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Field portable instrumentation, such as in situ geochemical analyzers or broader field of view instruments like multispectral imagers or other imaging capabilities, has the potential to dramatically increase the science return of a planetary surface exploration mission. However, more work is needed to determine how emerging portable technologies should be designed and implemented into evolving mission architectures. This work summarizes the efforts of the RIS4E (Remote, In Situ and Synchrotron Studies for Science and Exploration) SSERVI (Solar System Exploration Research Virtual Institute) team in investigating how field portable instruments should be including into planning for future exploration EVAs (extravehicular activities). EVA crews of geologists and astronauts tested a variety of portable and handheld technologies at both the December 1974 lava flow, Kilauea Volcano, Hawai'i, and Kilbourne Hole, New Mexico, both of which are planetary analog sites. The timeline data gathered during instrument deployment were then mapped onto EVA timelines used in large‐scale NASA planetary surface exploration analog missions. Results and recommendations for future instrument hardware and software development are discussed, as is the operational framework necessary for incorporating in situ analytical capabilities into future planetary surface exploration. Key Points: Advancements in field portable technologies have the capability to increase the science return from crewed planetary surface missionsSimulated extravehicular activities were conducted in planetary analog sites to investigate the utility of portable instrumentsMore integrated testing is needed to evaluate varying modes of integrating field portable instruments beyond a handheld capacity [ABSTRACT FROM AUTHOR]

For more than a decade, the CheMin X-ray diffraction instrument on the Mars Science Laboratory rover, Curiosity, has been returning definitive and quantitative mineralogical and mineral–chemistry data from ~3.5-billion-year-old (Ga) sediments in Gale crater, Mars. To date, 40 drilled rock samples and three scooped soil samples have been analyzed during the rover's 30+ km transit. These samples document the mineralogy of over 800 m of flat-lying fluvial, lacustrine, and aeolian sedimentary rocks that comprise the lower strata of the central mound of Gale crater (Aeolis Mons, informally known as Mt. Sharp) and the surrounding plains (Aeolis Palus, informally known as the Bradbury Rise). The principal mineralogy of the sedimentary rocks is of basaltic composition, with evidence of post-depositional diagenetic overprinting. The rocks in many cases preserve much of their primary mineralogy and sedimentary features, suggesting that they were never strongly heated or deformed. Using aeolian soil composition as a proxy for the composition of the deposited and lithified sediment, it appears that, in many cases, the diagenetic changes observed are principally isochemical. Exceptions to this trend include secondary nodules, calcium sulfate veining, and rare Si-rich alteration halos. A surprising and yet poorly understood observation is that nearly all of the ~3.5 Ga sedimentary rocks analyzed to date contain 15–70 wt.% of X-ray amorphous material. Overall, this >800 m section of sedimentary rock explored in lower Mt. Sharp documents a perennial shallow lake environment grading upward into alternating lacustrine/fluvial and aeolian environments, many of which would have been habitable to microbial life. [ABSTRACT FROM AUTHOR]

Since the advent of ChatGPT in November 2022, there has been a growing interest and widespread speculation on how Artificial Intelligence (AI), more specifically generative AI, has the potential to revolutionize research and applications across disciplines, with real-world implications. Applied linguistics researchers and practitioners have long adapted to the use of technology in language learning and teaching, where AI already plays a role in the form of Natural Language Processing (NLP), Machine Learning (ML), and other related technologies. This Expositions article introduces generative AI, explains how it works and what distinguishes it from other AI technologies, and discusses its growing influence in the applications relevant to applied linguists. The article concludes with some guidance on how to navigate the generative AI space as an applied linguist while acknowledging the current limitations, including how to use generative AI in research and practice. [ABSTRACT FROM AUTHOR]

The Sample Analysis at Mars-Evolved Gas Analyzer (SAM-EGA) on the Curiosity rover detected hydrogen chloride (HCl) and sulfur dioxide (SO2) gas evolutions above 600 °C and 700 °C, respectively, from several drilled rock and soil samples collected in Gale crater, which have been attributed to NaCl and Mg sulfates. Although NaCl and Mg sulfates do not evolve HCl or SO2 within the SAM temperature range (<~870 °C) when analyzed individually, they may evolve these gases at <870 °C and become detectable by SAM-EGA when mixed. This work aims to determine how Mg sulfate and NaCl interact during heating and how that affects evolved HCl and SO2 detection temperatures in SAM-EGA. Solid mixtures of NaCl and kieserite were analyzed using a thermogravimeter/differential scanning calorimeter furnace connected to a quadrupole mass spectrometer, configured to operate under similar conditions as SAM, and using X-ray diffraction of heated powders. NaCl analyzed individually did not evolve HCl; however, NaCl/kieserite mixtures evolved HCl releases with peaks above 600 °C. The results suggested that kieserite influenced HCl production from NaCl via two mechanisms: (1) kieserite depressed the melting point of NaCl, making it more reactive with evolved water; and (2) SO2 from kieserite decomposition reacted with NaCl and water (i.e., Hargreaves reaction). Additionally, NaCl catalyzed the thermal decomposition of kieserite, such that the evolved SO2 was within the SAM-EGA temperature range. The results demonstrated that SAM-EGA can detect chlorides and Mg sulfates when mixed due to interactions during heating. These phases can provide information on past climate and mineral formation conditions. [ABSTRACT FROM AUTHOR]

To accurately determine the chronological framework of climatic variations recorded by various Martian terrains, the absolute ages of Martian events and cratering rate need to be constrained by either in situ dating or returned samples. In situ K-Ar dating is currently a more plausible dating technique as compared with sample return. Jarosite (KFe3[SO4]2[OH]6) is the only confirmed K sulfate mineral that is widely present on Mars, as indicated by in situ detection, orbital remote sensing, and meteorite studies. Jarosite can be used for precise K-Ar and 40Ar/39Ar dating. The preservation of jarosite on Mars provides information about the nature and duration of aqueous processes on the Martian surface. Different ages of Martian jarosite represent the key to constraining the transition from Martian surface water activity to arid climatic conditions. This paper summarizes recent advances in our knowledge of the spatial distribution of Martian jarosite, its mineralogical properties and stability on Mars, the Ar diffusion kinetics of jarosite, and the current status of in situ K-Ar dating. Moreover, we examine the key scientific issues to be addressed for in situ K-Ar dating of jarosite and Martian sample return missions, and discuss future research directions. [ABSTRACT FROM AUTHOR]

The nitrogen isotopic compositions of lunar soil have important implications for the sources of lunar volatiles and even the evolution of the moon. At present, the research on the lunar nitrogen isotopic compositions is mainly based on the lunar meteorites and the samples brought back by the Apollo and Luna missions. However, volatiles adsorbed on the surface of the lunar soil may be lost due to changes in temperature and pressure, as well as vibration and shock effects when the sample is returned. At the same time, in the case of low N content in the sample, since N is the main component of the earth's atmosphere, it is easily affected by the atmosphere during the analysis process. Therefore, in situ nitrogen isotopic analysis of lunar soil on orbit is necessary to avoid the problems mentioned above and is one of the primary science goals for the Lunar Soil Volatile Measuring instrument on Chang'e-7 spacecraft. After the nitrogen purification procedure, the volatiles in lunar soil that are released through single-step or stepped heating techniques diffuse to the quadrupole mass spectrometer to obtain the N contents and isotopic compositions of the lunar soil. This paper introduces the ground test for N isotopic analysis of lunar soil in orbit according to the Lunar Soil Volatile Measuring Instrument. After long-term repeated measurements, the background and CO-corrected Air-STD 14N/15N ratio is 268.986 ± 4.310 (1SD, n = 35), and the overall reproducibility of measurements is 1.6%. The accuracy of N isotopic compositions is calculated to be better than 5%, which can distinguish different sources of N components in lunar soil. [ABSTRACT FROM AUTHOR]

