SO_2-rock interaction on Io 2. Interaction with pure SO_2

A Na-S mineral on the surface of Io is required to be the source of the famous atomic cloud. SO_2 is a confirmed atmospheric and surface constituent, and because of the rapid volcanic resurfacing rate, the SO_2 is buried within the crust, where at least occasionally, over many cycles of burial and eruption, it must contact silicate materials at midlevel crustal temperatures. Surface interaction experiments were performed for a wide variety of silicate compositions showing that interaction products of these with SO_2 could be observed at 1123 K on laboratory timescales, even in the absence of external redox agents. Not all experiments produced deposits that could be studied by scanning electron microscopy; some required the greater sensitivity of photoelectron spectroscopy (XPS). Characterization of the alteration products by XPS showed that both oxidized and reduced sulfur species were formed, indicating that a disproportionation mechanism producing a sulfate and a reduced S species although smaller amounts of interaction leading to Na_2SO_3 formation cannot be ruled out. The reduced sulfur species is best explained as elemental S which was independently documented for two compositions. Scanning electron microscopy studies for those compositions where reaction was extensive enough to be observed showed (1) Na_2SO_4 for a soda-lime composition, (2) a mixed Na-Ca-sulfate liquid and CaSO_4 for AbAnDi and a chondrule glass composition, and (3) Fe-sulfate for a natural obsidian. Infrared spectroscopy for the soda-lime glass composition showed peaks best explained by Na_2SO_4. We conclude that SO_2 disproportionation as well as direct formation from SO_3 under oxidizing conditions can produce Na_2SO_4 by interaction of SO_2 with silicates on Io, but Ca and Fe sulfates may form preferentially in more basaltic compositions. As highly oxidizing conditions may be unlikely for Io, the disproportionation mechanism may be more competitive on Io than it is in laboratory experiments. Very low rates of Na_2SO_4 production are required to supply the Io atomic cloud, so the interaction processes can be very inefficient

Field Studies of Crater Gradation in Gusev Crater and Meridiani Planum Using the Mars Exploration Rovers

The Mars Exploration Rovers Spirit and Opportunity investigated numerous craters since landing in Gusev crater (14.569degS, 175.473degE) and Meridiani Planum (1.946degS, 354.473degE) over the first 400 sols of their missions [1-4]. Craters at both sites are simple structures and vary in size and preservation state. Comparing observed and expected pristine morphology and using process-specific gradational signatures around terrestrial craters as a template [5-7] allows distinguishing gradation processes whose relative importance fundamentally differs from those responsible for most crater modification on the Earth

Correlation of Rock Spectra with Quantitative Morphologic Indices: Evidence for a Single Rock Type at the Mars Pathfinder Landing Site

The Mars Pathfinder (MPF) landing site was predicted to contain a broad sampling of rock types varying in mineralogical, physical, mechanical and geochemical characteristics. Although rocks have been divided into several spectral categories based on Imager for Mars Pathfinder (IMP) visible/near-infrared data, efforts in isolating and classifying spectral units among MPF rocks and soils have met with varying degrees of success, as many factors influencing spectral signatures cannot be quantified to a sufficient level to be removed. It has not been fully determined which spectral categories stem from intrinsic mineralogical differences between rocks or rock surfaces, and which result from factors such as physical or chemical weathering. This has made isolation of unique rock mineralogies difficult. Morphology, like composition, is a characteristic tied to the intrinsic properties and geologic and weathering history of rocks. Rock morphologies can be assessed quantitatively and compared with spectral data, to identify and classify rock types at the MPF landing site. They can also isolate actual rock spectra from spectral types that are surficial in origin, as compositions associated with mantling dust or chemical coatings would presumably not influence rock morphology during weathering events. We previously reported on an initial classification of rocks using the quantitative morphologic indices of size, roundness, sphericity and elongation. Here, we compare this database of rock characteristics with associated rock surface spectra to improve our ability to discriminate between spectra associated with rock types and those from other sources

