Title

Methane from UV-irradiated carbonaceous chondrites under simulated Martian conditions

Authors

Authors

A. C. Schuerger; J. E. Moores; C. A. Clausen; N. G. Barlow;D. T. Britt

Comments

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Abbreviated Journal Title

J. Geophys. Res.-Planets

Keywords

INTERPLANETARY DUST PARTICLES; MARS PATHFINDER; ORGANIC-COMPOUNDS; AMINO-ACIDS; BIOLOGICAL IMPLICATIONS; SPACECRAFT SURFACES; LANDING; SITES; ATMOSPHERE; LIFE; SOIL; Geochemistry & Geophysics

Abstract

A UV photolytic process was studied for the production of methane from carbonaceous chondrites under simulated Martian conditions. Methane evolution rates from carbonaceous chondrites were found to be positively correlated to temperature (-80 to 20 degrees C) and the concentration of carbon in the chondrites (0.2 to 1.69 wt%); and decreased over time with Murchison samples exposed to Martian conditions. The amount of evolved methane (EM) per unit of UV energy was 7.9 x 10(-13) mol J(-1) for UV irradiation of Murchison (1.69 wt%) samples tested under Martian conditions (6.9 mbar and 20 degrees C). Using a previously described Mars UV model (Moores et al., 2007), and the EM given above, an annual interplanetary dust particle (IDP) accreted mass of 2.4 x 10(5) kg carbon per year yields methane abundances between 2.2 to 11 ppbv for model scenarios in which 20 to 100% of the accreted carbon is converted to methane, respectively. The UV/CH4 model for accreted IDPs can explain a portion of the globally averaged methane abundance on Mars, but cannot easily explain seasonal, temporal, diurnal, or plume fluctuations of methane. Several impact processes were modeled to determine if periodic emplacement of organics from carbonaceous bolides could be invoked to explain the occurrence of methane plumes produced by the UV/CH4 process. Modeling of surface impacts of high-density bolides, single airbursts of low-density bolides, and multiple airbursts of a cascading breakup of a low-density rubble-pile comet were all unable to reproduce a methane plume of 45 ppbv, as reported by Mumma et al. (2009).

Journal Title

Journal of Geophysical Research-Planets

Volume

117

Publication Date

1-1-2012

Document Type

Article

Language

English

First Page

19

WOS Identifier

WOS:000307733600001

ISSN

2169-9097

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