In this paper, we propose an in-depth evaluation of the performance of the Archimede rover while traversing rough terrain with loose soil. In order to better analyze this, the reality gap is evaluated when simulating the behavior with an open-source simulator. To this extent, we implement a full model of the rover in the open-source dynamics simulator Gazebo, along with several types of terrains that replicate the experimental conditions. The rover control system is equipped with a kinematics model that allows for driving in different modes. We implement an odometric system aboard the rover, as well as an external optical absolute tracking system as reference. We estimate the drift occurring during driving in different configurations, two types of soil with corresponding wheel geometries. The results show good adherence of the odometry when the rover drives on planar ground; conversely, as expected, a marked influence of slope is seen on wheel drift. The reality gap between simulations and experimental results is kept comparatively small provided that slopes are not present. [ABSTRACT FROM AUTHOR]

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, Mn2+Fe3+2(PO4)2(OH)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. [ABSTRACT FROM AUTHOR]

This paper reports the results obtained for a distributed-feedback quantum cascade laser (DFB-QCL) exposed to different fluences of proton particles: 1014, 1015 and 1016 p/cm2. Dedicated laboratory setups were developed to assess the irradiation-induced changes in this device. Multiple parameters defining the QCL performances were investigated prior to and following each irradiation step: (i) voltage-driving current; (ii) emitted optical power-driving current; (iii) central emitting wavelength-driving current; (iv) emitted spectrum-driving current; (v) transversal mode structure-driving current, maintaining the system operating temperature at 20 °C. The QCL system presented, before irradiation, two emission peaks: a central emission peak and a side peak. After proton irradiation, the QCL presented a spectral shift, and the ratio between the two peaks also changed. Even though, after irradiation, the tunning spectral range was reduced, at the end of the tests, the system was still functional. [ABSTRACT FROM AUTHOR]

Within the perspective of the current and future space missions, the detection and separation of building blocks such as amino acids are important subjects which are becoming fundamental in the search for the origin of life and traces of life in the solar system. In this work, we have developed and optimized a strategy adapted to space experimentation to detect the presence of amino acid-like compounds using gas chromatography coupled to mass spectrometry (GC-MS). Selected derivatization methods meet the instrument design constraints imposed on in situ extraterrestrial experiments. Coupled to a fast selective extraction, GC analysis would be highly efficient for the detection of organic materials. In the future, the corresponding GC-MS TIC could facilitate simple and fast selection of sediments/dust samples onboard GC-MS-equipped rovers for sample return-to-Earth missions. [ABSTRACT FROM AUTHOR]

The composition the atmosphere of Venus results from the integration of many processes entering into play over the entire geological history of the planet. Determining the elemental abundances and isotopic ratios of noble gases (He, Ne, Ar, Kr, Xe) and stable isotopes (H, C, N, O, S) in the Venus atmosphere is a high priority scientific target since it could open a window on the origin and early evolution of the entire planet. This chapter provides an overview of the existing dataset on noble gases and stable isotopes in the Venus atmosphere. The current state of knowledge on the origin and early and long-term evolution of the Venus atmosphere deduced from this dataset is summarized. A list of persistent and new unsolved scientific questions stemming from recent studies of planetary atmospheres (Venus, Earth and Mars) are described. Important mission requirements pertaining to the measurement of volatile elements in the atmosphere of Venus as well as potential technical difficulties are outlined. [ABSTRACT FROM AUTHOR]

Recent and past observations of chemical and physical peculiarities in the atmosphere of Venus have renewed speculations about the existence of life in its clouds. To find signs of Venusian life, a dedicated astrobiological space exploration mission is required, and for this reason the Venus Life Finder mission is currently being prepared. A Venus Life Finder mission will require dedicated and specialized instruments to hunt for biosignatures and habitability indicators. In this contribution, we present the ORIGIN space instrument, a laser desorption/laser ablation ionization mass spectrometer. This instrument is designed to detect large, non-volatile molecules, specifically biomolecules such as amino acids and lipids. At the same time, it can also be used in ablation mode for elemental composition analysis. Recent studies with this space prototype instrument of amino acids, polycyclic aromatic hydrocarbons, lipids, salts, metals, sulphur isotopes, and microbial elemental composition are discussed in the context of studies of biosignatures and habitability indicators in Venus's atmosphere. The implementation of the ORIGIN instrument into a Venus Life Finder mission is discussed, emphasizing the low weight and low power consumption of the instrument. An instrument design and sample handling system are presented that make optimal use of the capabilities of this instrument. ORIGIN is a highly versatile instrument with proven capabilities to investigate and potentially resolve many of the outstanding questions about the atmosphere of Venus and the presence of life in its clouds. [ABSTRACT FROM AUTHOR]

NASA's Mars Science Laboratory mission, with its Curiosity rover, has been exploring Gale crater (5.4° S, 137.8° E) since 2012 with the goal of assessing the potential of Mars to support life. The mission has compiled compelling evidence that the crater basin accumulated sediment transported by marginal rivers into lakes that likely persisted for millions of years approximately 3.6 Ga ago in the early Hesperian. Geochemical and mineralogical assessments indicate that environmental conditions within this timeframe would have been suitable for sustaining life, if it ever were present. Fluids simultaneously circulated in the subsurface and likely existed through the dry phases of lake bed exposure and aeolian deposition, conceivably creating a continuously habitable subsurface environment that persisted to less than 3 Ga in the early Amazonian. A diversity of organic molecules has been preserved, though degraded, with evidence for more complex precursors. Solid samples show highly variable isotopic abundances of sulfur, chlorine, and carbon. In situ studies of modern wind-driven sediment transport and multiple large and active aeolian deposits have led to advances in understanding bedform development and the initiation of saltation. Investigation of the modern atmosphere and environment has improved constraints on the timing and magnitude of atmospheric loss, revealed the presence of methane and the crater's influence on local meteorology, and provided measurements of high-energy radiation at Mars' surface in preparation for future crewed missions. Rover systems and science instruments remain capable of addressing all key scientific objectives. Emphases on advance planning, flexibility, operations support work, and team culture have allowed the mission team to maintain a high level of productivity in spite of declining rover power and funding. [ABSTRACT FROM AUTHOR]

Chirality is a central feature in the evolution of biological systems, but the reason for biology's strong preference for specific chiralities of amino acids, sugars, and other molecules remains a controversial and unanswered question in origins of life research. Biological polymers tend toward homochiral systems, which favor the incorporation of a single enantiomer (molecules with a specific chiral configuration) over the other. There have been numerous investigations into the processes that preferentially enrich one enantiomer to understand the evolution of an early, racemic, prebiotic organic world. Chirality can also be a property of minerals; their interaction with chiral organics is important for assessing how post-depositional alteration processes could affect the stereochemical configuration of simple and complex organic molecules. In this paper, we review the properties of organic compounds and minerals as well as the physical, chemical, and geological processes that affect organic and mineral chirality during the preservation and detection of organic compounds. We provide perspectives and discussions on the reactions and analytical techniques that can be performed in the laboratory, and comment on the state of knowledge of flight-capable technologies in current and future planetary missions, with a focus on organics analysis and life detection. [ABSTRACT FROM AUTHOR]

For future lunar exploration and planetary missions, the digital elevation model (DEM) of the target object may not be well prepared before the mission, so developing a new robust crater detection algorithm (CDA) without prepared high-precision DEM is needed to meet the requirements of a high-reliability and high-precision detection and navigation system. In this paper, we presented a new robust lunar CDA method based on maximum entropy threshold segmentation. By calculating the entropy distribution of the ternary image, the threshold for retaining the maximum amount of image information is selected adaptively, a variety of evaluation indicators are proposed, and a multiple-indicator constraint matrix is constructed to realize the extraction and fitting of the craters. The proposed method has the following advantages: (1) it has strong robustness and is capable of extracting complete craters under multiple illumination conditions, which makes it suitable for the extraction of large-scale planetary and lunar images; (2) the extracted crater edges are clear and complete and do not merge with the surrounding environment edge; and (3) it avoids the problem of parameter sensitivity that is present in a traditional CDA algorithm. The proposed method was verified using an image taken by the Chang'e-2 lunar probe, and a comparison with the traditional method based on morphology and adaptive Canny edge detection shows that the number of craters detected increases by more than 35%, while the computational efficiency is improved by more than 40%. [ABSTRACT FROM AUTHOR]

