Abstract The outer slopes of the western Jezero crater rim are hypothesized to expose sections of Early‐ to Pre‐Noachian crust uplifted by the Jezero impact, providing an excellent opportunity to investigate the earliest geologic processes active on terrestrial planets. Here, we analyze a ∼75‐m‐thick layered bedrock succession explored by the Perseverance rover on the outer Jezero crater rim, informally named the Broom Point member of the Witch Hazel Hill formation, to reconstruct its emplacement processes. Layering is steeply inclined and offset by rim‐transverse faults, consistent with uplifted pre‐impact target rock of Noachian age. Lithofacies include clast‐ and matrix‐supported melt‐bearing breccias, a planar‐laminated to potentially cross‐stratified facies containing candidate accretionary lapilli, and an unstratified to weakly laminated facies, with angular silt‐sized grains. These lithofacies are interpreted as the products of concentrated, ground‐hugging density flows, dilute surges and fall produced by explosive volcanism or impacts. However, millimeter‐ to sub‐millimeter‐diameter glassy spherules with vesicular, fluidal and agglutinated morphologies are also present throughout the section, including as a ∼20‐cm‐thick framework‐supported layer. Their morphologies, compositions and distributions appear inconsistent with diagenetic or volcanic spherules, and instead resemble spherules produced by impacts, suggesting that the lithofacies of the Broom Point member were predominantly emplaced as impactites. Geological cross sections and stratigraphic columns were constructed through the unit, and allowed us to reconstruct the depositional evolution of these deposits. The section preserves repeated phases of flow and fall, and intercalated proximal and distal ejecta, suggesting that Mars' ancient stratified crust preserves evidence for repeated impacts early in its history.

Martian fluvial valleys provide evidence for the surface flow of liquid water, making them a key target for rover-based investigations of ancient habitability. The Mars 2020 Perseverance rover spent similar to 85 sols exploring the Bright Angel formation, exposed across the floor of Neretva Vallis: the western inlet channel of Jezero crater. This study documents the sedimentology and stratigraphy of the Bright Angel formation to reconstruct its depositional setting. The unit preserves a concave-up bedding structure consistent with a young channel-fill deposit, rather than an older unit exposed by incision of Neretva Vallis. The lower stratigraphy displays a fining-up sequence from coarse-grained sediments up to pebble-conglomerates (the Tuff Cliff member) into a >= 10-m-thick succession of laminated mudstone (the Walhalla Glades member), interpreted as a transgressive sequence recording the onset of lacustrine conditions in Neretva Vallis. Lenses of matrix-supported granule-conglomerate adjacent to the valley wall (the Fern Glen Rapids member) may preserve locally derived debris flows entering the lake. These are overlain by a polymict, matrix-supported, boulder-conglomerate (the Mount Spoonhead member), interpreted as a high-energy debrite derived from the watershed. The sequence is capped by cross-stratified sediments (the Serpentine Rapids member), preserving lake margin deposits. The Bright Angel lacustrine sequence occurs similar to 10-50 m higher in elevation than the lake level anticipated for the Jezero western delta, requiring an additional period of lacustrine activity. The structure and spatial distribution of the unit leads us to propose that a late-stage blockage of Neretva Vallis may have facilitated the formation of a perched, valley-confined lake upstream.

The Perseverance rover landed in Jezero crater on Mars, which once contained a lake of liquid water. We report the rock properties encountered by Perseverance during a 10-kilometer traverse extending over 400 meters in elevation, from beneath Jezero's western sedimentary fan to the upper crater rim. These rocks consist of coarse-grained olivine, magnesium and iron carbonates, silica, and phyllosilicates, including some of the oldest materials exposed within Jezero. We infer that these rocks formed by olivine accumulation in an igneous system of layered intrusions, followed by exposure to water and carbon dioxide, which caused extensive carbonation of the silicate minerals. Aqueous alteration was more pronounced at lower elevations. Higher-elevation exposures on the crater rim appear similar to olivine-rich rocks distributed over the wider Nili Fossae region.

