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