Athanasios Klidaras

The Mars 2020 rover is currently traversing the western rim of Jezero, a Middle to Late Noachian‐aged crater formed by an impactor that struck the northwest edge of Isidis Planitia (hereafter referred to as the Isidis basin) on Mars. Previous studies suggest that pre‐Isidis basin and Noachian outcrops are preserved throughout this region; however, the nature of these exposures in the Jezero crater rim is unclear. It has been hypothesized that crater‐forming processes should expose these ancient crustal rocks in the Jezero crater rim—presenting a unique opportunity to explore ancient Mars outcrops that are otherwise typically buried by younger units. Jezero's rim has undergone extensive erosion and modification since its formation ∼3.9 billion years ago. To investigate these ancient lithologies, the Mars 2020 Science Team produced a 1:2500 scale geologic map and interpreted a bedrock map of the ∼14.5 × 3.5 km area around the western Jezero crater rim. We identified, mapped, and defined nine bedrock units on Jezero crater's rim to make connections to regional geologic units and identify deposits or features unique to Jezero crater. We found that the rim likely preserves a record of pre‐Isidis bedrock, the Isidis and Jezero impacts, and post‐impact geologic processes. We also observed candidate megabreccia, hydrothermal ridges, and regional volcanics that may be targets for future rover‐based investigations. Our results show that in situ investigation of pre‐Isidis and Noachian‐aged lithologies preserved on the rim will provide insight into the nature of Mars' early crustal formation and cratering processes.

To meet the objectives of the many robotic and human missions planned for the Moon in the coming decade, new scientific instruments are currently under development. Laser‐induced breakdown spectroscopy (LIBS) is a robust technique for quantifying elemental abundances by focusing a pulsed laser to generate a plasma and collecting its emission spectrum. LIBS is particularly well suited for lunar applications because of its ability to detect key light elements, including hydrogen, an important resource for future human exploration. LIBS mapping is an emerging approach in which dense, regularly spaced grids comprising hundreds of analysis points are acquired, rather than sparse raster measurements. This technique enables the delineation of clasts in brecciated rocks, identification of chemical zoning, and quantification of bulk chemistry over the scanned area. In this work, a comprehensive quantitative LIBS calibration was developed under vacuum using lunar‐relevant geologic standards. This calibration was then applied to produce the first LIBS elemental map (6 × 6 mm using 150 micron raster spacing) of a lunar meteorite in lunar atmospheric conditions, with Laâyoune 002 as the target of the study. The derived major‐element chemistry is consistent with a feldspathic breccia dominated by Ca‐rich plagioclase (anorthite) with minor mafic clasts. The scanned area yields an estimated normative plagioclase abundance of 86%–89%, comparable to other feldspathic lunar meteorites thought to sample nearly pure lunar highlands material. These results demonstrate the utility of LIBS mapping for investigating sub‐millimeter‐scale chemical heterogeneity in lunar rocks and highlight its potential for future lunar surface missions.

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.

During its exploration of Neretva Vallis in Jezero crater, NASA's Mars 2020 Perseverance rover examined Mount Washburn, a set of light‐toned sedimentary mounds that exhibited a diverse array of float rocks. Mastcam‐Z visible/near‐infrared (VISIR) multispectral imaging revealed five spectral types dominated by low‐calcium pyroxene‐bearing rocks, although olivine‐bearing and ferric materials were also identified. SuperCam VISIR point spectroscopy of eight targets noted four spectral groups, including those with low‐Ca pyroxene, hydrated alteration products, and phyllosilicates. SuperCam laser‐induced breakdown spectroscopy data confirmed a wide compositional array among the targets. Overall, these data spanned much of the spectral and compositional range in rocks observed by Perseverance through Sol 1348, with no major outliers, although some rock textures were unique. The rock diversity at Mount Washburn is among the most extensive observed in situ at a single site on Mars, pointing to a multifaceted geological history. Bedrock beneath Mount Washburn exhibited high silica and iron content, closely resembling materials from the nearby Bright Angel sedimentary units and suggesting a possible stratigraphic link. Some geological models of Neretva Vallis are consistent with the idea that Bright Angel‐like materials may have formed the foundation of Mount Washburn, with subsequent deposition of cobbles and boulders as late‐stage fluvial events. These findings suggest that similar rocks—and possibly their source regions—may be encountered during future exploration of the Jezero crater rim and intracrater plains. Such materials would likely sample the olivine/carbonate‐bearing regional units and/or ancient Noachian basement, reflecting the rich geological complexity of the Neretva Vallis watershed.

