organics on titan, water on enceladus: worlds of possibilities for life
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Organics on Titan, Water on Enceladus: Worlds of possibilities for life. Chris McKay NASA Ames Research Center [email protected] This talk is a compilation based on the work of many colleagues over many years. My thanks and acknowledgements to all of them. - PowerPoint PPT PresentationTRANSCRIPT
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Organics on Titan, Water on Enceladus: Worlds of possibilities for life
Chris McKayNASA Ames Research Center
This talk is a compilation based on the work of many colleagues over many years. My thanks and acknowledgements to all of them.
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Why is Life on other Worlds Interesting?
• The possibility of a second genesis of life: comparative biochemistry life is common in the universe (yeah!)
• Information about the early planetary environment• Relevant to the origin of life on Earth
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Jets of H2O on Enceladus
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Given liquid water on Enceladus is there:
• a plausible origin of life?
•a plausible ecology?
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Davis & McKay, Origins Life Evol. Biosph. 26, 61-73, 1996.
OK for Enceladus
OK for Enceladus
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Plausible Ecologies
• The known laws of physicsenergy from thermal gradients, electric fields, radiation
• My favorite “extremophile” D. radiodurans radiation resistance, salt tolerance, etc.
• Actual ecosystems actual microbial ecosystems that require no light & no O2
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Examples of ecologically isolated microbial ecosystems
(no O2, no light, no organic input) Only three examples are known:
Two are are based on H2 from rock reactions(H2 + CO2 CH4 + H2O)
• Stevens, T.O. and J.P. McKinley 1995. Lithoautotrophic microbial ecosystems in deep basalt aquifers, Science 270, 450-454.
• Chapelle, F.H., K. O'Neill, P.M. Bradley, B.A. Methe, S.A. Ciufo, L.L. Knobel, and D.R. Lovley 2002. A hydrogen-based subsurface microbial community dominated by methanogens, Nature 415, 312-315.
One based on radioactive decay• Lin, L.-H., et al. 2006. Long-Term Sustainability of a High-Energy,
Low-Diversity Crustal Biome, Science 314, 479-482
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4H2 + H+ + SO42- -----> H2S + 2H2O + 2OH-
H2O
H2 O2, H2O2
Radiolysis
FeS2
SRB
GeochemicalReactions
Desulfoprofundis tokoloshe
Lin et al. 2006, slide courtesy of T. Kieft
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Ice Cover
Liquid Water
Biology: H2 + CO2 CH4 + H2O
Thermal processing, T>500oC: CH4+H2O H2 + CO2
CH4H2
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Stardust flys through the Plume of Enceladus for a Sample Return Mission
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If we find organic material in the plume of Enceladus (or Europa & Mars) how can we tell if it was ever
alive?
If its like us then easy, less interestingIf its alien then hard, but interesting
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Abiotic distributions are smoothBiotic distributions are spiked
McKay 2004 PLoS Biol 2(9)1260-12623
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Abiotic distributions are smoothBiotic distributions are spiked
McKay 2004 PLoS Biol 2(9)1260-12623
alien
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Earth Titan
Carbon based Carbon based
Liquid H2O Liquid CH4
Widespread ??
Possibilities for Widespread Life on Titan
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