Sazuna/UAT_keywords huggingface dataset:
A Geologic Map of Vesta Produced Using a Hybrid Method for Incorporating Spectroscopic and Morphologic Data. We have constructed a global geologic map of the minor planet Vesta at 1:300,000-scale using Dawn spacecraft imaging, spectroscopic, topographic, and elemental data. In this effort, we used a mapping method that requires creating two maps independently: the first map uses morphology and topography to define map units, while the second map relies on multispectral data ("color") to define units. The two are then combined into a hybrid product that retains the maximum amount of unique information from both maps in a readable format. This effort has revealed that for bodies where cratering is the dominant unit-forming process, and where there is not a close correlation between morphological feature types and multispectral signal, a hybrid mapping method better retains unique information carried by multispectral data during the mapping process than traditional morphology-based methods alone. Conversely, relying too heavily on color data risks placing too much emphasis on information drawn from the top few microns of the surface. To ensure both consistency and retention of unique information, we created a decision tree for determining which data would be primary in choosing where to draw unit boundaries. Also due to the significant amount of information borne by spectral data, we repurposed traditional mapping nomenclature so that subscripts carry color information. We recommend using this mapping methodology on bodies where (a) morphologic feature boundaries are commonly subtle, gradational, or both, and (b) spectral data carries a significant amount of unique data for identifying, characterizing, and interpreting geologic units.

Keywords: Geological processes, Vesta, Planetary geology
Plasma Sheath around Chandrayaan-3 Landing Site: A Case Study. India's lander-rover mission Chandrayaan-3 is scheduled to be launched in mid-2023. We have simulated a realistic scenario and investigated the electric potential development over the Chandrayaan-3 landing site under the influence of observed solar ultraviolet/extreme-ultraviolet radiation and real plasma parameters measured by THEMIS as a case study. The electric potential structures have been derived by solving Poisson's equation, which is coupled with latitude-dependent fermionic photoelectrons, non-Maxwellian plasma electrons, and cold ions. A dynamic variation of the potential structure around the sunlit landing site has been observed through the analysis. This study predicts a photoelectron density range from 10 to 40 cm-3 and mean energy range from 2.6 to 3 eV near the surface of the Chandrayaan-3 landing site, which may be tested by the in situ measurement.

Keywords: The Moon, Space plasmas, Solar wind
Stable Brine Layers beneath Europa's Chaos. The formation mechanism of Europa's large chaos terrain (&gt;~100 km diameter) and associated lenticulae (&lt;~10 km diameter) has been debated since their observations by the Galileo spacecraft. Their geomorphology and distribution suggest there may be reservoirs of saline liquid water 1-3 km beneath the surface-the "shallow water" model-generated by injection of ocean water or melting of the ice shell. Recent investigations on the evolution of small shallow-water bodies (≤103 km3) suggests that salts with a small effect on melting point (MgSO4) can extend the lifetime of saline bodies by ~5% compared to freshwater reservoirs. However, sodium chloride, identified as a potential oceanic salt, has a significantly stronger impact on the freezing point, suggesting a further extension of liquid lifetimes. Moreover, the substantial volumes of liquid water (~104 km3) beneath large chaos could be melted in situ rather than injected through a fracture, implying a distinct chemistry and formation environment. Here, we use numerical models to explore how the chemistry and disparate origins of shallow water control its evolution and lifetime. For small, injected sills, we find that NaCl can extend their liquid lifetime to ~140 kyr-up to a ~60% increase over freshwater sills. Saline melt lenses will last at least 175 kyr but, in contrast to sills, may persist as a stable layer of brine beneath the surface for over 500 kyr. Our results provide further support for the presence of liquid water at shallow depths within Europa's ice shell today.

