Evolved gas analyses of sedimentary rocks and eolian sediment in Gale Crater, Mars: Results of the Curiosity rover's sample analysis at Mars instrument from Yellowknife Bay to the Namib Dune

Abstract

The sample analysis at Mars instrument evolved gas analyzer (SAM-EGA) has detected evolved water, H 2 , SO 2 , H 2 S, NO, CO 2 , CO, O 2 , and HCl from two eolian sediments and nine sedimentary rocks from Gale Crater, Mars. These evolved gas detections indicate nitrates, organics, oxychlorine phase, and sulfates are widespread with phyllosilicates and carbonates occurring in select Gale Crater materials. Coevolved CO 2 (160 ± 248-2373 ± 820 μgC (CO2) /g) and CO (11 ± 3-320 ± 130 μgC (CO) /g) suggest that organic C is present in Gale Crater materials. Five samples evolved CO 2 at temperatures consistent with carbonate (0.32 ± 0.05-0.70 ± 0.1 wt % CO 3 ). Evolved NO amounts to 0.002 ± 0.007-0.06 ± 0.03 wt % NO 3 . Evolution of O 2 suggests that oxychlorine phases (chlorate/perchlorate) (0.05 ± 0.025-1.05 ± 0.44 wt % ClO 4 ) are present, while SO 2 evolution indicates the presence of crystalline and/or poorly crystalline Fe and Mg sulfate and possibly sulfide. Evolved H 2 O (0.9 ± 0.3-2.5 ± 1.6 wt % H 2 O) is consistent with the presence of adsorbed water, hydrated salts, interlayer/structural water from phyllosilicates, and possible inclusion water in mineral/amorphous phases. Evolved H 2 and H 2 S suggest that reduced phases occur despite the presence of oxidized phases (nitrate, oxychlorine, sulfate, and carbonate). SAM results coupled with CheMin mineralogical and Alpha-Particle X-ray Spectrometer elemental analyses indicate that Gale Crater sedimentary rocks have experienced a complex authigenetic/diagenetic history involving fluids with varying pH, redox, and salt composition. The inferred geochemical conditions were favorable for microbial habitability and if life ever existed, there was likely sufficient organic C to support a small microbial population.

Abiotic Input of Fixed Nitrogen by Bolide Impacts to Gale Crater During the Hesperian: Insights From the Mars Science Laboratory

“…Their concentrations were higher than for fixed nitrogen species with a (nitrate or nitrite)/oxychlorine mixing ratio from 0.06 to 0.49 (J. C. Stern et al, ). The oxygen evolution temperatures are lower than what is typical of perchlorates (Sutter et al, ) and appear to be more consistent with Mg (ClO 3 ) 2 and Ca (ClO 3 ) 2 (Sutter et al, ) or ClO 3 − /iron phases (Hogancamp et al, ). Consequently, NO evolved below 350 °C in the Martian samples could be assigned to NO 2 − and iron‐NO 3 − , and above 350 °C to NO 3 − .…”

“…Surprisingly the samples from lowest layers (JK and CB) showed major releases of NO below 350 °C, and at higher layers, the release of NO gradually shifted to higher temperatures. Most of these samples released oxygen during SAM analyses that suggest the presence of oxychlorine species (Sutter et al, ). Their concentrations were higher than for fixed nitrogen species with a (nitrate or nitrite)/oxychlorine mixing ratio from 0.06 to 0.49 (J. C. Stern et al, ).…”

“…This sample showed lower levels of fixed nitrogen (16 ± 7 μg N/cm 3 ), possibly because it was leached due to postdepositional aqueous alteration as evidenced by the presence of calcium sulfate veins. The levels of fixed nitrogen declined to ~10 ± 3 μg N/cm 3 for the Widjana sample extracted from a sandstone outcrop of likely eolian origin that occurs about 40 m above the Sheepbed mudstone samples (Sutter et al, ). The second less intense peak corresponds to the sample obtained from the Buckskin outcrop, with a value of 35 ± 8 μg N/cm 3 .…”

“…The N fixation was probably triggered by volcanic lightning, ultraviolet light, and bolide impacts on early Mars (Manning et al, ; Segura & Navarro‐González, ), but the role of H 2 has not yet been explored. So far the Sample Analysis at Mars (SAM) instrument suite of the NASA Mars Science Laboratory (MSL) has discovered the presence of NO 3 − in Hesperian sediments along a stratigraphic transect investigated by the Curiosity rover at Gale crater (Ming et al, ; Navarro‐González et al, ; J. C. Stern et al, , , ; Sutter et al, ); the origin of NO 3 − is thought to be from the shocks of bolide impacts (J. C. Stern et al, ).…”

Perchlorate‐Driven Combustion of Organic Matter During Pyrolysis‐Gas Chromatography‐Mass Spectrometry: Implications for Organic Matter Detection on Earth and Mars

“…However, it is also possible, based on the findings of the current study, that the organic matter contents of the two units are similar and that it is the decreased level of perchlorate in the lower Murray mudstone that has facilitated the detection of more complex, nonchlorinated, organic molecules. The lower Murray mudstone samples, which yielded the complex organic matter detection (Eigenbrode et al, ), have around 10 times less perchlorate than the Sheepbed mudstone samples which only yielded simple organochlorines (Freissinet et al, ; Sutter et al, ).…”