We present the scientific highlights and status from years 9-12 of NASA’s Mars Science Laboratory mission, with its Curiosity rover. A thermochemolysis-based sample analysis revealed a variety of organic molecules preserved in clay mineral-rich lake/lake margin deposits of the Glen Torridon region. The stratigraphically higher clay-sulfate mineral transition on Aeolis Mons was found to be associated with a lithological change from lacustrine to dry aeolian depositional environments. Water intermittently returned to the surface after the increase in aridity, including during the deposition of wave ripple strata which indicate a climate capable of sustaining an ice-free lake in the early Hesperian. The overlying Mg sulfate-bearing unit has both poly- and monohydrated Mg sulfates and is also enriched in iron carbonate of a purity consistent with chemical sedimentation and therefore atmospheric sequestration. A channel-incised canyon within Gediz Vallis and distal alluvial deposits recorded numerous fluvial and debris flow events after the deposition, lithification, and erosion of the clay- and sulfate-bearing units. Bright clasts found in Gediz Vallis canyon are composed of native sulfur. The investigation of the modern atmosphere and environment focused on the influence of the crater and mountain topography and captured high-altitude noctilucent and iridescent clouds. Radiation monitoring now spans an 11-year solar cycle. Rover systems and science instruments remain capable of addressing mission scientific objectives. All ten scientific instruments continue to return high-value data despite degradation of the Chemistry and Camera instrument’s high-voltage system, loss of multispectral imaging capability, and loss of active neutron spectroscopy. The mission has mitigated the loss of redundant brakes on two arm joints, additional wheel wear, and highly reduced capability of the redundant flight computer. Efficiency improvements in rover energy utilization and operations staffing have allowed the mission team to maintain a high level of productivity despite declining rover power generation and funding.

The search for organic matter on Mars has rapidly evolved in the past decade with simple aromatic, S-heterocycles, and aliphatic organic molecules detected in Gale crater. We report the in situ detection of >20 organic molecules from clay-bearing sandstones in the ~3.5-billion-year-old Knockfarrill Hill member of Glen Torridon, Gale crater, by the Sample Analysis at Mars instrument suite onboard the Curiosity rover. These molecules were liberated by the onboard tetramethylammonium hydroxide wet chemistry experiment. Diverse thermochemolysis products, including benzothiophene, methyl benzoate, and single and dicyclic aromatic molecules were released and detected by evolved gas analysis and gas chromatography-mass spectrometry. Results indicate the experiment successfully released molecules preserved in ancient macromolecular or free organic matter within Martian bedrock despite ~3.5 billion years of diagenesis and radiation exposure.

Terrestrial analog environments and their microbial communities are key elements to prepare for the exploration of extraterrestrial planetary environments that potentially sustained, or even may still sustain, the (bio)chemistry necessary for life to emerge. Characterization of terrestrial analogue environments reveals information on the distribution of (i) biomolecules produced by life as we know it and (ii) biomolecules potentially preserved and associated with ancient life (e.g., lipids). We developed and validated a new untargeted method to detect biomolecules that can be applied to both laboratory and in situ-space-based research to extract and detect biomolecules and/or biosignatures using gas chromatography coupled to mass spectrometry (GC-MS). The method consists of a one-pot reaction using a chemical reagent to enhance organic matter extraction and volatilization. The novelty of the study was based on the selection of temperature and time of reactivity to extract the wider range of organic molecules and led to the following optimal sample preparation conditions for nonstandard samples: (i) DMF-DMA at 300 °C for 1-3 min, (ii) MTBSTFA at 150 °C for 1-15 min, or (iii) TMAH at 600 °C for 1-30 s. This approach was first validated through investigation of biomolecules from two pure cultures of extremophiles (Chroococcidiopsis cubana cyanobacteria and Halobacterium salinarum halophilic archaea) to detect them in analog environments (the dry American Pilot Valley desert and the Icelandic Gunnuhver hot spring) that have been explored as analogs of Mars and likely ocean world surfaces, respectively. Our findings showed that this untargeted method inhibits the loss of organic matter and contamination compared to multistep extraction and purification in classical methods and benefit explorations by the current Curiosity rover at Mars. The method can be implemented in portable GC-MS in the field or used by spaceflight instrumentation to detect parts per trillion (ppt) to ppt of wide diversity of (bio)molecules (e.g., amino acids, carboxylic/fatty acids, alcohols/sugars, nucleic acids, etc.) and C,O,N,S-bearing compounds trapped in a geological matrix.