Keywords: Planetary geology, Planetary dynamics, Europa
Col-OSSOS: Evidence for a Compositional Gradient Inherited from the Protoplanetary Disk?. In the present-day Kuiper Belt, the number of compositional classes and the orbital distributions of these classes hold important cosmogonic implications for the solar system. The Colours of the Outer Solar System Origins Survey (Col-OSSOS) recently showed that the observed color distribution of small (H ⪆ 6) trans-Neptunian objects (TNOs) can be accounted for by the existence of only two composition classes, named BrightIR and FaintIR, where the range of colors in each class can be modeled as mixtures of two material end-members. Here, we combine the high-precision photometric measurements of Col-OSSOS with those of previous surveys to investigate the orbital distribution of the two color classes and reinterpret the known color-inclination correlation of TNOs in the context of the BrightIR/FaintIR taxonomy. In addition to confirming the previously reported distinct orbital distributions of these classes, we identify a trend of increasing orbital inclinations toward the bluer end of the optical and near-infrared color distribution of BrightIR objects. Using the output of numerical simulations investigating the orbital evolution of TNOs during their scattering phase with Neptune, we show that this trend could reflect a composition gradient in the early protoplanetary disk, in the range of heliocentric distances over which TNOs from the BrightIR class accreted. However, tensions between this interpretation and the existence of blue contaminants among cold classical TNOs, and possible alternative origins for the detected correlation, currently bear uncertainty on our proposed interpretation.

Keywords: Broad band photometry, Trans-Neptunian objects
Effects of the Librationally Induced Flow in Mercury's Fluid Core with an Outer Stably Stratified Layer. Observational constraints on Mercury's thermal evolution and magnetic field indicate that the top part of the fluid core is stably stratified. Here we compute how a stable layer affects the core flow in response to Mercury's main 88 day longitudinal libration, assuming various degrees of stratification, and study whether the core flow can modify the libration amplitude through viscous and electromagnetic torques acting on the core-mantle boundary (CMB). We show that the core flow strongly depends on the strength of the stratification near the CMB but that the influence of core motions on libration is negligible with or without a stably stratified layer. A stably stratified layer at the top of the core can, however, prevent resonant behavior with gravito-inertial modes by impeding radial motions and promote a strong horizontal flow near the CMB. The librationally driven flow is likely turbulent and might produce a nonaxisymmetric induced magnetic field with a strength of the order of 1% of Mercury's dipolar field.

Keywords: Internal waves, Astrophysical fluid dynamics, Libration, Mercury (planet), Magnetic fields
Stratigraphy, Crater Size-Frequency Distribution, and Chronology of Selected Areas of Ganymede's Light and Dark Terrains. The stratigraphy of the largest natural satellite of our solar system, Ganymede, is investigated using available global mosaic (basemap) and high-resolution images. We are focusing on the reconstruction of the formation and tectonic evolution of selected areas of dark and light terrain units and investigate their morphological characteristics and relative ages at a local scale using high-resolution images from the sub-Jovian and anti-Jovian hemispheres. For this, geological maps and crater size-frequency distributions for each of the terrain units were prepared, and relative as well as absolute ages were derived by applying the currently available lunar-derived impact chronology model and the Jupiter-family comet chronology model. The relative ages obtained from the cross-cutting relationships of terrain units are not always consistent with the ages derived from the crater size-frequency distributions. Some regions are influenced by secondary and sesquinary craters and tectonic resurfacing activities. Independent of the applied model, the derived crater size-frequency distribution showed that the light terrain started to form soon after the completion of dark terrain formation.

