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

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Science  08 Jun 2018:
Vol. 360, Issue 6393, pp. 1093-1096
DOI: 10.1126/science.aaq0131
  • Fig. 1 The TLS-SAM methane measurements versus martian solar longitude.

    All plotted values are listed in table S2, have error bars of ± 1 SEM, and are corrected to global mean annual values. MY, Mars year. (A) All measurements up to 27 May 2017, including those from direct ingests (squares) and enrichment ingests (circles with smaller error bars). (B) Background measurements from enrichment ingests show strong seasonal variation. The atmospheric pressure (inverted scale at right) from REMS is plotted for comparison, the solid line representing the mean values over the 3 Mars years.

  • Table 1 Curiosity TLS-SAM methane enrichment measurements at Gale crater (4.5oS, 137.4oE) over a 38-month period.

    SEM, standard error of the mean; EF, enrichment factor; Ls, solar longitude; CI, confidence interval. The global pressure multiplier is derived from in situ REMS pressure measurements; it is the number by which the original measured in situ values of methane (given in table S3) were multiplied to correct the results to the global mean annual mixing ratio given in the right two columns. Earth dates refer to the time when the gas ingest was started. The decimal portion of the sol is used so that sol 573.08 represents local time 01:57.

    Martian sol after landing on 6 August 2012Earth dateLs (degrees)Global pressure multiplierCH4 (ppbv)Error ± 1 SEM (ppbv)
    573.0817 March 2014103.480.9700.4190.089
    684.069 July 2014158.610.8770.6530.121
    965.9925 April 2015331.571.0030.6090.088
    1086.0626 August 201532.811.0500.2410.053
    1169.0219 November 201570.571.0620.2350.076
    1322.0024 April 2016142.460.8810.5020.097
    1451.064 September 2016216.581.0070.5000.078
    1527.0621 November 2016265.781.0760.3570.104
    1579.0013 January 2017298.761.0360.2460.069
    1709.0027 May 201710.841.0200.3190.098
    Mean value ± 1 SEM (68% CI) = 0.408 ± 0.049 ppbv
    Mean value including EF error ± 1 SEM (68% CI) = 0.408 ± 0.082 ppbv
    Mean value ± 2 SEM (95% CI) = 0.41 ± 0.16 ppbv

Supplementary Materials

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

    Christopher R. Webster, Paul R. Mahaffy, Sushil K. Atreya, John E. Moores, Gregory J. Flesch, Charles Malespin, Christopher P. McKay, German Martinez, Christina L. Smith, Javier Martin-Torres, Javier Gomez-Elvira, Maria-Paz Zorzano, Michael H. Wong, Melissa G. Trainer, Andrew Steele, Doug Archer Jr., Brad Sutter, Patrice J. Coll, Caroline Freissinet, Pierre-Yves Meslin, Raina V. Gough, Christopher H. House, Alexander Pavlov, Jennifer L. Eigenbrode, Daniel P. Glavin, John C. Pearson, Didier Keymeulen, Lance E. Christensen, Susanne P. Schwenzer, Rafael Navarro-Gonzalez, Jorge Pla-García, Scot C. R. Rafkin, Álvaro Vicente-Retortillo, Henrik Kahanpää, Daniel Viudez-Moreiras, Michael D. Smith, Ari-Matti Harri, Maria Genzer, Donald M. Hassler, Mark Lemmon, Joy Crisp, Stanley P. Sander, Richard W. Zurek, Ashwin R. Vasavada

    Materials/Methods, Supplementary Text, Tables, Figures, and/or References

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    • Materials and Methods 
    • Supplementary Text
    • Figs. S1 to S44
    • Tables S1 and S2 
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