Crater gradation in Gusev crater and Meridiani Planum, Mars

The Mars Exploration Rovers investigated numerous craters in Gusev crater and Meridiani Planum during the first ∼400 sols of their missions. Craters vary in size and preservation state but are mostly due to secondary impacts at Gusev and primary impacts at Meridiani. Craters at both locations are modified primarily by eolian erosion and infilling and lack evidence for modification by aqueous processes. Effects of gradation on crater form are dependent on size, local lithology, slopes, and availability of mobile sediments. At Gusev, impacts into basaltic rubble create shallow craters and ejecta composed of resistant rocks. Ejecta initially experience eolian stripping, which becomes weathering-limited as lags develop on ejecta surfaces and sediments are trapped within craters. Subsequent eolian gradation depends on the slow production of fines by weathering and impacts and is accompanied by minor mass wasting. At Meridiani the sulfate-rich bedrock is more susceptible to eolian erosion, and exposed crater rims, walls, and ejecta are eroded, while lower interiors and low-relief surfaces are increasingly infilled and buried by mostly basaltic sediments. Eolian processes outpace early mass wasting, often produce meters of erosion, and mantle some surfaces. Some small craters were likely completely eroded/buried. Craters \u3e100 m in diameter on the Hesperian-aged floor of Gusev are generally more pristine than on the Amazonian-aged Meridiani plains. This conclusion contradicts interpretations from orbital views, which do not readily distinguish crater gradation state at Meridiani and reveal apparently subdued crater forms at Gusev that may suggest more gradation than has occurred

Refining the transit-timing and photometric analysis of TRAPPIST-1: Masses, Radii, densities, dynamics, and ephemerides

We have collected transit times for the TRAPPIST-1 system with the Spitzer Space Telescope over four years. We add to these ground-based, HST and K2 transit time measurements, and revisit an N-body dynamical analysis of the seven-planet system using our complete set of times from which we refine the mass ratios of the planets to the star. We next carry out a photodynamical analysis of the Spitzer light curves to derive the density of the host star and the planet densities. We find that all seven planets' densities may be described with a single rocky mass-radius relation which is depleted in iron relative to Earth, with Fe 21 wt% versus 32 wt% for Earth, and otherwise Earth-like in composition. Alternatively, the planets may have an Earth-like composition, but enhanced in light elements, such as a surface water layer or a core-free structure with oxidized iron in the mantle. We measure planet masses to a precision of 3-5%, equivalent to a radial-velocity (RV) precision of 2.5 cm/sec, or two orders of magnitude more precise than current RV capabilities. We find the eccentricities of the planets are very small; the orbits are extremely coplanar; and the system is stable on 10 Myr timescales. We find evidence of infrequent timing outliers which we cannot explain with an eighth planet; we instead account for the outliers using a robust likelihood function. We forecast JWST timing observations, and speculate on possible implications of the planet densities for the formation, migration and evolution of the planet system

Attitudes towards treatment among patients suffering from sleep disorders. A Latin American survey

BACKGROUND: Although sleep disorders are common, they frequently remain unnoticed by the general practitioner. Few data are available about the willingness and reasons of patients with sleep disturbances to seek for medical assistance. METHODS: The results of a cross-sectional community-based multinational survey in three major Latin American urban areas, i.e. Buenos Aires, Mexico City and Sao Paulo, are reported. Two-hundred subjects suffering sleep disturbances and 100 non-sufferers were selected from the general population in each city (total number: 600 sufferers vs. 300 non-sufferers). A structured interview was conducted, sleep characteristics, feelings about sleep disturbances and strategies to cope with those problems being recorded. Data were analyzed by employing either t-test or analysis of variance (ANOVA) to the Z-transformed proportions. RESULTS: 22.7 ± 3.5 % (mean ± SEM) of subjects reported to suffer from sleep disturbances every night. About 3 out of 4 (74.2 ± 2.0 %) considered their disorder as mild and were not very concerned about it. Only 31 ± 2 % of sufferers reported to have sought for medical help. Although 45 ± 2 % of sufferers reported frequent daily sleepiness, trouble to remember things, irritability and headaches, they did not seek for medical assistance. Among those patients who saw a physician with complaints different from sleep difficulties only 1 out of 3 (33 ± 2 % of patients) were asked about quality of their sleep by the incumbent practitioner. Strategies of patients to cope with sleep problems included specific behaviors (taking a warm bath, reading or watching TV) (44 ± 1.6 %), taking herbal beverages (17 ± 1.2 %) or taking sleeping pills (10 ± 1.1 %). Benzodiazepines were consumed by 3 ± 0.6 % of sufferers. CONCLUSION: Public educational campaigns on the consequences of sleep disorders and an adequate training of physicians in sleep medicine are needed to educate both the public and the general practitioners about sleep disorders

