Report Series: Committee on Planetary Protection Planetary Protection for the Study of Lunar Volatiles (2020) / Chapter Skim
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2 Study of the History of the Solar System and Its Prebiotic Chemistry: Permanently Shadowed Regions on the Moon
2 Study of the History of the Solar System and Its Prebiotic Chemistry: Permanently Shadowed Regions on the Moon
Pages 8-18
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From page 8... ...
Material from comets and chondritic or carbonaceous meteorites that impacted the Moon may be protected in PSRs or the subsurface and serve as inventories of volatiles, including some organics, that penetrated the early solar system.2 Thus, PSRs in the lunar polar regions are of considerable astrobiological interest for their potential role in storing prebiotic chemicals and serving as a window to the early evolution of Earth and the other terrestrial planets and to the emergence of life. CURRENT SCIENTIFIC UNDERSTANDING Knowledge of Volatiles Likely to be Present on the Moon Knowledge of the lunar polar regions has grown substantially since the potential for retention of water and other volatiles within PSRs was first proposed by Urey in 1952 and detailed by Watson et al.
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From page 9... ...
Smith, and M.T. Zuber, 2018, "Evidence for Surface Water Ice in the Lunar Polar Regions Using Reflectance Measurements from the Lunar Orbiter Laser Altimeter and Temperature Measurements from the Diviner Lunar Radiometer Experiment," Lunar Polar Volatiles 2018, LPI Contrib.
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From page 10... ...
Smith, and M.T. Zuber, 2018, "Evidence for Surface Water Ice in the Lunar Polar Regions Using Reflectance Measurements from the Lunar Orbiter Laser Altimeter and Temperature Measurements from the Diviner Lunar Radiometer Experiment," Lunar Polar Volatiles 2018, LPI Contrib.
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From page 11... ...
22 D.J. Lawrence, 2017, "Permanently Shaded Regions: Future Exploration of a Unique Solar System Environment," Planetary Science Vision 2050 Workshop 2017, LPI Contrib.
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From page 12... ...
Dark mantles on Mercury are associated with the ice deposits that might be organic material that were either generated in situ or delivered by external sources, including impacts of comets, asteroids, and IDPs.27 Similar evidence exists for water ice within lunar PSRs. However, these lunar deposits do not appear to be as ubiquitous as the Mercury deposits, with large variability between PSRs.
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From page 13... ...
Although there is strong evidence for the presence of volatiles that are of interest in studies of prebiotic chemistry, the sources of lunar volatiles are not well-understood. Seven possible sources of lunar volatiles have been proposed: proton deposition by the solar wind, the Earth during formation of the Moon, internal degassing from the Moon, comets, asteroids, interplanetary dust, and giant interstellar molecular clouds.39 Solarwind deposition and impacts with interplanetary dust and small meteoroids are thought to be important continuous sources of volatiles,40 but volatiles deposited by larger impacts could yield important 36 Lunar Exploration Analysis Group, 2020, "Rapid Response Specific Action Team in Response to COSPAR Planetary Protection Inquiry," May 8, https://www.lpi.usra.edu/leag/reports/COSPARRRSAT_v2.pdf.
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From page 14... ...
Determination of D/H ratios of lunar water ice may provide a more robust estimate of comet or asteroid derived water, informing our understanding of the sources of water on Earth.9 Finding 1: The scientific potential of the Moon's poles and PSRs is significant, including for studies of prebiotic chemical evolution that have long been within the scope of national and international planetary protection policy. Finding 2: Understanding of the lunar poles and PSRs has advanced but remains incomplete concerning many scientific questions, including how "cold traps" on the lunar surface function with respect to volatile and organic chemicals, the nature and composition of water and other volatile deposits in PSRs, and how the water and other ice deposits inform the scientific understanding of prebiotic chemical evolution in the solar system.
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From page 15... ...
Finding 3: Tapping the scientific potential of the lunar poles and PSRs requires accelerating lunar science across orbital and in situ missions and building "ground truth" about these regions to inform planning for planetary protection approaches for future scientific, exploration, and commercial activities on the Moon. POTENTIAL THREAT OF ORGANIC AND BIOLOGICAL CONTAMINATION The interest in the Moon as a scientific target for investigations of prebiotic chemistry brings up questions about the potential for, and consequences of, organic and/or biological contamination from human activities.
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From page 16... ...
Rocket Exhaust from Landers Distant from Polar Regions Combustion byproducts of spacecraft propellants were a commonly cited concern in the LEAG response to the COSPAR planetary protection inquiry. Chapter 3 of this report addresses this topic in detail, where the committee concludes that this contamination is likely to be minimal and poses little threat to many studies of the PSRs.
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From page 17... ...
Requirements imposed to preserve the scientific integrity of individual sampling investigations of lunar prebiotic chemistry will be far more stringent than planetary protection requirements as a consequence of rigorous cleanliness provisions for the sampling instruments. Low Threat of Biological Contamination One cannot rule out the possibility that deeply frozen, ancient ice deposits in large PSRs contain remnants of microorganisms transported to the Moon by ejecta from terrestrial meteorite impacts over geologic time.
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From page 18... ...
biological contamination of the lunar surface will not contaminate the lunar subsurface through the operation of natural processes on the Moon; and (3) any biological material identified in samples from the lunar surface or subsurface can be tested against terrestrial organisms to determine its source.
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