Keywords: Ganymede, Natural satellite surfaces, Jupiter, Galilean satellites, Tectonics, Jovian satellites
Maps of Solar Wind Plasma Precipitation onto Mercury's Surface: A Geographical Perspective. Mercury is the closest planet to the Sun, possesses a weak intrinsic magnetic field, and has only a very tenuous atmosphere (exosphere). These three conditions result in a direct coupling between the plasma emitted from the Sun (namely, the solar wind) and Mercury's surface. The planet's magnetic field leads to a nontrivial pattern of plasma precipitation onto the surface that is expected to contribute to the alteration of the regolith over geological timescales. The goal of this work is to study the solar wind plasma precipitation onto the surface of Mercury from a geographical perspective, as opposed to the local time-of-day approach of previous precipitation modeling studies. We employ solar wind precipitation maps for protons and electrons from two fully kinetic numerical simulations of Mercury's plasma environment. These maps are then integrated over two full Mercury orbits (176 Earth days). We found that the plasma precipitation pattern at the surface is most strongly affected by the upstream solar wind conditions, particularly the interplanetary magnetic field direction, and less by Mercury's 3:2 spin-orbit resonance. We also found that Mercury's magnetic field is able to shield the surface from roughly 90% of the incoming solar wind flux. At the surface, protons have a broad energy distribution from below 500 eV to more than 1.5 keV, while electrons are mostly found in the range 0.1-10 keV. These results will help to better constrain space weathering and exosphere source processes at Mercury, as well as interpret observations by the ongoing ESA/JAXA BepiColombo mission.

Keywords: Space plasmas, Planetary surfaces, Planetary geology, Space weather, Solar wind, Interplanetary magnetic fields, Planetary science, Mercury (planet), Regolith, Magnetic fields
Adsorption Kinetics of Water and Argon on Lunar Grains. Adsorption residence times of water on lunar grains play an essential role for the migration and sequestration of water on the Moon, but estimates vary by over 10 orders of magnitude for the same temperature. Here, the physical chemistry literature for the interaction of water vapor and argon with silicates is reviewed, and available measurements of adsorption on lunar samples are used to quantify adsorption times. The wide range of adsorption energies, measured or postulated, is explained by activated surface sites with high desorption energies. Passivation, the opposite of activation, occurs quickly in laboratory settings and is expected on longer timescales at shallow depths on the Moon. A quantitative parameterization of desorption rates, intended for a wide range of adsorbate concentrations and temperatures, is constructed and used in model calculations. Grain surface diffusion plays a key role for desorption rates and also reduces photodestruction rates. For ice buried beneath lunar soil, multilayer adsorption is expected well before the depth of the ice is reached.

Keywords: Water vapor, Lunar regolith, Ice physics, The Moon, Astrochemistry, Lunar science, Lunar surface
Radar Observations of the Arid Meteor Shower Outburst from Comet 15P/Finlay. We report on observations of the anticipated, first time occurrence, Arid meteor shower produced by comet 15P/Finlay. This comet, which has not been noteworthy for over a century, produced two major outbursts of activity during perihelion passage between 2014 December and 2015 January. Various authors predicted that Earth would cross the resulting ejecta on 2021 October 6-7 UT with a radiant in the constellation Ara, optimally placed to be observed from the Southern Hemisphere. We observed two outbursts using the Southern Argentina Agile Meteor Radar-Orbital System: one on 2021 September 29 and a second more dominant peak on 2021 October 7, centered around α = 260.°34, δ = -57.°63 and α = 255.°01, δ = -48.°47, respectively. The 6.5 mag limit flux and zenithal hourly rates were 0.073 meteors km-2 hr-1 and 491 hr-1, respectively. The time of occurrence of the two detected peaks are in good agreement with predictions of this shower reported by several authors, confirming the validity of the models used for the predictions.

Keywords: Meteors, Radar observations, Meteor showers
Pre-landing Assessment of the Surface and Shallow Subsurface Thermal Setting of Mare Crisium of the Moon for the Heat Flow Measurement Planned on the Blue Ghost 1 Mission. In 2024, under NASA's Commercial Lunar Payload Services initiative, a robotic lander will touch down in Mare Crisium of the Moon and deploy a heat flow probe. Ideally, the probe should penetrate the regolith deep enough (1.5-2 m) to avoid the influence of insolation, but it is a major challenge to excavate such a hole on a robotic mission. The present study assesses the insolation-induced temperature fluctuation in the shallower subsurface of the landing site in case the heat flow probe does not reach past that depth. The assessment was based on a newly constructed, one-dimensional heat conduction model, which accounted for the history of solar heat intake at the landing site for the past 100 yr. The thermal properties of the subsurface regolith of the model were constrained by the previous surface temperature observations by flyovers of NASA's Lunar Reconnaissance Orbiter and the subsurface thermal measurement data from Apollo 17. The model showed that the amplitude of the insolation-induced annual subsurface temperature fluctuation is modulated by the 18.6 yr period precession of the Moon. The model also showed that the amplitude of this annual wave would be at (or close to) its minimum in 2024, when the mission would take place. Even though the thermal wave may be felt at depths greater than 1.5 m, because of its small amplitude, the thermal gradient in the depth range from 1 to 1.5 m would be within several percent of the gradient representative of the endogenic heat flow.

