Chlorate/Fe‐Bearing Phase Mixtures as a Possible Source of Oxygen and Chlorine Detected by the Sample Analysis at Mars (SAM) Instrument in Gale Crater, Mars

1J. V. Hogancamp, 2B. Sutter, 3R. V. Morris, 2P. D. Archer, 31D. W. Ming, 3E. B. Rampe, 4P. Mahaffy, 5R. Navarro‐Gonzalez
Journal of Geophysical Research, Planets (in Press) Link to Article [https://doi.org/10.1029/2018JE005691]
1Geocontrols Systems–Jacobs JETS Contract, NASA Johnson Space Center, Houston, TX, USA
2Jacobs, NASA Johnson Space Center, Houston, TX, USA
3NASA Johnson Space Center, Houston, TX, USA
4NASA Goddard Space Flight Center, Greenbelt, MD, USA
5Universidad Nacional Autonoma de Mexico, Mexico
Published by arrangement with John Wiley & Sons

Oxygen and HCl gas releases detected by the Sample Analysis at Mars (SAM) instrument on board the Mars Science Laboratory Curiosity rover in several Gale Crater samples have been attributed to the thermal decomposition of perchlorates and/or chlorates. Previous experimental studies of perchlorates mixed with Fe‐bearing phases explained some but not all of the evolved oxygen releases, and cannot explain the HCl releases. The objective of this paper was to evaluate the oxygen and HCl releases of chlorates and chlorate/Fe‐phase mixtures in experimental studies and SAM evolved gas analysis (EGA) datasets. Potassium, magnesium, and sodium chlorate were independently mixed with hematite, magnetite, ferrihydrite, and palagonite and analyzed in a thermal evolved gas analyzer configured to operate similarly to the SAM instrument. Fe‐phases depressed the chlorate decomposition temperature 3‐214 °C and consumed up to 75% of the evolved oxygen from chlorate decomposition. Chlorate/Fe‐phase mixtures have oxygen and HCl releases consistent with some samples analyzed by SAM. Reported oxychlorine abundances based on calculations using oxygen detected by SAM could be minimum values because Fe‐phases consume evolved oxygen. The results of this work demonstrate that chlorates could be present in the Martian soil and that oxygen and HCl release temperatures could be used to constrain which chlorate cation species are present in samples analyzed by SAM. Knowledge of which chlorates may be present in Gale Crater creates a better understanding of the detectability of organics by evolved gas analysis, habitability potential, and the chlorine cycle on Mars.

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