In situ detection of boron by ChemCam on Mars

We report the first in situ detection of boron on Mars. Boron has been detected in Gale crater at levels Curiosity rover ChemCam instrument in calcium-sulfate-filled fractures, which formed in a late-stage groundwater circulating mainly in phyllosilicate-rich bedrock interpreted as lacustrine in origin. We consider two main groundwater-driven hypotheses to explain the presence of boron in the veins: leaching of borates out of bedrock or the redistribution of borate by dissolution of borate-bearing evaporite deposits. Our results suggest that an evaporation mechanism is most likely, implying that Gale groundwaters were mildly alkaline. On Earth, boron may be a necessary component for the origin of life; on Mars, its presence suggests that subsurface groundwater conditions could have supported prebiotic chemical reactions if organics were also present and provides additional support for the past habitability of Gale crater

An insight into ancient aeolian processes and post‐Noachian aqueous alteration in Gale crater, Mars, using ChemCam geochemical data from the Greenheugh capping unit

Aeolian processes have shaped and contributed to the geological record in Gale crater, Mars, long after the fluviolacustrine system existed ∼3 Ga ago. Understanding these aeolian deposits, particularly those which have been lithified and show evidence for aqueous alteration, can help to constrain the environment at their time of deposition and the role of liquid water later in Mars’ history. The NASA Curiosity rover investigated a prominent outcrop of aeolian sandstone within the Stimson formation at the Greenheugh pediment as part of its investigation of the Glen Torridon area. In this study, we use geochemical data from ChemCam to constrain the effects of aeolian sedimentary processes, sediment provenance, and diagenesis of the sandstone at the Greenheugh pediment, comparing the Greenheugh data to the results from previous Stimson localities situated 2.5 km north and >200 m lower in elevation. Our results, supported by mineralogical data from CheMin, show that the Stimson formation at the Greenheugh pediment was likely sourced from an olivine-rich unit that may be present farther up the slopes of Gale crater’s central mound. Our results also suggest that the Greenheugh pediment Stimson formation was cemented by surface water runoff such as that which may have formed Gediz Vallis. The lack of alteration features in the Stimson formation at the Greenheugh pediment relative to those of the Emerson and Naukluft plateaus suggests that groundwater was not as available at this locality compared to the others. However, all sites share diagenesis at the unconformity

Overview of the Morphology and Chemistry of Diagenetic Features in the Clay‐Rich Glen Torridon Unit of Gale Crater, Mars

The clay-rich Glen Torridon region of Gale crater, Mars, was explored between sols 2300 and 3007. Here, we analyzed the diagenetic features observed by Curiosity, including veins, cements, nodules, and nodular bedrock, using the ChemCam, Mastcam, and Mars Hand Lens Imager instruments. We discovered many diagenetic features in Glen Torridon, including dark-toned iron- and manganese-rich veins, magnesium- and fluorine-rich linear features, Ca-sulfate cemented bedrock, manganese-rich nodules, and iron-rich strata. We have characterized the chemistry and morphology of these features, which are most widespread in the higher stratigraphic members in Glen Torridon, and exhibit a wide range of chemistries. These discoveries are strong evidence for multiple generations of fluids from multiple chemical endmembers that likely underwent redox reactions to form some of these features. In a few cases, we may be able to use mineralogy and chemistry to constrain formation conditions of the diagenetic features. For example, the dark-toned veins likely formed in warmer, highly alkaline, and highly reducing conditions, while manganese-rich nodules likely formed in oxidizing and circumneutral conditions. We also hypothesize that an initial enrichment of soluble elements, including fluorine, occurred during hydrothermal alteration early in Gale crater history to account for elemental enrichment in nodules and veins. The presence of redox-active elements, including Fe and Mn, and elements required for life, including P and S, in these fluids is strong evidence for habitability of Gale crater groundwater. Hydrothermal alteration also has interesting implications for prebiotic chemistry during the earliest stages of the crater’s evolution and early Mars

