An Astrobiology Strategy for the Exploration of Mars (2007) / Chapter Skim
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5 Methodologies for Advancing Astrobiology
5 Methodologies for Advancing Astrobiology
Pages 69-84
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From page 69... ...
The next logical step would be direct, in situ access to the subsurface via drilling. Measurements from the Mars Exploration Rovers and from the Mars Express orbiter, combined with other evidence, increasingly point to a warmer and/or wetter ancient environment compared to the present cold and dry climate.
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From page 70... ...
If such an environment existed in the past, then the geological history of that site must have allowed preservation of an environmental record and of traces of organisms that populated it. Past environments and historical geology can be retrieved from rocks using in situ instruments, as demonstrated by rovers such as Mars Pathfinder's Sojourner and the Mars Exploration Rovers, Spirit and Opportunity.1,2 These missions clearly demonstrate that the keys to unraveling geological and environmental context are mobility and a complementary suite of instruments for observations and measurements.
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From page 71... ...
Investigate the surfaces of selected exposed or acquired samples at fine scales for morphological, chemical, and molecular signatures suggesting preservation of prebiotic or biotic organic compounds. This may include directly detected compositional markers, evidence of minerals formed in or altered by liquid water, or particular sample textures.
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From page 72... ...
mass analyzers. Given the low expected abundances of organic molecules in Mars samples, attention should be paid to improving sensitivity over that of existing methodologies.
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From page 73... ...
18,19 Because those meteorites collected in Antarctica have spent most of their time on Earth fully encased in ice, they do not, in general, display the veins and cracks filled with alteration minerals commonly seen in meteorites found in hot deserts. Consequently, a concerted effort for the collection of martian meteorites in Antarctica should continue, given the potential scientific return from the recovery of new samples, particularly if they could provide a record of ancient and/or water-rich environments on Mars.
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From page 74... ...
Some analytical flexibility has been demonstrated in Mars Exploration Rover (MER) missions, in which adaptations of instrument protocols have been employed to analyze unexpected rock compositions, but changes in sample-handling capabilities and instrumentation are clearly impossible for investigations involving remote analysis by spacecraft.
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From page 75... ...
, sampling a variety of rocks and soils by using a rover, obtaining subsurface samples using a drill, conducting a Phobos sample return that might contain Mars ejecta from large impacts, or collection by astronauts. To maximize the astrobiological potential of a sample return from Mars, it will be important to recover a wide range of materials from a well-characterized site of astrobiological interest.
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From page 76... ...
significantly. Planning for the 2009 Mars Science Laboratory is too far advanced to allow adding even a simple samplecaching capability, but this strategy should be considered for any subsequent rover (or lander, if it is to acquire subsurface samples)
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From page 77... ...
NASA's 1995 report An Exobiological Strategy for Mars Exploration advocated sample return only after Mars had been thoroughly studied at global and regional scales, and following detailed local investigations that would ensure that any returned samples would have astrobiological relevance. NASA has implemented those recommendations in its exploration planning, with the unfortunate result that Mars sample return has been repeatedly pushed to (or beyond)
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From page 78... ...
30 However, the original results are now supported by more recent results reported by Chapelle and co-workers following studies at another site.31 The microbial communities associated with the CRB are numerically dominated by autotrophic microorganisms, bacteria capable of growth by oxidizing H 2 and fixing CO2, including high populations of acetogens.32 Subsequent cultivation-independent molecular analysis revealed that Archaea also accounted for 1 to 2 percent of the population of the CRB.33 Due to the common occurrence of similar rocks on Mars -- identified by their spectroscopic and morphological characteristics -- and the likelihood of liquid water in the subsurface, SLiME is an attractive analog in the search for microbial life on Mars. This same basic concept has been extended from the CRB to hydrothermal waters circulating through igneous rocks in southern Idaho and to the deep groundwater of the Fennoscandian Shield.
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From page 79... ...
Deeply buried sediments such as those beneath the seafloor on Earth are another important subsurface analog system that has yielded a wealth of new information on lithologic controls on microbial activity, especially at very low organic carbon concentrations, and on the ability of microbes to persist under extremely low nutrient conditions, leading to the requirement for refined definitions of life and death for very-slow-growing microorganisms. Parkes and colleagues have established that there is a diverse and active microbial community in deeply buried marine sediments35 and that these organisms can persist for extended periods in spite of a relative lack of circulating fluids.
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From page 80... ...
The remaining 9 percent represented beta- and deltaProteobacteria, Verrucomicrobiales, and candidate divisions. In contrast to the alkaliphilic Mono Lake, the acidic Rio Tinto River is host to communities that are dominated by microeukaryotes.40 It is very important to study the behavior of chemical and isotopic biosignatures over the full range of possible environmental conditions identified on Mars in order to best apply biosignature methods to Mars samples, both in situ and returned samples.
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From page 81... ...
Finally, Mars sample return will require that a sample-receiving facility on Earth be designed and constructed. Curated returned samples must be isolated from the terrestrial environment, not only for planetary protection, but also to preserve their scientific integrity for future studies.
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From page 82... ...
McCleese and the Mars Advanced Planning Group, Robotic Mars Exploration Strategy 200-201, JPL 400-1276 706, Jet Propulsion Laboratory, Pasadena, Calif., 2006; and D.W. Beaty, M.A.
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From page 83... ...
Edgett, "Mars Global Surveyor Mars Orbiter Camera: Interplanetary Cruise through Primary Mission," Journal of Geophysical Research 106(E10)
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