**Report of the joint NAI / MEPAG Mars Science Laboratory Caching
Working Group**

Carnegie Institution of Washington -- Geophysical Laboratory

October 8 -- 9^th^ 2007.

A. Steele -- Carnegie Institution of Washington -- Chair.

# This report may be freely circulated. Suggested citation:

# 

Steele, A. and 30 co-authors. (2008). Report of the joint NAI / MEPAG
Mars Science Laboratory Caching Working Group. Unpublished white paper,
17 p, posted Jan., 2008 by the Mars Exploration Program Analysis Group
(MEPAG) at http://mepag.jpl.nasa.gov/reports/index.html.

Or

Steele, A., L Beegle, D. DesMarais, B. Sherwood-Lollar, C. Neal, P.
Conrad, D. Glavin, T. McCollom, J. Karcz, C. Allen, E. Vicenzi, S. Cady,
J. Eigenbrode, D. Papineau, V. Starke, M. Glamoclija, M. Fogel, L. Kerr,
J. Maule, G. Cody, I. Ten Kate, K. Buxbaum, L. Borg, S Symes, D. Beaty,
C. Pilcher, M. Meyer, C. Conley, J. Rummel, R. Zurek, and J. Crisp
(2008). Report of the joint NAI / MEPAG Mars Science Laboratory Caching
Working Group. Unpublished white paper, 17 p, posted Jan., 2008 by the
Mars Exploration Program Analysis Group (MEPAG) at
http://mepag.jpl.nasa.gov/reports/index.html.

# Table of Contents

This report may be freely circulated. Suggested citation: 1

Table of Contents 2

List of Attendees 3

12.0 Executive summary of the major findings of the Workshop 4

2.0 Meeting Process 9

3.0 Introduction to Sample Caching by MSL (MSLSCas of October, 2007) 9

4.0 Report on Tasks 1 and 2. 12

4.1 Sample Context data. 12

4.2 Maintenance of sample integrity during storage on Mars and transport
to Earth. 13

4.3 Planetary Protection Issues 13

4.3.1 Requirements for planetary protection without sample cache 14

4.3.2 Assumptions for planetary protection made in designing the MSL
cache 14

4.3.3 Additional considerations 15

4.4 Heat Sterilization of Samples 15

4.3.4 Heat Sterilization of Samples Dave and Cassie, I don't think this
belongs here under the PP section 16

It is a common misconception that heat sterilization of samples would
only damage samples relative to astrobiological goals (MEPAG Goal 1). It
has been suggested that a regime of 500oC sterilization of the sample be
undertaken before the samples are released from the curation facility.
This treatment would impact the samples in several ways: 16

4.54 Site selection and type of sample collected. 16

4.65 Accurate assessment of the conditions to which the samples have
been subjected. 17

4.76 Curation of samples 18

5.0 Consider what capabilities would be needed to collect the samples
needed to address the remaining goals (Task 3). 18

NAI-MEPAG MSLC Working Group 20

Appendix 1 22

Addressing the specific questions to the Workshop 22

# List of Attendees

A Steele -- Carnegie Institution of Washington

L Beegle -- JPL

D. DesMarais -- NASA ARC.

B. Sherwood-Lollar -- Uni of Toronto

C. Neal -- Notre Dame

P. Conrad -- JPL

D. Glavin -- NASA GSFC

T McCollom -- Uni of Colarado

J. Karcz -- SETI Institute/NASA ARC

C. Allen -- NASA JSC

E. Vicenzi -- Smithsonian Institute

S. Cady -- Portland State University

J. Eigenbrode -- NASA GSFC

D. Papineau -- CIW-GL

V. Starke -- CIW-GL

M. Glamoclija -- CIW-GL

M. Fogel -- CIW-GL

L. Kerr -- CIW-GL

J. Maule -- CIW-GL

G. Cody -- CIW-GL

I. Ten Kate -- NASA GSFC

K. Buxbaum -- Mars Program Office

L. Borg -- LLNL

S Symes -- Univ. of Tennessee

D. Beaty -- Mars Program Office

C. Pilcher -- NAI

M. Meyer -- NASA HQ

C. Conley -- NASA HQ

J. Rummel -- NASA HQ

R. Zurek -- Mars Program Office

J. Crisp -- JPL

# 1.0 Executive summary of the major findings of the workshop

As of October 2007, the Mars Science Laboratory had been asked to
consider assembling a cache of samples for possible recovery by a future
Mars Sample Return mission. A combined NAI and MEPAG working group was
formed to review the astrobiological and Mars-relevant science that
could be undertaken on such samples. The goal of the working group was
to provide insight to both the Mars Exploration Program (MEP) and to the
NASA Astrobiology Institute (NAI) as to what is the expected scientific
value of these samples.  It was expected that this information would be
a primary input into the scientific planning for the MSR mission. A
two-day workshop was held to permit working group members to address the
tasks and questions put forth in the charter (Appendix I).