Organic molecules preserved in ancient Martian rocks provide a critical record of the past habitability of Mars and could be chemical biosignatures. Experiments conducted by the Sample Analysis at Mars instrument onboard the Curiosity rover have previously reported several classes of indigenous chlorinated and sulfur-containing organic compounds in Gale crater sedimentary rocks, with chemical structures of up to six carbons. Here, we report the detection of decane (C10H22), undecane (C11H24), and dodecane (C12H26) at the tens of pmol level, released from the Cumberland drilled mudstone sample, using a modified SAM analytical procedure optimized for the detection of larger organic molecules. Laboratory experiments support the hypothesis that the alkanes detected were originally preserved in the mudstone as long-chain carboxylic acids. The origin of these molecules remains uncertain, as they could be derived from either abiotic or biological sources.

The Mars 2020 Perseverance rover has examined and sampled sulfate-rich clastic rocks from the Hogwallow Flats member at Hawksbill Gap and the Yori Pass member at Cape Nukshak. Both strata are located on the Jezero crater western fan front, are lithologically and stratigraphically similar, and have been assigned to the Shenandoah formation. In situ analyses demonstrate that these are fine-grained sandstones composed of phyllosilicates, hematite, Ca-sulfates, Fe-Mg-sulfates, ferric sulfates, and possibly chloride salts. Sulfate minerals are found both as depositional grains and diagenetic features, including intergranular cement and vein- and vug-cements. Here, we describe the possibility of various sulfate phases to preserve potential biosignatures and the record of paleoenvironmental conditions in fluid and solid inclusions, based on findings from analog sulfate-rich rocks on Earth. The samples collected from these outcrops, Hazeltop and Bearwallow from Hogwallow Flats, and Kukaklek from Yori Pass, should be examined for such potential biosignatures and environmental indicators upon return to Earth.

Lipids are a geologically robust class of organics ubiquitous to life as we know it. Lipid-like soluble organics are synthesized abiotically and have been identified in carbonaceous meteorites and on Mars. Ascertaining the origin of lipids on Mars would be a profound astrobiological achievement. We enumerate origin-diagnostic features and patterns in two acyclic lipid classes, fatty acids (i.e., carboxylic acids) and acyclic hydrocarbons, by collecting and analyzing molecular data reported in over 1500 samples from previously published studies of terrestrial and meteoritic organics. We identify 27 combined (15 for fatty acids, 12 for acyclic hydrocarbons) molecular patterns and structural features that can aid in distinguishing biotic from abiotic synthesis. Principal component analysis (PCA) demonstrates that multivariate analyses of molecular features (16 for fatty acids, 14 for acyclic hydrocarbons) can potentially indicate sample origin. Terrestrial lipids are dominated by longer straight-chain molecules (C4-C34 fatty acids, C14-C46 acyclic hydrocarbons), with predominance for specific branched and unsaturated isomers. Lipid-like meteoritic soluble organics are shorter, with random configurations. Organic solvent-extraction techniques are most commonly reported, motivating the design of our novel instrument, the Extractor for Chemical Analysis of Lipid Biomarkers in Regolith (ExCALiBR), which extracts lipids while preserving origin-diagnostic features that can indicate biogenicity.

Sedimentary fans are key targets of exploration on Mars because they record the history of surface aqueous activity and habitability. The sedimentary fan extending from the Neretva Vallis breach of Jezero crater's western rim is one of the Mars 2020 Perseverance rover's main exploration targets. Perseverance spent similar to 250 sols exploring and collecting seven rock cores from the lower similar to 25 m of sedimentary rock exposed within the fan's eastern scarp, a sequence informally named the "Shenandoah" formation. This study describes the sedimentology and stratigraphy of the Shenandoah formation at two areas, "Cape Nukshak" and "Hawksbill Gap," including a characterization, interpretation, and depositional framework for the facies that comprise it. The five main facies of the Shenandoah formation include: laminated mudstone, laminated sandstone, low-angle cross stratified sandstone, thin-bedded granule sandstone, and thick-bedded granule-pebble sandstone and conglomerate. These facies are organized into three facies associations (FA): FA1, comprised of laminated and soft sediment-deformed sandstone interbedded with broad, unconfined coarser-grained granule and pebbly sandstone intervals; FA2, comprised predominantly of laterally extensive, soft-sediment deformed laminated, sulfate-bearing mudstone with lenses of low-angle cross-stratified and scoured sandstone; and FA3, comprised of dipping planar, thin-bedded sand-gravel couplets. The depositional model favored for the Shenandoah formation involves the transition from a sand-dominated distal alluvial fan setting (FA1) to a stable, widespread saline lake (FA2), followed by the progradation of a river delta system (FA3) into the lake basin. This sequence records the initiation of a relatively long-lived, habitable lacustrine and deltaic environment within Jezero crater. Fan-shaped deposits are important exploration targets on Mars because they record the activity of water and conditions suitable for life on the surface. The Mars 2020 Perseverance rover has been exploring an ancient impact crater, named Jezero, since landing on Mars in February 2021. One of the rover's main exploration targets is a fan-shaped deposit of sedimentary rock extending into the crater from the western rim. One Earth year into the rover's mission, Perseverance arrived at the eroded edge of this fan, exploring several outcrops of sedimentary rock, and collecting seven rock samples. This study uses images and data from Perseverance to describe these rocks, called the "Shenandoah" formation, and to determine how they formed. The oldest rocks of the Shenandoah formation contain sand and pebbles that were likely laid down at the edge of an alluvial fan. Next, very fine-grained rocks were deposited in a lake setting. Dipping layers of alternating sand and pebbles represent a change in the local setting and the growth of a delta into a relatively long-lived lake. The rover's observations of the Shenandoah formation show that past conditions in Jezero crater were capable of hosting and preserving signs of ancient life. The Shenandoah formation is a sand-dominated, clastic, sedimentary sequence comprising the lower 25 m of Jezero's western fan This sequence records the transition from an alluvial fan setting to a lacustrine setting, followed by progradation of a river delta This sequence records evidence for a warm, wet, habitable depositional setting with the potential to preserve biosignatures