Abstract The Margin Unit, explored by the Mars 2020 Perseverance rover in Jezero crater, is a distinct olivine‐rich lithology whose origin has remained unresolved due to extensive alteration and lack of preserved primary textures. While hypotheses for its formation range from sedimentary to igneous, recent geochemical data allow for quantitative testing of these scenarios. To test the igneous hypothesis, we applied Markov Chain Monte Carlo simulations with MELTS thermodynamic modeling to assess whether the observed olivine and spinel compositions in the Margin Unit are consistent with igneous fractional crystallization. Our simulations reproduce the observed systematic increase in spinel TiO 2 /Cr 2 O 3 with decreasing olivine forsterite content, a pattern difficult to reconcile with sedimentary mixing processes, providing strong evidence for an igneous origin for the Margin Unit. Furthermore, continuing evolution of the same magma leads to coexisting olivine and clinopyroxene compositions that suggest a genetic link between the Margin Unit and the crater floor olivine‐rich unit, Séítah, pointing toward the existence of an extensive igneous complex within Jezero crater. Modeled magma compositions for the Margin Unit are comparable to the parental melt compositions of the chassignite group of Martian meteorites, implying conditions necessary to produce chassignite‐like melts were already established early in Noachian Mars.

Magnesite (MgCO3) is a magnesium carbonate mineral that records the aqueous environmental conditions of its formation. On Earth, magnesite forms in metamorphic, diagenetic or pedogenic environments, and distinguishing between these environments is critical for understanding the nature of fluid chemistry during magnesite precipitation. Magnesite has been identified across the Nili Fossae region on Mars and in Jezero crater by orbital spectroscopic observations and in-situ instrument observations acquired with the Perseverance rover. Core samples with magnesite may provide constraints on the chemical conditions of the ancient aqueous environments of Jezero crater, and may also be an important phase to target for the preservation of potential biosignatures. This work explores pedogenic magnesite phases found in Vertisols of the Kunwarara Mine, Australia, as a potential analog environment for magnesite identified within Jezero crater, Mars. We document the principal microtextures and investigate the processes involved in the formation and diagenesis of magnesite nodules and magnecretes. Kunwarara magnesite nodules show complex textural relationships at the outcrop scale, and these relationships extend to the nanoscale in samples that were collected along a depth profile. By characterizing textural and chemical variations in magnesite at different scales, this work reveals a continuum between diagenetic and pedogenic magnesites. It illustrates that diagenetic reactions produce magnesite from ascending Mg²⁺-rich groundwater interacting with detrital phases; groundwater interaction with descending meteoric solutions result in the conversion of magnesite into authigenic dolomite. Overall, this work shows how the superposition of textures and elemental compositions permits reconstruction of pedogenic processes leading to magnesite authigenesis.

Using a Raman spectrometer onboard the Perseverance rover, we report the heterogeneous distribution of organic carbon within mudstones located in an ancient river valley on Mars. Measurements of two mudstones show hundreds of organic detections, making this the most robust organic detection in Jezero crater thus far, and, to our knowledge, the only detection of macromolecular carbon on a natural rock surface on Mars. Spectra of the interior of one rock reveal an association of organics with secondary carbonate and sulfate minerals, whereas another rock exhibits an association of organics with primary silicate-dominated matrix. Although in situ Raman analyses cannot determine whether these organics denote abiotic or biotic sources, the organic association with both depositional and diagenetic minerals and the detection of organics on the martian surface suggests that the organics observed ubiquitously at the Bright Angel outcrop may be resistant to radiation and oxidation or have been relatively recently exposed.

Mars Sample Return (MSR) has been the highest flagship mission priority in the last two Planetary Decadal Surveys of the National Academies of Science, Engineering, and Medicine (hereafter, “the National Academies”) and was the highest priority flagship for Mars in the Decadal Survey that preceded them. This inspirational and challenging campaign, like the Apollo program’s returned lunar samples, will potentially revolutionize our understanding of Mars and help inform how other planets are explored. MSR’s technological advances will keep the NASA and European Space Agency at the forefront of planetary exploration, and data on returned samples will fill knowledge gaps for future human exploration. Investigations of the ancient rocks collected in and around Jezero crater, as well as samples of the regolith and atmosphere, will be fundamentally different in scope, depth, and certainty from what is achievable with spaceborne observations. Returned Mars samples can address critical science issues including the discovery and characterization of ancient extraterrestrial life, prebiotic organic chemistry, the history of habitable planetary environments, planetary geological, geochemical, and geophysical evolution, orbital dynamics of bodies in the early Solar System, and the formation and evolution of atmospheres.

