Volatiles and especially halogens (F and Cl) have been recognized as important species in the genesis and melting of planetary magmas. Data from the Chemical Camera instrument on board the Mars ...Science Laboratory rover Curiosity now provide the first in situ analyses of fluorine at the surface of Mars. Two principal F‐bearing mineral assemblages are identified. The first is associated with high aluminum and low calcium contents, in which the F‐bearing phase is an aluminosilicate. It is found in conglomerates and may indicate petrologically evolved sources. This is the first time that such a petrologic environment is found on Mars. The second is represented by samples that have high calcium contents, in which the main F‐bearing minerals are likely to be fluorapatites and/or fluorites. Fluorapatites are found in some sandstone and may be detrital, while fluorites are also found in the conglomerates, possibly indicating low‐T alteration processes.
Key Points
First detection of fluorine at the Martian surface
High sensitivity of fluorine detection with LIBS
F‐bearing phases imply alteration and evolved magmatism
The ChemCam instrument package on the Mars rover, Curiosity, provides new capabilities to probe the abundances of certain trace elements in the rocks and soils on Mars using the laser‐induced ...breakdown spectroscopy technique. We focus on detecting and quantifying Li, Ba, Rb, and Sr in targets analyzed during the first 100 sols, from Bradbury Landing Site to Rocknest. Univariate peak area models and multivariate partial least squares models are presented. Li, detected for the first time directly on Mars, is generally low (<15 ppm). The lack of soil enrichment in Li, which is highly fluid mobile, is consistent with limited influx of subsurface waters contributing to the upper soils. Localized enrichments of up to ~60 ppm Li have been observed in several rocks but the host mineral for Li is unclear. Bathurst_Inlet is a fine‐grained bedrock unit in which several analysis locations show a decrease in Li and other alkalis with depth, which may imply that the unit has undergone low‐level aqueous alteration that has preferentially drawn the alkalis to the surface. Ba (~1000 ppm) was detected in a buried pebble in the Akaitcho sand ripple and it appears to correlate with Si, Al, Na, and K, indicating a possible feldspathic composition. Rb and Sr are in the conglomerate Link at abundances >100 ppm and >1000 ppm, respectively. These analysis locations tend to have high Si and alkali abundances, consistent with a feldspar composition. Together, these trace element observations provide possible evidence of magma differentiation and aqueous alteration.
Key Points
Quantitative models for Li, Ba, Rb and Sr using ChemCam data are presented
Abundances for the first 100 sols in Gale crater are discussed
These results represent the first in situ measurements of Li and Ba on Mars
Textural and compositional analyses using Chemistry Camera (ChemCam) remote microimager and laser‐induced breakdown spectroscopy (LIBS) have been performed on five float rocks and coarse gravels ...along the first 100 m of the Curiosity traverse at Bradbury Rise. ChemCam, the first LIBS instrument sent to another planet, offers the opportunity to assess mineralogic diversity at grain‐size scales (~ 100 µm) and, from this, lithologic diversity. Depth profiling indicates that targets are relatively free of surface coatings. One type of igneous rock is volcanic and includes both aphanitic (Coronation) and porphyritic (Mara) samples. The porphyritic sample shows dark grains that are likely pyroxene megacrysts in a fine‐grained mesostasis containing andesine needles. Both types have magnesium‐poor basaltic compositions and in this respect are similar to the evolved Jake Matijevic rock analyzed further along the Curiosity traverse both with Alpha‐Particle X‐ray Spectrometer and ChemCam instruments. The second rock type encountered is a coarse‐grained intrusive rock (Thor Lake) showing equigranular texture with millimeter size crystals of feldspars and Fe‐Ti oxides. Such a rock is not unique at Gale as the surrounding coarse gravels (such as Beaulieu) and the conglomerate Link are dominated by feldspathic (andesine‐bytownite) clasts. Finally, alkali feldspar compositions associated with a silica polymorph have been analyzed in fractured filling material of Preble rock and in Stark, a putative pumice or an impact melt. These observations document magmatic diversity at Gale and describe the first fragments of feldspar‐rich lithologies (possibly an anorthosite) that may be ancient crust transported from the crater rim and now forming float rocks, coarse gravel, or conglomerate clasts.