For the purpose of this analysis, the following factors were assumed to
be outside the scope of discussion---they will all be decided through
other processes, and other committees: 1) the final design of the cache
hardware (the present analysis is based on the design as it was
understood on October 8, 2007); 2) the way in which the cache hardware
will be used by the MSL science team; and 3) the choice of MSL landing
site. Given these uncertainties, there is a certain range of possibility
for the kinds of samples that could end up in the cache. Rather than
develop multiple "what-if" scenarios, this analysis uses the approach of
the mean expected value. It is of course possible that the samples
actually placed in the cache during MSL's operations in 2010-2011 will
significantly exceed the mean expected value.

For the purpose of planning MSR, two sample-related aspects of MSL need
to be separated: First, in retrospect, did MSL discover samples that
would be of major interest in Earth-based laboratories? Second, if so,
what are the issues related to using the samples in the cache as opposed
to having MSR recollect MSL's discoveries using better procedures?

The major findings:

1.  The cached samples will allow some progress towards many of MEPAG's
    Goals I and III and the astrobiology goals for Mars.

2.  However, the expected scientific utility of the cached samples might
    be affected by the following factors:

-   *The MSL samples will be collected by a sampling system that has not
    been sterilized. This may could lead to sample sterilization for
    planetary protection purposes as part of the Earth return.
    Sterilization of the samples, should it be necessary, would
    significantly degrade their scientific usefulness.*

-   *Since the cached samples will not be either labeled or separated
    from each other, there is a danger that the samples' context data
    will be lost. This would significantly affect our ability to link
    sample analytic data back to original field context, which could
    severely limit our ability to interpret the data.*

-   *The cache samples will not be separately encapsulated, so they will
    be vulnerable to disaggregation and mechanical mixing. This is
    particularly a concern for softer rocks, such as sedimentary rocks.*

-   *The cached samples, as per the present MSL sample acquisition
    system, will be limited to small rocks from the martian surface.
    These rocks may be heavily weathered.*

-   *The cached samples will be further exposed to the martian
    environment for several years before the earliest possible attempt
    to recover them.*

-   *MSL will be likely be designed and operated for a different state
    of contamination and with different contamination control procedures
    than MSR. The state of contamination of the cached samples at the
    time they are analyzed on Earth (if returned by a future mission),
    which will be the integral of all of the effects they have seen
    throughout the mission, will matter.*

The working group's discussions led to several recommendations that to
enhance the scientific value of the MSL cache;

1.  [Retain the ChemCam instrument on MSL]{.underline}. ChemCam on MSL
    is essential for remote and rapid analysis of lithologies of
    interest and will therefore significantly contribute to 'MSLs'
    capability to analyze a wide range of samples and choose interesting
    targets from a subset of the analyzed lithologies that represent the
    best samples to cache. Indeed, ChemCam is the only instrument
    currently onboard MSL capable of remotely analyzing samples in the
    size range to be collected. Inclusion of ChemCam will also minimize
    the impact of sample caching on MSL operations. This is important
    given the constraint that the cache is not supposed to impact MSL
    operations. Therefore, MSL instrumentation is key to mitigating the
    impact of deciding which samples to return as well as understanding
    common lithologies for future MSR missions. The use of MSL
    instrumentation is therefore important to the success of MSR.

2.  [Include a calibration blank]{.underline}. Inclusion of a well
    characterized calibration material into the cache before launch
    would serve to chart the contamination of both the sample cache
    hardware and subsequently the sample itself. Analysis of such a
    material on return to Earth would allow an accurate assessment of
    the conditions to which the cached samples had been subjected.

3.  [Include key *in situ* instrumentation in a future MSR.]{.underline}
    For a future MSR mission, any robotic capability should be augmented
    with a minimal suite of instrumentation capable of identifying
    target lithologies similar to those analyzed and known to be of
    interest based on MSL investigations. A high priority was placed on
    samples shown to contain organic carbon species.

