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.

Over the last several decades, investigations of Earth's subsurface and other extremely low-biomass systems have refined our understanding of the environmental limits of life, driven by methodological advances that permit agnostic life detection of biology and their respective physical biosignatures and chemical biomarkers. These advances enable mission concepts centered on microbiological processes that facilitate identification of both active life and preserved biosignatures through measurements of metabolism and associated biochemical markers that, on Mars, are more likely to be retained below the surface. Terrestrially, although biological processes can exert a significant influence on Earth's crust, the presence of habitable conditions does not necessarily imply the existence of cellular life. The Viking missions constituted the first direct life-detection experiments on Mars but produced equivocal outcomes, prompting subsequent exploration strategies to emphasize surface habitability rather than direct biological testing. Leveraging progress in subsurface microbiology and planetary exploration, we contend that Mars missions are now poised to shift toward direct tests for extant microbial activity in the subsurface, with metabolic processes serving as a broadly applicable indicator of life.

The NASA Mars 2020 mission Perseverance rover carries a piece of Martian meteorite Sayh al Uhaymir (SaU) 008 as part of the calibration payload for the SHERLOC science instrument. We report SHERLOC observations of the SaU 008 flight piece over the first 1,000 sols of the mission and compare them to measurements done prior to launch, showing consistent detection of the same deep‐ultraviolet (DUV) Raman and fluorescence signatures in the same locations. Co‐located X‐ray fluorescence (XRF) and DUV mapping of a reference SaU 008 piece on Earth confirm that the meteorite is comprised of an igneous mineral matrix consistent with shergottite, rich in olivine, maskelynite, and Fe‐Mg pyroxenes detectable by SHERLOC. Terrestrial weathering features consist of fractures and vugs filled with Ca‐carbonate. Fluorescence mapping reveals two major signatures: (a) broad‐spectrum fluorescence present throughout the igneous matrix but strongest in weathering features, attributed to organic material, and (b) narrow‐band 340 nm fluorescence spatially associated with ∼48 ppm cerium in <100 μm Ca‐phosphate grains. Raman revealed organic material in both the igneous matrix and terrestrial carbonate in the form of macromolecular carbon (MMC) with defect and graphitic bands at ∼1,380 and ∼1,600 cm −1 respectively. Raman band parameters suggest that MMC associated with terrestrial weathering is less thermally mature, most likely the result of chemical alteration after landing on Earth. This study serves as a demonstration of SHERLOC's capabilities when supported by co‐located XRF data from PIXL and suggests that SHERLOC can detect Ce in phosphate minerals at concentrations as low as 4 ppm.

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.

Airborne microplastics (MPs) could have negative impacts on human health and pollute water, soil, and sediment. This study explored the distributions, compositions, and morphology of airborne microplastics in the indoor and ambient air in New Jersey, United States. Microplastic fibers, films, and fragments of Polystyrene (PS), Polyethylene terephthalate (PET), Polyethyelene (PE), Polyvinyl chloride (PVC) and Polypropylene (PP) were identified in office, hallway, classroom, and single-family house in this study. The deposition rates of synthetic fibers with length from 35 mu m to 1000 mu m were highest in the single-family house ((1.96 +/- 1.09) x 10(4) fibers/ m(2)/day) and lowest in the classroom ((6.20 +/- 0.57) x 10(3) fibers/m(2)/day), suggesting that residential houses are a major source of microplastic fibers. However, for film-like plastics with surface areas ranging from 200 mu m(2) to 5000 mu m(2), a high deposition rate of (8.13 +/- 2.17) x 10(3) films/m(2)/day was observed in the classroom, whereas the lowest deposition rate of (4.45 +/- 0.27) x 10(3) films/m2/day was found in the hallway, probably because plastic films such as PE are intensively used in the classroom environments. The deposition rate of microplastics in the ambient air acquired on a building roof was only about 2-8% of the indoor deposition rates. The microplastics with similar textures but different sizes were identified in both total atmospheric deposition and particulate samples (PM2.5 and PM10), suggesting degradation from microplastics to nanoplastics. The main microplastics found in indoor air samples were PE fragments or fibers, different from those in the outdoor ambient air that were dominated by PVC fragments. These results unravel the properties of airborne microplastics in urban environments that are important to understanding their fate, transport, and potential health risks.

We present a synthesis of PIXL elemental data and SHERLOC Raman spectra collected on two targets investigated by the Perseverance rover during the first year of its exploration of Jezero Crater, Mars. The Bellegarde target (in the M acute accent aaz formation) and Dourbes target (in the Se acute accent itah formation) exhibit distinctive mineralogies that are an ideal case study for in situ analysis by SHERLOC and PIXL. Each instrument alone produces valuable data about the chemistry and spatial distribution of mineral phases at the sub-millimeter scale. However, combining data from both instruments provides a more robust interpretation that overcomes the limitations of either instrument, for example: 1) Detection of correlated calcium and sulfur in Bellegarde by PIXL is corroborated by the co-located detection of calcium sulfate by SHERLOC. 2) Detection of sodium and chlorine in Dourbes is consistent with either chloride or oxychlorine salts, but SHERLOC does not detect perchlorate or chlorate. 3) A Raman peak at 1120 cm-1 in Dourbes could be sulfate or pyroxene, but elemental abundances from PIXL at that location are a better match to pyroxene. This study emphasizes the importance of analyzing co-located data from both instruments together, to obtain a more complete picture of sub-millimeter -scale mineralogy measured in situ in Jezero crater, Mars, by the Perseverance rover.