Field reconnaissance geologic mapping of the Columbia Hills, Mars, based on Mars Exploration Rover Spirit and MRO HiRISE observations

Chemical, mineralogic, and lithologic ground truth was acquired for the first time on Mars in terrain units mapped using orbital Mars Reconnaissance Orbiter’s High Resolution Imaging Science Experiment (MRO HiRISE) image data. Examination of several dozen outcrops shows that Mars is geologically complex at meter length scales, the record of its geologic history is well exposed, stratigraphic units may be identified and correlated across significant areas on the ground, and outcrops and geologic relationships between materials may be analyzed with techniques commonly employed in terrestrial field geology. Despite their burial during the course of Martian geologic time by widespread epiclastic materials, mobile fines, and fall deposits, the selective exhumation of deep and well‐preserved geologic units has exposed undisturbed outcrops, stratigraphic sections, and structural information much as they are preserved and exposed on Earth. A rich geologic record awaits skilled future field investigators on Mars. The correlation of ground observations and orbital images enables construction of a corresponding geologic reconnaissance map. Most of the outcrops visited are interpreted to be pyroclastic, impactite, and epiclastic deposits overlying an unexposed substrate, probably related to a modified Gusev crater central peak. Fluids have altered chemistry and mineralogy of these protoliths in degrees that vary substantially within the same map unit. Examination of the rocks exposed above and below the major unconformity between the plains lavas and the Columbia Hills directly confirms the general conclusion from remote sensing in previous studies over past years that the early history of Mars was a time of more intense deposition and modification of the surface. Although the availability of fluids and the chemical and mineral activity declined from this early period, significant later volcanism and fluid convection enabled additional, if localized, chemical activity.Additional co-authors: D DesMarais, M Schmidt, NA Cabrol, A Haldemann, Kevin W Lewis, AE Wang, D Blaney, B Cohen, A Yen, J Farmer, R Gellert, EA Guinness, KE Herkenhoff, JR Johnson, G Klingelhöfer, A McEwen, JW Rice Jr, M Rice, P deSouza, J Hurowit

A super-Earth and a sub-Neptune orbiting the bright, quiet M3 dwarf TOI-1266

We report the discovery and characterisation of a super-Earth and a sub-Neptune transiting the bright (K = 8.8), quiet, and nearby (37 pc) M3V dwarf TOI-1266. We validate the planetary nature of TOI-1266 b and c using four sectors of TESS photometry and data from the newly-commissioned 1-m SAINT-EX telescope located in San Pedro Mártir (México). We also include additional ground-based follow-up photometry as well as high-resolution spectroscopy and high-angular imaging observations. The inner, larger planet has a radius of R = 2.37_(−0.12)^(+0.16) R_⊕ and an orbital period of 10.9 days. The outer, smaller planet has a radius of R = 1.56_(−0.13)^(+0.15) R_⊕ on an 18.8-day orbit. The data are found to be consistent with circular, co-planar and stable orbits that are weakly influenced by the 2:1 mean motion resonance. Our TTV analysis of the combined dataset enables model-independent constraints on the masses and eccentricities of the planets. We find planetary masses of M_p = 13.5_(−9.0)^(+11.0) M_⊕ (<36.8 M_⊕ at 2-σ) for TOI-1266 b and 2.2_(−1.5)^(+2.0) M_⊕ (<5.7 M_⊕ at 2-σ) for TOI-1266 c. We find small but non-zero orbital eccentricities of 0.09_(−0.05)^(+0.06) (<0.21 at 2-σ) for TOI-1266 b and 0.04 ± 0.03 (< 0.10 at 2-σ) for TOI-1266 c. The equilibrium temperatures of both planets are of 413 ± 20 and 344 ± 16 K, respectively, assuming a null Bond albedo and uniform heat redistribution from the day-side to the night-side hemisphere. The host brightness and negligible activity combined with the planetary system architecture and favourable planet-to-star radii ratios makes TOI-1266 an exquisite system for a detailed characterisation

