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)

1 JPL - Jet Propulsion Laboratory
2 GSFC - NASA Goddard Space Flight Center
3 CLaSP - Department of Climate and Space Sciences and Engineering
4 ESSE - Department of Earth and Space Science and Engineering [York University - Toronto]
5 ARC - NASA Ames Research Center
6 Department of Computer Science, Electrical and Space Engineering [Luleå]
7 IACT - Instituto Andaluz de Ciencias de la Tierra
8 CAB - Centro de Astrobiologia [Madrid]
9 Geophysical Laboratory [Carnegie Institution]
10 Jacobs Technology ESCG
11 LISA (UMR_7583) - Laboratoire Interuniversitaire des Systèmes Atmosphériques
12 PLANETO - LATMOS
13 IRAP - Institut de recherche en astrophysique et planétologie
14 Department of Chemistry and Biochemistry [Boulder]
15 CIRES - Cooperative Institute for Research in Environmental Sciences
16 Department of Geosciences [PennState]
17 OU - The Open University [Milton Keynes]
18 School of Environment, Earth and Ecosystem Sciences [Milton Keynes]
19 Instituto de Ciencias Nucleares [Mexico]
20 SSI - Space Science Institute [Boulder]
21 Department of Space Studies [Boulder]
22 FMI - Finnish Meteorological Institute
23 Department of Atmospheric Sciences [College Station]

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.

Domains: Environmental Sciences; Environmental and Society

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, 2018, 360 (6393), pp.1093-1096. ⟨10.1126/science.aaq0131⟩. ⟨insu-01887409⟩