The search for extraterrestrial extant or extinct life in our Solar System will require highly capable instrumentation and methods for detecting low concentrations of biosignatures. This paper introduces the Supercritical CO2 and Subcritical H2O Analysis (SCHAN) instrument, a portable and automated system that integrates supercritical fluid extraction (SFE), supercritical fluid chromatography (SFC), and subcritical water extraction coupled with liquid chromatography. The instrument is compact and weighs 6.3 kg, making it suitable for spaceflight missions to planetary bodies. Traditional techniques, such as gas chromatography-mass spectrometry (MS), face challenges with involatile and thermally labile analytes, necessitating derivatization. The SCHAN instrument, however, eliminates the need for derivatization and cosolvents by utilizing neat supercritical CO2 with water as an additive. This SFE-SFC-MS method gives efficient lipid biosignature separations with median detection limits of 10 pg/g (ppt) for fatty acids and 50 pg/g (ppt) for sterols. Several free fatty acids and cholesterol were among the detected peaks in biologically lean samples from the Atacama Desert, demonstrating the instrument's potential for in situ life detection missions. The SCHAN instrument addresses the challenges of conventional systems, offering a compact, portable, and spaceflight-compatible tool for the analysis of organics for future astrobiology-focused missions.

From Viking landers to Perseverance rover, Mars has been explored by several in situ missions capable of analyzing organic compounds. Results from the SAM and SHERLOC on Curiosity and Perseverance, respectively, support the detection of lean organic matter (at ppb-ppm levels) in the top surface samples, although the source (s) and preservation mechanisms are still ambiguous. Perseverance is currently exploring a fluvio-lacustrine system at Jezero crater and may explore an ancient volcanic terrain after exiting the crater. As Perseverance would collect samples for potential return to Earth, preparation is needed for sample return efforts through various means including i) the detection of trace organic compounds in various matrices, ii) validation of compounds identified by Martian rovers, and iii) better understanding of mechanisms of their production on Mars. On these returned samples, the community may be able to resolve the timing of organic matter formation and refine hypotheses regarding organic preservation in Martian soils despite the presence of numerous oxidants, salts, and pH-temperature intra and inter-site variations that are less conductive to long-term preservation of organic matter. For instance, acidic conditions promote clay catalyzed isomerization, but seem to benefit for the fatty acid preservation producing organic-salts or favoring salt dissolution in the matrix to protect organic compounds from radiations and water alteration. With a similar aim, we selected samples from Yellowstone National Park hot springs and silica sinters as analogs to locations visited by Curiosity and Perseverance or - in the future - Rosalind Franklin rover. The hot springs in this study developed over hundreds to thousands of years, providing optimal conditions (i.e., matrix composition, temperature, pH) of preservation for organic molecules, extremophilic and mesophilic cells. In our study, the most well preserved organic matter and biosignatures were detected in acidic silica sinters with a surface (water) temperature below 50 degrees C and a minor crystalline phase. The gas chromatography - mass spectrometry molecular analysis revealed a variety of organic compounds we classified as bioindicators (such as amino acids, nucleobases, and sugars), and biosignatures (such as long-chain branched and/or (poly)unsaturated lipids, secondary metabolites involved in the quorum sensing or communication between individuals). We validated with a SAM/MOMA-like benchtop extracting oven the organic matter extraction protocols performed with the SAM experiment. We identified using the different SAM and MOMA extraction protocols (pyrolysis and wet-chemistry derivatizations) eight microbial classes through a unique untargeted environmental metabolomics' method embracing space flight technology constraints. Additionally, we identified one (and likely two) agnostic biosignature(s): i) the concomitance of some elements and organic compounds in the analogs (correlation of organic matter elements: C, N, S, P and organic molecules colocated with essential biological elements: Fe, Mg, V, Mn and non-essential biological elements concentrated by