On Earth, salt environments are the most relevant analogues to Martian salt deposits with regard to the search for preserved biomolecules. In this study, we analyzed the distribution of lipids in salt samples from Dalangtan and Qarhan in the Qaidam Basin, which is the most important area to carry out analog research of Mars in China. Furthermore, we compared the lipids distribution results with that from other typical Martian analog sites such as the Atacama Desert. Salt samples in the Qaidam Basin are enriched with fatty acid compounds, including normal fatty acids, unsaturated fatty acids, branched fatty acids, and acyclic isoprene acids. In addtion, glycerol dialkyl glycerol tetraethers (GDGTs) and archaeol compounds were also detected in these salt samples. Compared with the hypersaline samples, the clay samples not only have higher abuandance of fatty acids, GDGTs and archaeol compounds, but also a more diversed lipids composition. Only a few lipids were detected in the pure-saline samples, such as archaeol compounds. These clues suggest that content of salt minerals is the major factor affecting the distribution of lipids. This study provides an analogy for detecting and evaluating the traces of life that may exist on Mars. [ABSTRACT FROM AUTHOR]

The discovery of life on other planets and moons in our solar system is one of the most important challenges of this era. The second ExoMars mission will look for traces of extant or extinct life on Mars. The instruments on board the rover will be able to reach samples with eventual biomarkers until 2 m of depth under the planet’s surface. This exploration capacity offers the best chance to detect biomarkers which would be mainly preserved compared to samples on the surface which are directly exposed to harmful environmental conditions. Starting with the studies of the endolithic meristematic black fungus Cryomyces antarcticus, which has proved its high resistance under extreme conditions, we analyzed the stability and the resistance of fungal biomarkers after exposure to simulated space and Mars-like conditions, with Raman and Gas Chromatography–Mass Spectrometry, two of the scientific payload instruments on board the rover. [ABSTRACT FROM AUTHOR]

Mass spectrometry (MS) has played a remarkable role in exploring the chemical make‐up of our solar system. In situ probes were historically developed to analyze inorganic/elemental compositions while leveraging native ions or harsh ionization methods to aid in exploring astrophysics applications (e.g., heliophysics). The part played by MS is demonstrated in a majority of scientific payloads focused on exploration, particularly at the turn of the century with missions including Cassini‐Huygens, Rosetta, and now Mars Science Laboratory. Plasma mass spectrometers have grown more sophisticated to interrogate fundamental inorganic analysis (e.g., solar wind and magnetospheres) including both native ions and neutrals. Cosmic dust floating in‐between and orbiting planetary bodies has been targeted by unique sampling via impact ionization. More complex systems rely on landed planetary instrumentation with lessons learned from pioneering missions in the 1970s and 1980s to near neighbors Mars and Venus. Modern probes have expanded applicable target chemicals by recognizing the needs to provide for molecular analyses, extended mass range, and high resolution to provide unequivocal detection and identification. Notably, as the field surrounding astrobiology has gained momentum, so has the in situ detection of complex molecular chemistry including the chemical evolution of organic molecules. Mission context often includes long term timelines from spacecraft launch to arrival and additionally the diverse target environments across various planets. Therefore, customized experimental designs for space MS have been born of necessity. To this point, the development of MS instrumentation on Earth has now far outpaced development for experiments in space. Therefore, exciting developments lie ahead among various international space agencies conducting current and future mission planning with increasingly enhanced instrumentation. For instance, near‐neighbor Mars has entertained considerable attention with complex MS instrumentation with laser desorption ionization aboard the Mars Organic Molecule Analyzer instrument. To study comets, the Rosetta mission employs a secondary ionization mechanism. Meanwhile, the various moons of Jupiter and Saturn have intriguing surface and subsurface properties that warrant more advanced analyzer systems. Instrumentation design will continue to evolve as requirements develop and this review serves as a reflection of the contribution of in situ MS to space exploration in the past 20 years and the anticipated contribution yet to come. © 2020 John Wiley & Sons Ltd. Mass Spec Rev [ABSTRACT FROM AUTHOR]

Over the past 150 million years, the Chilean Atacama Desert has been transformed into one of the most inhospitable landscapes by geophysical changes, which makes it an ideal Mars analog that has been explored for decades. However, a heavy rainfall that occurred in the Atacama in 2017 provides a unique opportunity to study the response of resident extremophiles to rapid environmental change associated with excessive water and salt shock. Here we combine mineral/salt composition measurements, amendment cell culture experiments, and next-generation sequencing analyses to study the variations in salts and microbial communities along a latitudinal aridity gradient of the Atacama Desert. In addition, we examine the reshuffling of Atacama microbiomes after the rainfall event. Analysis of microbial community composition revealed that soils within the southern arid desert were consistently dominated by Actinobacteria, Chloroflexi, Proteobacteria, Firmicutes, Bacteroidetes, Gemmatimonadetes, Planctomycetes, and Acidobacteria, and Verrucomicrobia. Intriguingly, the hyperarid microbial consortia exhibited a similar pattern to the more southern desert. Salts at the shallow subsurface were dissolved and leached down to a deeper layer, challenging indigenous microorganisms with the increasing osmotic stress. Microbial viability was found to change with aridity and rainfall events. This study sheds light on the structure of xerotolerant, halotolerant, and radioresistant microbiomes from the hyperarid northern desert to the less arid southern transition region, as well as their response to changes in water availability. [ABSTRACT FROM AUTHOR]

Northwest Africa (NWA) 2737, one of the only three discovered Martian chassignites, provides critical constraints on the evolution of the Martian mantle and crust. Because of chassignites' cumulative nature, they contain abundant melt inclusions (MI). MI are small droplets of melts trapped by crystals during the cooling of magma. They are critical to the study of pre‐eruptive parental magma compositions, and thus, provide snapshots of the composition and evolution of Martian magmatic systems. Here, we present fractional crystallization models using parental magma composition calculated from NWA 2737 melt inclusions as starting compositions. We used the thermodynamic modeling software MELTS to model fractional crystallization of NWA 2737 parental magma compositions with a wide range of parameters (pressure, water content, oxygen fugacity). Our models show that the felsic compositions recently analyzed at the Martian surface in Gale crater, especially Sparkle and Angmaat, the two rocks thought to be analogous to the earliest continental crust on Earth, can be obtained by fractional crystallization of chassignite‐like parental melts. Our results suggest a link between the processes that resulted in chassignites and the rocks analyzed in situ at Gale crater. To assess the possible scenarios for Martian magma migration and storage processes, we compared chassignites to terrestrial analogs formed via various mechanisms and proposed two mechanisms that may explain the intrusive and effusive rocks found in situ at Gale crater: (1) emplacement and fractionation in a closed‐system crustal reservoir and (2) eruption of mafic to intermediate lavas of a relatively open system subject to constant replenishment. [ABSTRACT FROM AUTHOR]

