Signs of Life A Report Based on the April 2000 Workshop on Life Detection Techniques (2002) / Chapter Skim
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Workshop Papers Session 2: Sample Return
Workshop Papers Session 2: Sample Return
Pages 79-102
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Session 2: Sample Return 79
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The resulting liquid water then modified these rocks. Many of the primitive meteorites we have were thus relatively warm wet rocks for millions of years, and their parent asteroids may have had a much higher content of water in them than we see today.
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Sample Return Missions: Stardust Figure 1 shows the Stardust spacecraft, which is a Discovery mission, with the collector and then the canister (on top) , which is coming back to Earth in 2006.
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From page 83... ...
However, the basic components of sample return will remain the same: spacecraft assembly, launch, transit to Mars, landing on Mars, sample retrieval, launch of the sample to Mars orbit, sample retrieval in Mars orbit, return to Earth, Earth entry, sample retrieval and containment, and sample analysis. Life detection will play a prominent role throughout the mission, from the point of view of planetary protection, science protection, and life detection of terrestrial life forms, either extant or extinct.
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From page 84... ...
This would seem to be an area that is ripe for improvement and adaptation to Bioburden assessment, as recommended by the 1992 National Research Council report.3 Molecular Tagging of Earthly Organisms Another approach being tested is that of developing molecular tags for labeling bacteria that may be attached to the spacecraft and end up in the sample chamber or interfere with in situ life detection experiments. Such methods, if successful, would allow treatment of the parts of the spacecraft that will come into contact with the Mars sample, so that any organisms (dead or alive, intact or fragmented)
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From page 85... ...
Acknowledgments The help of many agencies in support of our work in life detection is gratefully acknowledged: the National Science Foundation in support of planetary atmospheric signatures; Department of Energy Natural and Accelerated Bioremediation Research program in support of methods for studying life associated with mineral interfaces; NASA Exobiology Program; and NASA Astrobiology Program for support in the development of biosignatures.
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From page 86... ...
An important lesson from the Viking missions to Mars is that searches for extraterrestrial life on Europa should establish the geological and chemical context needed to inform the results. The amount of sample available for life detection analysis could be maximized by the melting and filtration (and possibly the evaporation)
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In this case, it seems unlikely for the first lander that more than one life detection experiment will be present. In this case, the Viking experience suggests that the biochemical definition trumps other definitions.
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present in the water, and a search for organic molecules. In fact, the latter probably represents the highest-priority life detection experiment to be conducted.
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From page 89... ...
In the case of sample return missions, both pristine and concentrated samples should be returned. Moreover, sample acquisition from some depth into Europa's surface is essential.
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From page 90... ...
A biomass of~108 g corresponds to ~5 x 102~ aquatic cells.45 Were these cells distributed evenly throughout Europa's putative ocean an unlikely scenari~average cell densities would be only about 1 cell per liter. Even if this water reached the surface and froze, such low cell densities would render life detection extremely difficult.
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From page 91... ...
Soon in situ analysis will be conducted by the Huygens Probe. Further in situ and possibly sample return missions may be needed to provide a detailed understanding of how the atmospheric methane and nitrogen are converted to organic, possibly prebiotic, molecules.
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From page 92... ...
Further in situ experiments are warranted as well as continued laboratory simulations. If these point to enduring mysteries about Titan's organic haze, then such mysteries would warrant a sample return mission.
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Implementing a satisfactory and successful planetary quarantine effort demands a great deal of both sophistication and accuracy in assessing the presence and viability of Earth life, while straining the boundaries of life detection as practiced when searching for unknown life forms in poorly understood materials returned from other planets. Introduction .
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From page 94... ...
of the National Academy of Sciences [National Research Council] ."72 Working both directly and through the Associate Administrator for Space Science, the PPO imposes constraints on program and project managers to meet the biological and organic contamination control requirements of the NASA policy in the conduct of research, development, test, preflight, and operational activities associated with solar system exploration missions.
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From page 95... ...
Forward Contamination of Europa One example of a decision on forward contamination deals with future missions to Europa—perhaps Jupiter's most compelling satellite and the planned Europa Orbiter mission in particular. With a likely liquid water ocean under a crust of water-ice which may be only a few kilometers thick, Europa may harbor environments that could be used by Earth organisms if they were to be introduced into them.
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From page 96... ...
In 1997, the SSB reported advice to NASA on provisions for Mars sample return missions,79 complementing its 1992 report on the prevention of forward contamination on Mars,8° and completing the initial update of planetary protection recommendations made by the SSB after the Viking missions of the mid-1970s.~ More recently, the SSB has provided recommendations on provisions to be taken to protect Earth when conducting sample return missions to small bodies of the solar system, including places as disparate as Europa, asteroids, and comets.82 The case for Mars is instructive as a model for the general problem of returning samples from another world where extraterrestrial life may exist, and it doesn't matter whether the life on that other body had a separate origin or is somehow related to life already on Earth. The SSB's 1997 Mars report, Mars Sample Return: issues and Recommendations, provides a careful look at the subject of sample return, and conservative guidelines for the handling of samples from Mars.83 The basic recommendations of the report were the following: · Samples returned from Mars should be contained and treated as though potentially hazardous until proven otherwise; · If sample containment cannot be verified en route to Earth, the sample and spacecraft should be either sterilized in space or not returned to Earth; · Integrity of sample containment should be maintained through reentry and transfer to a receiving facility; · Controlled distribution of unsterilized materials should occur only if analyses determine that the sample does not contain a biological hazard; and · Planetary protection measures adopted for the first sample return should not be relaxed for subsequent missions without thorough scientific review and concurrence by an appropriate independent body.
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From page 97... ...
Selection of Earth landing sites to minimize possible dangers and to ensure that the potential for life in a returned sample does not introduce nontechnical issues that are incompatible with mission goals and effective sample analysis and assessment; 3. Reliable isolation of the exterior of the sample return container from the martian surface during mission operations and subsequent containment of martian samples so that they are not released inadvertently on Earth (a high level of operational reliability, especially in the critical phase of Earth entry, and the ability to certify containment prior to committing to Earth entry, will be necessary)
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From page 98... ...
If it occurs, planetary cross-contamination is a genie that almost certainly could not be put back into its bottle and given the potential assessment of the benefits of space exploration versus the costs incurred by the introduction of any new harmful biological entity onto Earth, the cost of not conducting a sound planetary protection program is much greater than any of the real costs of implementing contamination controls. Increasingly as well, ethical considerations are becoming much more obvious and compelling in our assessment of a future for humans,84 and their robots, in the universe as a whole.
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From page 99... ...
2. Space Studies Board, National Research Council, Mars Sample Return: Issues and Recommendations, National Academy Press, Washington, D.C., 1997.
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From page 100... ...
, Biological Contamination Control for Outbound and Inbound Planetary Spacecraft, NPD 8020.7E, NASA Headquarters, Washington, D.C, 1999.
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From page 101... ...
83. Space Studies Board, National Research Council, Mars Sample Return: Issues and Recommendations, National Academy Press, Washington, D.C., 1997.
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