Examinando por Autor "McAdam, A. C."

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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
Detection of Reduced Sulfur on Vera Rubin Ridge by Quadratic Discriminant Analysis of Volatiles Observed During Evolved Gas Analysis.
(American Geophysical Union: Advancing Earth and Space Science, 2020-06-10) Wong, K. H.; Lewis, J.; Knudson, C. A.; Millan, M.; McAdam, A. C.; Eigenbrode, J. L.; Andrejkovičová, S.; Gómez, F.; Navarro González, R.; House, C. H.; Universidad Nacional Autónoma de México (UNAM); Navarro González, R. [0000-0002-6078-7621]; Knudson, C. A. [0000-0003-3875-2200]; Andrejkovicova, S. [0000-0001-8429-6926]; Gómez, F. [0000-0001-9977-7060]; McAdam, A. [0000-0001-9120-2991]; House, C. [0000-0002-4926-4985]; Unidad de Excelencia Científica María de Maeztu Centro de Astrobiología del Instituto Nacional de Técnica Aeroespacial y CSIC, MDM-2017-0737
The Mars Science Laboratory mission investigated Vera Rubin ridge, which bears spectral indications of elevated amounts of hematite and has been hypothesized as having a complex diagenetic history. Martian samples, including three drilled samples from the ridge, were analyzed by the Sample Analysis at Mars instrument suite via evolved gas analysis‐mass spectrometry (EGA‐MS). Here, we report new EGA‐MS data from Martian samples and describe laboratory analogue experiments. Analyses of laboratory analogues help determine the presence of reduced sulfur in Martian solid samples, which could have supported potential microbial life. We used evolved carbonyl sulfide (COS) and carbon disulfide (CS2) to identify Martian samples likely to contain reduced sulfur by applying a quadratic discriminant analysis. While we report results for 24 Martian samples, we focus on Vera Rubin ridge samples and select others for comparison. Our results suggest the presence of reduced sulfur in the Jura member of Vera Rubin ridge, which can support various diagenetic history models, including, as discussed in this work, diagenetic alteration initiated by a mildly reducing, sulfite‐containing groundwater.