The Mars 2020 mission will seek the signs of ancient life on Mars and will identify, prepare, document, and cache a set of samples for possible return to Earth by a follow-on mission. Mars 2020 and its Perseverance rover thus link and further two long-held goals in planetary science: a deep search for evidence of life in a habitable extraterrestrial environment, and the return of martian samples to Earth for analysis in terrestrial laboratories. The Mars 2020 spacecraft is based on the design of the highly successful Mars Science Laboratory and its Curiosity rover, but outfitted with a sophisticated suite of new science instruments. Ground-penetrating radar will illuminate geologic structures in the shallow subsurface, while a multi-faceted weather station will document martian environmental conditions. Several instruments can be used individually or in tandem to map the color, texture, chemistry, and mineralogy of rocks and regolith at the meter scale and at the submillimeter scale. The science instruments will be used to interpret the geology of the landing site, to identify habitable paleoenvironments, to seek ancient textural, elemental, mineralogical and organic biosignatures, and to locate and characterize the most promising samples for Earth return. Once selected, ∼35 samples of rock and regolith weighing about 15 grams each will be drilled directly into ultraclean and sterile sample tubes. Perseverance will also collect blank sample tubes to monitor the evolving rover contamination environment. In addition to its scientific instruments, Perseverance hosts technology demonstrations designed to facilitate future Mars exploration. These include a device to generate oxygen gas by electrolytic decomposition of atmospheric carbon dioxide, and a small helicopter to assess performance of a rotorcraft in the thin martian atmosphere. Mars 2020 entry, descent, and landing (EDL) will use the same approach that successfully delivered Curiosity to the martian surface, but with several new features that enable the spacecraft to land at previously inaccessible landing sites. A suite of cameras and a microphone will for the first time capture the sights and sounds of EDL. Mars 2020’s landing site was chosen to maximize scientific return of the mission for astrobiology and sample return. Several billion years ago Jezero crater held a 40 km diameter, few hundred-meter-deep lake, with both an inflow and an outflow channel. A prominent delta, fine-grained lacustrine sediments, and carbonate-bearing rocks offer attractive targets for habitability and for biosignature preservation potential. In addition, a possible volcanic unit in the crater and impact megabreccia in the crater rim, along with fluvially-deposited clasts derived from the large and lithologically diverse headwaters terrain, contribute substantially to the science value of the sample cache for investigations of the history of Mars and the Solar System. Even greater diversity, including very ancient aqueously altered rocks, is accessible in a notional rover traverse that ascends out of Jezero crater and explores the surrounding Nili Planum. Mars 2020 is conceived as the first element of a multi-mission Mars Sample Return campaign. After Mars 2020 has cached the samples, a follow-on mission consisting of a fetch rover and a rocket could retrieve and package them, and then launch the package into orbit. A third mission could capture the orbiting package and return it to Earth. To facilitate the sample handoff, Perseverance could deposit its collection of filled sample tubes in one or more locations, called depots, on the planet’s surface. Alternatively, if Perseverance remains functional, it could carry some or all the samples directly to the retrieval spacecraft. The Mars 2020 mission and its Perseverance rover launched from the Eastern Range at Cape Canaveral Air Force Station, Florida, on July 30, 2020. Landing at Jezero Crater will occur on Feb 18, 2021 at about 12:30 PM Pacific Time. [ABSTRACT FROM AUTHOR]

This brief review will discuss the current knowledge on the origin and evolution of the nitrogen atmospheres of the icy bodies in the solar system, particularly of Titan, Triton and Pluto. An important tool to analyse and understand the origin and evolution of these atmospheres can be found in the different isotopic signatures of their atmospheric constituents. The 14N/15N ratio of the N2-dominated atmospheres of these bodies serve as a footprint of the building blocks from which Titan, Triton and Pluto originated and of the diverse fractionation processes that shaped these atmospheres over their entire evolution. Together with other measured isotopic and elemental ratios such as 12C/13C or 36Ar/N2 these atmospheres can give important insights into the history of the icy bodies in the solar system, the diverse processes that affect their N2-dominated atmospheres, and the therewith connected solar activity evolution. Titan’s gaseous envelope most likely originated from ammonia ices with possible contributions from refractory organics. Its isotopic signatures can yet be seen in the – compared to Earth – comparatively heavy 14N/15N ratio of 167.7, even though this value slightly evolved over its history due to atmospheric escape and photodissociation of N2. The origin and evolution of Pluto’s and Triton’s tenuous nitrogen atmospheres remain unclear, even though it might be likely that their atmospheres originated from the protosolar nebula or from comets. An in-situ space mission to Triton such as the recently proposed Trident mission, and/or to the ice giants would be a crucial cornerstone for a better understanding of the origin and evolution of the icy bodies in the outer solar system and their atmospheres in general. Due to the importance of the isotopic measurements for understanding the origin and evolution of the icy bodies in the solar system, this review will also give a brief discussion on the diverse isotope measurement techniques with a focus on nitrogen. [ABSTRACT FROM AUTHOR]

This paper provides an overview of the Curiosity rover's exploration at Vera Rubin ridge (VRR) and summarizes the science results. VRR is a distinct geomorphic feature on lower Aeolis Mons (informally known as Mount Sharp) that was identified in orbital data based on its distinct texture, topographic expression, and association with a hematite spectral signature. Curiosity conducted extensive remote sensing observations, acquired data on dozens of contact science targets, and drilled three outcrop samples from the ridge, as well as one outcrop sample immediately below the ridge. Our observations indicate that strata composing VRR were deposited in a predominantly lacustrine setting and are part of the Murray formation. The rocks within the ridge are chemically in family with underlying Murray formation strata. Red hematite is dispersed throughout much of the VRR bedrock, and this is the source of the orbital spectral detection. Gray hematite is also present in isolated, gray‐colored patches concentrated toward the upper elevations of VRR, and these gray patches also contain small, dark Fe‐rich nodules. We propose that VRR formed when diagenetic event(s) preferentially hardened rocks, which were subsequently eroded into a ridge by wind. Diagenesis also led to enhanced crystallization and/or cementation that deepened the ferric‐related spectral absorptions on the ridge, which helped make them readily distinguishable from orbit. Results add to existing evidence of protracted aqueous environments at Gale crater and give new insight into how diagenesis shaped Mars' rock record. Plain Language Summary: Vera Rubin ridge is a feature at the base of Mount Sharp with a distinct texture and topography. Orbiter observations showed hematite, a mineral that sometimes forms by chemical reactions in water environments, was present atop the ridge. The presence of both water and chemical activity suggested the area preserved a past habitable environment. In this paper, we detail how the Curiosity science team tested this and other orbital‐based hypotheses. Curiosity data suggested that most ridge rocks were lain down in an ancient lake and had similar compositions to other Mount Sharp rocks. Curiosity confirmed that hematite was present in the ridge but no more abundantly than elsewhere. Larger grain size or higher crystallinity probably account for the ridge's hematite being more visible from orbit. We conclude Vera Rubin ridge formed because groundwater recrystallized and hardened the rocks that now make up the ridge. Wind subsequently sculpted and eroded Mount Sharp, leaving the harder ridge rocks standing because they resisted erosion compared with surrounding rocks. The implication of these results is that liquid water was present at Mount Sharp for a very long time, not only when the crater held a lake but also much later, likely as groundwater. Key Points: We summarize Curiosity's campaign at Vera Rubin ridge (Sols 1726–2302) and the high‐level results from articles in this special issueVera Rubin ridge formed when diagenesis hardened rocks along the base of Aeolis Mons; wind subsequently etched the feature into a ridgeResults add evidence for protracted aqueous environments at Gale crater and give new insight into how diagenesis shaped Mars' rock record [ABSTRACT FROM AUTHOR]

