Sazuna/UAT_keywords huggingface dataset:
Asteroid Impact Hazard Warning from the Near-Earth Object Surveyor Mission. NASA's Near-Earth Object Surveyor mission, scheduled for launch in 2027 September, is designed to detect and characterize at least two-thirds of the potentially hazardous asteroids with diameters larger than 140 m in a nominal 5 yr mission. We describe a model to estimate the survey performance using a faster approach than the time domain survey simulator described in Mainzer et al. (2023). This model is applied to explain how the completeness for 5 and 10 yr surveys varies with orbit type and asteroid size and to identify orbits with notably high or low likelihoods of detection. Size alone is an incomplete proxy for impact hazard, so for each asteroid orbit, we also calculate the associated hazard based on the impact velocity and the relative likelihood of impact. We then estimate how effective the mission will be at anticipating impacts as a function of impact energy, finding that a 5 yr mission will identify 87% of potential impacts larger than 100 Mt (Torino-9, "Regional Devastation"). For a 10 yr mission, this increases to 94%. We also show how the distribution of warning time varies with impact energy.

Keywords: Near-Earth objects, Sky surveys, Asteroids, Surveys, Infrared astronomy
Using Hydrodynamic Similarity as a Verification Method for Impact Cratering Simulations in the FLAG Hydrocode. Hydrodynamic codes (hydrocodes) are common tools for modeling hypervelocity impacts to provide insight into the physical phenomenon. Hydrocodes can simulate impacts from micrometer to kilometer spatial scales and reach impact velocities difficult to achieve in experimental settings. However, numerical models are approximations, and demonstrating that a numerical method is capable of providing physical results for these models is essential. In this work, we employ a hydrocode verification technique that leverages hydrodynamic similarity, a mathematical property of the conservation equations of fluid mechanics that form the basis for hydrocode models. Using the FLAG hydrocode, we simulate aluminum (Al) and basalt projectiles and targets at spatial scales spanning 7 orders of magnitude (hundreds of micrometers to kilometers). These materials were chosen because Al-6061 is a common material in spacecraft and satellites and basalt is a useful approximation of rocky astronomical bodies. Our results show that hydrodynamic similarity holds for each material model used and across spatial scales. We show that under certain conditions hydrodynamic similarity can apply in the presence of gravity and that similarity does not hold in the presence of strength models. We conclude that the FLAG hydrocode preserves important mathematical properties of fluid dynamics in hypervelocity impacts of Al-6061 and basalt.

Keywords: Impact phenomena, Hydrodynamical simulations, Planetary surfaces, Hydrodynamics, Space debris, Meteorites, Craters
Thermodynamic Predictions of Hydrogen Generation during the Serpentinization of Harzburgite with Seawater-derived Brines. Salty aqueous solutions (brines) occur on Earth and may be prevalent elsewhere. Serpentinization represents a family of geochemical reactions where the hydration of olivine-rich rocks can release aqueous hydrogen, H2(aq), as a byproduct, and hydrogen is a known basal electron donor for terrestrial biology. While the effects of lithological differences on serpentinization products have been thoroughly investigated, effects focusing on compositional differences of the reacting fluid have received less attention. In this contribution, we investigate how the chemistry of seawater-derived brines affects the generation of biologically available hydrogen resulting from the serpentinization of harzburgite. We numerically investigate the serpentinization of ultramafic rocks at equilibrium with an array of brines at different water activities (a proxy for salt concentration in aqueous fluids and a determinant for habitability) derived from seawater evaporation. Because the existing supersaturation of aqueous calcium carbonate, a contributor to dissolved inorganic carbon (DIC) in natural seawater, cannot be captured in equilibrium calculations, we bookend our calculations by enabling and suppressing carbonate minerals when simulating serpentinization. We find that the extent of DIC supersaturation can provide an important control of hydrogen availability. Increased DIC becomes a major sink for hydrogen by producing formate and associated complexes when the reacting fluids are acidic enough to allow for CO2. Indeed, H2(aq) reduces CO2(aq) to formate, leading to a hydrogen deficit. These conclusions provide additional insights into the habitability of brine systems, given their potential for serpentinization across diverse planetary bodies such as on Mars and ocean worlds.

