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The article discusses Hematite has a common oxidization product on Earth, Mars, and asteroids. Topics include oxygen delivered from Earth's upper atmosphere have the major oxidant that forms lunar hematite; and oxygen isotope measurements test hypothesis and help reveal the evolution of Earth's atmosphere.

Fields of parallel, regularly-spaced, bedrock ridges observed on Mars and rarely on Earth have been interpreted as aeolian surface features oriented perpendicular to a formative wind. The exact formation process for these ridges, however, including the role of aeolian erosion versus deposition, continues to be debated. We identified forty fields of bedrock ridges on and within the sedimentary strata of Gale crater's central mound, Aeolis Mons. To better constrain the development of these landforms and the winds responsible for their formation, we characterized ridge morphology, orientation, geographic distribution, stratigraphic relationships, and interactions with other aeolian landforms. The study area of Aeolis Mons was chosen to leverage the extensive high-resolution image coverage from orbit, as well as to build upon the detailed stratigraphy compiled from in situ exploration with the Mars Science Laboratory Curiosity rover. Using the orientation of the ridges, we present a wind vector map of Aeolis Mons. The orientation of bedrock ridges in the Mound Skirting Unit, which unconformably drapes Aeolis Mons, suggests the average wind direction in Gale crater may have remained consistent since that unit was emplaced (∼3.8–3.1 Ga). This study explores the implications of these ridges for the history of wind, deposition, and erosion in Gale crater. • Bedrock ridges are an enigmatic landform sculpted by the wind. • Using orbiter data, forty fields of ridges were found on Aeolis Mons (Mount Sharp). • Our analysis indicates that some ridges formed via erosion, while others may be depositional. • Ridge morphology, orientation, and distribution were used to create a wind vector map. [ABSTRACT FROM AUTHOR]

Purpose: To quantify the hepatic safety of pazopanib and comparator anti-vascular endothelial growth factor (VEGF) therapies in clinical practice among renal cell carcinoma (RCC) patients.Methods: A population-based cohort study of new anti-VEGF users was conducted in two US healthcare databases, Department of Veterans Affairs (VA) and an oncology practice network (Altos), and the PHARMO Database Network in The Netherlands. A common protocol was used to collect liver chemistry (LC) data from anti-VEGF initiation through 4 years of follow-up. In the VA population, suspected drug-induced liver injury (DILI) outcomes were investigated via chart review, with adjudication by hepatologists.Results: In Altos and VA, respectively, the total RCC patients were: pazopanib (156, 243), bevacizumab (122, 99), sorafenib (82, 249) and sunitinib (285, 751). PHARMO contained too few patients to be included. Few cases of alanine aminotransferase (ALT) ≥8× the upper limit of normal were seen across the anti-VEGF cohorts; incidence rates (per 100 person-years) ranged from 0 (sunitinib) to 8.2 (pazopanib) in Altos and from 0 (bevacizumab and sorafenib) to 2.1 (pazopanib) among VA patients. No cases of Hy's law identified by combination LC elevations were seen in patients treated with pazopanib or bevacizumab; one case was observed in those treated with sorafenib, and two cases were found among sunitinib users. One case of adjudicated DILI was observed in a sunitinib-treated patient; none were found among patients treated with pazopanib, bevacizumab or sorafenib.Conclusions: Severe liver injury occurred infrequently during exposure to pazopanib and other anti-VEGF therapies in a population-based setting. [ABSTRACT FROM AUTHOR]

