TY - JOUR
T1 - Methane from UV-irradiated carbonaceous chondrites under simulated Martian conditions
AU - Schuerger, Andrew C.
AU - Moores, John E.
AU - Clausen, Christian A.
AU - Barlow, Nadine G.
AU - Britt, Daniel T.
PY - 2012
Y1 - 2012
N2 - 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°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 × 10-13 mol J-1 for UV irradiation of Murchison (1.69 wt%) samples tested under Martian conditions (6.9 mbar and 20°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 × 105 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).
AB - 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°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 × 10-13 mol J-1 for UV irradiation of Murchison (1.69 wt%) samples tested under Martian conditions (6.9 mbar and 20°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 × 105 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).
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U2 - 10.1029/2011JE004023
DO - 10.1029/2011JE004023
M3 - Article
AN - SCOPUS:84865530152
SN - 0148-0227
VL - 117
JO - Journal of Geophysical Research: Planets
JF - Journal of Geophysical Research: Planets
IS - 8
M1 - E08007
ER -