspan="2">VH</td>
<td></td>
<td>√</td>
<td colspan="2">Unm</td>
<td colspan="2">Unm</td>
<td><p>LMW - Unm</p>
<p>HMW - Unm</p></td>
</tr>
<tr class="odd">
<td colspan="2"><strong>Nitrogen-Containing Compounds</strong></td>
<td colspan="2">amines, amides</td>
<td colspan="2">H</td>
<td></td>
<td></td>
<td colspan="2"><p>LMW- Vol</p>
<p>HMW-Unm</p></td>
<td colspan="2"><p>LMW - Vol /PDec</p>
<p>HMW -Unm/ Mob</p></td>
<td><p>LMW – Vol /PDec</p>
<p>HMW – Vol /PDec</p></td>
</tr>
<tr class="even">
<td colspan="2"></td>
<td colspan="2">tetrapyrroles, porphines, siderophores</td>
<td colspan="2">VH</td>
<td>√</td>
<td>√</td>
<td colspan="2">Unm</td>
<td colspan="2">Unm</td>
<td>PDec</td>
</tr>
<tr class="odd">
<td colspan="2"><strong>Peptides</strong></td>
<td colspan="2">polar and non-polar</td>
<td colspan="2">H</td>
<td></td>
<td>√</td>
<td colspan="2">Unm</td>
<td colspan="2">Unm</td>
<td>Mob /PDec</td>
</tr>
<tr class="even">
<td colspan="2"><strong>Functionalized Lipids</strong></td>
<td colspan="2">glycerides, fats</td>
<td colspan="2">VH</td>
<td></td>
<td>√</td>
<td colspan="2">Unm</td>
<td colspan="2">Unm- Mob /PDec</td>
<td>PDec</td>
</tr>
<tr class="odd">
<td colspan="2"></td>
<td colspan="2">ether lipids</td>
<td colspan="2">VH</td>
<td></td>
<td></td>
<td colspan="2">Unm</td>
<td colspan="2">Unm</td>
<td>Unm</td>
</tr>
<tr class="even">
<td colspan="2"></td>
<td colspan="2">esters, ketones, aldehydes</td>
<td colspan="2">H</td>
<td>√</td>
<td>√</td>
<td colspan="2">Unm</td>
<td colspan="2"><p>LMW - Mob</p>
<p>HMW -Unm</p></td>
<td><p>LMW -PDec</p>
<p>HMW -PDec</p></td>
</tr>
<tr class="odd">
<td colspan="2"></td>
<td colspan="2">alcohols</td>
<td colspan="2">H</td>
<td></td>
<td>√</td>
<td colspan="2"><p>LMW- Mob</p>
<p>HMW-Unm</p></td>
<td colspan="2"><p>LMW - Mob</p>
<p>HMW - Mob</p></td>
<td><p>LMW -PDec</p>
<p>HMW -PDec</p></td>
</tr>
<tr class="even">
<td colspan="2"><strong>Humic and Fulvic Acids</strong></td>
<td colspan="2"></td>
<td colspan="2">M</td>
<td>√</td>
<td>√</td>
<td colspan="2">Unm</td>
<td colspan="2">Mob /PDec</td>
<td>PDec/Dec</td>
</tr>
<tr class="odd">
<td colspan="2"><strong>Unresolved Complex Molecules</strong></td>
<td colspan="2"></td>
<td colspan="2">H</td>
<td></td>
<td></td>
<td colspan="2">Unm</td>
<td colspan="2">Mob</td>
<td>Mob /PDec</td>
</tr>
<tr class="even">
<td colspan="2"><strong>Phospholipids</strong></td>
<td colspan="2"></td>
<td colspan="2">VH</td>
<td></td>
<td>√</td>
<td colspan="2">Unm</td>
<td colspan="2">Mob/PDec</td>
<td>Mob /PDec</td>
</tr>
<tr class="odd">
<td colspan="2"><strong>Nucleic Acids, Nucleotides</strong></td>
<td colspan="2">DNA, RNA, TNA</td>
<td colspan="2">VH</td>
<td>√</td>
<td>√</td>
<td colspan="2">Unm</td>
<td colspan="2">Unm</td>
<td>DNA -Unm<br />
RNA -PDec</td>
</tr>
<tr class="even">
<td colspan="2"><strong>Nitrogen-Containing Gases</strong></td>
<td colspan="2">NH<sub>3</sub>, HCN, NO<sub>2</sub>, N<sub>2</sub>O,
NO</td>
<td colspan="2">H</td>
<td></td>
<td></td>
<td colspan="2">Mob</td>
<td colspan="2">Vol</td>
<td>Vol</td>
</tr>
<tr class="odd">
<td colspan="2"><strong>Sulfur-Containing Gases</strong></td>
<td colspan="2">H<sub>2</sub>S, (CH<sub>3</sub>)<sub>2</sub>S</td>
<td colspan="2">H</td>
<td></td>
<td></td>
<td colspan="2">Mob / Vol</td>
<td colspan="2">Vol</td>
<td>Vol /PDec</td>
</tr>
<tr class="even">
<td colspan="13"><em><strong>Abbreviations and
acronyms</strong></em></td>
</tr>
<tr class="odd">
<td></td>
<td colspan="2">VH = very high<br />
H = high</td>
<td colspan="2">M = moderate<br />
L = low</td>
<td colspan="4">Unm = unmobilized<br />
Mob = mobilized<br />
Vol = volatilized</td>
<td colspan="2">PDec = partially decomposed<br />
Dec = decomposed</td>
<td colspan="2">LMW = low molecular weight<br />
HMW = high molecular weight</td>
</tr>
</tbody>
</table>

[^1]: This idea is alternatively known as The Golombek Manifesto, The
    Golombek Prophecy, The Golombek Miracle...