Iron minerals are highly reactive drivers of abiotic/prebiotic organic chemistry, and in the presence of ammonia (NH 3 /NH 4 +) or other reduced nitrogen (N) compounds, have been shown to promote amino acid synthesis from organic precursors. On early Mars, oxidized nitrogen species (NO x −) such as NO 3 − and/or NO 2 − may have been present, which could be reduced by Fe(II) to form various species including N 2 O and/or NH 3 /NH 4 +. The production of NH 3 /NH 4 + from Fe(II)-driven NO 3 − or NO 2 − reduction may be able to feed into prebiotic organic reactions including amino acid formation. In this study, we tested whether iron mineral-driven reduction of NO 3 − or NO 2 − could provide a source of NH 3 /NH 4 + to form amino acids from two prebiotically relevant precursors (pyruvate and glyoxylate); or, whether an exogeneous source of NH 3 /NH 4 + would be required. We observed that pyruvate and glyoxylate reacted with Fe-oxyhydroxide minerals in NO x −-containing experiments to form reduced hydroxy acid products; and in experiments containing only NH 3 /NH 4 +, amino acids were also formed. However, significant amino acid formation was not observed in any experiments containing NO 3 − or NO 2 − unless sufficient NH 4 + was also added; furthermore, colorimetric analysis did not show any generation of NH 4 + from NO 3 −/NO 2 − reduction at these conditions. NO 2 − was observed to be highly reactive with Fe2+ and Fe(II)-bearing minerals, resulting in Fe oxidation during mineral precipitation and the formation of oxidized mineral phases (hematite). The Fe(II)/Fe(III) ratio in oxyhydroxide minerals is an important parameter for determining organic product distributions from pyruvate and glyoxylate; therefore, Fe-mediated NO x − reduction does impact organic chemistry. However, amino acid formation, at least under these conditions, would also require an exogenous source of NH 3 /NH 4 + or other reduced N species. These results have implications for organic-N chemistry on early Mars, as well as for some early Earth origin of life scenarios regarding organic synthesis in mineral-containing systems. [ABSTRACT FROM AUTHOR]

BACKGROUND: Chemotherapy-induced anemia (CIA) commonly occurs in cancer patients receiving conventional myelosuppressive chemotherapy. Two national guidelines regarding the use of erythropoiesis-stimulating agents (ESAs) in CIA were released in 2002. Because of poorer disease outcomes and increased risk of adverse events associated with ESAs in recent studies, the use of ESAs has been increasingly restricted in practice guidelines in the years 2007 and 2008. Objective: The aim of this study was to provide a baseline for adherence to national guidelines in the use of ESAs for CIA between 2002 and 2006. METHODS: This retrospective study used the Varian Medical Oncology database (Varian Medical Systems, Inc., Palo Alto, California) of electronic medical records, representing 17 outpatient oncology organizations at 71 clinic locations in the United States. Adults diagnosed with any malignant neoplasm who started conventional cytotoxic chemotherapy between January 1, 2002, and September 30, 2006, were included. The proportion of patients receiving an ESA was calculated by hemoglobin (Hb) level during each chemotherapy cycle, stratified by line of chemotherapy and year. Logistic regression modeling identified predictors of ESA use in anemic patients during the first chemotherapy cycle. RESULTS: The records of 17,731 cancer patients were evaluated. Median (SD) age was 61 (13) years, and 58.9% were female. Most patients (84.1%) had a solid tumor. Many patients (41.3%) received platinum containing chemotherapy and 74.4% received combination chemotherapy. During the first 5 cycles of first-line chemotherapy among patients with CIA (Hb <11 g/dL), ESAs were used by 55.8% of patients at cycle 1 and 68.9% at cycle 5. ESA use in CIA patients increased across lines of chemotherapy and time. Few patients (2.8%) received an ESA at Hb >13 g/dL. The statistically significant predictors of ESA use included age >65 years, eastern US residence, private health insurance, community-based care, and solid tumors, especially lung cancer. CONCLUSION: The patterns we observed were generally consistent with prevailing ESA labels and national guidelines during 2002 through 2006. Although ESA use in patients with CIA increased over chemotherapy cycles, lines of chemotherapy, and time, <70% of CIA episodes were treated with ESAs during the initial 5 chemotherapy cycles. [ABSTRACT FROM AUTHOR]

