A new paper published online today in Geophysical Research Letters:

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Summers, Michael E.; Lieb, B. Joseph; Chapman, Emily; Yung, Yuk L.
Atmospheric biomarkers of subsurface life on Mars
10.1029/2002GL015377
20 December 2002

Abstract

If life exists beneath the Martian surface similar to terrestrial
bacteria that rely upon chemical reactions involving H2 and/or CO as
energy sources, then it may be possible to infer its existence by
observing metabolic by-products that would appear as trace gases in
the Martian atmosphere. We have studied the fate of organic trace
gases in the Martian atmosphere and find that most have very short
chemical lifetimes, however CH4 has a chemical lifetime of about 300
yrs and thus it will tend to be uniformly distributed in the Martian
atmosphere. Using the current observational upper limit on
atmospheric CH4 we deduce that its flux, from all sources, into the
Martian atmosphere must be at least 10^5 times less than terrestrial
value. If there are abiotic sources of CH4 on Mars then the
biological component of the CH4 must be even less.

Received 24 April 2002; revised 19 June 2002; accepted 18 July 2002;
published 20 December 2002.

Index Terms: 5405 Planetology: Solid Surface Planets: Atmospheres—
composition and chemistry; 6225 Planetology: Solar System Objects:
Mars.

Citation: Summers, M. E., B. J. Lieb, E. Chapman, and Y. L. Yung,
Atmospheric biomarkers of subsurface life on Mars, Geophys. Res.
Lett., 29(24), 2171, doi:10.1029/2002GL015377, 2002.

Alex R. Blackwell
University of Hawaii