Manganese-Iron Phosphate Nodules at the Groken Site, Gale Crater, Mars

The MSL Curiosity rover investigated dark, Mn-P-enriched nodules in shallow lacustrine/fluvial sediments at the Groken site in Glen Torridon, Gale Crater, Mars. Applying all relevant information from the rover, the nodules are interpreted as pseudomorphs after original crystals of vivianite, (Fe2+,Mn2+)3(PO4)2·8H2O, that cemented the sediment soon after deposition. The nodules appear to have flat faces and linear boundaries and stand above the surrounding siltstone. ChemCam LIBS (laser-induced breakdown spectrometry) shows that the nodules have MnO abundances approximately twenty times those of the surrounding siltstone matrix, contain little CaO, and have SiO2 and Al2O3 abundances similar to those of the siltstone. A deconvolution of APXS analyses of nodule-bearing targets, interpreted here as representing the nodules’ non-silicate components, shows high concentrations of MnO, P2O5, and FeO and a molar ratio P/Mn = 2. Visible to near-infrared reflectance of the nodules (by ChemCam passive and Mastcam multispectral) is dark and relatively flat, consistent with a mixture of host siltstone, hematite, and a dark spectrally bland material (like pyrolusite, MnO2). A drill sample at the site is shown to contain minimal nodule material, implying that analyses by the CheMin and SAM instruments do not constrain the nodules’ mineralogy or composition. The fact that the nodules contain P and Mn in a small molar integer ratio, P/Mn = 2, suggests that the nodules contained a stoichiometric Mn-phosphate mineral, in which Fe did (i.e., could) not substitute for Mn. The most likely such minerals are laueite and strunzite, (Fe2+,Mn2+)3(PO4)2·8H2O and –6H2O, respectively, which occur on Earth as alteration products of other Mn-bearing phosphates including vivianite. Vivianite is a common primary and diagenetic precipitate from low-oxygen, P-enriched waters. Calculated phase equilibria show Mn-bearing vivianite could be replaced by laueite or strunzite and then by hematite plus pyrolusite as the system became more oxidizing and acidic. These data suggest that the nodules originated as vivianite, forming as euhedral crystals in the sediment, enclosing sediment grains as they grew. After formation, the nodules were oxidized—first to laueite/strunzite yielding the diagnostic P/Mn ratio, and then to hematite plus an undefined Mn oxy-hydroxide (like pyrolusite). The limited occurrence of these Mn-Fe-P nodules, both in space and time (i.e., stratigraphic position), suggests a local control on their origin. By terrestrial analogies, it is possible that the nodules precipitated near a spring or seep of Mn-rich water, generated during alteration of olivine in the underlying sediments

Detection of Copper by the ChemCam Instrument Along Curiosity's Traverse in Gale Crater, Mars: Elevated Abundances in Glen Torridon

Laser‐induced breakdown spectroscopy, as utilized by the ChemCam instrument onboard the Curiosity rover, detected enhanced abundances of the element copper. Since landing in Gale crater (6 August 2012), 10 enhancements in copper abundance were observed during 3007 Martian days (sols) of rover operations and 24 km of driving (as of 20 January 2021). The most prominent ones were found in the Kimberley area on the crater floor (Aeolis Palus) and in Glen Torridon (GT) on the lower flanks of Aeolis Mons (Mt. Sharp). Enhancements in copper record the former existence of modestly acidic and oxidizing fluids, which were more oxidizing in Kimberley than in GT. Of the two main types of bedrock in the lowest part of GT, Mg‐rich “coherent” and K‐rich “rubbly” (named based on their outcrop expression), copper was detected only in coherent, not in rubbly bedrock. The difference between these two types of bedrock may be due to difference in provenance. Alternatively, based on a recently developed lacustrine‐groundwater mixing model, we suggest that rubbly bedrock was altered by modestly acidic, shallow‐subsurface lake water that leached out both copper and manganese, while coherent bedrock was affected by dominantly alkaline fluids which would be consistent with its mineralogical composition (including siderite) as returned by the CheMin instrument onboard the rover. Higher up in GT, ChemCam data indicated significant gradients in the copper concentration in coherent bedrock on a local scale of only a few meters, which suggests a different alteration style and possibly different types of diagenetic fluids.Plain Language Summary: Gale crater, Mars, about 152‐km in diameter and 3.6 Ga in age, has a central mound that is partly of sedimentary origin. To date (July 2022), the NASA rover Curiosity has been exploring the crater floor and the lower‐most 600 m (in elevation) of sediments of that mound. ChemCam, an instrument mounted on top of the remote‐sensing mast utilizing Laser‐Induced Breakdown Spectroscopy, has been measuring chemical composition and specifically copper abundances along the rover traverse. We identified 10 areas of copper enhancement along Curiosity's traverse. In the Kimberley formation on the crater floor, copper was identified in a manganese‐rich sandstone. Later on, some 350 m above Kimberley, high copper abundances were detected in magnesium‐rich mudstone and in iron‐rich sandstone in the Jura and Knockfarril Hill member, respectively. Following earlier work about copper in Gale crater (Payré et al., 2019, https://doi.org/10.1016/j.icarus.2018.12.015), we postulate a copper‐rich source region north of Gale crater and suggest that copper‐rich detrital material delivered to these areas in Gale crater. Taking into account the chemical and mineralogical composition of these types of bedrock, we conclude that copper was mobilized by later acidic and oxidizing fluids.Key Points: High copper abundances (200–400 ppm) are found in specific areas along the rover traverse. In the Jura member in Glen Torridon (GT), copper is detected only in coherent bedrock, not in rubbly bedrock. In the Knockfarril Hill member in GT, there is evidence for the redistribution of copper and iron by acidic, oxidizing fluids.DFGNASA Mars Exploration ProgramCNESCNR