Data returned by NASA's Mars Science Laboratory Curiosity rover showed evidence for abundant secondary materials, including Fe‐oxides, phyllosilicates, and an amorphous component on and below Vera Rubin ridge in the Murray formation. We used equilibrium thermochemical modeling to test the hypothesis that altered sediments were deposited as detrital igneous grains and subsequently underwent diagenesis. Chemical compositions of the Murray formations' altered components were calculated using data returned by the chemistry and mineralogy X‐ray diffraction instrument and the alpha particle X‐ray spectrometer on board Curiosity. Reaction of these alteration compositions with a CO2‐poor and oxidizing dilute aqueous solution was modeled at 25–100 °C, with 10–50% Fe3+/Fetot of the host rock. The modeled alteration assemblages included abundant phyllosilicates and Fe‐oxides at water‐to‐rock ratios >100. Modeled alteration abundances were directly comparable to observed abundances of hematite and clay minerals at a water‐to‐rock ratio of 10,000, for system temperatures of 50–100 °C with fluid pH ranging from 7.9 to 9.3. Modeling results suggest that the hematite–clay mineral assemblage is primarily the result of enhanced groundwater flow compared to the Sheepbed mudstone observed at Yellowknife Bay, and underwent further, localized alteration to produce the mineralogy observed by Curiosity. [ABSTRACT FROM AUTHOR]

Diffraction gratings are commonly used in optical instruments such as in spectrometers, monochromators, and wavelength division multiplexing devices. The diffraction efficiency is directly related to the ratio of the grating spacing or pitch to the wavelength of the light. In a sinusoidal grating (or holographic grating) the efficiency is generally lower than a blazed grating with a saw tooth profile, but the spectral coverage can be broader. To address a large spectral range, advanced spectrometers use a number of diffraction gratings with a fixed pitch. In this paper, we show for the first time, the use of a tunable-frequency surface acoustic wave (SAW) delay line as a broad-band sinusoidal diffraction grating. To tune the frequency, we tune the effective spacing of the interdigitated transducers (IDTs) by applying specific phases to each IDT finger. The prototype SAW grating covers frequency range of 86 MHz to 360 MHz corresponding to optical range of $1.3~\mu \text{m}$ to $9~\mu \text{m}$. [2020-0189] [ABSTRACT FROM AUTHOR]

Background: Mutations in STK11 (STK11m) and frequently co-occurring KRAS mutations (KRASm/STK11m) are associated with poor survival in metastatic NSCLC (mNSCLC) immuno-oncology trials. There are limited data regarding the prognostic significance of these mutations in a real-world setting. Methods: This retrospective cohort study analyzed de-identified electronic medical records from the Flatiron Clinico-Genomic database to identify patients with mNSCLC who had initiated first-line immunotherapy (IO; alone or in combination) or chemotherapy under routine care between January 1, 2013 and June 30, 2017. The primary objectives were to assess the prevalence of STK11m and KRASm/STK11m and to determine associations of these mutations with overall and progression-free survival (OS, PFS). Results: Of 2407 patients with mNSCLC, STK11m and KRASm/STK11m were present in 13.6% and 6.5% of patients, respectively. Worse OS outcomes were observed in patients with STK11m versus STK11wt mNSCLC receiving IO (first-line, HR [95% CI], 1.4 [0.9–2.3; p = 0.1]; second-line [subset of first-line cohort], HR, 1.6 [1.3–2.0; p = 0.0002]) or chemotherapy (first-line, HR, 1.4 [1.2–1.6; p < 0.0001]); PFS outcomes showed similar trends. KRASm/STK11m double mutations were associated with worse OS and PFS outcomes versus KRASwt/STK11wt with IO and chemotherapy, similar to the single mutation (STK11m vs STK11wt) findings. Conclusions: This large observational genomic study among patients receiving routine care highlights the negative prognostic impact of STK11m in patients with mNSCLC treated with IO or chemotherapy. These results complement previous clinical trial data and provide further evidence in the real world of a patient population that would benefit from new treatment options. [ABSTRACT FROM AUTHOR]