Images from the Mars Science Laboratory (MSL) mission of lacustrine sedimentary rocks of Vera Rubin ridge on "Mt. Sharp" in Gale crater, Mars, have shown stark color variations from red to purple to gray. These color differences crosscut stratigraphy and are likely due to diagenetic alteration of the sediments after deposition. However, the chemistry and timing of these fluid interactions is unclear. Determining how diagenetic processes may have modified chemical and mineralogical signatures of ancient Martian environments is critical for understanding the past habitability of Mars and achieving the goals of the MSL mission. Here we use visible/near‐infrared spectra from Mastcam and ChemCam to determine the mineralogical origins of color variations in the ridge. Color variations are consistent with changes in spectral properties related to the crystallinity, grain size, and texture of hematite. Coarse‐grained gray hematite spectrally dominates in the gray patches and is present in the purple areas, while nanophase and fine‐grained red crystalline hematite are present and spectrally dominate in the red and purple areas. We hypothesize that these differences were caused by grain‐size coarsening of hematite by diagenetic fluids, as observed in terrestrial analogs. In this model, early primary reddening by oxidizing fluids near the surface was followed during or after burial by bleaching to form the gray patches, possibly with limited secondary reddening after exhumation. Diagenetic alteration may have diminished the preservation of biosignatures and changed the composition of the sediments, making it more difficult to interpret how conditions evolved in the paleolake over time. Plain Language Summary: Sedimentary rocks found in deserts on Earth often exhibit striking color differences from red and purple to white, which are caused by groundwater dissolving and reprecipitating iron oxides within the rocks. NASA's Mars Science Laboratory (MSL) mission has observed similar color differences on Mars within the sedimentary rocks of Vera Rubin ridge in Gale crater, which were laid down in an ancient lake. We use color images and spectral data from the Mastcam cameras on MSL to investigate the origin of these color differences and find that they are consistent with changes in iron oxides through the ridge. This variation in iron oxides suggests that groundwater flowed through and altered these rocks multiple times before and after they were buried by later sediments. The MSL mission has shown that habitable lake environments once existed in Gale crater, through detections of the building blocks of life, including organic molecules, and by showing that conditions that existed in the lake were clement for life. However, later alteration by groundwater may have diminished the preservation of organics and changed the composition of these rocks, making it more difficult to interpret the details of how conditions evolved in the lake over time. Key Points: Vera Rubin ridge exhibits strong color differences that crosscut stratigraphy, consistent with postdepositional alteration (diagenesis)Color differences correspond to variations in spectral signatures of nanophase, fine‐grained, and coarse‐grained hematiteBased on terrestrial analogs, these variations can be explained by early oxidation and later coarsening of hematite by diagenetic fluids [ABSTRACT FROM AUTHOR]

The Curiosity rover investigated a topographic structure known as Vera Rubin ridge, associated with a hematite signature in orbital spectra. There, Curiosity encountered mudstones interpreted as lacustrine deposits, conformably overlying the 300 m‐thick underlying sedimentary rocks of the Murray formation at the base of Mount Sharp. While the presence of hematite (α‐Fe2O3) was confirmed in situ by both Mastcam and ChemCam spectral observations and by the CheMin instrument, neither ChemCam nor APXS observed any significant increase in FeOT (total iron oxide) abundances compared to the rest of the Murray formation. Instead, Curiosity discovered dark‐toned diagenetic features displaying anomalously high FeOT abundances, commonly observed in association with light‐toned Ca‐sulfate veins but also as crystal pseudomorphs in the host rock. These iron‐rich diagenetic features are predominantly observed in "gray" outcrops on the upper part of the ridge, which lack the telltale ferric signature of other Vera Rubin ridge outcrops. Their composition is consistent with anhydrous Fe‐oxide, as the enrichment in iron is not associated with enrichment in any other elements, nor with detections of volatiles. The lack of ferric absorption features in the ChemCam reflectance spectra and the hexagonal crystalline structure associated with dark‐toned crystals points toward coarse "gray" hematite. In addition, the host rock adjacent to these features appears bleached and shows low‐FeOT content as well as depletion in Mn, indicating mobilization of these redox‐sensitive elements during diagenesis. Thus, groundwater fluid circulations could account for the remobilization of iron and recrystallization as crystalline hematite during diagenesis on Vera Rubin ridge. Plain Language Summary: The NASA rover Curiosity investigated Vera Rubin ridge, a specific landform within the Gale crater on Mars. Scientific missions in orbit around the planet had previously discovered high concentrations of hematite on top of the ridge, an iron‐oxide mineral that commonly forms in water. However, it was not clear from orbit if such conditions existed at the time of the deposition of the sediments (around 3.5 billion years ago) or occurred much later during "diagenesis," after deposition of the sediments and up to their transformation into rocks. On the surface, the rover did not observe significant differences between the ridge and the terrains encountered before it, except for small, dark geologic features that formed during diagenesis. Their analysis by the ChemCam instrument revealed that these features are composed of hematite—the same iron‐oxide mineral that was observed from orbit—and, interestingly, that the iron required to form them was removed from the adjacent rocks by groundwaters. As such, it appears that groundwaters played an important role in shaping Vera Rubin ridge, and thus partially obscure interpretations on the environmental conditions that existed on the surface of Mars at the time of sedimentation. Key Points: Images from the Curiosity rover show the presence of dark‐toned diagenetic features at Vera Rubin ridgeChemCam analyses of these features point toward an Fe‐oxide composition, consistent with crystalline hematiteDepletion of Fe and Mn in bleached halos around the Fe‐oxide features indicates mobility of Fe and Mn during the later stages of diagenesis [ABSTRACT FROM AUTHOR]

Vera Rubin ridge (VRR) is a topographic high within the layers of Mount Sharp, Gale crater, that exhibits a strong hematite spectral signature from orbit. The Mars Science Laboratory Curiosity rover carried out a comprehensive investigation to understand the depositional and diagenetic processes recorded in the rocks of VRR. Sample Analysis at Mars (SAM) evolved gas analyses (EGA) were performed on three samples from the ridge and one from directly beneath the ridge. SAM evolved H2O data suggested the presence of an Fe‐rich dioctahedral smectite, such as nontronite, in the sample from beneath the ridge. H2O data are also consistent with ferripyrophyllite in VRR samples. SAM SO2 data indicated that all samples contained Mg sulfates and some Fe sulfate. Several volatile detections suggested trace reduced sulfur sources, such as Fe sulfides and/or S‐bearing organic compounds, in two samples while significant O2 and NO evolved from one sample indicated the presence of oxychlorine and nitrate/nitrite salts, respectively. The O2 evolution was the second highest to date and the first observed in ~1,200 sols. HCl released from all samples likely resulted, in part, from trace chloride salts. All samples evolved CO2 and CO consistent with oxidized carbon compounds (e.g., oxalates), while some CO2 may result from carbonate. SAM‐derived constraints on the mineralogy and chemistry of VRR materials, in the context of additional mineralogy, geochemistry, and sedimentology information obtained by Curiosity, support a complex diagenetic history that involved fluids of a range of possible salinities, redox characteristics, pHs, and temperatures. Plain Language Summary: The Mars Science Laboratory Curiosity rover conducted a detailed study of the rocks that make up the Vera Rubin ridge (VRR) feature in Gale crater, Mars, to better understand Martian geologic history. The Curiosity rover's Sample Analysis at Mars (SAM), a suite of scientific instruments on the rover, measured several diagnostic gases when it was used to heat samples from on and beneath VRR. These gases provided information about the mineralogy and chemistry of VRR samples that, together with additional information from other instruments on the rover, indicated that several different types of fluids affected the rocks in the ridge over geologic time. These fluids varied in temperature, salt content, and acidity. Key Points: Vera Rubin ridge experienced a complicated diagenetic history involving alteration by fluids with a variety of chemistries and temperaturesSample Analysis at Mars instrument suite data support an Fe‐rich composition for phyllosilicates detected on and near Vera Rubin ridgeSeveral salts were detected, including sulfate, chloride, nitrate, and oxychlorine salts, enabling constraints on diagenetic fluid chemistry [ABSTRACT FROM AUTHOR]

