The Mars Science Laboratory Curiosity rover is traversing a sequence of stratified sedimentary rocks in Gale crater that contain varied eolian, fluviodeltaic, and lake deposits, with phyllosilicates, ...iron oxides, and sulfate salts. Here, we report the chloride salt distribution along the rover traverse. Chlorine is detected at low levels (<3 wt.%) in soil and rock targets with multiple MSL instruments. Isolated fine‐scale observations of high chlorine (up to ≥15 wt.% Cl), detected using the ChemCam instrument, are associated with elevated Na2O and interpreted as halite grains or cements in bedrock. Halite is also interpreted at the margins of veins and in nodular, altered textures. We have not detected halite in obvious evaporitic layers. Instead, its scattered distribution indicates that chlorides emplaced earlier in particular members of the Murray formation were remobilized and reprecipitated by later groundwaters within Murray formation mudstones and in diagenetic veins and nodules.
Plain Language Summary
Chlorine is measured in soils and rocks in Gale crater by multiple instruments on the Mars Science Laboratory Curiosity rover. Fine‐scale points of enriched chlorine are detected by the ChemCam instrument in bedrock, nodules, and at the margins of veins in the Murray formation. Chlorine content is correlated with weight percent Na2O indicating halite composition, corroborated by CheMin and SAM data. The scattered distribution of chlorides in the Murray formation indicates they were dissolved by later groundwaters then recrystallized. The chlorides may have been emplaced as small‐scale primary deposits in particular members of the Murray formation, consistent with varying salinity in the waters that deposited the Murray.
Key Points
Isolated Cl enrichments in bedrock, in nodular textures, and at calcium sulfate vein margins, correlated with Na, indicate halite
Mapping of Cl along the Curiosity traverse in Gale Crater indicates Cl enrichments are more common in select Murray formation members
The scattered, isolated occurrences of chlorides are consistent with late groundwater reworking and remobilization of original deposits
All planetary materials sampled thus far vary in their relative abundance of the major isotope of oxygen, 16 O, such that it has not been possible to define a primordial solar system composition. We ...measured the oxygen isotopic composition of solar wind captured and returned to Earth by NASA's Genesis mission. Our results demonstrate that the Sun is highly enriched in 16 O relative to the Earth, Moon, Mars, and bulk meteorites. Because the solar photosphere preserves the average isotopic composition of the solar system for elements heavier than lithium, we conclude that essentially all rocky materials in the inner solar system were enriched in 17 O and 18 O, relative to 16 O, by ∼7%, probably via non—mass-dependent chemistry before accretion of the first planetesimals.
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.
Evidence for water ice near the lunar poles Feldman, W. C.; Maurice, S.; Lawrence, D. J. ...
Journal of Geophysical Research,
25 October 2001, Letnik:
106, Številka:
E10
Journal Article, Conference Proceeding
Recenzirano
Odprti dostop
Improved versions of Lunar Prospector thermal and epithermal neutron data were studied to help discriminate between potential delivery and retention mechanisms for hydrogen on the Moon. Improved ...spatial resolution at both poles shows that the largest concentrations of hydrogen overlay regions in permanent shade. In the north these regions consist of a heavily cratered terrain containing many small (less than ∼10‐km diameter), isolated craters. These border circular areas of hydrogen abundance (H) that is only modestly enhanced above the average equatorial value but that falls within large, flat‐bottomed, and sunlit polar craters. Near the south pole, H is enhanced within several 30‐km‐scale craters that are in permanent shade but is only modestly enhanced within their sunlit neighbors. We show that delivery by the solar wind cannot account for these observations because the diffusivity of hydrogen at the temperatures within both sunlit and permanently shaded craters near both poles is sufficiently low that a solar wind origin cannot explain their differences. We conclude that a significant portion of the enhanced hydrogen near both poles is most likely in the form of water molecules.
The sound of a Martian dust devil Murdoch, N; Stott, A E; Gillier, M ...