Key Points
The converging of LIBS data processing points to a mineralogical coherency
Mg‐poor basaltic rocks correspond to fractionated evolved rocks
Feldspath‐rich rocks, gravels, and conglomerates, with possible felsic pumice.
•Impact crater processes observed during MSL’s first 360 Sols were studied.•Possible impactites are scarce, but include shatter cones and disrupted bedrock.•Loose igneous and sedimentary blocks ...identified near the rover may be distal ejecta.•The smallest observed crater is 0.6m in diam., consistent with atmospheric filtering.•Crater counts constrain the aeolian erosion rate to ~10mm per million years.•The erosion rate is consistent with the observed erosion of the Peace Vallis fan.
Impact processes at all scales have been involved in the formation and subsequent evolution of Gale crater. Small impact craters in the vicinity of the Curiosity MSL landing site and rover traverse during the 364 Sols after landing have been studied both from orbit and the surface. Evidence for the effect of impacts on basement outcrops may include loose blocks of sandstone and conglomerate, and disrupted (fractured) sedimentary layers, which are not obviously displaced by erosion. Impact ejecta blankets are likely to be present, but in the absence of distinct glass or impact melt phases are difficult to distinguish from sedimentary/volcaniclastic breccia and conglomerate deposits. The occurrence of individual blocks with diverse petrological characteristics, including igneous textures, have been identified across the surface of Bradbury Rise, and some of these blocks may represent distal ejecta from larger craters in the vicinity of Gale. Distal ejecta may also occur in the form of impact spherules identified in the sediments and drift material. Possible examples of impactites in the form of shatter cones, shocked rocks, and ropy textured fragments of materials that may have been molten have been observed, but cannot be uniquely confirmed. Modification by aeolian processes of craters smaller than 40m in diameter observed in this study, are indicated by erosion of crater rims, and infill of craters with aeolian and airfall dust deposits. Estimates for resurfacing suggest that craters less than 15m in diameter may represent steady state between production and destruction. The smallest candidate impact crater observed is ∼0.6m in diameter. The observed crater record and other data are consistent with a resurfacing rate of the order of 10mm/Myr; considerably greater than the rate from impact cratering alone, but remarkably lower than terrestrial erosion rates.
The SuperCam instrument on the Perseverance Mars 2020 rover uses a pulsed 1064 nm laser to ablate targets at a distance and conduct laser induced breakdown spectroscopy (LIBS) by analyzing the light ...from the resulting plasma. SuperCam LIBS spectra are preprocessed to remove ambient light, noise, and the continuum signal present in LIBS observations. Prior to quantification, spectra are masked to remove noisier spectrometer regions and spectra are normalized to minimize signal fluctuations and effects of target distance. In some cases, the spectra are also standardized or binned prior to quantification. To determine quantitative elemental compositions of diverse geologic materials at Jezero crater, Mars, we use a suite of 1198 laboratory spectra of 334 well-characterized reference samples. The samples were selected to span a wide range of compositions and include typical silicate rocks, pure minerals (e.g., silicates, sulfates, carbonates, oxides), more unusual compositions (e.g., Mn ore and sodalite), and replicates of the sintered SuperCam calibration targets (SCCTs) onboard the rover. For each major element (SiO2, TiO2, Al2O3, FeOT, MgO, CaO, Na2O, K2O), the database was subdivided into five “folds” with similar distributions of the element of interest. One fold was held out as an independent test set, and the remaining four folds were used to optimize multivariate regression models relating the spectrum to the composition. We considered a variety of models, and selected several for further investigation for each element, based primarily on the root mean squared error of prediction (RMSEP) on the test set, when analyzed at 3 m. In cases with several models of comparable performance at 3 m, we incorporated the SCCT performance at different distances to choose the preferred model. Shortly after landing on Mars and collecting initial spectra of geologic targets, we selected one model per element. Subsequently, with additional data from geologic targets, some models were revised to ensure results that are more consistent with geochemical constraints. The calibration discussed here is a snapshot of an ongoing effort to deliver the most accurate chemical compositions with SuperCam LIBS.