We performed a multi-scale characterization of aqueous alteration of Mars analog basaltic rock from a Mauna Kea drill core using high-resolution visible and short-wave infrared (VIS-SWIR) spectral imaging, scanning electron microscopy, X‑ray diffraction, and point VIS-SWIR spectra. Several types of smectites, zeolites, and primary minerals were identified. Mineral classes were mapped in cut sections extracted from the drill core and used to represent the range of alteration products seen in field data collected over 1000 m depth (Calvin et al. 2020). Ten distinct spectral end-members identified in the cut sections were used to map the field point spectra. Trioctahedral Fe- and Mg-rich smectites were present toward the top of the zone of analysis (972 m below the surface) and increased in abundance toward the bottom of the drill core (1763 m depth). The mineralogy demonstrates a general trend of discontinuous alteration that increases in intensity with depth, with less pervasive phyllosilicate alteration at the top, several zones of different mixtures of zeolites toward the center, followed by more abundant phyllosilicates in the lowest sections. Distinctly absent are Fe-Mg phyllosilicates other than smectites, as well as carbonates, sulfates, and Al phyllosilicates such as kaolinite or illite. Furthermore, hematite was only detected in two of 24 samples. The suite of assemblages points to aqueous alteration at low-to-moderate temperatures at neutral to basic pH in low-oxygen conditions, with little evidence of extensive surface interaction, presenting a possible analog for an early Mars subsurface environment. We also present a library of VIS-SWIR spectra of the analyzed cut sections, including both spatial averages (i.e., unweighted linear mixtures) of spectral images of each cut section and single point spectra of the cut sections. This will allow for consideration of nonlinear mixing effects in point spectra of these assemblages from natural surfaces in future terrestrial or planetary work. [ABSTRACT FROM AUTHOR]

As part of the Phase 2 Bagnold Dune campaign at Gale Crater, Mars, constraints on the geochemistry, mineralogy, and oxidation state of pristine and disturbed linear sand ripples were made using visible/near‐infrared spectral observations for comparison to Phase 1 spectra of the barchan dunes to the north. Spectra acquired by the ChemCam and Mastcam instruments (400–1,000 nm) at four Phase 2 locations revealed similar overall spectral trends between the two regions, but most Phase 2 sands were redder in the visible wavelengths. The majority of targets exhibited lower red/infrared ratios, higher ~530‐nm band depths, and higher red/blue ratios than Phase 1 samples, suggesting a greater proportion of redder, fine‐grained, ferric sands in Phase 2 samples. This is consistent with the slightly greater proportion of hematite in Phase 2 samples as determined from CheMin analyses of the Ogunquit sands, which may reflect contamination from the surrounding hematite‐bearing Murray formation bedrock. Plain Language Summary: The Mars Science Laboratory Curiosity rover visited the southern portion of the Bagnold Dunes to look for differences in the types of sand grains that comprised the dunes and ripples. The rover's cameras and spectrometers provided information about the color of the sands, which was used to infer the composition and types of minerals. Overall, the sands in this part of the Bagnold Dunes were a bit redder than those further to the north that were studied previously. We interpreted this to mean that the southern sands contained more oxidized (rusted) iron particles. Because the rocks surrounding these dunes were known to contain a fair amount of red, iron‐rich minerals, it is probable that the sands were mixed with a small amount of broken fragments from these rocks. Key Points: Bagnold Phase 2 sands exhibit higher 535‐nm band depths and red/blue ratios and lower 600‐/700‐nm ratios than Bagnold Phase 1 sandsPhase 2 sands contain a greater amount of redder, ferric materials, likely owing to minor hematite contamination from nearby bedrock [ABSTRACT FROM AUTHOR]

Curiosity landed on plains to the north of Mount Sharp in August 2012. By June 2016 the rover had traversed 12.9 km to the southwest, encountering extensive strata that were deposited in a fluvial-deltaic-lacustrine system. Initial drives across sharp sandstone outcrops initiated an unacceptably high rate of punctures and cracks in the thin aluminum wheel skin structures. Initial damage was found to be related to the drive control mode of the six wheel drive actuators and the kinematics of the rocker-bogie suspension. Wheels leading a suspension pivot were forced onto sharp, immobile surfaces by the other wheels as they maintained their commanded angular velocities. Wheel damage mechanisms such as geometry-induced stress concentration cracking and low-cycle fatigue were then exacerbated. A geomorphic map was generated to assist in planning traverses that would minimize further wheel damage. A steady increase in punctures and cracks between landing and June 2016 was due in part because of drives across the sharp sandstone outcrops that could not be avoided. Wheel lifetime estimates show that with careful path planning the wheels will be operational for an additional ten kilometers or more, allowing the rover to reach key strata exposed on the slopes of Mount Sharp. [ABSTRACT FROM AUTHOR]