Apatite, a major hydrous mineral in Martian meteorites, has the potential to reveal history of volatiles on Mars. Here we report the H and Cl isotopic systematics of apatite from the enriched basaltic shergottite Northwest Africa (NWA) 8657 to better understand the processes influencing volatiles at or near the Martian (sub)surface. The apatite in NWA 8657 has the highest reported δD value (up to 6,509‰) of any phosphates in Martian meteorites. The positive correlation between the H2O contents (72–2,251 ppm) and δD values (3,965–6,509‰) as well as between the Cl contents (1.28–6.17wt%) and δ37Cl values (−1.7–4.0‰) in NWA 8657 apatite are consistent with mixing between volatiles derived from the Martian mantle and meteoric water/fluid. The D‐ and 37Cl‐enrichment of apatite in NWA 8657 implies isotopic exchange with subsurficial fluids during postcrystallization hydrothermal event(s). Plain Language Summary: Mars was probably a wet and warm world during its earliest geological history, supported by many lines of evidence. Present‐day Mars is cold and arid although recent remote sensing data support the existence of subsurface glaciers and seasonal fluid activities at some locations. In this study, our aim was to use ground truth about the potential water‐rock interaction on or near‐surface environments on recent Mars via measuring the H and Cl isotopic compositions of apatite from a geologically young meteorite from Mars: the enriched basaltic shergottite Northwest Africa (NWA) 8657. The petrography and mineral chemistry of apatite and other associated phases, for example, merrillite, maskelynite, mesostasis, and pyroxene, were documented prior to in situ H and Cl isotopes analysis. The water contents of apatite, merrillite, maskelynite, mesostasis, and pyroxene are positively correlated with the δD values. All of the data sets can be reconciled in terms of mixing between two end‐members, a D‐poor (~0‰) mantle reservoir and a D‐rich (5,920 ± 500‰) near‐surface/underground water reservoir. Moreover, apatite in NWA 8657 displays 37Cl‐enriched (~1 ± 1‰ in average) characteristics. These signatures are consistent with D‐ and 37Cl‐rich fluid‐assisted isotopic exchange in recent near‐surface environment on Mars. Key Points: First report of H and Cl isotopic systematics of apatite from the Martian meteorite NWA 8657NWA 8657 apatite has the highest reported δD value (up to 6,509‰) of any phosphates in Martian meteoritesThe H and Cl isotopic compositions of apatite in NWA 8657 imply D‐ and 37Cl‐rich fluids on surface of Mars [ABSTRACT FROM AUTHOR]

Aeolian sediment transport, deposition, and erosion have been ongoing throughout Mars's history. This record of widespread aeolian processes is preserved in landforms and geologic units that retain important clues about past environmental conditions including wind patterns. In this study we describe landforms within Melas Chasma, Valles Marineris, that occur in distinct groups with linear to crescentic shapes, arranged with a characteristic wavelength; some possess slope profiles analogous to modern sand dunes yet show evidence for lithification. Based on the features' dimensions, asymmetry, and spatial patterns relative to modern equivalents, we interpret these landforms to be two classes of aeolian bedforms: decameter‐scale megaripples and sand dunes. The presence of superposed erosional features and depositional units indicates that these landforms were cemented and likely ancient. Melas paleodunes are found atop Hesperian‐aged layered deposits, but we estimate them to be younger, likely lithified in the Amazonian period. Although a range of degradation was observed, some paleodunes are >10 m tall and maintain steep lee sides (>25°), an uncommon scenario for terrestrial examples as other geologic processes lead to dune obliteration. The preserved paleobedform geometries are largely consistent with those of modern aeolian indicators, suggesting no major shifts in wind regime or contributing boundary conditions. Finally, we propose that their appearance and context require sequential periods of dune migration, stabilization following catastrophic burial, cementation, differential erosion, exposure, and burial. The presence of wholly preserved duneforms appears to be more common on Mars compared to the Earth and may signal something important about Martian landscape evolution. Plain Language Summary: Wind‐driven sand dunes are common on modern Mars, and the presence of certain sedimentary rock layers indicates that these landforms occurred there in the past. Here, we explore features in the canyons of Valles Marineris that show characteristics frequently attributed to dunes, yet evidence for their lithification and burial is clear. Their horizontal extent, height, shape, slopes, and collective spatial patterns led to our interpretation of them as lithified dune fields. The heavily eroded appearance along with superposed elements such as craters and boulders led to the conclusion that these are relatively ancient landforms. Despite this erosion, this level of preservation is rare for terrestrial sand dunes due to erosion and tectonics, thus providing an opportunity to reconstruct the various factors contributing to their history. Understanding the circumstances that led to the preservation of these ancient duneforms will yield crucial information regarding planetary sedimentary processes and the geologic history of the region. Key Points: Sedimentary deposits were identified in Valles Marineris and interpreted as ancient aeolian dune fields with a range of preservation statesTheir preservation indicates a complex history with periods of migration, burial, stabilization, cementation, exhumation, and erosionPaleodune morphologies compared with modern indicators suggest no major shifts in wind regime have occurred since their stabilization [ABSTRACT FROM AUTHOR]

Geochemical results are presented from Curiosity's exploration of Vera Rubin ridge (VRR), in addition to the full chemostratigraphy of the predominantly lacustrine mudstone Murray formation up to and including VRR. VRR is a prominent ridge flanking Aeolis Mons (informally Mt. Sharp), the central mound in Gale crater, Mars, and was a key area of interest for the Mars Science Laboratory mission. ChemCam data show that VRR is overall geochemically similar to lower‐lying members of the Murray formation, even though the top of VRR shows a strong hematite spectral signature as observed from orbit. Although overall geochemically similar, VRR is characterized by a prominent decrease in Li abundance and Chemical Index of Alteration across the ridge. This decrease follows the morphology of the ridge rather than elevation and is inferred to reflect a nondepositionally controlled decrease in clay mineral abundance in VRR rocks. Additionally, a notable enrichment in Mn above baseline levels is observed on VRR. While not supporting a single model, the results suggest that VRR rocks were likely affected by multiple episodes of postdepositional groundwater interactions that made them more erosionally resistant than surrounding Murray rocks, thus resulting in the modern‐day ridge after subsequent erosion. Plain Language Summary: Results from the ChemCam instrument on Vera Rubin ridge (VRR) in Gale crater, Mars, are presented and compared with observations from similar rocks leading up to the ridge. VRR is a prominent ridge, flanking the central mound, Aeolis Mons, in Gale crater, Mars. The ridge attracted early attention because it displays strong iron‐oxide spectral signatures. Surprisingly, ChemCam data show that VRR rocks do not show an overall increase in iron abundance relative to the comparable bedrock analyzed for almost 300 m in elevation leading up to the ridge. While similar overall, some notable variations were observed on VRR relative to lower‐lying rocks. In particular, geochemical variations suggest a strong decrease in clay content on the ridge, above which, a notable enrichment in Mn is observed. No single geological process confidently explains all observations on the ridge. Rather, we think that VRR rocks underwent a series of interactions with groundwater that caused the rocks of VRR to become more resistant to erosion than their surroundings, thus emerging as a ridge as the rocks around them eroded. This likely implies that groundwater persisted in Gale crater even long after the disappearance of the ancient lake. Key Points: A decrease in Li and Chemical Index of Alteration, reflecting clay mineral content, is observed across Vera Rubin ridge (VRR)A Mn‐rich interval is observed stratigraphically above the decrease in clay mineral content on VRRVRR likely resulted from increased induration from late‐stage fluid interactions long after the lake environment in Gale crater ceased [ABSTRACT FROM AUTHOR]

