Bradley Garczynski

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.

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.

During the NASA Perseverance rover's exploration of the Jezero crater floor, coatings were commonly observed on rocks. These features may record past water‐rock‐atmosphere interactions on the crater floor, and understanding their origin is important for constraining the timing of potential water activity and habitability at Jezero. Here, we characterize the morphologic, chemical, and spectral properties of the crater floor rock coatings using color images, visible/near‐infrared reflectance spectra, and chemical data from the Mastcam‐Z and SuperCam instruments. We show that coatings are common and compositionally similar across the crater floor, and consistent with a mixture of dust, fine regolith, sulfates, and ferric oxides indurated as a result of one or more episodes of widespread surface alteration. All coatings exhibit a similar smooth homogenous surface with variable thickness, color, and spatial extent on rocks, likely reflecting variable oxidation and erosional expressions related to formation and/or exposure age. Coatings unconformably overlie eroded natural rock surfaces, suggesting relatively late deposition that may represent one of the last alteration episodes on the Jezero crater floor. While more common at Jezero, these coatings may be consistent with rock coatings previously observed in situ at other landing sites and may be related to duricrust formation, suggesting a global alteration process on Mars that is not unique to Jezero. The Perseverance rover likely sampled these rock coatings on the crater floor and the results from this study could provide important context for future investigations by the Mars Sample Return mission aimed at constraining the geologic and alteration history of Jezero crater.

The Perseverance rover has explored and sampled igneous and sedimentary rocks within Jezero Crater to characterize early Martian geological processes and habitability and search for potential biosignatures^1-7. Upon entering Neretva Vallis, on Jezero Crater's western edge⁸, Perseverance investigated distinctive mudstone and conglomerate outcrops of the Bright Angel formation. Here we report a detailed geological, petrographic and geochemical survey of these rocks and show that organic-carbon-bearing mudstones in the Bright Angel formation contain submillimetre-scale nodules and millimetre-scale reaction fronts enriched in ferrous iron phosphate and sulfide minerals, likely vivianite and greigite, respectively. This organic carbon appears to have participated in post-depositional redox reactions that produced the observed iron-phosphate and iron-sulfide minerals. Geological context and petrography indicate that these reactions occurred at low temperatures. Within this context, we review the various pathways by which redox reactions that involve organic matter can produce the observed suite of iron-, sulfur- and phosphorus-bearing minerals in laboratory and natural environments on Earth. Ultimately, we conclude that analysis of the core sample collected from this unit using high-sensitivity instrumentation on Earth will enable the measurements required to determine the origin of the minerals, organics and textures it contains.

In Jezero crater, Mars, the Perseverance rover has explored the western fan and encountered loose pieces of rock separated from outcrops or “float” rocks. Comparing float rocks to in‐place outcrops can provide key insights into the crater's erosional history and the diversity of units in the Jezero watershed that Perseverance cannot visit in situ. Here, we used multispectral observations from Perseverance's Mastcam‐Z instrument to investigate the lithology and origin of float rocks found on the western Jezero fan front (sols 415–707). We identified four textural classes of float rocks (conglomerates, layered, massive, and light‐toned) and investigated their physical characteristics, spectral properties, and distribution to interpret their source and mode of transport. Likely derived from local sedimentary fan outcrops, conglomerate and layered float rocks are highly spectrally variable and altered with differing ferric and ferrous signatures. Massive float rocks are the least altered with ferrous signatures and likely derived from local outcrop sources or more distal sources (∼50–250 km) in the Jezero watershed. Massive float rocks separate into two subclasses: massive olivine and massive pyroxene, which are likely derived from the regional olivine‐carbonate‐bearing watershed unit and the crustal Noachian basement unit, respectively. The unique light‐toned float rocks have variable hydration and low Fe‐abundance, but there is no local outcrop equivalent of these rocks on the crater floor or fan front, suggesting transport into the basin from a source region outside Jezero. Perseverance found no meteorites at the western fan, implying that fan sediments may be in the youngest ages estimated from crater counts (Hesperian).

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.

The Mars 2020 Perseverance rover has explored the escarpment at the front of the western fan in Jezero crater, Mars, where it encountered a variety of rock units as in-place outcrops and as loose pieces of rock separated from outcrops, or “float” rocks. Comparing float rocks to in-place outcrops can provide key insights into the crater’s erosional history and the diversity of units in the Jezero watershed that the Perseverance rover cannot visit in-situ. Here, we used multispectral observations from Perseverance’s Mastcam-Z instrument to investigate the lithology and origin of float rocks found on the western Jezero fan front (sols 415-707). We identified four textural classes of float rocks (conglomerates, layered, massive, and light-toned) and investigated their physical characteristics, spectral properties, and distribution to interpret their source and constrain their mode of transport. We found that the conglomerate and layered float rocks are highly spectrally variable and altered with differing ferric and ferrous signatures, and they likely derived from local sedimentary outcrops in the western fan front. Massive float rocks are the least altered, exhibit ferrous signatures, and could have derived from local outcrop sources or more distal sources in the Jezero watershed. Massive float rocks separate into two subclasses: massive olivine and massive pyroxene, which likely derived from the regional olivine-carbonate-bearing watershed unit and the crustal Noachian basement unit respectively. The unique light-toned float rocks have variable hydration and low Fe-abundance, but there are no local outcrop equivalent of these rocks in the western Jezero fan or crater floor.

The Mars 2020 Perseverance Rover imaged diagenetic textural features in four separate sedimentary units in its exploration of the 25‐m‐thick Shenandoah formation at Jezero Crater, Mars, that we interpreted as probable concretions. These concretions were most abundant in the Hogwallow Flats member of the Shenandoah formation and were restricted to the light‐toned, platy, sulfur‐cemented bedrock at outcrop surfaces, whereas the finely laminated, darker toned, mottled and deformed strata lack concretions. The concretions also had a wide range of morphologies including concentric, oblate, urn, and spheroidal shaped forms that were not clustered, and ranged in size from ∼1 to 16 mm with a median of 2.65 mm. The elemental composition of the concretions compared to the bedrock had greater abundance of magnesium and calcium salts, silicates, and possibly hematite. We compared these Jezero Crater concretions to the geochemistry of concretions from previously published studies and from two new terrestrial analog sites (Gallup Formation, New Mexico and Torrey Pines, California). In addition, we measured organic carbon content of three terrestrial sedimentary analogs of increasing age that contain concretions (Torrey Pines (Pleistocene), Gallup Formation (∼89 Ma), and Moodies Group (∼3.2 Ga)). All measured concretions contained significant concentrations of organic carbon with the maximum organic carbon content (∼2 wt. % Total organic carbon) found in the Moodies Group concretions. Organic carbon abundances in terrestrial concretions was controlled more by the formation mechanism and relative timing of concretion development rather than deposit age. These findings suggested that concretions at Jezero Crater reflect local sites of enhanced biosignature preservation potential.