Magnesium carbonates in surficial environments act as CO2 sinks and can record aspects of the palaeohydrological cycles on Earth and Mars. In natural environments, magnesium carbonates can be intimately intermixed at the micrometer scale with complex assemblages of other non-carbonate minerals. To better determine magnesium carbonate composition in complex samples and minimize contamination from secondary Fe/Mn-oxides/hydroxides, we developed and assessed methods for sample cleaning, selective digestion, and quadrupole inductively coupled plasma mass spectrometry to measure the trace and minor elemental composition. By pre-cleaning and selectively digesting carbonate, we identified previously unrecognized geochemical trends in magnesite +/- dolomite nodules and their host fluvial sediments collected along a depth profile at the Kunwarara magnesite mine, Queensland, Australia. In particular, Ce anomalies in magnesite diminishes with depth coincident with decreasing abundances of authigenic Fe/Mn-oxides/hydroxide minerals in the host sediments. These results reveal how the magnesium carbonates capture interactions between the ascending groundwaters and descending surface waters. We further demonstrate the value of magnesium carbonate-specific trace element data with reanalysis of previously published ion microprobe data from Martian meteorite ALH84001, which also shows Ce fractionation. Accurate mineral-specific trace and minor element measurements in Earth and Martian magnesium carbonate samples improve our understanding of the timing and identities of carbonate mineral-forming reactions that occurred on both planets.

The Mars 2020 Perseverance rover landing site is located within Jezero crater, a  $\sim50~\mbox{km}$ diameter impact crater interpreted to be a Noachian-aged lake basin inside the western edge of the Isidis impact structure. Jezero hosts remnants of a fluvial delta, inlet and outlet valleys, and infill deposits containing diverse carbonate, mafic, and hydrated minerals. Prior to the launch of the Mars 2020 mission, members of the Science Team collaborated to produce a photogeologic map of the Perseverance landing site in Jezero crater. Mapping was performed at a 1:5000 digital map scale using a 25 cm/pixel High Resolution Imaging Science Experiment (HiRISE) orthoimage mosaic base map and a 1 m/pixel HiRISE stereo digital terrain model. Mapped bedrock and surficial units were distinguished by differences in relative brightness, tone, topography, surface texture, and apparent roughness. Mapped bedrock units are generally consistent with those identified in previously published mapping efforts, but this study’s map includes the distribution of surficial deposits and sub-units of the Jezero delta at a higher level of detail than previous studies. This study considers four possible unit correlations to explain the relative age relationships of major units within the map area. Unit correlations include previously published interpretations as well as those that consider more complex interfingering relationships and alternative relative age relationships. The photogeologic map presented here is the foundation for scientific hypothesis development and strategic planning for Perseverance’s exploration of Jezero crater.

We present a step-heat method for isolating cosmogenic 3He (3Hec) from mantle He in olivine xenocrysts to date the eruption of four of the morphologically youngest nephelinite lava flows from Volcano Mountain (VM), the youngest cone in the Fort Selkirk volcanic field in Yukon, Canada. In these olivines, the standard procedure of powdering grains to <30 µm failed to effectively remove mantle helium prior to fusion: samples from four different flows yielded unusually high powder fusion 4He concentrations of 1.8 to 6.3 pmol g−1, with 3He/4He ratios of 7.9 to 9.6 RA. When combined with the 3He/4He ratios obtained by crushing (average 8.1±0.2 RA), these measurements yield Holocene cosmogenic exposure ages but with very large uncertainties arising from the large mantle 3He correction. The inability to effectively isolate 3Hec from these samples likely arises from the survival of small (≪30 µm) fluid inclusions hosting mantle He through the powdering step. The presence of such unusually small fluid inclusions may relate to the origin of the olivines as disaggregated peridotite xenoliths rather than the more commonly analyzed olivine phenocrysts. We circumvented this problem by step-heating powdered olivine in steps of 800, 1000, and 1400 °C. Helium isotopic systematics indicate that 70 %–90 % of 3Hec was released in the low temperature step, and the rest was released in the middle temperature step. By the highest temperature step, the released He had a mantle-like 3He/4He ratio. Combining results from the step-heating and crush–fusion methods, we determined that the four Volcano Mountain lava flows erupted approximately coevally, at 10.5±1.7 ka.

