Discoveries in Planetary Sciencehttp://dps.aas.org/education/dpsdisc/ Mars,Methane and Methane Producers Bob Christian With considerable help from John Rummel Biology Department East Carolina University

Discoveries in Planetary Sciencehttp://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 Sciencehttp://dps.aas.org/education/dpsdisc/ Mars Rover “Curiosity” Measured methane directly on Mars Measured for about 1 Mars year Discovered periods of low and high methane concentrations Webster et al Science

Discoveries in Planetary Sciencehttp://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 UV photons have enough energy to break molecules apart

Discoveries in Planetary Sciencehttp://dps.aas.org/education/dpsdisc/ Martian Methane Cycle

Discoveries in Planetary Sciencehttp://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 water- rock interactions 2.Methane is produced by bacteria, in regions where liquid water is found Either theory implies that the Martian subsurface is dynamic Future observations can test for trace chemicals associated with each process Methane on Mars could be produced chemically through liquid/rock interactions (top) or biologically (bottom) methane liquid water hot rock surface methane bacteria ~2 µm

Discoveries in Planetary Sciencehttp://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 Sciencehttp://dps.aas.org/education/dpsdisc/ Getting carbon and energy

Discoveries in Planetary Sciencehttp://dps.aas.org/education/dpsdisc/ Getting energy with different “terminal electron acceptors”

Discoveries in Planetary Sciencehttp://dps.aas.org/education/dpsdisc/ Chemolithotrophic Methanogenesis (as we know it on Earth) 4 H 2 + CO 2  CH H 2 O 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 Non-chemolithotrophic also

Discoveries in Planetary Sciencehttp://dps.aas.org/education/dpsdisc/ For more information… Press Releases space.com - 1/15/09 - “Mars Methane: Geology or Biology?” Images All images (and accompanying animations) can be found at: 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 DOI: /science , 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: /science , Krasnopolsky et al., ‘Detection of methane in the martian atmosphere: evidence for life?’, Icarus, 172, p.537, doi: /j.icarus , Prepared for the Division for Planetary Sciences of the American Astronomical Society by David Brain and Nick Schneider Released 24 April 2009