Background levels of methane in Mars’ atmosphere show strong seasonal variations

Christopher R. Webster 1 Paul R. Mahaffy 2 Sushil K. Atreya 3 John E. Moores 4 Gregory Flesch 1 Charles Malespin 2 Christopher P. Mckay 5 German Martinez 3 Christina L. Smith 4 Javier Martin-Torres 6, 7 Javier Gomez-Elvira 8 Maria-Paz Zorzano 8, 6 Michael H. Wong 3 Melissa Grady Trainer 2 Andrew Steele 9 P. Douglas Archer Jr. 10 Brad Sutter 10 Patrice J. Coll 11 Caroline Freissinet 12 Pierre-Yves Meslin 13 Raina V. Gough 14, 15 Christopher H House 16 Alexander Pavlov 2 Jennifer L. Eigenbrode 2 Daniel P. Glavin 2 John Pearson 1 Didier Keymeulen 1 Lance Christensen 1 Susanne P. Schwenzer 17, 18 Rafael Navarro-González 19 Jorge Pla-Garcia 8, 20 Scot C. R. Rafkin 21 Álvaro Vicente-Retortillo 3 Henrik Kahanpää 22 Daniel Viudez-Moreiras 8 Michael D. Smith 2 Ari Matti Harri 22 Maria Genzer 22 Donald M. Hassler 21 Mark Lemmon 23 Joy A. Crisp 1 Stanley P. Sander 1 Richard W. Zurek 1 Ashwin Vasavada 1
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.
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Submitted on : Thursday, October 4, 2018 - 10:01:35 AM
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Christopher R. Webster, Paul R. Mahaffy, Sushil K. Atreya, John E. Moores, Gregory Flesch, et al.. Background levels of methane in Mars’ atmosphere show strong seasonal variations. Science, American Association for the Advancement of Science, 2018, 360 (6393), pp.1093-1096. ⟨10.1126/science.aaq0131⟩. ⟨insu-01887409⟩

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