Nature communications,
12/2022, Letnik:
13, Številka:
1
Journal Article
Recenzirano
Odprti dostop
Dust devils (convective vortices loaded with dust) are common at the surface of Mars, particularly at Jezero crater, the landing site of the Perseverance rover. They are indicators of atmospheric ...turbulence and are an important lifting mechanism for the Martian dust cycle. Improving our understanding of dust lifting and atmospheric transport is key for accurate simulation of the dust cycle and for the prediction of dust storms, in addition to being important for future space exploration as grain impacts are implicated in the degradation of hardware on the surface of Mars. Here we describe the sound of a Martian dust devil as recorded by the SuperCam instrument on the Perseverance rover. The dust devil encounter was also simultaneously imaged by the Perseverance rover's Navigation Camera and observed by several sensors in the Mars Environmental Dynamics Analyzer instrument. Combining these unique multi-sensorial data with modelling, we show that the dust devil was around 25 m large, at least 118 m tall, and passed directly over the rover travelling at approximately 5 m s
. Acoustic signals of grain impacts recorded during the vortex encounter provide quantitative information about the number density of particles in the vortex. The sound of a Martian dust devil was inaccessible until SuperCam microphone recordings. This chance dust devil encounter demonstrates the potential of acoustic data for resolving the rapid wind structure of the Martian atmosphere and for directly quantifying wind-blown grain fluxes on Mars.
In 2012, NASA's Curiosity rover landed on Mars to assess its potential as a habitat for past life and investigate the paleoclimate record preserved by sedimentary rocks inside the ...~150-kilometer-diameter Gale impact crater. Geological reconstructions from Curiosity rover data have revealed an ancient, habitable lake environment fed by rivers draining into the crater. We synthesize geochemical and mineralogical data from lake-bed mudstones collected during the first 1300 martian solar days of rover operations in Gale. We present evidence for lake redox stratification, established by depth-dependent variations in atmospheric oxidant and dissolved-solute concentrations. Paleoclimate proxy data indicate that a transition from colder to warmer climate conditions is preserved in the stratigraphy. Finally, a late phase of geochemical modification by saline fluids is recognized.
The neutron-rich nucleus Ba-144 (t(1/2) = 11.5 s) is expected to exhibit some of the strongest octupole correlations among nuclei with mass numbers A less than 200. Until now, indirect evidence for ...such strong correlations has been inferred from observations such as enhanced E1 transitions and interleaving positive- and negative-parity levels in the ground-state band. In this experiment, the octupole strength was measured directly by sub-barrier, multistep Coulomb excitation of a post-accelerated 650-MeV Ba-144 beam on a 1.0-mg/cm(2) Pb-208 target. The measured value of the matrix element, < 3(1)(-)parallel to M(E3)parallel to 0(1)(+)> = 0.65((+17)(-23)) eb(3/2,) corresponds to a reduced Bd(E3) transition probability of 48((+25)(-34)) W.u. This result represents an unambiguous determination of the octupole collectivity, is larger than any available theoretical prediction, and is consistent with octupole deformation.
In-situ analyses reveal the presence of hydrogen within calcium sulfate veins crosscutting the sediments found in Gale crater. Laboratory experiments were performed to calibrate the hydrogen signal ...measured by laser induced breakdown spectroscopy (LIBS) in a range applicable to martian data. The analyses indicate that all veins targeted so far at Gale consist predominantly of bassanite which most likely formed by dehydration of gypsum. This scenario suggests that the percolating water produced gypsum, possibly by hydration of anhydrite in aqueous solution, and remained at temperatures below ∼60 °C at that time. Desiccating conditions followed, consistent with a hyperarid climate and favored by burial or impacts. Additionally, anhydrite with lesser bassanite has been found by XRD in samples of sediments hosting the veins. Our result suggests bassanite is likely found in the veins and anhydrite may be more common as a fine-grained component within the sediments.
•Experiments on calcium sulfate pellets were performed to calibrate the LIBS hydrogen signal.•Bright veins analyzed in situ at Gale crater are made predominantly of bassanite.•Bassanite could have resulted from the desiccation of gypsum.
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