Justin N. Maki

The Mars 2020 Perseverance rover mission spent ∼250 sols investigating the Otis Peak formation (OPfm), a sequence of rocks containing the youngest recorded interval of sediment deposition via aqueous activity on Jezero crater’s western fan. This study uses orbiter and rover observations to interpret the formation and emplacement history of the OPfm. Orbiter images reveal a series of superimposed fan‐shaped to elongate crosscutting deposits on the western fan's upper surface that highlights a complex, prolonged depositional history. Perseverance and Ingenuity observations reveal that the OPfm comprises: planar bedded and cross‐stratified sandstones and pebble conglomerates, which are the main lobe‐ and ridge‐forming units, a boulder conglomerate that overlies the sandstone to pebble conglomerate, and a massive mafic unit whose boulders armor the western fan. We interpret the sandstone to be pebble conglomerate facies and the boulder conglomerate to have formed via fluvial deposition in an alluvial fan emanating from Neretva Vallis. The boulders armoring the fan have previously been interpreted as detrital clasts transported into the crater via Neretva Vallis, but we consider an alternative hypothesis that the majority may represent the degraded remnants of a younger igneous unit emplaced in situ within the crater. This study provides a depositional model for a fluvial system capable of transporting boulders on Mars and new insights into the extraordinary preservation of the Jezero western fan.

Mars is primarily composed of mafic mineral assemblages and their alteration products, but small, scattered rocks strewn across the landscape offer clues to greater petrological diversity. While traversing the Jezero crater rim, the Perseverance rover encountered several plagioclase‐rich light‐toned float rocks. SuperCam identified the distinctive signature of corundum (α‐Al ₂ O ₃ ) in these rocks using time‐resolved luminescence spectroscopy. Two strong peaks (692.7 and 694.1 nm) with millisecond lifetimes, and additional supporting lines, are consistent with Cr ³⁺ substitution for Al ³⁺ in corundum. Corundum forms in Al‐rich, Si‐depleted environments through magmatic or metamorphic processes. Given the rocks' small size, association with plagioclase, and location on the crater rim, we interpret the most plausible formation scenario to be impact induced metamorphism at the interface of a felsic and a mafic/ultramafic member with the likely action of fluids at some stage, although other possibilities are not excluded.

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.

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.

The JPL rover Perseverance's investigations of Jezero crater's floor reveal that the ultramafic Séítah formation and the overlying mafic Máaz formation are deformed into a broad, low‐amplitude structural dome. Mastcam‐Z stereo images processed into digital outcrop models, together with RIMFAX ground‐penetrating radar profiles, were used to reconstruct the three‐dimensional stratal geometry of both units along a SW–NE transect across a southern domain of the dome called south Séítah. Measurements from 3‐D reconstructions show a progression from sub‐horizontal layers in the central parts of the dome to dips <20° away from the dome on its flanks, with Máaz and underlying Séítah layers dipping concordantly. RIMFAX profiles and imaging around the dome confirm that limb dips are continuous into the subsurface and form a flat‐crested composite quaquaversal fold structure. Séítah rocks in the fold core are up to 17 m higher than adjacent Máaz lava flows, despite stratigraphically underlying them, a relationship attributed to structural uplift. Fold geometry, wavelength (∼1 km), and amplitude (∼30–50 m), match models of forced folding produced by inflation of shallow igneous intrusions. The most likely cause is the emplacement of a sill or laccolith beneath the crater floor, generating elastic bending of the overlying layers. This intrusion‐driven uplift explains Séítah's elevated position, constrains the deformation history of Jezero's crater floor units post‐emplacement of the Séítah and Máaz formations, and supports a significant role for shallow magmatic intrusion in shaping intracrustal structures on Mars.

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.

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.