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GEOPHYSICAL RESEARCH LETTERS, VOL. 32, L13201, doi:10.1029/2004GL022161, 2005

Formation of methane on Mars by fluid-rock interaction in the crust

James R. Lyons

Institute of Geophysics and Planetary Physics, Center for Astrobiology, University of California, Los Angeles, California, USA


Craig Manning

Department of Earth and Space Sciences, University of California, Los Angeles, California, USA


Francis Nimmo

Department of Earth Sciences, University of California, Santa Cruz, California, USA


Abstract

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 ∼1 × 1 × 10 km intruded 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.

Received 7 December 2004; accepted 25 May 2005; published 1 July 2005.

Index Terms: 1011 Geochemistry: Thermodynamics (0766, 3611, 8411); 1034 Geochemistry: Hydrothermal systems (0450, 3017, 3616, 4832, 8135, 8424); 5220 Planetary Sciences: Astrobiology: Hydrothermal systems and weathering on other planets; 5405 Planetary Sciences: Solid Surface Planets: Atmospheres (0343, 1060); 6225 Planetary Sciences: Solar System Objects: Mars.

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Citation: Lyons, J. R., C. Manning, and F. Nimmo (2005), Formation of methane on Mars by fluid-rock interaction in the crust, Geophys. Res. Lett., 32, L13201, doi:10.1029/2004GL022161.