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•We quantify the following oxides: SiO2, TiO2, Al2O3, FeOT, MgO, CaO, Na2O, K2O.•Multivariate regression models were trained on a diverse suite of spectra.•Of the algorithms considered, ensemble methods performed well but had limitations.•We evaluated models based on laboratory and Mars results.•Work is ongoing to improve major element results and quantify additional elements.
•First ChemCam analysis of hydrogen.•Description of data acquisition and processing for hydrogen.•Analysis of hydrogen within different clusters defined by multivariate methods.•Almost all data seems ...hydrated to a variable extent.•Results consistent with fluvial lacustrine context observed by the Curiosity rover.
One of the main advantages of ChemCam’s LIBS (Laser-Induced Breakdown Spectroscopy) instrument onboard the Curiosity rover is its potential to detect light elements such as hydrogen at fine scales, which has never been achieved on Mars. Hydrogen lines are detected in most of the data obtained within the first 320 sols of the mission at Gale crater, Mars. This work is a description of the hydrogen signal and its variability in the ChemCam LIBS spectra; it discusses the challenges of qualitative and quantitative analysis. Data acquisition and processing steps are investigated and optimized for the detection of hydrogen on Mars. Subtraction of an appropriate dark spectrum and the deconvolution of the superimposed emission of carbon from the low-pressure CO2-dominated atmosphere are particularly important. Because the intensities of hydrogen are also affected by matrix effects, the hydrogen signal was investigated within groups of targets sharing common chemical features and similar matrices. The different groups cover a variety of rock and soil compositions encountered along the traverse (calcium sulfate veins, mafic soils, felsic, Mg-rich and Fe-rich rocks) including data from both drill holes and their tailings. Almost all these targets were found to be hydrated to variable extents. Soils have systematically higher hydrogen signals than rocks and pebbles, probably as a result of their alteration. The results from rocks suggest that various alteration processes leading to their hydration have taken place, which is consistent with the fluvial lacustrine context, the diagenetic features, and the mineralogy observed by Curiosity in Yellowknife Bay.
•Martian soils are analyzed for the first time at sub millimeter scale.•Three different groups of coarse grains have been distinguished.•Fine particles seem to derive from one group of coarse ...grains.•Presence of amorphous component in fine particles and some coarse grains.•Fine particles have undergone limited interaction with water.
The ChemCam instrument onboard the Curiosity rover provides for the first time an opportunity to study martian soils at a sub-millimeter resolution. In this work, we analyzed 24 soil targets probed by ChemCam during the first 250sols on Mars. Using the depth profile capability of the ChemCam LIBS (Laser-Induced Breakdown Spectroscopy) technique, we found that 45% of the soils contained coarse grains (>500μm). Three distinct clusters have been detected: Cluster 1 shows a low SiO2 content; Cluster 2 corresponds to coarse grains with a felsic composition, whereas Cluster 3 presents a typical basaltic composition. Coarse grains from Cluster 2 have been mostly observed exposed in the vicinity of the landing site, whereas coarse grains from Clusters 1 and 3 have been detected mostly buried, and were found all along the rover traverse. The possible origin of these coarse grains was investigated. Felsic (Cluster 2) coarse grains have the same origin as the felsic rocks encountered near the landing site, whereas the origin of the coarse grains from Clusters 1 and 3 seems to be more global. Fine-grained soils (particle size<laser beam diameter which is between 300 and 500μm) show a homogeneous composition all along the traverse, different from the composition of the rocks encountered at Gale. Although they contain a certain amount of hydrated amorphous component depleted in SiO2, possibly present as a surface coating, their overall chemical homogeneity and their close-to-basaltic composition suggest limited, or isochemical alteration, and a limited interaction with liquid water. Fine particles and coarse grains from Cluster 1 have a similar composition, and the former could derive from weathering of the latter. Overall martian soils have a bulk composition between that of fine particles and coarse grains. This work shows that the ChemCam instrument provides a means to study the variability of soil composition at a scale not achievable by bulk chemical analyses.