Terrestrial supergene goethites of known ages record information on changes in weathering conditions through time. Here we present a database of (U-Th) / He ages and U and Th contents of goethites from different weathering environments around the globe. By consolidating published data collected at four different laboratories and unpublished data collected at the Noble Gas Laboratory at Caltech, we aim to give an overview of the work carried out by geochronologists and geochemists in the last 20 years. The database contains 2609 (U-Th) / He ages of goethites from 10 countries; most of the ages come from Brazil and Australia.

NASA’s Mars 2020 mission has initiated collection of samples from Mars’ Jezero Crater, which has a wide range of ancient rocks and rock types from lavas to lacustrine sedimentary rocks. The Mars Sample Return (MSR) Campaign, a joint effort between NASA and ESA, aims to bring the Perseverance collection back to Earth for intense scientific investigation. As the first return of samples from a habitable world, there are important challenges to overcome for the successful implementation of the MSR Campaign from the point of sample collection on Mars to the long-term curation of the samples on Earth. In particular, the successful execution of planetary protection protocols adds well-warranted complexity to every step of the process from the two MSR Program flight elements to the ground element at the sample receiving facility (SRF). In this contribution, we describe the architecture of the MSR Campaign, with a focus on infrastructure needs for the curation (i.e., the clean storage, processing, and allocation) of pristine Martian samples. Curation is a science-enabling and planetary protection-enabling activity, and the curation practices described in this contribution for the SRF and any long-term curation facility will enable the sample safety assessment, initial scientific investigations of the samples, and establish the MSR collection as a scientific resource that will enable generations of science and discovery through studies of the returned Mars samples. The planetary protection and curation processes established for MSR will provide critical insights into potential future sample return missions from other habitable worlds like Enceladus and Europa.

Arctic sea-ice loss affects biological productivity, sustenance in coastal communities, and geopolitics. Forecasting these impacts requires mechanistic understanding of how Arctic sea ice responds to climate change, but this is limited by scarce long-term records. We present continuous 30,000-year reconstructions of sea-ice coverage from the Arctic Ocean based on measurements of two isotopes, thorium-230 and extraterrestrial helium-3, whose burial ratio changes with sea-ice coverage. We found that the central Arctic was perennially covered by sea ice during the last glaciation. Sea-ice cover retreated during the deglaciation approximately 15,000 years ago, culminating in seasonal sea-ice coverage in the warm early Holocene, before ice coverage increased into the late Holocene. Sea-ice changes closely correlate with biological nutrient consumption, supporting projections of a nutrient-starved central Arctic Ocean with continued sea-ice loss.

The NASA Mars 2020 Perseverance Rover Mission has collected samples of rock, regolith, and atmosphere within the Noachian-aged Jezero Crater, once the site of a delta-lake system with a high potential for habitability and biosignature preservation. Between sols 109 and 1,088 of the mission, 27 sample tubes have been sealed, including witness tubes. Each sealed sample tube has been collected along with detailed documentation provided by the Perseverance instrument payload, preserving geological and environmental context. Samples representative of the stratigraphy within each of four campaigns have been collected: samples from the Crater Floor Campaign represent a suite of potentially petrogenetically related igneous rocks displaying variable degrees of aqueous alteration; samples from the Fan Front record fluvial to deltaic sediments formed by the transport and deposition of materials from the Jezero watershed; regolith samples from the Fan Front preserve material possibly representative of global dust as well as diverse, locally derived clasts; Upper Fan samples record the latest stages of aqueous activity within Jezero; and samples from the Margin Campaign preserve lacustrine, littoral, or possibly igneous processes that may have occurred early in the history of the crater. Along with anticipated samples from the older rocks within the rim of Jezero Crater, Perseverance promises to deliver a suite of samples preserving a diversity of formation environments and ages. Upon return to Earth and analysis in terrestrial laboratories, these samples would address longstanding questions pertaining to the geologic evolution of Mars, its habitability, and the potential for life outside the Earth.

