Seasonal Variations in Atmospheric Composition as Measured in Gale Crater, Mars

Melissa G. Trainer*, Michael H. Wong, Timothy H. McConnochie, Heather B. Franz, Sushil K. Atreya, Pamela G. Conrad, Franck Lefèvre, Paul R. Mahaffy, Charles A. Malespin, Heidi L. K. Manning, Javier Martín-Torres, Germán. M. Martínez, Christopher P. McKay, Rafael Navarro-González, Álvaro Vicente-Retortillo, Christopher R. Webster, María-Paz Zorzano

*Corresponding author for this work

Research output: Contribution to journalArticle

2 Citations (Scopus)

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.
Original languageEnglish
Pages (from-to)3000-3024
Number of pages25
JournalJournal of Geophysical Research - Planets
Volume124
Issue number11
Early online date21 Nov 2019
DOIs
Publication statusPublished - Nov 2019

Keywords

  • atmospheric composition
  • Mars atmosphere
  • Mars seasonal cycle
  • Mars Science Laboratory
  • MSL/SAM
  • sample analysis mars

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    Trainer, M. G., Wong, M. H., McConnochie, T. H., Franz, H. B., Atreya, S. K., Conrad, P. G., Lefèvre, F., Mahaffy, P. R., Malespin, C. A., Manning, H. L. K., Martín-Torres, J., Martínez, G. M., McKay, C. P., Navarro-González, R., Vicente-Retortillo, Á., Webster, C. R., & Zorzano, M-P. (2019). Seasonal Variations in Atmospheric Composition as Measured in Gale Crater, Mars. Journal of Geophysical Research - Planets, 124(11), 3000-3024. https://doi.org/10.1029/2019JE006175