Signs of Life A Report Based on the April 2000 Workshop on Life Detection Techniques (2002) / Chapter Skim
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5 Conclusions and Recommendations
5 Conclusions and Recommendations
Pages 29-40
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From page 29... ...
The table includes techniques that were not covered in the workshop presentations, but whose inclusion here in summary form provides a comprehensive basis for comparing the approaches. DETERMINING IF LIVING ORGANISMS ARE ON A SPACECRAFT BEFORE LAUNCH The most strikingly definitive result evident from the workshop is the dramatic improvement in laboratory techniques designed to detect terrestrial organisms, with principal application to spacecraft sterilization and, hence, planetary protection issues relating to forward contamination.
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34 an .= o Cal ¢ EM ;^ sit ~ z ca o ~ Cd o ., ~ .F ~ ;^ .> · ~ V, o C)
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. organic residue Typically 2.5 Mrad problems encounteredinclude optical changes in glasses, damage exposed to electronics and solar cells, and altered organics 1-10 MeV problems arise because of limited penetration 6 mg per liter of H2O2 problems encountered because unexposed surfaces remain untreated 5,000-20,000 J/m2 problems arise because unexposed surfaces remain untreated Toxic gases problems encountered because unexposed surfaces remain untreated and because the gases may catalyze chemical reactions between metals and other components SOURCE: Space Studies Board, National Research Council, Preventing the Forward Contamination of Europa, 2000, and The Quarantine and Certification of Martian Samples, 2002, National Academy Press, Washington, D.C.
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From page 36... ...
Although techniques for amplification of nucleic acids have, for example, improved somewhat in the breadth of genetic material amplified, they are still extraordinarily narrow compared with the range of possible encoding schemes one can imagine. Imaging techniques that reveal structures indicative of processes that would be unexpected in abiotic chemistry, and whose detectable presence is independent of chemispecific amplification techniques, are promising in the sense of being quite general.
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From page 37... ...
The committee recommends that special near-term emphasis be given to the issues of sample selection, spacecraft sample handling, and sample characterization. DETERMINING IF LIVING ORGANISMS HAVE BEEN PRESENT AT SOME EARLIER EPOCH AND HAVE LEFT FOSSIL REMNANTS BEHIND IN A RETURNED SAMPLE The committee concludes that the search strategy for evidence of extinct life must include the identification of suitable landing sites, the selection of the appropriate rock types, and multiple analytical techniques that, in the aggregate, are capable of distinguishing between abiogenic and biogenic signatures.
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From page 38... ...
Identification of isotopic biosignatures in elements more robust against alteration, such as iron, is promising, but more measurements are needed to establish fractionation patterns and decide whether the approach is reliably diagnostic of past biological activity. Morphological signatures, such as mineralogical or textural alteration of minerals by organisms, can reveal the past presence of life when carefully documented and compared to known alteration signatures in the terrestrial rock record.
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From page 39... ...
Because of the continuing rapid improvements in technology, it is not appropriate at this time to recommend a specific set of techniques for in situ life detection, but in situ life detection will require commitment to a small set of potential techniques with significant lead time to ensure that they can be space qualified. Some of the approaches available for the detection of living organisms are available in miniaturized form and are potentially space qualifiable for an in situ life detection mission.
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This was of particular value in analyzing the SNC meteorite ALH84001, in which it was found that most of the organic material is a terrestrial contaminant and the remainder resembles pnm~tive meteoritic or interstellar matenal. The development of more sensitive techniques to detect organic molecules and characterize the extent to which organic chemical systems may be evolving toward life in a planetary environment is an important pnonty.
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