Discoveries in Planetary Science http://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 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”

• Measured methane directly on Mars

• Measured for about 1 Mars year

• Discovered periods of low and high methane concentrations

Webster et al. 2014. Science

http://mars.jpl.nasa.gov/news/whatsnew/index.cfm?FuseAction=ShowNews&NewsID=1767

Discoveries in Planetary 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

UV photons have enough energy to break molecules apart

Discoveries in Planetary Science 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 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

methanebacteria

~2 µm

Discoveries in Planetary Science http://dps.aas.org/education/dpsdisc/

LifeMetabolism 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• Non-chemolithotrophic also

Discoveries 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. 1041DOI: 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.1758DOI: 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 dpsdisc@aas.org - http://dps.aas.org/education/dpsdisc/ - Released 24 April 2009