Sulfur plays a major role in martian geochemistry and sulfate minerals are important repositories of water. However, their hydration states on Mars are poorly constrained. Therefore, understanding the hydration and distribution of sulfate minerals on Mars is important for understanding its geologic, hydrologic, and atmospheric evolution as well as its habitability potential. NASA's Perseverance rover is currently exploring the Noachian-age Jezero crater, which hosts a fan-delta system associated with a paleolake. The crater floor includes two igneous units (the Seitah and Maaz formations), both of which contain evidence of later alteration by fluids including sulfate minerals. Results from the rover instruments Scanning Habitable Environments with Raman and Luminescence for Organics and Chemistry and Planetary Instrument for X-ray Lithochemistry reveal the presence of a mix of crystalline and amorphous hydrated Mg-sulfate minerals (both MgSO4 center dot[3-5]H2O and possible MgSO4 center dot H2O), and anhydrous Ca-sulfate minerals. The sulfate phases within each outcrop may have formed from single or multiple episodes of water activity, although several depositional events seem likely for the different units in the crater floor. Textural and chemical evidence suggest that the sulfate minerals most likely precipitated from a low temperature sulfate-rich fluid of moderate pH. The identification of approximately four waters puts a lower constraint on the hydration state of sulfate minerals in the shallow subsurface, which has implications for the martian hydrological budget. These sulfate minerals are key samples for future Mars sample return. The history of water on Mars is a puzzle that is of interest to scientists as well as the general public. Mars currently has water in the form of ice at the poles, trace amounts of gas in the atmosphere, and an unknown amount beneath the surface as ground water, bound in minerals, and in ice. However, there is strong evidence that ancient Mars may have had long-lived streams, rivers, and lakes. There is still much to learn about what Mars was like and how it transformed over time. One approach is to study the inventory of water at different times. In this work, we report the presence of hydrated magnesium sulfate (similar to Epsom salts) and dehydrated calcium sulfate that were formed by water flowing through cracks in volcanic rocks at the bottom of the 3.8-billion-year-old Jezero crater. These hydrated minerals trap water within themselves and record the history of how and when they formed. Returning samples of these minerals to Earth would allow researchers to explore the history of Mars' water and climate, and possibly evidence of ancient life with the most sensitive instruments possible. Sulfate phases detected by Scanning Habitable Environments with Raman and Luminescence for Organics and Chemistry and PIXL in igneous units consists of crystalline/amorphous Mg-sulfate minerals with 3-5 waters and anhydrous Ca-sulfate minerals Hydration of sulfate minerals sets a lower constraint on how much subsurface water is stored in sulfate minerals The sulfate minerals of Jezero crater floor were deposited in moderate pH, likely at low temperature, and during several episodes

The Mars 2020 Perseverance rover discovered fine-grained clastic sedimentary rocks in the "Hogwallow Flats" member of the "Shenandoah" formation at Jezero crater, Mars. The Hogwallow Flats member shows evidence of multiple phases of diagenesis including Fe/Mg-sulfate-rich (20-30 wt. %) outcrop transitioning downward into red-purple-gray mottled outcrop, Fe/Mg clay minerals and oxides, putative concretions, occasional Ca sulfate-filled fractures, and variable redox state over small (cm) spatial scales. This work uses Mastcam-Z and SuperCam instrument data to characterize and interpret the sedimentary facies, mineralogy and diagenetic features of the Hogwallow Flats member. The lateral continuity of bedrock similar in tone and morphology to Hogwallow Flats that occurs over several km within the western Jezero sedimentary fan suggests widespread deposition in a lacustrine or alluvial floodplain setting. Following deposition, sediments interacted with multiple fluids of variable redox state and salinity under habitable conditions. Three drilled sample cores were collected from this interval of the Shenandoah formation as part of the Mars Sample Return campaign. These samples have very high potential to preserve organic compounds and biosignatures. Drill cores may partially include dark-toned mottled outcrop that lies directly below light-toned, sulfate-cemented outcrop. This facies may represent some of the least oxidized material observed at this interval of the Shenandoah formation. This work reconstructs the diagenetic history of the Hogwallow Flats member and discusses implications for biosignature preservation in rock samples for possible return to Earth.

