Evidence for methane in Martian meteorites

Abstract

The putative occurrence of methane in the Martian atmosphere has had a major influence on the exploration of Mars, especially by the implication of active biology. The occurrence has not been borne out by measurements of atmosphere by the MSL rover Curiosity but, as on Earth, methane on Mars is most likely in the subsurface of the crust. Serpentinization of olivine-bearing rocks, to yield hydrogen that may further react with carbon-bearing species, has been widely invoked as a source of methane on Mars, but this possibility has not hitherto been tested. Here we show that some Martian meteorites, representing basic igneous rocks, liberate a methane-rich volatile component on crushing. The occurrence of methane in Martian rock samples adds strong weight to models whereby any life on Mars is/was likely to be resident in a subsurface habitat, where methane could be a source of energy and carbon for microbial activity.

A cometary origin for martian atmospheric methane

“…Methane that was recently reported in martian meteorites (Blarney et al, 2015) may arise from serpentinisation or condensation from a carbon-bearing gas during crystallisation of its parent magma at low oxygen fugacity (Steele et al, 2012). It is not clear at present whether the meteorite-hosted methane reported in Blarney et al (2015) is related to atmospheric methane.…”

“…Methane that was recently reported in martian meteorites (Blarney et al, 2015) may arise from serpentinisation or condensation from a carbon-bearing gas during crystallisation of its parent magma at low oxygen fugacity (Steele et al, 2012). It is not clear at present whether the meteorite-hosted methane reported in Blarney et al (2015) is related to atmospheric methane. Since neither total methane abundance nor mineralogical context are provided by the method used, it is not currently clear whether the methane is a new discovery or a component of the reduced carbon already known to exist at 20 ± 6 ppm concentration in martian meteorites (Steele et al, 2012).…”

Hydrogen from Radiolysis of Aqueous Fluid Inclusions during Diagenesis

“…The amount of gas was calculated by matrix multiplication to provide quantitative results. Volatiles are reported in mol % and the 3-sigma detection limit for gases is about 0.3 ppm (~1 × 10 −15 mol) [17,18]. Precision and accuracy of seven capillary tubes with encapsulated atmosphere were N2 (1.43, 0.05), O2 (5.13, 0.05) and Ar (6.86, 4.60) relative percent, respectively.…”

“…The sample is placed between two metal disks and the act of incrementally closing the valve sandwiches the disks together and crushes the sample. Blanks are taken into account as described in Blamey et al (2015); as sylvite is very soft, the blank signal is almost indistinguishable from the mass spectrometer noise. Crushes were of equal magnitude, and produced 5 to 12 successive gas bursts before crushing was completed.…”

“…Crushes were of equal magnitude, and produced 5 to 12 successive gas bursts before crushing was completed. Data acquisition was performed with two Pfeiffer Prisma (Berlin, Germany) quadrupole mass spectrometers operating in crush-fast scan (CFS) peak-hopping mode [7,17]. The instrument was calibrated using Scott Gas Mini-mix gas mixtures (with 2% uncertainty), and verified with capillary tubes (with 1% uncertainty) filled with gas mixtures, and three in-house fluid inclusion gas standards.…”