Keywords: Astrobiology, Planetary geology
Updated Catalog of Kepler Planet Candidates: Focus on Accuracy and Orbital Periods. We present a new catalog of Kepler planet candidates that prioritizes accuracy of planetary dispositions and properties over uniformity. This catalog contains 4376 transiting planet candidates, including 1791 residing within 709 multiplanet systems, and provides the best parameters available for a large sample of Kepler planet candidates. We also provide a second set of stellar and planetary properties for transiting candidates that are uniformly derived for use in occurrence rate studies. Estimates of orbital periods have been improved, but as in previous catalogs, our tabulated values for period uncertainties do not fully account for transit timing variations (TTVs). We show that many planets are likely to have TTVs with long periodicities caused by various processes, including orbital precession, and that such TTVs imply that ephemerides of Kepler planets are not as accurate on multidecadal timescales as predicted by the small formal errors (typically 1 part in 106 and rarely &gt;10‑5) in the planets' measured mean orbital periods during the Kepler epoch. Analysis of normalized transit durations implies that eccentricities of planets are anticorrelated with the number of companion transiting planets. Our primary catalog lists all known Kepler planet candidates that orbit and transit only one star; for completeness, we also provide an abbreviated listing of the properties of the two dozen nontransiting planets that have been identified around stars that host transiting planets discovered by Kepler.

Keywords: Exoplanet dynamics, Planetary theory, Exoplanet catalogs, Exoplanets, Transit photometry
Short-timescale Spatial Variability of Ganymede's Optical Aurora. Ganymede's auroras are the product of complex interactions between its intrinsic magnetosphere and the surrounding Jovian plasma environment and can be used to derive both atmospheric composition and density. In this study, we analyzed a time series of Ganymede's optical auroras taken with Keck I/HIRES during eclipse by Jupiter on 2021 June 8 UTC, one day after the Juno flyby of Ganymede. The data had sufficient signal-to-noise in individual 5 minute observations to allow for the first high-cadence analysis of the spatial distribution of the optical aurora brightness and the ratio between the [O I] 630.0 and 557.7 nm disk-integrated auroral brightnesses—a quantity diagnostic of the relative abundances of O, O2, and H2O in Ganymede's atmosphere. We found that the hemisphere closer to the centrifugal equator of Jupiter's magnetosphere (where electron number density is highest) was up to twice as bright as the opposing hemisphere. The dusk (trailing) hemisphere, subjected to the highest flux of charged particles from Jupiter's magnetosphere, was also consistently almost twice as bright as the dawn (leading) hemisphere. We modeled emission from simulated O2 and H2O atmospheres during eclipse and found that if Ganymede hosts an H2O sublimation atmosphere in sunlight, it must collapse on a faster timescale than expected to explain its absence in our data given our current understanding of Ganymede's surface properties.

Keywords: Optical astronomy, Natural satellite atmospheres, Ganymede, Aurorae
Simulated Climate of TRAPPIST-1e Using MPAS-A and Comparisons with Other GCMs. Dayside convection is one of the most important contributors to a tidally locked planet's climate. Considering the long-standing challenge of simulating convections, we employ a convection-resolving model known as the Model for Prediction across Scales—Atmosphere and perform a series of simulations with spatial resolution ranging from 960 to 10 km. With TRAPPIST-1e, a potentially habitable exoplanet, as the target, we aim to draw a comparative analysis against the results from the TRAPPIST-1 Habitable Atmosphere Intercomparison project. Regarding the overall climate states, our simulations reaffirm the findings of the previous general circulation model (GCM). Both the extensive substellar cloud cluster and the intricate cloud street feature are successfully reproduced. The influence of varying grid resolution exhibits a remarkably marginal impact across our resolution spectrum, albeit with a slightly heightened sensitivity observed at the nightside. Major differences center around the cloud-related variables, including cloud phase (liquid and ice), amount, and height, in both the grid resolution assessments and GCM intercomparison scenarios. Furthermore, we explore the repercussions on the phase curve and transit spectrum.

