Examinando por Autor "Mahaffy, Paul R."

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Acceso Abierto
A Review of Sample Analysis at Mars-Evolved Gas Analysis Laboratory Analog Work Supporting the Presence of Perchlorates and Chlorates in Gale Crater, Mars
(Multidisciplinary Digital Publishing Institute (MDPI), 2021-04-20) Clark, J.; Sutter, B.; Douglas Archer, P.; Ming, D.; Rampe, E.; McAdam, A. C.; Navarro González, R.; Eigenbrode, J. L.; Glavin, D.; Zorzano, María Paz; Martín Torres, Javier; Morris, Richard V.; Tu, V.; Ralston, S. J.; Mahaffy, Paul R.; Agencia Estatal de Investigación (AEI)
The Sample Analysis at Mars (SAM) instrument on the Curiosity rover has detected evidence of oxychlorine compounds (i.e., perchlorates and chlorates) in Gale crater, which has implications for past habitability, diagenesis, aqueous processes, interpretation of in situ organic analyses, understanding the martian chlorine cycle, and hazards and resources for future human exploration. Pure oxychlorines and mixtures of oxychlorines with Mars-analog phases have been analyzed for their oxygen (O2) and hydrogen chloride (HCl) releases on SAM laboratory analog instruments in order to constrain which phases are present in Gale crater. These studies demonstrated that oxychlorines evolve O2 releases with peaks between ~200 and 600 °C, although the thermal decomposition temperatures and the amount of evolved O2 decrease when iron phases are present in the sample. Mg and Fe oxychlorines decompose into oxides and release HCl between ~200 and 542 °C. Ca, Na, and K oxychlorines thermally decompose into chlorides and do not evolve HCl by themselves. However, the chlorides (original or from oxychlorine decomposition) can react with water-evolving phases (e.g., phyllosilicates) in the sample and evolve HCl within the temperature range of SAM (<~870 °C). These laboratory analog studies support that the SAM detection of oxychlorine phases is consistent with the presence of Mg, Ca, Na, and K perchlorate and/or chlorate along with possible contributions from adsorbed oxychlorines in Gale crater samples.
Acceso Abierto
Advective Fluxes in the Martian Regolith as a Mechanism Driving Methane and Other Trace Gas Emissions to the Atmosphere
(American Geophysical Union: Advancing Earth and Space Science, 2020-01-15) Viúdez Moreiras, Daniel; Arvidson, R. E.; Gómez Elvira, J.; Webster, C.; Newman, C. E.; Mahaffy, Paul R.; Vasavada, A. R.; 0000-0002-9068-9846; Unidad de Excelencia Científica María de Maeztu Centro de Astrobiología del Instituto Nacional de Técnica Aeroespacial y CSIC, MDM-2017-0737
Advective fluxes influence methane and CO2 soil emissions into the atmosphere on Earth and may drive trace gas emissions in the Mars atmosphere. However, their relevance in the Martian regolith has not been evaluated to date. Our regolith transport simulations show that advective fluxes can be relevant under Martian conditions and may drive the methane abundance detected by Mars Science Laboratory. Trace gas emissions would be highest in regions where winds interact with topography. Emissions in these regions may be further enhanced by time‐varying pressure fields produced by diurnal thermal tides and atmospheric turbulence. Trace gases such as methane should be emitted or produced from the first layers of regolith, or quickly transported to this region from a deeper reservoir through fractured media.