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Träfflista för sökning "WFRF:(McConnochie Timothy H.) ;pers:(Mahaffy Paul R.)"

Sökning: WFRF:(McConnochie Timothy H.) > Mahaffy Paul R.

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1.
  • G. Trainer, Melissa, et al. (författare)
  • Seasonal Variations in Atmospheric Composition as Measured in Gale Crater, Mars
  • 2019
  • Ingår i: Journal of Geophysical Research - Planets. - : John Wiley & Sons. - 2169-9097 .- 2169-9100. ; 124:11, s. 3000-3024
  • Tidskriftsartikel (refereegranskat)abstract
    • The Sample Analysis at Mars (SAM) instrument onboard the Mars Science Laboratory Curiosity rover measures the chemical composition of major atmospheric species (CO2, N2, 40Ar, O2, and CO) through a dedicated atmospheric inlet. We report here measurements of volume mixing ratios in Gale Crater using the SAM quadrupole mass spectrometer, obtained over a period of nearly 5 years (3 Mars years) from landing. The observation period spans the northern summer of MY 31 and solar longitude (LS) of 175° through spring of MY 34, LS = 12°. This work expands upon prior reports of the mixing ratios measured by SAM QMS in the first 105 sols of the mission. The SAM QMS atmospheric measurements were taken periodically, with a cumulative coverage of four or five experiments per season on Mars. Major observations include the seasonal cycle of CO2, N2, and Ar, which lags approximately 20–40° of LS behind the pressure cycle driven by CO2 condensation and sublimation from the winter poles. This seasonal cycle indicates that transport occurs on faster timescales than mixing. The mixing ratio of O2 shows significant seasonal and interannual variability, suggesting an unknown atmospheric or surface process at work. The O2 measurements are compared to several parameters, including dust optical depth and trace CH4 measurements by Curiosity. We derive annual mean volume mixing ratios for the atmosphere in Gale Crater: CO2 = 0.951 (±0.003), N2 = 0.0259 (±0.0006), 40Ar = 0.0194 (±0.0004), O2 = 1.61 (±0.09) x 10‐3, and CO = 5.8 (±0.8) x 10‐4.
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2.
  • Webster, Christopher R., et al. (författare)
  • Mars methane detection and variability at Gale crater
  • 2015
  • Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 347:6220, s. 415-417
  • Tidskriftsartikel (refereegranskat)abstract
    • Reports of plumes or patches of methane in the Martian atmosphere that vary over monthly timescales have defied explanation to date. From in situ measurements made over a 20-month period by the Tunable Laser Spectrometer (TLS) of the Sample Analysis at Mars (SAM) instrument suite on Curiosity at Gale Crater, we report detection of background levels of atmospheric methane of mean value 0.69 ± 0.25 ppbv at the 95% confidence interval (CI). This abundance is lower than model estimates of ultraviolet (UV) degradation of accreted interplanetary dust particles (IDP’s) or carbonaceous chondrite material. Additionally, in four sequential measurements spanning a 60-sol period, we observed elevated levels of methane of 7.2 ± 2.1 (95% CI) ppbv implying that Mars is episodically producing methane from an additional unknown source.
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