4.  [Plan appropriately for curation]{.underline}. Planning for MSR
    should include suitable curation of the samples so as to minimize
    the contamination and degradation of the samples for the lifetime of
    their scientific usefulness.

5.  [[Monitor the environment of the cache for as long as
    feasible.]{.underline} It is important to]{.mark} understand the
    environment to which the samples have been subjected. This can be
    undertaken in 2 ways:

    a.  By analysis of the *[in situ]{.mark}* radiation monitoring
        [data, plus]{.mark} modeling from existing MSL instrumentation
        and experiments (RAD). By extrapolating the radiation flux
        monitored by RAD on MSL, it is possible that a realistic
        assessment of the degradation of organic species in the MSL
        cache samples can be undertaken. These data can be used to
        extrapolate conditions over the time that the cache will be on
        the surface of Mars. Experimentation in exposure chambers on
        [Earth]{.mark} could then be used to accurately assess sample
        degradation and add [further]{.mark} data as to the utility of
        the MSL cache.

    b.  [Through]{.mark} the use of witness plates that could include
        the sample cache material itself. These witness plates could act
        as a monitor for the presence of organic contaminants that have
        degassed from MSL itself. The sample cache hardware will
        naturally act as a witness plate given its proximity to the
        samples. Therefore it would be prudent to curate this assembly
        along with the samples. This lesson was learned from analysis of
        Stardust particles were analysis of the capture assembly became
        extremely important in understanding the presence of aliphatic
        species in Stardust samples.

6.  Conduct a full analysis of microbial contamination of MSL before
    launch. This step significantly enhances the science that can be
    undertaken on the samples by alleviating the need to subject the
    samples to harsh sterilization protocols upon return. (As a side
    note, this has been incorporated into MSL\'s plan.)

# 2.0 Meeting Process

The meeting was conducted with the participants splitting into 3 teams:
geology / geophysics, organic geochemistry, and biology. Each team was
asked to compile input on whether the MSLSC (Mars Science Laboratory
Sample Cache) can address the science objectives described in the MEPAG
Goals Document with an emphasis on Astrobiological investigations. There
were several variable parameters that the teams were asked to
contemplate during this exercise including context data needed to
interpret the data, whether the investigation was relevant to
Astrobiology science, and the significance of planetary protection
issues, sample character, and curation issues to the investigations.

# 3.0 Introduction to Sample Caching by MSL (as of October, 2007)

The MSL sample cache is intended as a means to provide the proposed MSR
the option of retrieving a diverse set of previously acquired rock
samples. It would allow the proposed MSR to take advantage of MSL\'s
traverse and analytical capabilities, which are expected to be
significantly greater than those of a future MSR rover. MSL is designed
for a primary mission of one Mars year and a range of 20 km (Vasavada et
al. 2006). The cache will not necessarily be retrieved by MSR---that
decision will be made in the context of a future sample return mission,
based on a future evaluation of the value of the (by then known)
contents of the cache and the difficulty of retrieving it. Thus, the MSL
sample cache is an option for the proposed MSR, but not a requirement.

The cache is intended to be an unobtrusive payload on MSL, and its
design is tightly constrained by the already-mature state of MSL\'s
development. MSL\'s existing sample acquisition systems, a pulverizing
drill and a scoop, cannot be changed. As MSL carries no coring drill,
the scoop is the only mechanism by which to acquire rock samples.

The cache is also constrained by the expected capabilities of the future
MSR mission. The cache has been designed based on certain assumptions
about MSR\'s capabilities. It is being designed for easy retrieval by
the future MSR and sized to fit within the volume and mass constraints
of the latest proposed MSR designs for the sample canister. Given the
roughly ten-year span for which the samples are expected to be on Mars
before being retrieved, and the limited sample-collection tools
available to MSL, the cached samples are not expected to be optimal for
all investigations. The cache has therefore been sized to occupy, if
retrieved, only about 40 % of the capacity of the assumed MSR canister,
leaving room for freshly acquired samples. Specifically, it will fit
within a cylinder 7 cm in diameter and 2--3 cm in height (roughly the
size of a hockey puck) and should have a total filled mass of no more
200 g. To give the future MSR the ability to repackage or otherwise
directly handle the samples, provision will be made for a means for the
future MSR to open the sample container.

