Background levels of methane in Mars’ atmosphere show strong seasonal variations
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Caroline Freissinet
- Function : Author
- PersonId : 183739
- IdHAL : caroline-freissinet
- ORCID : 0000-0002-6528-330X
- IdRef : 152939725
Pierre-Yves Meslin
- Function : Author
- PersonId : 757063
- ORCID : 0000-0002-0703-3951
- IdRef : 132431114
Rafael Navarro-González
- Function : Author
- PersonId : 766149
- ORCID : 0000-0002-6078-7621
Daniel Viudez-Moreiras
- Function : Author
- PersonId : 792803
- ORCID : 0000-0001-8442-3788
Mark Lemmon
- Function : Author
- PersonId : 760817
- ORCID : 0000-0002-4504-5136
Abstract
Variable levels of methane in the martian atmosphere have eluded explanation partly because the measurements are not repeatable in time or location. We report in situ measurements at Gale crater made over a 5-year period by the Tunable Laser Spectrometer on the Curiosity rover. The background levels of methane have a mean value 0.41 ± 0.16 parts per billion by volume (ppbv) (95% confidence interval) and exhibit a strong, repeatable seasonal variation (0.24 to 0.65 ppbv). This variation is greater than that predicted from either ultraviolet degradation of impact-delivered organics on the surface or from the annual surface pressure cycle. The large seasonal variation in the background and occurrences of higher temporary spikes (~7 ppbv) are consistent with small localized sources of methane released from martian surface or subsurface reservoirs.