Keywords: Atmospheric clouds, Atmospheric circulation, Planetary climates, Habitable planets, Exoplanet atmospheres
Global Lunar Crater Density Using Buffered Nonsparseness Correction. The density of craters on a planetary surface directly relates to the age of the surface. As the surface ages, however, craters can be erased by subsequent large impacts via direct overprinting, known as geometric crater obliteration. Such counts become increasingly limited as surfaces become more heavily cratered. Techniques to infer the statistics of the regions obliterated by craters were developed in the past decade. Such techniques, however, have only been used for regional studies. Herein, we present a study of the global density of lunar impact craters ≥20 km in diameter using both traditional crater-counting and buffered nonsparseness correction (BNSC) crater-counting techniques. By comparing the measurements, we quantify the influence of geometric crater obliteration on the visible lunar crater record. Our results reveal that geometric crater obliteration erased up to three-fifths of craters ≥20 km in diameter that formed on the most ancient lunar terrains, whereas younger surfaces, like the Procellarum KREEP Terrane, show little to no evidence of such crater obliteration. The differences in derived crater densities highlight ancient surfaces in which the effects of geometric crater obliteration must be considered to characterize their cratering histories. Furthermore, our results identify the most heavily cratered area on the Moon, a region of the lunar highlands between Smythii basin and the South Pole–Aitken (SPA) basin (Smythii–SPA–Highlands); the number of impacts revealed by the BNSC technique for this region is consistent with estimates derived from the abundance of highly siderophile elements and from modeling crustal porosity.

Keywords: Planetary surfaces, Surface processes, The Moon, Lunar impacts, Planetary geology, Impact gardening
Simulations on Levitation and Spatial Distribution of Charged Dust on the Moon Surface. The levitation of charged dust, which may cause serious hazards to astronauts and lunar rovers, has been one of the most significant challenges in lunar exploration. Here we simulate lunar sheath potentials in different solar wind conditions and solar zenith angles (SZAs) on the lunar surface by the particle-in-cell method. The simulated potentials exhibit two types of distributions as a function of height, depending on the SZAs. For SZA ∼ 0°–70°, the nonmonotonic distribution with positive surface potential dominates in the photoelectron sheath. For SZA &gt;∼81°, the monotonic distribution with negative surface potential is observed in the plasma sheath. With the calculated potentials and the assumption that the dust radius distribution exponentially decreases, we further investigate spatial distributions of the dust levitated above the surface. It is found that number density of the levitating lunar dust is enhanced at the terminator (SZA ∼ 81°) in the plasma sheath. In the photoelectron sheath it gradually decreases as the SZA increases from 0° to 70°. Further calculations of the potential and the derived electrostatic field suggest that the dust spatial distributions can be influenced by the bulk velocity, number density, and temperature of the solar wind. Those findings deepen our understanding of lunar surface charging and the mechanism of lunar dust levitation, which can provide technical support for lunar explorations.

Keywords: The Moon, Lunar science
Where Is That Crater? Best Practices for Obtaining Accurate Coordinates from LROC NAC Data. The Lunar Reconnaissance Orbiter Camera (LROC) Narrow Angle Camera (NAC) images and their derived products make up one of the highest-resolution and most spatially accurate data sets available for the Moon, making them a crucial resource for planners of landed lunar missions. However, it is essential to understand the best uses for each data type and the limits on the accuracy and resolution of the data sets available. With this understanding, users can better interpret and communicate their results. In this paper, we describe what assumptions may be made about the accuracy of LROC NAC images and the various derived products created by the LROC team. NAC digital terrain models and their corresponding orthophotos have the best accuracy of all NAC products, usually better than 10 m horizontally, and should be used where available. Other controlled NAC products usually have accuracies better than 30 m. For areas without controlled products, we describe how to process NAC images to obtain coordinates with the highest possible accuracy. We also recommend best practices for data users interacting with LROC data through online map servers, such as QuickMap or Lunaserv, and for processing LROC data locally using the US Geological Survey Integrated Software for Imagers and Spectrometers.

