Seasonal Variation of Mars Methane Background Indicates that Gale Crater May Be a Containment Region for Local Microseepage

C. R. Webster, P. R. Mahaffy, S. K. Atreya, J. E. Moores, J. Pla-García, S. C. Rafkin

Research output: Contribution to conferenceUnpublished paper

Abstract

In situ measurements of atmospheric methane have been made over a 6-year period at Gale Crater on Mars using the Tunable Laser Spectrometer (TLS) instrument in the Sample Analysis at Mars (SAM) suite on the Curiosity rover. We observe a low mean background level of 0.41 ±0.16 (2sem) ppbv that is a factor of 6 times lower than some model predictions based on methane generation from UV degradation of micro-meteorites or interplanetary dust delivered to the martian surface1. In addition, these very low background levels exhibit a strong seasonal cycle in which the methane abundance varies from 0.24 to 0.65 ppbv, a factor of 3 increase seasonally1 that is much bigger than expected. We show that following supply from subsurface microseepage, a surface adsorption-mediated release2 is a promising mechanism for amplifying the seasonal variation. However, a reduction (dilution) of measured methane when the planetary boundary layer is above the crater rim3 suggests that transport and mixing play a role4 and further indicate that lower methane mixing ratios exist outside the crater. As presented5 at COSPAR 2018, we believe that the methane abundance and its seasonal amplitude size may be diminished outside the region of Gale crater. We will discuss our results in context with any reports that may come out before this AGU meeting from the ESA ExoMars mission's Trace Gas Orbiter.

- "Background levels of methane in the Mars' atmosphere show strong seasonal variations", C. R. Webster et al., Science, 360, 1093-1096 (2018) and references therein.

- "The methane seasonal cycle at Gale Crater, Mars suggests adsorption-mediated microseepage", J.E. Moores et al., submitted to Nature Geosciences, (2018).

- "Planetary boundary layer (PBL) and circulation dynamics at Gale Crater, Mars", R. M. Fonseca, M-P. Zorzano-Mier, J. Martín-Torres, Icarus, 302, 537-559 (2018).

- "Martian winds drive seasonal methane variations observed by MSL-SAM", Jorge Pla-Garcia et al., EGU General Assembly Conference Abstracts. EGU2018-18277.

- "Mars methane: atmospheric chemistry…..or global transport", C.R. Webster et al., COSPAR 2018.

The research described here was carried out in part at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration (NASA).

Original languageEnglish
PagesP31A-04
Publication statusPublished - 1 Dec 2018
EventAmerican Geophysical Union, Fall Meeting 2018: AGU - Walter E Washington Convention Center - 202A, Washington D.C., United States
Duration: 10 Dec 201814 Dec 2018
https://agu.confex.com/agu/fm18/prelim.cgi/Session/51933

Conference

ConferenceAmerican Geophysical Union, Fall Meeting 2018
Abbreviated titleAGU
Country/TerritoryUnited States
CityWashington D.C.
Period10/12/1814/12/18
Internet address

Keywords

  • 3346 Planetary meteorology
  • ATMOSPHERIC PROCESSESDE: 6225 Mars
  • PLANETARY SCIENCES: SOLAR SYSTEM OBJECTSDE: 5405 Atmospheres
  • PLANETARY SCIENCES: SOLID SURFACE PLANETSDE: 5445 Meteorology
  • PLANETARY SCIENCES: SOLID SURFACE PLANETS

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