Constraining the Potential Liquid Water Environment at Gale Crater, Mars

The Mars Science Laboratory (MSL) Rover Environmental Monitoring Station (REMS) has now made continuous in situ meteorological measurements for several Martian years at Gale crater, Mars. Of importance in the search for liquid formation are REMS’ measurements of ground temperature and inâ air measurements of temperature and relative humidity, which is with respect to ice. Such data can constrain the surface and subsurface stability of brines. Here we use updated calibrations to REMS data and consistent relative humidity comparisons (i.e., with respect to liquid versus with respect to ice) to investigate the potential formation of surface and subsurface liquids throughout MSL’s traverse. We specifically study the potential for the deliquescence of calcium perchlorate. Our data analysis suggests that surface brine formation is not favored within the first 1648 sols as there are only two times (sols 1232 and 1311) when humidityâ temperature conditions were within error consistent with a liquid phase. On the other hand, modeling of the subsurface environment would support brine production in the shallow subsurface. Indeed, we find that the shallow subsurface for terrains with low thermal inertia (Î â ²300 J mâ 2 Kâ 1 sâ 1/2) may be occasionally favorable to brine formation through deliquescence. Terrains with Î â ²175 J mâ 2 Kâ 1 sâ 1/2 and albedos of â ³0.25 are the most apt to subsurface brine formation. Should brines form, they would occur around Ls 100°. Their predicted properties would not meet the Special nor Uncertain Region requirements, as such they would not be potential habitable environments to life as we know it.Plain Language SummaryThe Mars Science Laboratory (MSL) has now made continuous measurements of the local weather at Gale crater, Mars. Such measurements can help guide our search for the formation of liquid water on presentâ day Mars. Specifically, when the right temperature and humidity conditions are met, certain salts can take in water vapor from the atmosphere to produce liquids. Here we use data from MSL along with experimental results on the stability of a Marsâ relevant salt to search for time periods when liquids could potentially form at the surface. Additionally, we use simulations and MSL data to understand the potential to form such liquids in the subsurface. Our results suggest that surface formation of liquids is unlikely throughout MSL’s travels; however, the shallow subsurface may experience conditions that would allow for liquid formation. Not much liquid would form, though, and the properties of these liquids would not permit life as we know it to persist.Key PointsMeasured surface environmental conditions at Gale crater are not favorable to brine formation via deliquescence of calcium perchlorateLiquids may have formed in the shallow subsurface of low thermal inertia units within MSLâ traversed terrainsMSL may best find liquids in the subsurface of units with thermal inertia less than or equal to 175 J mâ 2 Kâ 1 sâ 1/2 and albedo > 0.25 around Ls 100°Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/144585/1/jgre20830-sup-0001-supinfo.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/144585/2/jgre20830_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/144585/3/jgre20830.pd

Merkuriuksen pohjoisnapaesiintymien paikallisen kokoluokan heterogeenisyyksien luonnehdinta Arecibon S-kaistan tutkalla

Peer reviewe

Asteroids Inside Out: Radar Tomography

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Synergies between ground-based and space-based observations in the solar system and beyond

The goal of this white paper is to provide examples where ground-based and space-based observations are combined, and used to obtain understanding or constrain parameters beyond what the separate measurements could yield

Arecibon planetaarisen tutkan Maan lähiasteroidihavainnot: 2017 joulukuu - 2019 joulukuu

We successfully observed 191 near-Earth asteroids using the Arecibo Observatory's S-band planetary radar system from 2017 December through 2019 December. We present radar cross sections for 167 asteroids; circular-polarization ratios for 112 asteroids based on Doppler-echo-power spectra measurements; and radar albedos, constraints on size and spin periods, and surface-feature and shape evaluation for 37 selected asteroids using delay-Doppler radar images with a range resolution of 75 m or finer. Out of 33 asteroids with an estimated effective diameter of at least 200 m and sufficient image quality to give clues of the shape, at least 4 (∼12%) are binary asteroids, including 1 equal-mass binary asteroid, 2017 YE5, and at least 10 (∼30%) are contact-binary asteroids. For 5 out of 112 asteroids with reliable measurements in both circular polarizations, we measured circular-polarization ratios greater than 1.0, which could indicate that they are E-type asteroids, while the mean and the 1σ standard deviation were 0.37 ± 0.23. Further, we find a mean opposite-sense circular-polarization radar albedo of 0.21 ± 0.11 for 41 asteroids (0.19 ± 0.06 for 11 S-complex asteroids). We identified two asteroids, 2011 WN15 and (505657) 2014 SR339, as possible metal-rich objects based on their unusually high radar albedos, and discuss possible evidence of water ice in 2017 YE5.Peer reviewe

Science Opportunities offered by Mercury's Ice-Bearing Polar Deposits

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Biophysical Manipulation of the Extracellular Environment by Eurotium halophilicum

Eurotium halophilicum is psychrotolerant, halophilic, and one of the most-extreme xerophiles in Earth’s biosphere. We already know that this ascomycete grows close to 0 °C, at high NaCl, and—under some conditions—down to 0.651 water-activity. However, there is a paucity of information about how it achieves this extreme stress tolerance given the dynamic water regimes of the surface habitats on which it commonly occurs. Here, against the backdrop of global climate change, we investigated the biophysical interactions of E. halophilicum with its extracellular environment using samples taken from the surfaces of library books. The specific aims were to examine its morphology and extracellular environment (using scanning electron microscopy for visualisation and energy-dispersive X-ray spectrometry to identify chemical elements) and investigate interactions with water, ions, and minerals (including analyses of temperature and relative humidity conditions and determinations of salt deliquescence and water activity of extracellular brine). We observed crystals identified as eugsterite (Na4Ca(SO4)3·2H2O) and mirabilite (Na2SO4·10H2O) embedded within extracellular polymeric substances and provide evidence that E. halophilicum uses salt deliquescence to maintain conditions consistent with its water-activity window for growth. In addition, it utilizes a covering of hair-like microfilaments that likely absorb water and maintain a layer of humid air adjacent to the hyphae. We believe that, along with compatible solutes used for osmotic adjustment, these adaptations allow the fungus to maintain hydration in both space and time. We discuss these findings in relation to the conservation of books and other artifacts within the built environment, spoilage of foods and feeds, the ecology of E. halophilicum in natural habitats, and the current episode of climate change