Carbonate rocks record the oldest forms of life on Earth, and their geologic reconstruction requires multiple methods to determine physical and chemical processes before conclusions of ancient biosignatures are made. Since crystal orientation within rock fabric may be used to infer geologic settings, we present here a complementary Raman method to study the orientation of calcite (CaCO3) and dolomite [CaMg (CO3)2] minerals. The relative peak intensity ratio of the carbonate lattice Eg modes T and L reveals the crystallographic orientation of calcite and dolomite with respect to the incident light polarization. Our results for calcite show that when the incident laser light propagates down the crystallographic a/b axis: (1) the L mode is always greater in intensity than the T mode (IT < IL), and (2) the spectra are most intense at 45° and least intense at 90° polarization angles measured from around the c axis. Our results for dolomite show that (1) IT > IL when the incident light propagation is down the crystallographic c axis and (2) IT < IL when the incident light propagation is down the crystallographic a/b axis. This study reveals mineral orientation variation related to deposition and paragenesis within limestone and dolostone samples. The method presented yields information related to growth and deformation during diagenetic and metamorphic alteration and may be used in research seeking to identify the fabric parameters of any calcite or dolomite containing rock. The compositional and structural data obtained from Raman mapping is useful in structural geology, materials science, and biosignature research.

Stromatolites have been a major focus in the search for ancient microbial life, however, the organic carbon biosignatures of dolomitized stromatolites have not yet been fully characterized or correlated with their dolomitizing conditions. Although dolomitization rarely preserves microbial morphology, the presence of organic carbon can provide valuable information for characterization of fossils' biogenicity, syngenicity, and indigeneity to their host rock. The Cambrian Allentown Formation in New Jersey, USA, is an excellent example of dolomitized stromatolites and thrombolites containing diagenetically modified microbial biosignatures. Based on XRD and EPMA data, the dolomite composition is typically stoichiometric, with varying degrees of cationic ordering. The outcrop underwent early dolomitization in a marginal-marine setting and later burial diagenesis resulting in multi-generational dolomite formation: (1) microspar dolomite formed by early diagenetic replacement at or near the surface, (2) zoned dolomite formed penecontemporaneously with the microspar phase as rhombohedral crystals by infilling primary pore spaces within the microspar matrix. The rhombic crystals continued to grow outward in alternating stages of Fe-enriched and -depleted fluids, which were preserved in zoned rims and revealed by cathodoluminescence, and (3) saddle dolomite formed during late stage deep burial with Fe- and Mn-rich fluids, and occurs as a void-filling, high-temperature phase. Organic carbon, characterized using confocal Raman microscopy, has an exclusive distribution within the microspar dolomite, and the D and G bands' characteristics reveal similar thermal alteration to the host rock, indicating that the mapped organic carbon is indigenous and syngenetic with the Cambrian carbonates. The findings presented in this study reveal organic matter found within microspar of various dolomitized facies deriving from different source pools of organic carbon. This study sheds light on biosignatures in secondary dolostones and may aid biosignature detection in older carbonate rocks on Earth and Mars.

Introduction: The occurrence of Mg carbonates on the Martian surface [1,2,3,4,5,6,7] and the inferred presence of dolomites at Nili Fossae [1,2] brings renewed attention to investigations of dolomitization processes, especially those associated with past evidence of microbial life. Two Martian missions, the MRO’s CRISM (Nili Fossae) and the MER’s Spirit rover (Gusev crater, a possible Mars2020 landing site), revealed the presence of Mg carbonates [3,7]. This implies that carbonate rocks may have been more common than previously thought during the Noachian Period on Mars [7]. Diagenetic and metamorphic processes will alter and even erase traces of microbial life preserved in rocks of Earth [8], making interpreting biosignatures difficult and often controversial. Understanding dolomitized microbial carbonates on Earth is important for interpreting the ancient life record, so that the evidence of life on other planets (Mars) does not go overlooked due to post-diageneses or metamorphic effects. In this study, we aim to interpret the mode of dolomitization and how it affected the biosignatures using high-resolution microscopic and spectroscopic analysis. Our intention is to constrain the origin and formation of multiple generations of dolomite within a formation to assess the level of diagenetic and metamorphic processes, and their influence on the biosignatures in obvious microbially maintained structures (stromatolites). The results will contribute to a better understanding of the debatable formation of dolomite [9,10,11,12,13] and interpretation of ~500 Ma old biosignatures. Geologic Setting: The 500-515 Ma old, Allentown Formation (New Jersey and Pennsylvania), contains the large convex mound (round-headed columnar layered mats), thrombolite-like structures (chaotic texture) and wavy bed types (undulatory and laterally linked mats) of stromatolitic morphologies [14]. The first two types were collected from an outcrop in New Jersey and these will be discussed here. This formation has been interpreted as a subtidal setting with limestone deposition [15]. Methods: Petrological Microscopy was conducted using a transmitted light microscope and polished thin sections of each stromatolite type. Powder X-ray Diffraction (XRD) using a Bruker D8 Advance to determine bulk mineral composition of both stromatolitic morphologies. The XRD employed a CuKα source running 40 kV and 25 mA and a LynxEye detector. Samples were scanned in steps of 3526 at 0.250 seconds from 5° to 75° 2Ɵ. Peak finding and matching with XRD patterns were performed in DIFFRAC.suite. Eva V3.1 software using the International Center for Diffraction Data database (version PDF2013). Scanning Electron Microscopy / Energy Dispersive X-ray Spectroscopy (SEM/EDS) using a Hitachi S-4800 with an Apollo X EDAX using standard vacuum and 20 kV beam voltage. Cathodoluminescence (CL) analyzed using the electron microprobe (JEOL 8200), beam conditions were 15 kV accelerating voltage, 13.9 nA beam current, 1μm step size, and 30 ms dwell time. Confocal Raman Spectroscopy using a WITec alpha300 with a 532 nm wavelength laser.