Keywords: The Moon, Remote sensing, Pointing accuracy, Lunar geodesy
Global Mapping of HCl on Mars by IRTF/iSHELL. Hydrogen chloride (HCl)—a key marker of the chlorine cycle on Mars—has been recently discovered in the Martian atmosphere by the ExoMars/TGO mission. In-orbit data indicate that this molecule appears in the atmosphere only in a limited time period and specifically in the southern summer season. A snapshot global mapping of HCl is indispensable to examine its sources and sinks, but such observations are not currently possible from any orbiters. Here, we present the first spatially resolved map of HCl obtained with the ground-based NASA InfraRed Telescope Facility. We find clear features of HCl, demonstrating that HCl is present close to the surface. HCl is detected in the equatorial region for the first time, revealing that HCl is widely distributed on Mars. However, the spatial distribution of HCl is not uniform, and it is enhanced in the southern polar region. Interestingly, this nonuniform spatial distribution of HCl column abundance is strikingly similar to that of water vapor column abundance. This highlights the important role of water vapor in the evolution of HCl through the atmosphere, as previously noted, and suggests its potential involvement in the atmospheric chlorine source processes.

Keywords: Planetary atmospheres
Quantitative Criteria for Defining Planets. The current International Astronomical Union (IAU) definition of "planet" is problematic because it is vague and excludes exoplanets. Here, we describe aspects of quantitative planetary taxonomy and examine the results of unsupervised clustering of solar system bodies to guide the development of possible classification frameworks. Two unsurprising conclusions emerged from the clustering analysis: (1) satellites are distinct from planets and (2) dynamical dominance is a natural organizing principle for planetary taxonomy. To generalize an existing dynamical dominance criterion, we adopt a universal clearing timescale applicable to all central bodies (brown dwarfs, stars, and stellar remnants). Then, we propose two quantitative, unified frameworks to define both planets and exoplanets. The first framework is aligned with both the IAU definition of planet in the solar system and the IAU working definition of an exoplanet. The second framework is a simpler mass-based framework that avoids some of the difficulties ingrained in current IAU recommendations.

Keywords: Accretion, Classification systems, Exoplanets, Solar system planets, Classification, Orbits, Natural satellites (Solar system), Dwarf planets, Clustering, Planetary dynamics
Accretion of Meteoric Organic Matter at the Surface of Mars and Potential Production of Methane by Ultraviolet Radiation. In this study, a comprehensive model of the meteoric organic cycle on Mars for the current geological period is developed, which characterizes the ablation of exogenous organic matter in the upper atmosphere, the accretion of intact carbon at the surface, and the potential production of methane by UV photolysis from the surface reservoir. The model accounts for both the latitudinal and seasonal variation of the meteoroids' input from the most relevant populations in the inner solar system. A recent version of the University of Leeds Chemical Ablation Model, which includes a semiempirical model to describe the pyrolysis kinetics of the meteoric organic matter, is then combined with this meteoroid input function and a semiempirical model that quantifies the UV production of methane. The minimum and maximum accretion rates of organics are between 18 and 90 kg sol‑1 at aphelion and 45–134 kg sol‑1 at the first crossing of the ecliptic plane. The resulting mixing ratios of carbon, in the top 200 μm of the surface layer, range from 0.09–0.43 ppm at 20°N to 4.8–8.9 ppm around the south pole. To be consistent with the methane upper limit of 0.02 ppbv measured by the NOMAD instrument on the ExoMars Trace Gas Orbiter, the UV photolysis yields for methane production need to be around 3% assuming a meteoric carbon content in comets of 25.6 wt% and an atmospheric lifetime of methane of 329 Earth yr. Alternatively, a laboratory estimate of 20% for the methane production yield would require a lifetime of 60 Earth yr.

