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Science. 2018 Jun 8;360(6393):1093-1096. doi: 10.1126/science.aaq0131.

Background levels of methane in Mars' atmosphere show strong seasonal variations.

Author information

1
NASA Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA. chris.r.webster@jpl.nasa.gov.
2
NASA Goddard Space Flight Center, Greenbelt, MD, USA.
3
Department of Climate and Space Sciences and Engineering, University of Michigan, Ann Arbor, MI, USA.
4
Department of Earth and Space Science and Engineering, York University, Toronto, ON, Canada.
5
NASA Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA.
6
NASA Ames Research Center, Moffett Field, CA, USA.
7
Department of Computer Science, Electrical and Space Engineering, Luleå University of Technology, Luleå, Sweden.
8
Instituto Andaluz de Ciencias de la Tierra, Granada, Spain.
9
Centro de Astrobiología, Instituto National de Tecnica Aerospacial, Madrid, Spain.
10
Geophysical Laboratory, Carnegie Institution for Science, Washington, DC, USA.
11
Jacobs Technology, NASA Johnson Space Center, Houston, TX, USA.
12
Laboratoire Interuniversitaire des Systèmes Atmosphériques, Creteil Cedex, France.
13
Laboratoire Atmosphères, Milieux, Observations Spatiales, Paris Cedex 05, France.
14
Institut de Recherche en Astrophysique et Planétologie, Toulouse, France.
15
Department of Chemistry and Biochemistry and Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, CO, USA.
16
Department of Geosciences, Pennsylvania State University, University Park, PA, USA.
17
School of Environment, Earth and Ecosystem Sciences, Open University, Milton Keynes, UK.
18
Instituto de Ciencias Nucleares, Universidad Nacional Autonoma de Mexico, Ciudad Universitaria, Mexico City, Mexico.
19
Space Science Institute, Boulder, CO, USA.
20
Department of Space Studies, Southwest Research Institute Boulder, Boulder, CO, USA.
21
Finnish Meteorological Institute, Helsinki, Finland.
22
Department of Atmospheric Sciences, Texas A&M University, College Station, TX, USA.

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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PMID:
29880682
DOI:
10.1126/science.aaq0131

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