The Mars Sample Return (MSR) Campaign aims to collect and transport to Earth samples of martian atmosphere contained in sample tubes onboard the Mars 2020 rover, Perseverance. Understanding and mitigating the potential impact of terrestrial noble gas contamination is critical to ensuring the scientific integrity of these samples. This study quantifies the desorption of terrestrial argon (40Ar) and xenon (129Xe) from the interior of a flight-like Mars 2020 sample tube under high vacuum and provides critical insights into the potential contamination risks for returned martian atmospheric samples. Our results show that desorption rates decrease exponentially with time over ∼19 months and that desorbed terrestrial 40Ar and 129Xe will contribute less than 0.01% and 0.1%, respectively, to the martian noble gas inventory within a sealed sample tube that consists of martian atmosphere at a pressure of ∼7 mbar. This study suggests that the Mars 2020 sample tubes are suitable for capturing and preserving atmospheric samples from Mars for future scientific investigation.

Northwest Africa 13134 is a coarse‐grained gabbro with an oxygen isotopic composition consistent with a Martian origin and is classified as an enriched shergottite based on its bulk trace element abundances and bulk La/Yb ratio of 1.53. The meteorite is composed of a framework of large pyroxene rods up to 6 mm in longest dimension (64% by area) with interstitial maskelynite (formerly plagioclase; 28% by area). Minor phases include merrillite and apatite, Fe‐Ti oxides, and Fe‐sulfides; trace phases such as baddeleyite, tranquillityite, fayalitic olivine, silica, and a felspathic phase are observed in evolved mesostasis pockets and partially crystallized magmatic inclusions in minerals. Individual pyroxene rods display a distinctive patchy Ca zoning pattern of juxtaposed low‐Ca (pigeonite) and high‐Ca (augite) patches with a common crystallographic orientation indicating epitaxial growth. Low‐Ca pigeonite is the volumetrically dominant pyroxene phase (~70% of exposed pyroxene) and was the primary liquidus phase, followed closely by augite. Plagioclase crystallized along with the other minor phases from the residual melt between cumulus pyroxene rods. Pyroxenes display ubiquitous exsolution lamellae with typical widths and spacings of 1–2 μm. Sulfide grains are characterized by flame‐shaped lamellar intergrowths of hexagonal pyrrhotite (Fe 0.90 S) and slightly metal‐deficient pyrrhotite (Fe 0.98 S), along with minor pentlandite and chalcopyrite. The pyroxene and sulfide microtextures suggest that the gabbro experienced slow and protracted subsolidus cooling. Ilmenite‐oxide pairs imply an oxygen fugacity of ~1 log unit below the fayalite–magnetite–quartz buffer at a closure T ≈ 875°C. Collectively, the texture and bulk composition suggest that Northwest Africa 13134 represents a slowly cooled and coarsely crystalline portion of a solidified magma body similar to the source of the enriched basaltic shergottites. Magnetite occurs locally as veins crosscutting pyrrhotite grains and in oxide–phosphate symplectites observed at merrillite–apatite phase boundaries. The presence of magnetite in the sample suggests that at various stages of cooling, the gabbro interacted with relatively oxidized fluids, which could be of deuteric or exogeneous origin. A cosmic‐ray exposure age of 2.8–4.0 Ma was calculated based on 3 He measured in pyroxene grain separates and overlaps with other shergottites. Finally, we present the first bulk uranium isotope measurement of a Martian meteorite: δ 238 U = −0.22 ± 0.10‰ and δ 234 U sec = +9.57 ± 0.35‰. These values indicate slight excesses in heavy U but overlap with the distribution of U isotope compositions of the Earth and other solar system materials.

A major objective of the Mars 2020 mission is to sample rocks in Jezero crater that may preserve organic matter for later return to Earth. Using an ultraviolet Raman and luminescence spectrometer, the Perseverance rover detected luminescence signals with maximal intensities at 330 to 350 nanometers and 270 to 290 nanometers that were initially reported as consistent with organics. Here, we test the alternative hypothesis that the 330- to 350-nanometer and 270- to 290-nanometer luminescence signals trace Ce3+ in phosphate and silicate defects, respectively. By comparing the distributions of luminescence signals with the rover detections of x-ray fluorescence from P2O5 and Si-bearing materials, we show that, while an organic origin is not excluded, the observed luminescence can be explained by purely inorganic materials. These findings highlight the importance of eventual laboratory analyses to detect and characterize organic compounds in the returned samples.