The cache is designed to accommodate 5--10 separately collected rock
samples with diameter of roughly 0.5--1.5 cm. Due to the future
MSR-constrained small size of the sample container, inherent
uncertainties in dropping material from the scoop, and the lack of
actuators in the cache, the cache holds the samples in a common
container. Further, since the volume of the scoop is a large fraction of
the volume of the cache, and since any capability of MSL\'s sample
acquisition system to dump fine soil while retaining targeted rocks will
not be well understood until it is built, the cache container has mesh
sides to allow the fine fraction to fall out. Due to the mesh and the
open funnel through which samples are cached, the samples will be
exposed to the environment during their entire stay on Mars.

Photo-documentation of the samples, along with information from other
instruments, such as APXS and ChemCam, will be used to aid
re-identification of the samples after they are returned to Earth. The
cache will be compatible with imaging by MSL\'s microscopic imager,
MAHLI, from above. Samples will also be imaged by MAHLI on the ground
prior to scooping, and by the HazCams while in the scoop if they are
uncovered by soil.

![](media/image1.png){width="2.41259842519685in"
height="2.1397637795275593in"}![](media/image2.png){width="1.758267716535433in"
height="2.1397637795275593in"}![](media/image3.png){width="4.174409448818897in"
height="2.5700787401574803in"}

Figure 1A shows a 3-D CAD representation of the MSL sample cache system.
Fig 1B is an exploded view of the storage basket. Fig 1C is an exploded
view of the whole sample caching system.

The full container will be able to accommodate at least 60 cm^3^ of
material. The cache\'s ability to accommodate 5--10 samples assumes each
scoopful contains one targeted rock along with an appropriate amount of
soil and that the cache experiences a gentle ride on MSL (with no
vibration to aid liberating any fines from the cache). In this case, the
full cache might contain perhaps 5-10 cm^3^ of targeted rock with the
remainder of the cache occupied by untargeted soil. Depending on the
vibration environment experienced during the traverse, the possible
ability of the sample-acquisition system to separate soil from rock, and
the properties of the retained soil, the ratio of the volumes of
targeted samples to retained soil---and hence the cacheable number of
targeted rocks could be considerably higher.

*Figure 2. Operational considerations in sampling for the sample cache*

![](media/image4.png){width="5.715972222222222in"
height="3.189583333333333in"}

# 4.0 Report on Tasks 1 and 2 of the charter

**Assess the capabilities of MSL for acquiring and caching samples for a
proposed sample return mission. With the anticipated samples returned,
what information could be extracted with state of the art laboratory
instrumentation circa 2020? Define what goals of Astrobiology and MEP
could be addressed with the MSL cached samples.**

The return of the MSL cache would provide samples of scientific interest
but the applicability of these samples to answer MEPAG goals for Mars
are dependent on several factors that are currently unknown and include:

-   Accurate determination of the context from which the samples were
    collected.

-   Maintenance of sample integrity during storage on Mars and transport
    to Earth.

-   Planetary protection issues and the possibility of sterilization
    (see later section).

-   Site selection and type of sample collected.

-   Accurate assessment of the conditions to which the samples have been
    subjected.

-   Preservation of the samples and preservation of sample integrity.

***To summarize, the working group felt that without these points being
addressed the applicability of the MSL cache to answer the list of
investigations in Goals I and III of the MEPAG goals was severely
compromised.***

## 4.1 Sample context data 

Mars meteorites represent the best sample set we currently have to test
instrumentation for sample return. Future instruments and techniques for
analyzing samples will rely heavily on previous analysis undertaken on
Martian meteorites. Instrument development by 2020 was impossible to
reliably predict and that a peer review process similar to that used for
the Stardust return samples will be the best course of action to pursue
for any future Mars sample return. The weakness of undertaking analysis
on Martian meteorites has been the small sample size and the lack of
context data. Only rudimentary speculation is available as to the origin
of the meteorites on the surface of Mars. The MSL cache must provide
accurate context information for the samples. To do anything less would
mean that the samples might not yield a science return that
significantly improves on the information garnered from studies of
Martian meteorites.