Identifying unequivocal signs of life on Mars is one of the most important objectives for sending missions to the red planet. Here we report Red Stone, a 163-100 My alluvial fan-fan delta that formed ...under arid conditions in the Atacama Desert, rich in hematite and mudstones containing clays such as vermiculite and smectites, and therefore geologically analogous to Mars. We show that Red Stone samples display an important number of microorganisms with an unusual high rate of phylogenetic indeterminacy, what we refer to as "dark microbiome", and a mix of biosignatures from extant and ancient microorganisms that can be barely detected with state-of-the-art laboratory equipment. Our analyses by testbed instruments that are on or will be sent to Mars unveil that although the mineralogy of Red Stone matches that detected by ground-based instruments on the red planet, similarly low levels of organics will be hard, if not impossible to detect in Martian rocks depending on the instrument and technique used. Our results stress the importance in returning samples to Earth for conclusively addressing whether life ever existed on Mars.
Background Practice variation in breast cancer surgery has raised concerns about the quality of treatment decisions. We sought to evaluate the quality of decisions about surgery for early-stage ...breast cancer by measuring patient knowledge, concordance between goals and treatments, and involvement in decisions. Study Design A mailed survey of stage I/II breast cancer survivors was conducted at 4 sites. The Decision Quality Instrument measured knowledge, goals, and involvement in decisions. A multivariable logistic regression model of treatment was developed. The model-predicted probability of mastectomy was compared with treatment received for each patient. Concordance was defined as having mastectomy and predicted probability >0.5 or partial mastectomy and predicted probability <0.5. Frequency of discussion about partial mastectomy was compared with discussion about mastectomy using chi-square tests. Results Four hundred and forty patients participated (59% response rate). Mean overall knowledge was 52.7%; 45.9% knew that local recurrence risk is higher after breast conservation and 55.7% knew that survival is equivalent for the 2 options. Most participants (89.0%) had treatment concordant with their goals. Participants preferring mastectomy had lower concordance (80.5%) than those preferring partial mastectomy (92.6%; p = 0.001). Participants reported more frequent discussion of partial mastectomy and its advantages than of mastectomy, and 48.6% reported being asked their preference. Conclusions Breast cancer survivors had major knowledge deficits, and those preferring mastectomy were less likely to have treatment concordant with goals. Patients perceived that discussions focused on partial mastectomy, and many were not asked their preference. Improvements in the quality of decisions about breast cancer surgery are needed.
During the development activities of SuperCam Calibration Target, target intended for one of the two first Raman instruments to be deployed on another planetary body, our group developed a laboratory ...instrument that could simulate to some extent the Raman capabilities of one of such instruments and could provide data with similar quality. The use of this kind of laboratory instruments has demonstrated its utility in the evaluation of potential calibration targets or anticipating the science outcome that an instrument could provide. The present work describes our laboratory setup to support SuperCam, evaluating similarities between both instruments, despite of differences in the hardware. Evaluation of data gathered by SuperCam on Mars and the availability of one replica of SuperCam’s Calibration Target allowed the comparison on the same set of targets, demonstrating how similar Signal-to-Noise Ratio (SNR) could be achieved from both instruments. The higher energy per pulse on SimulCam is compensated by a greater analytical footprint and the use of smaller collection optics. The results show how spectra obtained at representative distances of SuperCam are comparable. Operational principles are also comparable in terms of time resolution, and close in terms of spectral resolution.
This similarity has allowed different science support works using SimulCam data, as well as the support to Mars detections using our setup. We provide examples of this support that will be shared with the community in different papers, as well as examples of possible operations activities that could benefit from experiments performed with SimulCam. We show how this setup can complement the two laboratory replicas in Los Alamos and Toulouse in providing support data to different experiments.
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