This study provides the first systematic comparison of orbital facies maps with detailed ground-based geology observations from the Mars Science Laboratory (MSL) Curiosity rover to examine the validity of geologic interpretations derived from orbital image data. Orbital facies maps were constructed for the Darwin, Cooperstown, and Kimberley waypoints visited by the Curiosity rover using High Resolution Imaging Science Experiment (HiRISE) images. These maps, which represent the most detailed orbital analysis of these areas to date, were compared with rover image-based geologic maps and stratigraphic columns derived from Curiosity's Mast Camera (Mastcam) and Mars Hand Lens Imager (MAHLI). Results show that bedrock outcrops can generally be distinguished from unconsolidated surficial deposits in high-resolution orbital images and that orbital facies mapping can be used to recognize geologic contacts between well-exposed bedrock units. However, process-based interpretations derived from orbital image mapping are difficult to infer without known regional context or observable paleogeomorphic indicators, and layer-cake models of stratigraphy derived from orbital maps oversimplify depositional relationships as revealed from a rover perspective. This study also shows that fine-scale orbital image-based mapping of current and future Mars landing sites is essential for optimizing the efficiency and science return of rover surface operations. [ABSTRACT FROM AUTHOR]

Wind blowing over sand on Earth produces decimeter-wavelength ripples and hundred-meter- to kilometer-wavelength dunes: bedforms of two distinct size modes. Observations from the Mars Science Laboratory Curiosity rover and the Mars Reconnaissance Orbiter reveal that Mars hosts a third stable wind-driven bedform, with meter-scale wavelengths. These bedforms are spatially uniform in size and typically have asymmetric profiles with angle-of-repose lee slopes and sinuous crest lines, making them unlike terrestrial wind ripples. Rather, these structures resemble fluid-drag ripples, which on Earth include water-worked current ripples, but on Mars instead form by wind because of the higher kinematic viscosity of the low-density atmosphere. A reevaluation of the wind-deposited strata in the Burns formation (about 3.7 billion years old or younger) identifies potential wind-drag ripple stratification formed under a thin atmosphere. [ABSTRACT FROM AUTHOR]

Relative reflectance point spectra (400–840 nm) were acquired by the Chemistry and Camera (ChemCam) instrument on the Mars Science Laboratory (MSL) rover Curiosity in passive mode (no laser) of drill tailings and broken rock fragments near the rover as it entered the lower reaches of Mt. Sharp and of landforms at distances of 2–8 km. Freshly disturbed surfaces are less subject to the spectral masking effects of dust, and revealed spectral features consistent with the presence of iron oxides and ferric sulfates. We present the first detection on Mars of a ~433 nm absorption band consistent with small abundances of ferric sulfates, corroborated by jarosite detections by the Chemistry and Mineralogy (CheMin) X-ray diffraction instrument in the Mojave, Telegraph Peak, and Confidence Hills drilled samples. Disturbed materials near the Bonanza King region also exhibited strong 433 nm bands and negative near-infrared spectral slopes consistent with jarosite. ChemCam passive spectra of the Confidence Hills and Mojave drill tailings showed features suggestive of the crystalline hematite identified by CheMin analyses. The Windjana drill sample tailings exhibited flat, low relative reflectance spectra, explained by the occurrence of magnetite detected by CheMin. Passive spectra of Bonanza King were similar, suggesting the presence of spectrally dark and neutral minerals such as magnetite. Long-distance spectra of the "Hematite Ridge" feature (3–5 km from the rover) exhibited features consistent with crystalline hematite. The Bagnold dune field north of the Hematite Ridge area exhibited low relative reflectance and near-infrared features indicative of basaltic materials (olivine, pyroxene). Light-toned layers south of Hematite Ridge lacked distinct spectral features in the 400–840 nm region, and may represent portions of nearby clay minerals and sulfates mapped with orbital near-infrared observations. The presence of ferric sulfates such as jarosite in the drill tailings suggests a relatively acidic environment, likely associated with flow of iron-bearing fluids, associated oxidation, and/or hydrothermal leaching of sedimentary rocks. Combined with other remote sensing data sets, mineralogical constraints from ChemCam passive spectra will continue to play an important role in interpreting the mineralogy and composition of materials encountered as Curiosity traverses further south within the basal layers of the Mt. Sharp complex. [ABSTRACT FROM AUTHOR]