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.

Jezero crater is located in Mars’ largest olivine-rich region, which is variously interpreted as lava flows, intrusive plutons, clastic sediments, or pyroclastics. In Jezero crater, several olivine-rich units have been investigated by the Perseverance rover, including an olivine cumulate in the crater floor (Séítah formation) and the enigmatic “Margin Unit”; an olivine- and carbonate-rich unit commonly interpreted as either a lake shore deposit or a local expression of the regional olivine-carbonate unit. We developed a method incorporating X-ray diffraction energy and spatial information to accurately determine the forsterite content (molar percentage of MgO/(MgO+FeOT)) of monocrystalline olivine encountered by Perseverance . Forsterite content in clastic sediments of the western Jezero fan indicate multiple olivine sources. In contrast, forsterite content analysed in the Margin Unit is similar to the Séítah formation, suggesting that at least some of the Margin Unit may represent an altered igneous cumulate with similar origins to the Séítah formation.

Olivine‐ and carbonate‐bearing rocks are key exploration targets on Mars because of the information they can provide about magma evolution and source characteristics, implications for surface water availability and climate, and their biosignature preservation potential. The NASA Mars 2020 Perseverance rover has explored olivine‐ and carbonate‐bearing rocks in the Séítah formation and the Margin unit within Jezero crater, thought to be part of the largest exposures of such rocks on Mars. This study uses Mastcam‐Z red‐green‐blue (RGB) and multispectral (442–1,022 nm) data to assess and compare the Séítah formation and the Margin unit, constrain their potential origins, and determine whether they might share a genetic relationship. Mastcam‐Z data shows that the Séítah formation is a series of layered, olivine‐dominated crystalline igneous rocks, and that the Issole member is more altered and/or more evolved than the Bastide and Caille members, consistent with data from other Perseverance instruments. In the more carbonate‐bearing Margin unit, pervasive alteration complicates the interpretation of its original emplacement mechanism. The unit may be consistent with an igneous deposit(s) that has experienced varying amounts of aqueous alteration and, in the East Margin, sedimentary reworking, possibly related to a past lake in Jezero. Margin unit rocks found at higher elevations on the inner rim are most similar to the Séítah formation and may represent a relatively unaltered component of the Margin unit. The extent to which local versus regional processes have formed olivine and carbonate rocks in this area of Mars remains an important area of study.

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 ∼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 ∼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.

Martian carbonate‐bearing rocks are compelling targets for exploration because they preserve detailed records of past aqueous processes, climate, and habitability. The Margin unit in Jezero crater is a distinct olivine‐ and carbonate‐bearing unit stratigraphically underlying the western fan, lining the inner margin of the western crater rim and has a contested origin. Perseverance spent ∼350 sols investigating the unit as part of its fourth mission campaign, aiming to constrain its origin, alteration history and biosignature preservation potential. This study reports on the lithofacies and stratigraphy of the unit by analyzing Mastcam‐Z mosaics and derived 3D outcrop models, supplemented by long‐distance SuperCam observations and detailed textural analyses from SHERLOC WATSON and ACI images. We find that the Margin unit comprises two distinct sub‐units. The Eastern Margin Unit (EMU) comprises well‐stratified, low‐angle basinward‐, rimward‐ and sub‐horizontally inclined medium‐grained sandstones which preserve angular to rounded grains, occasional cross‐stratification, convex‐up bedding, and erosion surfaces. The Western Margin Unit (WMU) comprises distinctly structureless to decimeter‐scale parallel‐layered rocks which drape the crater rim and are inclined into the crater. The origin of the WMU is uncertain but may be most consistent with a variably carbonated olivine cumulate. The favored depositional model for the EMU is a lacustrine shore zone environment where sediments derived from the adjacent WMU have been locally reworked by wave action along a paleoshoreline at around –2,400 m elevation. These observations suggest that the Margin unit preserves diverse subsurface and surface aqueous environments and further extends the habitability window at Jezero crater.