Methane on Mars: What Does It Mean?
When: March 28, 2005 11AM PST
Recent spectroscopic detections of CH4 in the atmosphere of Mars are the
first definitive observations of an organic compound on that planet. The
relatively short photochemical lifetime of CH4 (~300 years) argues for a
geologically young source. We demonstrate here that low-temperature
alteration of basaltic crust by carbon-bearing hydrothermal fluid can
produce the required CH4 flux of 1 × 107 moles year-1, assuming conservative
values for crustal permeability and oxygen fugacity as implied by martian
basaltic meteorites. The crustal thermal disturbance due to a single dike ~
10 × 1 × 10 km during the past 104 years is capable of driving the
alteration, if all carbon is supplied by magmatic degassing from a dike with
only 50 ppm C. Atmospheric methane strongly suggests ongoing magmatism and
hydrothermal alteration on Mars.
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