The Mars Science Laboratory (MSL) Curiosity rover is exploring the Murray formation, a sequence of heterolithic mudstones and sandstones recording fluvial deltaic and lake deposits that comprise over 350 m of sedimentary strata within Gale crater. We examine >4,500 Murray formation bedrock points, employing recent laboratory calibrations for ChemCam laser‐induced breakdown spectroscopy H measurements at millimeter scale. Bedrock in the Murray formation has an interquartile range of 2.3–3.1 wt.% H2O, similar to measurements using the Dynamic Albedo of Neutrons and Sample Analysis at Mars instruments. However, specific stratigraphic intervals include high H targets (6–18 wt.% H2O) correlated with Si, Mg, Ca, Mn, or Fe, indicating units with opal, hydrated Mg sulfates, hydrated Ca sulfates, Mn‐enriched units, and akageneite or other iron oxyhydroxides, respectively. One stratigraphic interval with higher hydrogen is the Sutton Island unit and Blunts Point unit contact, where higher hydrogen is associated with Fe‐rich, Ca‐rich, and Mg‐rich points. A second interval with higher hydrogen occurs in the Vera Rubin ridge portion of the Murray formation, where higher hydrogen is associated with Fe‐rich, Ca‐rich, and Si‐rich points. We also observe trends in the H signal with grain size, separate from chemical variation, whereby coarser‐grained rocks have higher hydrogen. Variability in the hydrogen content of rocks points to a history of water‐rock interaction at Gale crater that included changes in lake water chemistry during Murray formation deposition and multiple subsequent groundwater episodes. Plain Language Summary: We measured the water content of bedrock targets in the Murray formation, a sequence of mudstones and sandstones part of Gale crater's Mt. Sharp, by applying recent laboratory calibrations to measurements from the Curiosity ChemCam instrument. While most rocks contained 2.3–3.1 wt.% H2O, consistent with measurements by other Mars Science Laboratory instruments, we found some stratigraphic intervals contained high water content (6–18 wt.% H2O) rocks including the Vera Rubin ridge. Based on our analysis of the corresponding major element composition, these are likely clays, Ca sulfates, Mn‐enriched units, and akageneite or other iron oxyhydroxides. The variation in water content indicates a history of water‐rock interaction at Gale crater that included changes in lake water chemistry during Murray formation deposition and multiple subsequent groundwater episodes. Key Points: Murray formation bedrock points measured by ChemCam have an interquartile range of 2.3–3.1 wt.% H2OSpecific intervals like the Vera Rubin ridge contain high H and indicate phases including iron oxyhydroxides, akageneite, and jarositeVariations in water content indicate changes in depositional lake water chemistry and multiple subsequent groundwater episodes [ABSTRACT FROM AUTHOR]

Wind erosion is integral to the evolution of arid landscapes on Earth and Mars, but the nature of long‐term wind erosion of bedrock is poorly understood. Here we describe the Salina del Fraile (SdF) depression in the Puna Plateau of the Central Andes, NW Argentina, as a landform excavated by wind over several million years. New structural cross sections and a compilation of chronostratigraphic ages rule out the hypothesis that the depression was created by transtensional tectonics. Dated remnant lacustrine and alluvial deposits in the floor of the depression constrain the rate and timing of erosion. Late Oligocene‐Miocene compressional folding uplifted friable strata that were preferentially eroded, resulting in the high‐relief (900 m) depression. Up to 1.95 km and an average of 1.05 km of strata were eroded during the last 8.2 to 17 Ma, at rates of 0.06 to 0.23 mm/yr. These rates are similar to long‐term average wind erosion rates reported in other regions. Coarse‐grained eolian megaripples, yardangs, and elongated ridges indicate ongoing eolian abrasion and deflation, aided by salt weathering, of the floor of the depression. Megaripple migration across stony lag surfaces exposes fresh bedrock to continued erosion. The SdF also contains kilometer‐scale mesas and ridges that we interpret as erosional remnants. These landforms are similar to megayardangs and erosional topography identified on the lower flanks of Mount Sharp, Gale crater, Mars. In such hyperarid landscapes characterized by lithologic heterogeneities, high‐relief landforms can be generated and sustained by wind erosion, without significant fluvial or glacial incision. Plain Language Summary: We investigated the origin of a large topographic depression in the arid Puna Plateau of the Central Andes, NW Argentina. Previous research interpreted the depression as formed by faulting, but we found that it is likely formed by wind erosion. While rivers and glaciers are usually responsible for erosion on Earth, there is no evidence for river or glacier action in the Salina del Fraile. Rather, much like the surface of Mars, wind was primarily responsible for forming the depression and surrounding landscape over several million years. We show that wind was able to excavate the depression because tectonic folding brought fine‐grained rocks close to the surface, where they were exposed to strong winds and breakdown by salt weathering. Wind erosion was active for the last 8.2 to 17 million years and, as evidenced by large dust storms originating from this region, is ongoing today. Wind is lowering the surface at an average rate of 0.06 to 0.23 mm/yr, similar to previous studies. The Salina del Fraile can help researchers understand the long‐term effects of wind erosion on Earth and Mars. Key Points: The Salina del Fraile depression in the arid Puna Plateau was excavated by wind over the last 17 to 8.2 MaCross sections imply up to 2 km of erosion along fold hinges, with remnant kilometer‐scale ridges and mesas analogous to landforms on MarsWind can generate and sustain high‐relief topography, even without significant fluvial or glacial incision [ABSTRACT FROM AUTHOR]

Orbiter and rover data have revealed a complex and intermittent hydrological history in Gale Crater on Mars, where habitable environments appear to have endured for at least thousands of years. The intermittency may be the result of a dominantly cold climate punctuated by geologically brief periods of warmth and active hydrology. However, the time required to establish an integrated hydrological cycle in a warming climate is difficult to ascertain and has not been thoroughly investigated. Here we model the transient evolution of groundwater flow and subsurface temperature, the slowest evolving components of the hydrological cycle, during a warm departure from cold conditions. We find that tens of thousands of years are likely required before groundwater could be a meaningful source for large lakes in Gale. With highly favorable conditions, primarily high permeability, significant flow might develop in thousands of years. This implies that surface water dominates during the beginning of a warm phase. Annual mean surface temperatures in Gale below 290 K would likely leave the nearby highlands frozen at the surface. In that case, deep aquifers beneath a highlands permafrost layer could deliver water to Gale, where low temperatures would have reduced evaporation. Plain Language Summary: Satellite imagery and data from the National Aeronautics and Space Administration (NASA)'s Curiosity rover indicate that Gale Crater, on Mars, hosted large lakes more than 3 billion yr ago. The climate during this period is not well understood but may have been mostly frozen, only occasionally warming up to the point where lakes could form. If so, warm periods must have been long enough to thaw frozen sources of water and supply the lakes. The slowest thawing source is groundwater. We simulate the thawing and flow of groundwater in the region surrounding Gale to understand whether it could have been a significant source for lakes during a warm climate period. We find that it could only be significant with the most generous assumptions about flow speed and aquifer recharge. Even with generous assumptions, tens of thousands of years are required to thaw enough groundwater to have an impact on large lakes. After long enough, though, the ground would thaw entirely, possibly enabling a higher rate of groundwater delivery. Key Points: Tens of thousands of years are likely required to generate significant groundwater flow to Gale Crater with a thawing crustSurface water would likely be the dominant source for Gale lakes at the beginning of a warm episodeDeep aquifers may have played a role later on if complete thaw occurred beneath Gale [ABSTRACT FROM AUTHOR]

