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Mars,Methane and Methane Producers Bob Christian With considerable help from John Rummel Biology Department East Carolina University Discoveries in Planetary Science http://dps.aas.org/education/dpsdisc/ Methane in the Martian Atmosphere • Methane gas was recently detected in Mars’ atmosphere using groundbased telescopes • The methane gas distribution is patchy and changes with time • Most methane in Earth’s atmosphere is produced by life, raising questions about its origin on Mars View of Mars colored according to the methane concentration observed in the atmosphere. Warm colors depict high concentrations. Discoveries in Planetary Science http://dps.aas.org/education/dpsdisc/ Mars Rover “Curiosity” http://mars.jpl.nasa.gov/news/whatsnew/index.cfm?FuseAction=ShowNews&NewsID=1767 • Measured methane directly on Mars • Measured for about 1 Mars year • Discovered periods of low and high methane concentrations Discoverieset in Planetary Science Webster al. 2014. Science http://dps.aas.org/education/dpsdisc/ Recent Release of Methane • Methane in the atmosphere should be destroyed by UV light within a few hundred years • Methane observed now must therefore have been produced recently • Variations in space and time suggest that it was recently released from the subsurface in localized areas Discoveries in Planetary Science UV photons have enough energy to break molecules apart http://dps.aas.org/education/dpsdisc/ Martian Methane Cycle Discoveries in Planetary Science http://dps.aas.org/education/dpsdisc/ The Big Picture • Where can the methane come from? From analogy with Earth, there are two leading theories for the origin of recent subsurface methane at Mars: 1. Methane is produced by waterrock interactions surface methane liquid water hot rock 2. Methane is produced by bacteria, in regions where liquid water is found ~2 µm Either theory implies that the Martian subsurface is dynamic • Future observations can test for trace chemicals associated with each process Discoveries in Planetary Science methane bacteria Methane on Mars could be produced chemically through liquid/rock interactions (top) or biologically (bottom) http://dps.aas.org/education/dpsdisc/ Life Metabolism is part of definitions • Energy Source • Carbon Source • Way to extract energy by moving electrons from more to less “energetic states” • Processing materials for growth Discoveries in Planetary Science http://dps.aas.org/education/dpsdisc/ Getting carbon and energy Discoveries in Planetary Science http://dps.aas.org/education/dpsdisc/ Getting energy with different “terminal electron acceptors” Discoveries in Planetary Science http://dps.aas.org/education/dpsdisc/ Chemolithotrophic Methanogenesis (as we know it on Earth) 4 H2 + CO2 CH4 + 2 H2O Hydrogen Carbon dioxide Methane Water • • • • Only by certain bacteria Began early in Earth’s history Requires anoxia Found in many places • Wetlands to cows and termites • Greenhouse gas • Discoveries Non-chemolithotrophic also in Planetary Science http://dps.aas.org/education/dpsdisc/ For more information… Press Releases • space.com - 1/15/09 - “Mars Methane: Geology or Biology?” http://www.space.com/scienceastronomy/090115-mars-methane-news.html Images • All images (and accompanying animations) can be found at: http://www.nasa.gov/mission_pages/mars/news/marsmethane_media.html Source Article • (on-campus login may be required to access journals) Mumma et al., ‘Strong Release of Methane on Mars in Northern Summer 2003’, Science, 323, p. 1041 DOI: 10.1126/science.1165243, 2009. http://www.sciencemag.org/cgi/content/abstract/323/5917/1041 Related Articles • (on-campus login may be required to access journals) Formisano et al., ‘Detection of Methane in the Atmosphere of Mars’, Science, 306, p.1758 DOI: 10.1126/science.1101732, 2004. http://www.sciencemag.org/cgi/content/abstract/306/5702/11758 • Krasnopolsky et al., ‘Detection of methane in the martian atmosphere: evidence for life?’, Icarus, 172, p.537, doi:10.1016/j.icarus.2004.07.004, 2004. http://tinyurl.com/krasnopolskyIcarus2004 Prepared for the Division for Planetary Sciences of the American Astronomical Society by David Brain and Nick Schneider [email protected] - http://dps.aas.org/education/dpsdisc/ - Released 24 April 2009 Discoveries in Planetary Science http://dps.aas.org/education/dpsdisc/