The article proposes a methodology for real-world studies in multiple sclerosis (MS) using administrative claims databases that provide data for assessing the effect of treatments in clinical practice. It concludes that the methods can help in performing real-world research in MS that will allow evidence from different studies and can be combined in current research practice.

Clay minerals, recently discovered to be widespread in Mars's Noachian terrains, indicate long-duration interaction between water and rock over 3.7 billion years ago. Analysis of how they formed should indicate what environmental conditions prevailed on early Mars. If clays formed near the surface by weathering, as is common on Earth, their presence would indicate past surface conditions warmer and wetter than at present. However, available data instead indicate substantial Martian clay formation by hydrothermal groundwater circulation and a Noachian rock record dominated by evidence of subsurface waters. Cold, arid conditions with only transient surface water may have characterized Mars's surface for over 4 billion years, since the early-Noachian period, and the longest-duration aqueous, potentially habitable environments may have been in the subsurface. [ABSTRACT FROM AUTHOR]

NASA’s MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) mission will further the understanding of the formation of the planets by examining the least studied of the terrestrial planets, Mercury. During the one-year orbital phase (beginning in 2011) and three earlier flybys (2008 and 2009), the X-Ray Spectrometer (XRS) onboard the MESSENGER spacecraft will measure the surface elemental composition. XRS will measure the characteristic X-ray emissions induced on the surface of Mercury by the incident solar flux. The Kα lines for the elements Mg, Al, Si, S, Ca, Ti, and Fe will be detected. The 12° field-of-view of the instrument will allow a spatial resolution that ranges from 42 km at periapsis to 3200 km at apoapsis due to the spacecraft’s highly elliptical orbit. XRS will provide elemental composition measurements covering the majority of Mercury’s surface, as well as potential high-spatial-resolution measurements of features of interest. This paper summarizes XRS’s science objectives, technical design, calibration, and mission observation strategy. [ABSTRACT FROM AUTHOR]

Aim: To identify which individual-, physician-, and the healthcare system-related factors can predict individualized hemoglobin A1c (HbA1c) targets and the likelihood of reaching those targets after initial insulin therapy over a two-year follow-up period.Methods: Real-world data, including baseline characteristics of people with type 2 diabetes mellitus (T2DM), psychosocial data, and diabetes medication use, collected from the Multinational Observational Study Assessing Insulin Use (MOSA1c) study in 18 countries were analyzed.Results: Overall, 225 of 1194 people with T2DM (18.8%) who received initial insulin therapy for ≥3 months reached HbA1c targets at two-year follow-up; most were likely to be White (64.9%) and perceptions of their relationship with physicians were less positive than those who did not reach HbA1c targets. Higher baseline HbA1c (>8%) was the strongest predictor of being assigned an HbA1c target >7% (odds ratio [OR] 6.06, 95% confidence interval [CI] 3.97, 9.26). A smaller difference between baseline and target HbA1c levels was the strongest predictor of reaching an HbA1c target at two-year follow-up (large vs small difference, OR 0.28, 95% CI 0.17, 0.47).Conclusions: Several factors were significantly associated with establishing individualized HbA1c targets and reaching these targets. A small proportion of people with T2DM on insulin therapy reached their HbA1c target. Personalized management of glycemic targets necessitates the adoption of multi-factorial strategies, as several factors could influence an individual's glycemic outcome. CLINICALTRIALS.Gov Identifier: NCT01400971. [ABSTRACT FROM AUTHOR]