A super-Earth and a sub-Neptune orbiting the bright, quiet M3 dwarf TOI-1266

We report the discovery and characterisation of a super-Earth and a sub-Neptune transiting the bright ($K=8.8$), quiet, and nearby (37 pc) M3V dwarf TOI-1266. We validate the planetary nature of TOI-1266 b and c using four sectors of TESS photometry and data from the newly-commissioned 1-m SAINT-EX telescope located in San Pedro M\'artir (Mexico). We also include additional ground-based follow-up photometry as well as high-resolution spectroscopy and high-angular imaging observations. The inner, larger planet has a radius of $R=2.37_{-0.12}^{+0.16}$ R$_{\oplus}$ and an orbital period of 10.9 days. The outer, smaller planet has a radius of $R=1.56_{-0.13}^{+0.15}$ R$_{\oplus}$ on an 18.8-day orbit. The data are found to be consistent with circular, co-planar and stable orbits that are weakly influenced by the 2:1 mean motion resonance. Our TTV analysis of the combined dataset enables model-independent constraints on the masses and eccentricities of the planets. We find planetary masses of $M_\mathrm{p}$ = $13.5_{-9.0}^{+11.0}$ $\mathrm{M_{\oplus}}$ ($<36.8$ $\mathrm{M_{\oplus}}$ at 2-$\sigma$) for TOI-1266 b and $2.2_{-1.5}^{+2.0}$ $\mathrm{M_{\oplus}}$ ($<5.7$ $\mathrm{M_{\oplus}}$ at 2-$\sigma$) for TOI-1266 c. We find small but non-zero orbital eccentricities of $0.09_{-0.05}^{+0.06}$ ($<0.21$ at 2-$\sigma$) for TOI-1266 b and $0.04\pm0.03$ ($<0.10$ at 2-$\sigma$) for TOI-1266 c. The equilibrium temperatures of both planets are of $413\pm20$ K and $344\pm16$ K, respectively, assuming a null Bond albedo and uniform heat redistribution from the day-side to the night-side hemisphere. The host brightness and negligible activity combined with the planetary system architecture and favourable planet-to-star radii ratios makes TOI-1266 an exquisite system for a detailed characterisation

Warm terrestrial planet with half the mass of Venus transiting a nearby star

The advent of a new generation of radial velocity instruments has allowed us to break the one Earth-mass barrier. We report a new milestone in this context with the detection of the lowest-mass planet measured so far using radial velocities: L 98-59 b, a rocky planet with half the mass of Venus. It is part of a system composed of three known transiting terrestrial planets (planets b to d). We announce the discovery of a fourth nontransiting planet with a minimum mass of 3.06_{-0.37}^{+0.33} MEarth and an orbital period of 12.796_{-0.019}^{+0.020} days and report indications for the presence of a fifth nontransiting terrestrial planet. With a minimum mass of 2.46_{-0.82}^{+0.66} MEarth and an orbital period 23.15_{-0.17}^{+0.60} days, this planet, if confirmed, would sit in the middle of the habitable zone of the L 98-59 system. L 98-59 is a bright M dwarf located 10.6 pc away. Positioned at the border of the continuous viewing zone of the James Webb Space Telescope, this system is destined to become a corner stone for comparative exoplanetology of terrestrial planets. The three transiting planets have transmission spectrum metrics ranging from 49 to 255, which makes them prime targets for an atmospheric characterization with the James Webb Space Telescope, the Hubble Space Telescope, Ariel, or ground-based facilities such as NIRPS or ESPRESSO. With an equilibrium temperature ranging from 416 to 627 K, they offer a unique opportunity to study the diversity of warm terrestrial planets. L 98-59 b and c have densities of 3.6_{-1.5}^{+1.4} and 4.57_{-0.85}^{+0.77} this http URL^{-3}, respectively, and have very similar bulk compositions with a small iron core that represents only 12 to 14 % of the total mass, and a small amount of water. However, with a density of 2.95_{-0.51}^{+0.79} this http URL^{-3} and despite a similar core mass fraction, up to 30 % of the mass of L 98-59 d might be water