Understanding the context from which a sample was collected was an
overriding concern of all groups at the meeting. Crudely represented, 7
of 12 investigations in Goal I and 9 of 13 investigations in Goal III
require adequate context information (note - Goal III investigations A7,
A9 and B4 were not considered). In the specific case of the MSL cache,
some concerns of the scientists were addressed by the instrumentation
that MSL will use. It became obvious in the course of the debate that
the philosophy of MSL operations and the decision to cache a sample will
rely on suitable science investigations on that sample. MSL will analyze
as wide a variety of lithologies as is presented by its landing site, in
order to achieve maximum sample diversity. Rapid analysis of targets by
an instrument such as ChemCam will be essential. This information will
feed forward to any proposed sample return mission itself, and the plans
for instrumentation on the future MSR rover. The use of spectroscopic
and imaging techniques to select samples will be necessary whatever MSL
finds, so as to select the most diverse and scientifically interesting
samples. However, without the ability to rapidly characterize all of the
lithologies in a target area with an instrument like ChemCam, further
analytic capability will be needed on the future MSR rover to ensure a
similar sample diversity. ChemCam is the only instrument other than the
imagers which will be able to directly analyze both large outcrops and
small rocks of the size cachable by MSL. ChemCam\'s ability to target
rocks of that size is probably more important, from the perspective of
collecting samples, than its speed.

## 4.2 Maintenance of sample integrity during storage on Mars and transport to Earth.

If after the collection of samples by MSL, and collection of context
data by imaging of the sample scoop, the samples are subjected to
excessive vibration or shock then the more friable lithologies will be
destroyed and/or leave the samples altered beyond recognition from
sample context imagery. There is also some concern/speculation about
chemical alteration of adjacent samples by each other if they are
allowed to mix.

## 4.3 Planetary Protection Issues

The purpose of planetary protection is to prevent forward contamination
of other solar system bodies by Earth organisms and to prevent harmful
contamination of the Earth by extraterrestrial organisms in returned
samples. Forward contamination controls protect science by reducing the
risk that future experiments could be affected by spacecraft-associated
contamination. This aspect of planetary protection is also enhanced by
any practices that improve our ability to distinguish between Earth and
extraterrestrial organisms, thus avoiding false-positive life detection
events.

Planetary protection also requires that any potential samples returned
to Earth from Mars be contained in extremely reliable enclosures, moved
to a quarantine facility, and shown to harbour no biologically hazardous
materials. Samples for which this cannot be demonstrated will have to
remain in the sample quarantine facility unless definitively sterilized
prior to release.

Planetary protection is relevant to the current discussion of an MSL
cached samples because of the possibility of forward contamination and
the potential for false positive life detection events upon return to
Earth.

### 4.3.1 Requirements for planetary protection without sample cache

Planetary protection requirements for the Mars Science Laboratory are
detailed in the MSL Planetary Protection Plan. In brief, the landed
portions of the spacecraft must be cleaned to a level of ≤ 300 spores
per square meter, as measured by the NASA standard assay. This is
equivalent to Viking pre-sterilization levels. Other rules and practices
are in place to avoid possible contamination of the martian subsurface.
Beyond what is required for planetary protection, MSL has plans in place
for molecular contamination control to protect its own science plans and
priorities.

### 4.3.2 Assumptions for planetary protection made in designing the MSL cache

The addition of hardware to the MSL rover to receive and store a cached
sample results in additional planetary protection considerations. To
meet the baseline MSL planetary protection forward contamination
controls, the cache hardware was designed to be compatible with
precision cleaning, sampling for bioassay, and subsequent dry heat
microbial reduction.

The planetary protection requirements associated with high-reliability
containment did not affect the design of the MSL cache, because the
controls to assure containment will be the responsibility of any future
Mars Sample Return mission. However, the requirements associated with
the potential for false positive life detection during biological hazard
assessment did affect planning for the sample cache.

At the time of this NAI-MEPAG study of the science value of the MSL
cache, it was unknown whether "false positives" would be avoided through
a requirement to sterilize the returned sample or through a pre-launch
requirement to acquire a comprehensive microbial inventory of possible
terrestrial contamination. In the early stages of planning, the cache
science goals appeared to tolerate the possibility of heat sterilization
of the cached sample if required for MSR. However, the NAI-MEPAG study
team considered the possible impact of sample sterilization on each of
the MEPAG goals.

### 4.3.3 Additional considerations

Performing a microbial inventory of MSL prior to launch would preserve
the option of leaving samples unsterilized and would be responsive to
the recommendations of the Space Studies Board given in the NRC-PREVCOM
report. The availability of a microbial inventory would enable much more
extensive analyses to be performed on the cached samples after return,
and would greatly reduce the risk that false positive life detection
events would prevent the release of unsterilized material from
containment.

