Igneous compositions preserved in Gale crater's geological record

Gale crater’s geological record has two stratigraphic groups deposited in an early Hesperian fluviolacustrine system[1, 2]. The Bradbury Group (sols 1-750) is dominated by fluvial conglomerate and sandstone with lacustrine mudstone in Yellowknife Bay[1,2]. The Mt Sharp Group (Murray formation) is mainly well laminated lacustrine mudstone[2]. We have analysed NASA Curiosity rover ChemCam[3] observation point compositions for targets up to sol 1482 that have hit in situ host rock lacking obvious diagenetic features. ChemCam data are plotted on scatter and density contour plots for their associated stratigraphic units to replicate whole rock composition[4]. Our results show that coarse grained (>1 mm) targets are dominated by trachybasalt[5] and subalkaline basalt[5] igneous endmembers. Sandstone (0.062 – 1 mm) targets indicate a mixture of subalkaline basalt[5], trachybasalt[5] and potassic igneous[6] sources. Finally, mudstone units are dominated by the subalkaline basalt[5] at Yellowknife Bay, and a relatively silica-rich, subalkaline basalt endmember in most of the Murray formation[4], with an even more silica-rich volcanic component at Marias Pass[7]. This demonstrates that Gale crater sediments record a variety of igneous compositions, with subalkaline basalts dominant, but also including lesser amounts of alkaline and silica oversaturated igneous components. References: [1] Grotzinger et al. (2014) doi:10.1126/science.1242777, [2] Grotzinger et al. (2015) doi:10.1126/science.aac7575. [3] Wiens et al. (2012) doi:10.1007/s11214-012-9902-4. [4] Bedford et al. (subm.) GCA. [5] Edwards et al., (2017) MAPS, doi:10.1111/maps.12953. [6] Treiman et al. (2016) doi: 10.1002/2015JE004932. [7] Morris et al. (2016) doi: 10.1073/pnas.1607098113

Comparison of Manganese Abundance in Gale and Jezero Craters

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Comparison of Manganese Abundance in Gale and Jezero Craters

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CLIMATE CHANGE AND TOPOGRAPHY FOCUSED AEOLIAN EROSION IN GALE CRATER, MARS -TEN-YEARS OF MSL OBSERVATIONS

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CLIMATE CHANGE AND TOPOGRAPHY FOCUSED AEOLIAN EROSION IN GALE CRATER, MARS -TEN-YEARS OF MSL OBSERVATIONS

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Constraining Alteration Processes Along the Siccar Point Group Unconformity, Gale Crater, Mars: Results from the Sample Analysis at Mars Instrument

International audienceResults from the Sample Analysis at Mars (SAM)-evolved gas analyzer (EGA) on board the Mars Science Laboratory Curiosity rover constrained the alteration history and habitability potential of rocks sampled across the Siccar Point unconformity in Gale crater.The Glasgow member (Gm) mudstone just below the unconformity had evidence of acid sulfate or Si-poor brine alteration of Fe-smectite to Fe amorphous phases, leaching loss of Fe-Mg-sulfate and exchange of unfractionated sulfur 34S (δ34S=2±7‰) with enriched 34S (20±5‰, V-CDT). Carbon abundances did not significantly change (322-661 μgC/g) consistent with carbon stabilization by amorphous Al- and Fe-hydroxide phases. The Gm mudstone had no detectable oxychlorine and extremely low nitrate. Nitrate (0.06 wt.% NO3), oxychlorine (0.13 wt% ClO4), high C (1472 μg C/g), and low Fe/Mg-sulfate concentration (0.24 wt.% SO3) depleted in 34S (δ34S = -27‰ ± 7), were detected in the Stimson formation (Sf) eolian sandstone above the unconformity. Redox disequilibrium through the detections of iron sulfide and sulfate supported limited aqueous processes in the Sf sandstone. Si-poor brines or acidic fluids altered the Gm mudstone just below the unconformity but did not alter underlying Gm mudstones further from the contact. Chemical differences between the Sf and Gm rocks suggested that fluid interaction was minimal between the Sf and Gm rocks. These results suggested that the Gm rocks were altered by subsurface fluids after the Sf placement. Aqueous processes along the unconformity could have provided habitable conditions and in some cases, C and N levels could have supported heterotrophic microbial populations

Carbonate Detection with SuperCam in Igneous Rocks on the floor of Jezero Crater, Mars

Perseverance explored two geological units on the floor of Jezero Crater over the first 420 Martian days of the Mars2020 mission. These units, the Máaz and Séítah formations, are interpreted to be igneous in origin, with traces of alteration. We report the detection of carbonate phases along the rover traverse based on laser-induced breakdown spectroscopy (LIBS), infrared reflectance spectroscopy (IRS), and time-resolved Raman (TRR) spectroscopy by the SuperCam instrument. Carbonates are identified through direct detection of vibrational modes of CO3 functional groups (IRS and TRR), major oxides content, and ratios of C and O signal intensities (LIBS). In Séítah, the carbonates are consistent with magnesite-siderite solid solutions (Mg# of 0.42-0.70) with low calcium contents (<5 wt.% CaO). They are detected together with olivine in IRS and TRR spectra. LIBS and IRS also indicate a spatial association of the carbonates with clays. Carbonates in Máaz are detected in fewer points, as: (i) siderite (Mg# as low as 0.03); (ii) carbonate-containing coatings, enriched in Mg (Mg# ∼0.82) and spatially associated with different salts. Overall, using conservative criteria, carbonate detections are rare in LIBS (∼30/2000 points), IRS (∼15/2000 points), and TRR (1 /150 points) data. This is best explained by (i) a low carbonate content overall, (ii) small carbonate grains mixed with other phases, (iii) intrinsic complexity of in situ measurements. This is consistent with orbital observations of Jezero crater, and similar to compositions of carbonates previously reported in Martian meteorites. This suggests a limited carbonation of Jezero rocks by locally equilibrated fluids