Science Priorities for Mars Sample Return

VII.SUMMARY OF FINDINGS AND RECOMMENDED FOLLOW-UP STUDIES

1. 
   MSR landing site selection process and timing. How would the specific candidate landing sites for MSR be identified and screened for safety? Which sites optimize the science return by effectively addressing the most MSR science objectives? Would it be prudent to use the instruments on MRO for this purpose while the orbiter is still healthy? We need to take into consideration the expected availability of orbital instruments during the second decade.
   
2. 
   Contamination limits. All of the arguments related to contamination limits and priorities discussed above in Section VI-K will need to be reconsidered. Substantial amounts of information now exist (including unpublished data) about contamination relevant to many different missions or sample collections - Antarctic meteorites, lunar samples, Stardust, Genesis, maybe soon Hayabusa. In addition we will need to consider experience and results from the 2007 Mars Phoenix mission, the 2009 Mars Science Laboratory, and the 2013 ExoMars mission. It would be useful to compile a summary for these different cases with an aim to identify common problems, solution philosophies, and lessons learned. Note that for scientific purposes, contamination management planning must address flight system activities as well as sample handling in the SRF, post-SRF curation, and PI laboratories. There is no point in keeping the samples substantially cleaner during any one of these phases than during the others—we need a contamination management plan for the entire life-cycle of the samples.
   
3. 
   Depth of subsurface access. A major open question for MSR is the nature of the relationship between the oxidizing surface zone, and the inferred reduced subsurface zone. What is the depth scale of this gradient into the near subsurface? How does this depth scale vary as a function of the permeability of the particular subsurface material? As we acquire relevant new information either during on-going missions, through new missions, or from new modelling methods, this question needs to be reconsidered. We will require assistance in order to make informed decisions regarding the hardware necessary to access subsurface materials during the MSR mission.
   
4. 
   For core samples: length vs. diameter. This report recommends that a mini-corer be utilized to acquire rock samples and that these samples must be larger than about 10 grams (or if the engineering requirement is defined in terms of volume, about 3.5 cc). However, the ND-SAG team did not attempt to evaluate the optimal combination of length and diameter of these core samples. Preliminary thought within the ND-SAG team was that a mini-core length of about 5 cm would be desirable, but more systematic analysis is required.
   
5. 
   Strategy for splitting the samples in the SRF. A strategy should be devised in advance for splitting the rock samples that arrive intact at the SRF. For the purpose of planetary protection, it will be necessary to take statistically significant sub-samples in order to reach conclusions that can be applied to the entire sample. The decision on how the samples are subdivided will affect the subsequent scientific investigation plan.
   
6. 
   Relationship between landing site targeting precision, minimum roving distance, and time on the surface. If the landing error ellipse has a radius of 3 km, and the sample acquisition traverse is about 2 or 2.5 km, then, if the landing site is a "go-to" site, the total rover distance would be 8.5 km (3 + 3 + 2.5). If landing site targeting precision is reduced to 1 km, this would reduce range to 4.5 km (1 + 1 + 2.5). A relatively firm time constraint might be imposed by the limitations on thermal cycling of the MAV, accordingly it would have to launch within 12 months. This is independent of planetary alignment considerations. Given estimates of rover distance per day, time to use the instruments to do sample selection, and the time to drill and encapsulate each of the rock samples, there is a possibility that all of the work needed cannot fit within the allowable 12 months. These issues would be more severe in ND-SAG’s "Case A", where MSR is sent to a virgin site (time required to determine the geologic context). Thus, it seems likely that the relationships between time on the surface, rover mobility range, landing site targeting precision, and spatial distribution of samples will need more detailed study. Develop strategic ground operation scenarios; e.g., conduct multiple sample collection sorties with periodic sample deliveries to MAV?
   
7. 
   Preparation of a Design Reference Mission. It would be helpful to prepare a Design Reference Mission that would summarize how we would achieve the following: 1) collect samples and characterize the site, 2) address the key questions that this exploration was designed to answer, and 3) respond to new discoveries.  We suggest that we do such a study for the Columbia Hills.  Such an analysis would tell us how much documentation we have to do to understand the context of a site, how much sample we have to take to characterize a specific type of rock (or process), and how far we have to go to obtain the samples for MSR needed to address key scientific goals and objectives.
   
8. 
   Engineering/cost studies of each of the factors indicated in Section VI. Each of the factors described in Section VI of this report should be evaluated more rigorously for their engineering and costs. (For example, re: Number of Samples - optimal number of encapsulated samples; potential value of an additional large “MSL-like” chamber for local regolith plus “durable” rock chips, etc.)
   

VIII.ACKNOWLEDGEMENTS

MEPAG Goal I. Anderson, Marion (Monash U., Australia), Carr, Mike (USGS-retired), Conrad, Pamela (JPL), Glavine, Danny (GSFC), Hoehler, Tori (NASA/ARC), Jahnke, Linda (NASA/ARC), Mahaffy, Paul (GSFC), Schaefer, Bruce (Monash U., Australia), Tomkins, Andy (Monash U., Australia), Zent, Aaron (ARC)

MEPAG Goal II. Bougher, Steve (Univ. Michigan), Byrne, Shane (Univ. Arizona), Dahl-Jensen, Dorthe (Univ. of Copenhagen), Eiler, John (Caltech), Engelund, Walt (LaRC), Farquahar, James (Univ. Maryland), Fernandez-Remolar, David (CAB, Spain), Fishbaugh, Kate (Smithsonian), Fisher, David (Geol. Surv. Canada), Heber, Veronika (Switzerland), Hecht, Mike (JPL), Hurowitz, Joel (JPL), Hvidberg, Christine (Univ. of Copenhagen), Jakosky, Bruce (Univ. Colorado), Levine, Joel (LaRC), Manning, Rob(JPL), Marti, Kurt (U.C. San Diego), Tosca, Nick (Harvard University)

MEPAG Goal III. Banerdt, Bruce (JPL), Barlow, Nadine (Northern Ariz. Univ.), Clifford, Steve (LPI), Connerney, Jack (GSFC), Grimm, Bob (SwRI), Kirschvink, Joe (Caltech), Leshin, Laurie (GSFC), Newsom, Horton, (Univ. New Mexico), Weiss, Ben (MIT)

MEPAG Goal IV. McKay, David (JSC), Allen, Carl ((JSC), Jolliff, Brad (Washington University), Carpenter, Paul (Washington University), Eppler, Dean (JSC), James, John (JSC), Jones, Jeff (JSC), Kerschman, Russ (NASA/ARC), Metzger, Phil (KSC)

Part of this work was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration. The contribution to this work performed by Lars Borg was done under the auspices of the U.S. DOE by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. D. J. Des Marais and Lisa Pratt acknowledge support from the NASA Astrobiology Institute.