## 4.4 Heat sterilization of samples  {#heat-sterilization-of-samples .unnumbered}

It has been observed that a regime of 500^o^C sterilization of the
sample may need to be undertaken before the samples can be released from
the sample receiving facility. It is a common misconception that heat
sterilization of samples would damage samples only relative to
astrobiological goals (MEPAG Goal I). This treatment would impact the
samples in several ways:

1.  Destroy or alter a significant proportion of any organic material
    within the sample.

2.  Destroy any hydrous mineralogy such as clays, goethite, jarosite,
    etc.

3.  Potentially redistribute raw materials released from the destruction
    of the phases mentioned in 1 and 2 into different phases therefore
    causing potentially misleading results.

4.  Adversely affect studies of unknown oxidant phases.

Therefore, not only would heating to these temperatures destroy
materials of interest, significantly impacting Goals I and III of the
MEPAG Goals Document, redistribution and condensation of released
volatiles such as H~2~O, CO~2~, CO, SO~2~, etc. could lead to misleading
interpretations of the nature of these species on Mars.

## 4.5 Site selection and type of sample collected

Site selection for the MSL mission is currently underway and will not be
affected by sample caching considerations. However, samples collected
for the cache will (should?) be as diverse a set possible given the
mineralogy at the landing site. Desirable characteristics for a suitable
sample are:

-   Organic material content

-   Macroscopic structuring similar to those found in terrestrial
    settings to contain or been influenced by life, such as
    stromatolites

-   Hydrous minerals, clays, etc. content

-   Carbonate deposits

-   Evidence of hydrothermal deposits, e.g., amorphous silica deposits

-   Mantle derived samples

-   Concretions

-   Carbon rich meteoritic samples

-   Samples from rocks within ancient terrains

Where possible the least weathered examples of each of the sample types
above should be collected. While little subsurface access is available
to MSL, the MER rovers have shown the value of trenching and using the
wheels to crush and flip rock samples. Samples for caching should take
advantage of the ability of MSL to utilize such techniques.

Consideration should be given during sample collection to the friability
of the sample collected. If a choice is offered, those samples that will
not obviously break apart and be significantly altered from the context
imagery data obtained should be chosen.

It is desirable to limit the number of samples from similar lithologies.
This would help preserve sample context data and avoid ambiguity in the
measurements made on the MSL rover itself. For example if five clay
samples are collected and the samples are jumbled in the cache, then the
chances of understanding to which analysis a sample belongs becomes more
difficult. By caching only single or at most two samples of a particular
lithology the chances of preserving context data is improved.

If possible, sample collection should attempt to minimize the amount of
regolith collected. While a scoop will be used to liberate the samples
from the Martian surface, the presence of a large amount of regolith
will have several consequences:

1.  Obscure accurate photo documentation of the samples within the scoop
    therefore compromising context data.

2.  Cross-contaminate sample already contained within the cache with
    regolith from a different area. This could become ingrained within
    cracks and holes in the collected samples thus confusing context
    data.

3.  Cross contaminate the sample cached by a later proposed sample
    return mission.

4.  Increase the risk that any oxidant within the regolith may degrade
    organic material close to the surface of any organic rich sample.

## 4.6 Accurate assessment of the conditions to which the samples have been subjected

One obvious concern for the sample cache is alteration of the samples
from the time they are collected to the moment that they are stowed and
transported to Earth. Understanding the conditions to which the samples
have been subjected is the key to mitigating adverse effects due to
sampling and therefore misleading science results upon analysis. There
are several mitigation strategies that became apparent:

-   Use the data collected by RAD on MSL to monitor the radiation
    environment of Mars and then to predict the fluxes of radiation to
    which the sample will be subjected to during storage on MSL.

-   Use the data collected from Phoenix on the oxidation state of
    Martian regolith.

-   Undertake suitable laboratory studies on similar sample lithologies
    to measure and predict damage to the samples from the effects of the
    factors above.

A further consideration is the material of the sample cache itself. This
material will be subjected to outgassing and accumulation of
contamination during its stay on Mars. If an accurate understanding of
the organic contamination that results from fabrication, integration,
launch and travel to Mars could be obtained, then an accurate assessment
of the build up of organic contaminants on the samples could be
obtained. Therefore, the sample cache box itself should be considered as
a witness plate to the conditions the samples will be subjected to and
treated / curated as such. This strategy has been key to understanding
the contamination of Stardust particles. (This is definitely the plan.)