Mars' sedimentary rock record preserves information on geological (and potential astrobiological) processes that occurred on the planet billions of years ago. The Curiosity rover is exploring the lower reaches of Mount Sharp, in Gale crater on Mars. A traverse from Vera Rubin ridge to Glen Torridon has allowed Curiosity to examine a lateral transect of rock strata laid down in a martian lake ~3.5 billion years ago. We report spatial differences in the mineralogy of time-equivalent sedimentary rocks <400 meters apart. These differences indicate localized infiltration of silica-poor brines, generated during deposition of overlying magnesium sulfate-bearing strata. We propose that destabilization of silicate minerals driven by silica-poor brines (rarely observed on Earth) was widespread on ancient Mars, because sulfate deposits are globally distributed., (Copyright © 2021 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works.)

This paper provides an overview of the Curiosity rover's exploration at Vera Rubin ridge (VRR) and summarizes the science results. VRR is a distinct geomorphic feature on lower Aeolis Mons (informally known as Mount Sharp) that was identified in orbital data based on its distinct texture, topographic expression, and association with a hematite spectral signature. Curiosity conducted extensive remote sensing observations, acquired data on dozens of contact science targets, and drilled three outcrop samples from the ridge, as well as one outcrop sample immediately below the ridge. Our observations indicate that strata composing VRR were deposited in a predominantly lacustrine setting and are part of the Murray formation. The rocks within the ridge are chemically in family with underlying Murray formation strata. Red hematite is dispersed throughout much of the VRR bedrock, and this is the source of the orbital spectral detection. Gray hematite is also present in isolated, gray-colored patches concentrated toward the upper elevations of VRR, and these gray patches also contain small, dark Fe-rich nodules. We propose that VRR formed when diagenetic event(s) preferentially hardened rocks, which were subsequently eroded into a ridge by wind. Diagenesis also led to enhanced crystallization and/or cementation that deepened the ferric-related spectral absorptions on the ridge, which helped make them readily distinguishable from orbit. Results add to existing evidence of protracted aqueous environments at Gale crater and give new insight into how diagenesis shaped Mars' rock record., (©2020. The Authors.)

During 2018 and 2019, the Mars Science Laboratory Curiosity rover investigated the chemistry, morphology, and stratigraphy of Vera Rubin ridge (VRR). Using orbital data from the Compact Reconnaissance Imaging Spectrometer for Mars, scientists attributed the strong 860 nm signal associated with VRR to the presence of red crystalline hematite. However, Mastcam multispectral data and CheMin X-ray diffraction (XRD) measurements show that the depth of the 860 nm absorption is negatively correlated with the abundance of red crystalline hematite, suggesting that other mineralogical or physical parameters are also controlling the 860 nm absorption. Here, we examine Mastcam and ChemCam passive reflectance spectra from VRR and other locations to link the depth, position, and presence or absence of iron-related mineralogic absorption features to the XRD-derived rock mineralogy. Correlating CheMin mineralogy to spectral parameters showed that the ~860 nm absorption has a strong positive correlation with the abundance of ferric phyllosilicates. New laboratory reflectance measurements of powdered mineral mixtures can reproduce trends found in Gale crater. We hypothesize that variations in the 860 nm absorption feature in Mastcam and ChemCam observations of VRR materials are a result of three factors: (1) variations in ferric phyllosilicate abundance due to its ~800-1,000 nm absorption; (2) variations in clinopyroxene abundance because of its band maximum at ~860 nm; and (3) the presence of red crystalline hematite because of its absorption centered at 860 nm. We also show that relatively small changes in Ca-sulfate abundance is one potential cause of the erosional resistance and geomorphic expression of VRR., (©2020. The Authors.)