Keywords: Meteorite composition, Methane, Meteoroids, Zodiacal cloud, Mars, Short period comets, Long period comets, Meteors, Meteorites, Asteroid belt, Comets, Complex organic molecules
Photometric Properties within the Reiner Gamma Swirl: Constraining Formation Mechanisms. The area in the Reiner Gamma swirl studied by Weirich et al. for topographic correlations also displays correlations with the Hapke-model-derived single-scattering albedo, surface roughness, and particle scattering properties with swirl unit. The correlations with single-scattering albedo associate compositional variations in plagioclase and FeO content with swirl unit. The correlations with photometric surface roughness show a rougher surface on-swirl, implying a potentially more porous surface on-swirl compared to off-swirl. This suggests the variations in single-scattering albedo are dominated by the compositional differences and not structural differences, such as compaction. Grain-size differences could still contribute to the albedo variations. Differences in particle scattering properties between on-swirl and off-swirl are counter-indicative of the trend expected from variations in space weathering, unless there is a process to initiate either size sorting or compositional differences. The photometric properties point to a complex interaction of multiple processes to form the swirl units, not a singular dominant process. Variations in weathering, dust mobilization and entrapment, and impact modification may all play a key role.

Keywords: Surface photometry, Mercury (planet)
Predictions for Sparse Photometry of Jupiter-family Comet Nuclei in the LSST Era. The Legacy Survey of Space and Time (LSST) at Vera C. Rubin Observatory will deliver high-quality, temporally sparse observations of millions of solar system objects on an unprecedented scale. Such data sets will likely enable the precise estimation of small-body properties on a population-wide basis. In this work, we consider the possible applications of photometric data points from LSST to the characterization of Jupiter-family comet (JFC) nuclei. We simulate sparse-in-time lightcurve points with an LSST-like cadence for the orbit of a JFC between 2024 and 2033. Convex lightcurve inversion is used to assess whether the simulation input parameters can be accurately reproduced for a sample of nucleus rotation periods, pole orientations, activity onsets, shapes, and sizes. We find that the rotation period and pole direction can be reliably constrained across all nucleus variants tested, and that the convex shape models, while limited in their ability to describe complex or bilobed nuclei, are effective for correcting sparse photometry for rotational modulation to improve estimates of nucleus phase functions. Based on this analysis, we anticipate that LSST photometry will significantly enhance our present understanding of the spin state and phase function distributions of JFC nuclei.

Keywords: Comet nuclei, Light curves, Short period comets, Sky surveys
Doomed Worlds. I. No New Evidence for Orbital Decay in a Long-term Survey of 43 Ultrahot Jupiters. Ultrahot Jupiters (UHJs) are likely doomed by tidal forces to undergo orbital decay and eventual disruption by their stars, but the timescale over which this process unfolds is unknown. We present results from a long-term project to monitor UHJ transits. We recovered WASP-12 b's orbital decay rate of ms yr‑1, in agreement with prior work. Five other systems initially had promising nonlinear transit ephemerides. However, a closer examination of two—WASP-19 b and CoRoT-2 b, both with prior tentative detections—revealed several independent errors with the literature timing data; after correction, neither planet shows signs of orbital decay. Meanwhile, a potential decreasing period for TrES-1 b, ms yr‑1, corresponds to a tidal quality factor and likely does not result from orbital decay if driven by dissipation within the host star. Nominal period increases in two systems, WASP-121 b and WASP-46 b, rest on a small handful of points. Only 1/43 planets (WASP-12 b) in our sample is experiencing detectable orbital decay. For nearly half (20/42), we can rule out as high as observed for WASP-12 b. Thus, while many UHJs could still be experiencing rapid decay that we cannot yet detect, a sizable subpopulation of UHJs are decaying at least an order of magnitude more slowly than WASP-12 b. Our reanalysis of Kepler-1658 b with no new data finds that it remains a promising orbital decay candidate. Finally, we recommend that the scientific community take steps to avoid spurious detections through better management of the multi-decade-spanning data sets needed to search for and study planetary orbital decay.

Keywords: Hot Jupiters, Exoplanets, Exoplanet tides, Transit timing variation method, Transit photometry