CHEMISTRY OF MANGANESE-BEARING MATERIALS AT THE GROKEN DRILL SITE, GALE CRATER, MARS

International audienceIn July 2020, the Curiosity rover encountered a region of bedrock that contained an abundance of layered nodular features and highly unusual Mn- and sometimes P-rich chemistries (Fig.1a) in Glen Torridon (GT), a phyllosilicate-rich mudstone to sandstone deposit [1]. This sampling location was originally targeted at a distance as a site for the Sample Analysis at Mars (SAM) instrument to perform one of its two tetramethylammonium hydroxide (TMAH) wet chemistry experiments [2] in the hopes that the new location would provide similar rocks to the previously analyzed clay-rich Glen Etive targets at approximately the same elevation [3]

Multiple evolution modes of Aeolian Megaripples and implications for mars

International audienceMartian aeolian sedimentary rocks can unveil past wind-regimes and climates. Curiosity is exploring the layered sulphate-bearing unit exposed in the lower foothills of Aeolis Mons, Gale crater. Sedimentary structures indicate these strata were predominantly deposited within aeolian dune and sandsheet environments. Here, we report enigmatic erosional surfaces embedded within the sulphate-bearing strata and discuss their processes of formation. The surfaces form a set of concave-up scour-and-fill structures (width ~60 m; amplitude ~6 m). Their cross-sectional profiles show a planar central section with limbs inclined < 20°. The scour fill consists of: (1) low-angle inclined bedsets at the base which conformably drape the scour surface, overlain by (2) light-toned, relatively-planar strata lacking distinct bounding surfaces. Nearfield observations indicate that the scour-enclosing facies are composed of fine, even-in-thickness, laterally-extensive, planar laminations which are resemble the upper scour-fill strata. We interpret these laminations as wind-ripple strata. The geometry of the scours with broad cross-sectional concave profiles, flat central portions, and similar facies outside of and within the scour-and-fill structures suggest that the scours likely formed by aeolian processes. The scour-fill do not show evidence of fluvial facies. One plausible interpretation of the scours is that they represent saucer-shaped aeolian ‘blowout’ structures. Such structures, observed in both modern and ancient aeolian settings on Earth, commonly form through wind deflation from intense winds. The absence of such scour-and-fill structures in the lower part of the aeolian sulphate-bearing succession suggests that the presence of scours may indicate transition to enhanced wind deflation

SULFATE-BEARING STRATA SEQUENCE EXTENDS EARLY MARS ENVIRONMENTS CONDUCIVE TO PREBIOTIC EVOLUTION

International audienceMars sedimentary record dates as far back as 4.3 Ga, perhaps earlier [1], and the early presence of habitable environments is now welldocumented [2]. Yet, much more uncertain is whether early surface conditions were conducive to an independent emergence of life [3,4]. Prebiotic chemistry which may lead to incipient life forms is thought to be restricted not only to certain limited conditions, but may even require a specific succession of distinct environmental changes for it to succeed [5]. As such, it differs substantially from more broadly defined requirements for habitability.After exploring strata dominated by clay-bearing mudstones in Gale crater, the Curiosity rover reached the sulfate-bearing unit, which is hundreds of meters thick and represents evidence for a major environmental transition characteristic of stratified terrains found in other regions across Mars [6]. At this transition data collected by the rover uncovered a new type of sulfateenriched stratigraphic sequence

Overview of halite detections by chemcam in Gale Crater, Mars

International audienceSince 2012, the Curiosity rover has been exploring geological records of a paleo-lacustrine environment in Gale crater. It started with the fluvio-deltaic and lacustrine deposits in the Bradbury Group, followed by ∼300 m of stratigraphy through the Murray formation (from the Pahrump Hills to the Jura member) dominated by mudstones and occasionally heterolithic mudstones, siltstones and sandstones. It also crossed the unconformity with the overlying Stimson formation, dominated by aeolian sandstones, and the Vera Rubin Ridge, an erosion-resistant section of the Murray fm., which has undergone extensive diagenesis[1]. From Sol 2300 to 3072, Curiosity has explored the Glen Torridon region, previously named “Clay-bearing unit”. Since Sol 3100 (Mont Mercou), the rover entered the basal Layered Sulfate unit with the objective of documenting a possible major change in Mars climate history. Evaporitic salts could represent a geochemical marker of this transition. Here, we provide an overview of previous halite detections by ChemCam [2, 3] and report on new detections made in the sulfate-bearing unit