Aromatic organic salts such as benzoates or phthalates may be widespread degradation products of organic molecules at the surface of Mars. The low volatility of these aromatic carboxylic salts could have compromised their detection through thermal extraction in situ analyses such as those performed by the Viking landers. However, over the years, analytical chemistry laboratories on board current and future Martian surface missions, such as the Sample Analysis at Mars (SAM) instrument suite on board the Curiosity rover and the Mars Organic Molecule Analyzer (MOMA) instrument of the Rosalind Franklin ExoMars rover, respectively, have evolved. These instruments have improved in efficiency to detect refractory and polar organic compounds, which could influence the detection of aromatic organic salts. To evaluate the capability of detecting aromatic organic salts on Mars with in situ instruments, we performed laboratory experiments under Viking, SAM, and MOMA-like Gas Chromatography-Mass Spectrometry (GC-MS) conditions with two carboxylic acid/salt couples: phthalic acid/ calcium phthalate and benzoic acid/calcium benzoate. We studied the behavior and signatures of both molecular forms when using pyrolysis and derivatization experiments and the implications of these results in the search for organic molecules on Mars. This study showed that the Viking experiments could not have detected the presence of aromatic carboxylic salts in Martian samples because its maximum pyrolysis temperature was too low (500 C). However, we showed that calcium benzoate and calcium phthalate, despite their refractory nature, could be identified indirectly through the detection of thermal and derivatized degradation products, both with SAM and MOMA. No conclusive proof of the presence of these aromatic organic salt species have been found in the SAM in situ data but given the right instrumental set-up they could be detected if present. The conclusions of this work raise essential questions on the detectability of refractory molecules, the analytical efficiency of flight instruments, and the interpretation of in situ data.

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.

The presence and distribution of preserved organic matter on the surface of Mars can provide key information about the Martian carbon cycle and the potential of the planet to host life throughout its history. Several types of organic molecules have been previously detected in Martian meteorites 1 and at Gale crater, Mars 2 – 4 . Evaluating the diversity and detectability of organic matter elsewhere on Mars is important for understanding the extent and diversity of Martian surface processes and the potential availability of carbon sources 1 , 5 , 6 . Here we report the detection of Raman and fluorescence spectra consistent with several species of aromatic organic molecules in the Máaz and Séítah formations within the Crater Floor sequences of Jezero crater, Mars. We report specific fluorescence-mineral associations consistent with many classes of organic molecules occurring in different spatial patterns within these compositionally distinct formations, potentially indicating different fates of carbon across environments. Our findings suggest there may be a diversity of aromatic molecules prevalent on the Martian surface, and these materials persist despite exposure to surface conditions. These potential organic molecules are largely found within minerals linked to aqueous processes, indicating that these processes may have had a key role in organic synthesis, transport or preservation.

The Sample Analysis at Mars (SAM) instrument aboard the Curiosity Rover at Gale crater can characterize organic molecules from scooped and drilled samples via pyrolysis of solid materials. In addition, SAM can conduct wet chemistry experiments which enhance the detection of organic molecules bound in macromolecules and convert polar organic compounds into volatile derivatives amenable to gas chromatography-mass spectrometry analyses. Specifically, N-tert-butyldimethylsilyl-N-methyltrifluoroacetamide (MTBSTFA) is a silylation reagent whereas tetramethylammonium hydroxide (TMAH) is a thermochemolysis methylation reagent. Shortly after arriving at Mars, the SAM team discovered that at least one of the MTBSFTA cups was leaking, contributing to a continuous background inside SAM with the potential to interfere with future TMAH reactions. Therefore, here we characterized possible interactions between the two reagents to determine byproducts and implications for the detection of indigenous organics. SAM-like pyrolysis experiments supplemented with flash pyrolysis were accordingly conducted with fragments of the Murchison meteorite as a reference for exogenous organic matter delivered to Mars. Flash TMAH experiments yielded various aromatic acids, dicarboxylic acids, and amino acids while SAM-like pyrolysis presented mixtures of methylated and non-methylated compounds due to decreased reaction efficiency at slower ramp rates. All experiments in the presence of simulated MTBSTFA vapor produced pervasive silylated byproducts which co-elute and obscure the identification of Murchison-derived compounds. Despite challenges, a significant diversity of pyrolyzates and TMAH derivatives could still be identified in flash pyrolysis in presence of MTBSTFA. However SAM-like experiments with TMAH and MTBSTFA are hindered by both decreased methylation yields and additional co-eluting compounds.