While the charter of the meeting prevented any changes to the current
planning of MSLSC, a further point made by the committee was the
desirability of a calibration standard that would travel along with the
MSLSC. This standard would contain organic and mineral material able to
accurately record degradation and alteration during the mission. This
recommendation, while apparently unrealistic in terms of MSLSC, should
be seriously considered by the proposed MSR itself. Inclusion of such a
standard would allow a better understanding of the radiation condition
to which the samples had been exposed.

### 4.7 Preservation of samples

The workshop considered several types of curation regimes. While no
precise recommendations were made, the importance of preserving organic
materials and hydrated minerals is a priority. This could be
accomplished either by storing under Martian ambient conditions or an
inert gas at low temperatures. If samples are to be sterilized by
heating before being released to external investigators, then
Astrobiology (and Goal 1) priorities should be addressed by suitable
instrumentation within the sample receiving facility.

# 5.0 Report on Task 3 of the charter

# Consider what capabilities would be needed to collect the samples needed to address the remaining goals. 

The use of MSL instrumentation in conjunction with the MSL cache greatly
increases the utility of these samples. However, the concerns about
preserving the context of the samples brings this utility into question.
Therefore, a critical capability for any futureMSR mission sample
collection rover should be to ensure sample context data. Further
capabilities of importance to address the remaining goals are:

-   Precision sub-sampling and coring of lithologies of interest
    allowing stratigraphic information to be preserved and accurate
    assessment of depositional environments over time to be measured.
    Just as importantly, coring allows direct sampling of outcrops,
    which is preferable to collecting loose small rocks.

-   Storing of individual samples in such a way as to isolate them from
    each other to preserve sample integrity and context data.

-   Basic instrument suite to ensure that the samples collected are from
    the target lithology (based on MSL measurements), greatly increasing
    the scientific utility and diversity of the samples.

-   Design of planetary protection and sample sterilization protocols,
    which preserve enough material for analysis to satisfy the science
    requirements of Goals I and III. Failure to undertake basic
    research, technology development, modelling of the martian and deep
    space radiation environment and its effect on biological and organic
    material will severely restrict our ability to definitively analyze
    the returned samples.

**Appendix I.**

**CHARTER**

#### NAI-MEPAG MSLC Working Group

**Mars Science Laboratory (MSL) has been asked to cache sample for a
future Mars Sample Return (MSR) mission. The goal of this working group
is to review what Astrobiology and Mars relevant science that can be
undertaken on these samples. This will provide a valuable insight to
both the Mars program and the NAI as to what investigations and science
can be conducted with the current architecture. The charter is outlined
below.**

**\
**[Requested Tasks]{.underline}

1.  Assess the capabilities of MSL for acquiring and caching samples for
    a future sample return mission. With the anticipated samples
    returned, what information could be extracted with state of the art
    laboratory instrumentation circa 2020?

2.  Define what goals of Astrobiology and MEP could be addressed with
    the MSL cached samples.

3.  Consider what capabilities would be needed to collect the samples
    needed to address the remaining goals.

[Assumptions]{.underline}

-   MSL does not change its presently planned tool set and analytic
    capabilities

```{=html}
<!-- -->
```
-   MSL collects rock fragments (not cores)

-   The samples are not separated, but placed in the same open mesh box,
    exposed to the atmosphere and daily cycles of temperature and
    humidity

-   The number of samples depends on the fragment size and the cache
    volume

-   Sample canister would be hermetically sealed on Earth return

-   Total mass less than 50 gm

```{=html}
<!-- -->
```
-   The cache does not drive requirements on MSL including landing site
    selection

[Questions for the Committee]{.underline}

1.  What questions can be addressed with the MSL cached samples, given
    their nature and collection method?

    -   How well does MSL-SR address the goals of Astrobiology and the
        Mars Exploration Program?

```{=html}
<!-- -->
```
1.  What are the strengths and weaknesses of the collection and
    characterization methods?

    -   What role does the MSL analytic capability play with respect to
        the sample selection?

    -   What changes may occur in the samples from initial state, to
        collection, storage, transit, and analysis on return?

    -   What are the impacts of the limited sample volume/mass?

    -   How does the PP approach affect the applicability of the
        samples?

2.  How will the landing site selection impact the utility of the
    samples?

[Schedule]{.underline}

-   Telecon meeting in late September (after MSL cache PDR)

-   Face to face meeting October 8-9 at Carnegie Institution

-   Report by end of October