Understanding magmatic processes is critical to understanding Mars as a system, but Curiosity's investigation of dominantly sedimentary rocks has made it difficult to constrain igneous processes. Igneous classification of float rocks is challenging because of the following: (1) the possibility that they have been affected by sedimentary processes or weathering, and (2) grain size heterogeneity in the observed rock textures makes the small‐scale compositions measured by rover instruments unreliable for bulk classification. We avoid these ambiguities by using detrital igneous mineral chemistry to constrain models of magmatic processes in the source region for the fluvio‐deltaic Bradbury group. Mineral chemistry is obtained from X‐ray diffraction of three collected samples and a new stoichiometric and visual filtering of ~5,000 laser induced breakdown spectroscopy (LIBS) spots to identify compositions of individual igneous minerals. Observed mineral chemistries are compared to those produced by MELTS thermodynamic modeling to constrain possible magmatic conditions. Fractionation of two starting primary melts derived from different extent of adiabatic decompression melting of a primitive mantle composition could result in the crystallization of all minerals observed. Crystal fractionation of a subalkaline and an alkaline magma is required to form the observed minerals. These results are consistent with the collection of alkaline and subalkaline rocks from Gale as well as clasts from the Martian meteorite Northwest Africa 7034 and paired stones. This new method for constraining magmatic processes will be of significant interest for the Mars 2020 mission, which will also investigate an ancient volcaniclastic‐sedimentary environment and will include a LIBS instrument. Plain Language Summary: Using instruments on Mars rovers, classification of rocks as igneous or sedimentary can be ambiguous, as many of the sedimentary rocks are made of barely altered igneous minerals. We avoid this issue by using the chemistry of individual igneous minerals found in both sedimentary and igneous rocks to assess possible magmatic processes. We focus on rocks in the Bradbury group observed by the Curiosity rover, which includes river and lake deposits coming from a source area to the north of Gale crater. We report the chemistry of pure igneous minerals hit by the ChemCam laser. Then, using modeling, we assess several scenarios for magmatic processes to identify conditions that could have reproduced the mineral chemistries observed. This new method shows that fractional crystallization of two compositionally distinct parental melts formed during the ascent of a mantle composition can explain the igneous mineral chemistry observed. These results are consistent with previous works in Gale, and are interesting because (1) both alkaline and subalkaline magmas were likely produced very early in Mars history, and (2) this provides a new way to constrain magmatic processes from observations of sedimentary rocks, which will be important for the Mars 2020 mission. Key Points: Detrital feldspar and pyroxene mineral compositions were estimated for the first time from stoichiometric analyses of ChemCam compositionsMELTS modeling was used to constrain possible ancient magmatic contributions to the Martian surface mineral chemistry without igneous outcropsOur method is important for future missions like Mars 2020 where igneous outcrops may be rare but detrital minerals are preserved [ABSTRACT FROM AUTHOR]

The Curiosity rover's exploration of rocks and soils in Gale crater has provided diverse geochemical and mineralogical data sets, underscoring the complex geological history of the region. We report the crystalline, clay mineral, and amorphous phase distributions of four Gale crater rocks from an 80‐m stratigraphic interval. The mineralogy of the four samples is strongly influenced by aqueous alteration processes, including variations in water chemistries, redox, pH, and temperature. Localized hydrothermal events are evidenced by gray hematite and maturation of amorphous SiO2 to opal‐CT. Low‐temperature diagenetic events are associated with fluctuating lake levels, evaporative events, and groundwater infiltration. Among all mudstones analyzed in Gale crater, the diversity in diagenetic processes is primarily captured by the mineralogy and X‐ray amorphous chemistry of the drilled rocks. Variations indicate a transition from magnetite to hematite and an increase in matrix‐associated sulfates suggesting intensifying influence from oxic, diagenetic fluids upsection. Furthermore, diagenetic fluid pathways are shown to be strongly affected by unconformities and sedimentary transitions, as evidenced by the intensity of alteration inferred from the mineralogy of sediments sampled adjacent to stratigraphic contacts. Plain Language Summary: The mineralogy of mudstones and sandstones investigated by the Mars Science Laboratory rover illustrates a varied and complex history of aqueous alteration in Gale crater sediments. We present the mineralogy of four rocks determined by the CheMin X‐ray diffraction instrument onboard the rover. The results exhibit evidence of multiple diagenetic events, including aqueous alteration by warm groundwaters and a fluctuation of lake levels and evaporative events. Overall, the mineralogy of rocks sampled from the lowermost ~160 m of Gale crater stratigraphy explored by the Curiosity rover shows a decrease in Mg‐Fe‐silicates (i.e., olivine and pyroxene), a transition from magnetite to hematite, an increase in Ca‐sulfates, and a shift from Mg‐phyllosilicates to Al‐phyllosilicates. These trends imply an intensifying influence from oxic, diagenetic fluids. Furthermore, sites adjacent to unconformities and sedimentary transitions show more intense alteration suggesting that these physical boundaries play a key role in driving the path of diagenetic fluids. Key Points: CheMin‐determined mineralogy indicates pervasive low‐temperature diagenesis and localized hydrothermal alteration events at Gale craterThe diagenetic history of Gale crater is characterized by a diverse range in fluid chemistry, Eh, pH, and temperatureThe distribution of SiO2 and FeOT among crystalline and amorphous materials constrains the temperature and duration of diagenesis [ABSTRACT FROM AUTHOR]

The NASA Curiosity rover's ChemCam instrument suite has detected boron in calcium‐sulfate‐filled fractures throughout the sedimentary strata of Gale crater including Vera Rubin ridge. The presence of elevated B concentration provides insights into Martian subsurface aqueous processes. In this study we extend the data set of B in Ca‐sulfate veins across Gale crater, comparing the detection frequency and relative abundances with Li. We report 33 new detections of B within veins analyzed between Sols 1548 and 2311 where detections increase in Pettegrove Point and Jura members, which form Vera Rubin ridge. The presence of B and Li in the Ca‐sulfate veins is possibly due to dissolution of preexisting B in clays of the bedrock by acids or neutral water and redistribution of the elements into the veins. Elevated frequency of B detection in veins of Gale crater correlates with presence of dehydration features such as desiccation cracks, altered clay minerals and detections of evaporites such as Mg‐sulfates and chloride salts in the host rocks. The increased observations of B also coincide with decreased Li concentration in the veins (average Li concentration of veins drops by ~15 ppm). Boron and Li have varying solubilities, and Li does not form salts as readily upon dehydration as B, causing it to remain in the solution. So the weak negative correlation between B and Li may reflect the crystallization sequence during dehydration on Vera Rubin ridge. Plain Language Summary: Boron and lithium were measured in cracks in the rocks that were filled with whitish, calcium sulfate. These were found in Gale crater using the ChemCam instrument on the Mars Science Laboratory Curiosity rover. Both elements are highly water soluble and may indicate late‐stage ground water activity. Boron's lower solubility compared to that of lithium means it forms salts relatively easily, while Li remains dissolved in the brine with progressive evaporation. In our study we find that on Vera Rubin ridge, boron detection frequency is inversely proportional to the concentration of lithium. This finding suggests that, based on their different solubilities, boron may have precipitated in the fractures before lithium. Lithium possibly moved away with the remaining brine, leaving boron behind as precipitates. Key Points: ChemCam analyses of calcium sulfate veins in Vera Rubin ridge (VRR) show the presence of boron and lithiumBoron detection frequency in the Ca‐sulfate veins increases in the Jura member of VRR and is inversely correlated with lithiumThe relationship between B and Li suggests an evaporative sequence formed during dehydration on higher elevations of VRR [ABSTRACT FROM AUTHOR]

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. Plain Language Summary: The Mars Science Laboratory studied the chemical composition of Vera Rubin ridge in Gale crater, Mars. The Sample Analysis at Mars, a set of scientific instruments designed to study rock chemistry, observed a number of gases released during the heating of Martian drilled samples. The same gases were observed when Mars‐relevant minerals were analyzed with similar instruments on Earth. From these two sets of data, we applied statistical analyses to determine which Mars samples on Vera Rubin ridge contained important sulfur compounds. Two samples on the ridge showed evidence for these compounds, which could have supported the energetic requirements for life. The results presented here improve both the understanding of the history of Gale crater and the potential for ancient life to have existed. Key Points: The Sample Analysis at Mars instrument suite studied carbon‐sulfur gases released during evolved gas analysis of Vera Rubin ridge samplesQuadratic discriminant analysis compared laboratory and flight data to identify Martian samples that contain reduced sulfurTwo Vera Rubin ridge samples from the Jura member were identified as likely to include reduced sulfur [ABSTRACT FROM AUTHOR]