Visible/short-wave infrared spectral data from the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) show absorptions attributed to hematite at Vera Rubin ridge (VRR), a topographic feature on northwest Mt. Sharp. The goals of this study are to determine why absorptions caused by ferric iron are strongly visible from orbit at VRR and to improve interpretation of CRISM data throughout lower Mt. Sharp. These goals are achieved by analyzing coordinated CRISM and in situ spectral data along the Curiosity Mars rover's traverse. VRR bedrock within areas that have the deepest ferric absorptions in CRISM data also has the deepest ferric absorptions measured in situ. This suggests strong ferric absorptions are visible from orbit at VRR because of the unique spectral properties of VRR bedrock. Dust and mixing with basaltic sand additionally inhibit the ability to measure ferric absorptions in bedrock stratigraphically below VRR from orbit. There are two implications of these findings: (1) Ferric absorptions in CRISM data initially dismissed as noise could be real, and ferric phases are more widespread in lower Mt. Sharp than previously reported. (2) Patches with the deepest ferric absorptions in CRISM data are, like VRR, reflective of deeper absorptions in the bedrock. One model to explain this spectral variability is late-stage diagenetic fluids that changed the grain size of ferric phases, deepening absorptions. Curiosity's experience highlights the strengths of using CRISM data for spectral absorptions and associated mineral detections and the caveats in using these data for geologic interpretations and strategic path planning tools., (©2020. The Authors.)

The Mars Science Laboratory Curiosity rover performed coordinated measurements to examine the textures and compositions of aeolian sands in the active Bagnold dune field. The Bagnold sands are rounded to subrounded, very fine to medium sized (~45-500 μm) with ≥6 distinct grain colors. In contrast to sands examined by Curiosity in a dust-covered, inactive bedform called Rocknest and soils at other landing sites, Bagnold sands are darker, less red, better sorted, have fewer silt-sized or smaller grains, and show no evidence for cohesion. Nevertheless, Bagnold mineralogy and Rocknest mineralogy are similar with plagioclase, olivine, and pyroxenes in similar proportions comprising >90% of crystalline phases, along with a substantial amorphous component (35% ± 15%). Yet Bagnold and Rocknest bulk chemistry differ. Bagnold sands are Si enriched relative to other soils at Gale crater, and H 2 O, S, and Cl are lower relative to all previously measured Martian soils and most Gale crater rocks. Mg, Ni, Fe, and Mn are enriched in the coarse-sieved fraction of Bagnold sands, corroborated by visible/near-infrared spectra that suggest enrichment of olivine. Collectively, patterns in major element chemistry and volatile release data indicate two distinctive volatile reservoirs in Martian soils: (1) amorphous components in the sand-sized fraction (represented by Bagnold) that are Si-enriched, hydroxylated alteration products and/or H 2 O- or OH-bearing impact or volcanic glasses and (2) amorphous components in the fine fraction (<40 μm; represented by Rocknest and other bright soils) that are Fe, S, and Cl enriched with low Si and adsorbed and structural H 2 O.

We have developed a refined geologic map and stratigraphy for lower Mount Sharp using coordinated analyses of new spectral, thermophysical, and morphologic orbital data products. The Mount Sharp group consists of seven relatively planar units delineated by differences in texture, mineralogy, and thermophysical properties. These units are (1-3) three spatially adjacent units in the Murray formation which contain a variety of secondary phases and are distinguishable by thermal inertia and albedo differences, (4) a phyllosilicate-bearing unit, (5) a hematite-capped ridge unit, (6) a unit associated with material having a strongly sloped spectral signature at visible near-infrared wavelengths, and (7) a layered sulfate unit. The Siccar Point group consists of the Stimson formation and two additional units that unconformably overlie the Mount Sharp group. All Siccar Point group units are distinguished by higher thermal inertia values and record a period of substantial deposition and exhumation that followed the deposition and exhumation of the Mount Sharp group. Several spatially extensive silica deposits associated with veins and fractures show that late-stage silica enrichment within lower Mount Sharp was pervasive. At least two laterally extensive hematitic deposits are present at different stratigraphic intervals, and both are geometrically conformable with lower Mount Sharp strata. The occurrence of hematite at multiple stratigraphic horizons suggests redox interfaces were widespread in space and/or in time, and future measurements by the Mars Science Laboratory Curiosity rover will provide further insights into the depositional settings of these and other mineral phases.