Keywords: The Moon
Stereophotoclinometry for OSIRIS-REx Spacecraft Navigation. We summarize a decade of effort by the Origins, Spectral Interpretation, Resource Identification, and Security-Regolith Explorer (OSIRIS-REx) mission team to build up the unique capabilities, processes, and procedures required to accomplish the unprecedented navigation performance required during proximity operations at asteroid (101955) Bennu. Stereophotoclinometry was a key technology used for digital terrain model (DTM) generation and landmark navigation, enabling estimation of spacecraft trajectories and Bennu's geophysical parameters. We outline the concept of operations for OSIRIS-REx landmark navigation and the wide array of testing and verification efforts leading up to OSIRIS-REx's arrival at Bennu. We relate the outcome of these efforts to the experiences during proximity operations. We discuss navigation and DTM performance during operations, including detailed lessons learned to carry forward for future missions.

Keywords: Astrodynamics, Near-Earth objects, Astronomical models, Astronomy data modeling, Asteroids, Asteroid dynamics, Optical astronomy, Orbits, Astronomical methods, Orbit determination, Astronomical simulations, Asteroid surfaces
The Collisional Evolution of the Primordial Kuiper Belt, Its Destabilized Population, and the Trojan Asteroids. The tumultuous early era of outer solar system evolution culminated when Neptune migrated across the primordial Kuiper Belt (PKB) and triggered a dynamical instability among the giant planets. This event led to the ejection of ∼99.9% of the PKB (here called the destabilized population), heavy bombardment of the giant planet satellites, and the capture of Jupiter's Trojans. While this scenario has been widely tested using dynamical models, there have been fewer investigations into how the PKB, its destabilized population, and the Trojans experienced collisional evolution. Here we examined this issue for all three populations with the code Boulder. Our constraints included the size–frequency distributions (SFDs) of the Trojan asteroids and craters on the giant planet satellites. Using this combination, we solved for the unknown disruption law affecting bodies in these populations. The weakest ones, from an impact energy per mass perspective, were diameter D ∼ 20 m. Overall, collisional evolution produces a power-law-like shape for multikilometer Trojans and a wavy-shaped SFD in the PKB and destabilized populations. The latter can explain (i) the shapes of the ancient and younger crater SFDs observed on the giant planet satellites, (ii) the shapes of the Jupiter family and long-period comet SFDs, which experienced different degrees of collision evolution, and (iii) the present-day impact frequency of superbolides on Jupiter and smaller projectiles on Saturn's rings. Our model results also indicate that many observed comets, the majority which are D &lt; 10 km, are likely to be gravitational aggregates formed by large-scale collision events.

Keywords: Collisional processes, Kuiper belt, Uranian satellites, Plutonian satellites, Short period comets, Dynamical evolution, Jupiter trojans, Long period comets, Trans-Neptunian objects, Comet origins, Saturnian satellites, Jovian satellites
Origin-of-life Molecules in the Atmosphere after Big Impacts on the Early Earth. The origin of life on Earth would benefit from a prebiotic atmosphere that produced nitriles, like HCN, which enable ribonucleotide synthesis. However, geochemical evidence suggests that Hadean air was relatively oxidizing with negligible photochemical production of prebiotic molecules. These paradoxes are resolved by iron-rich asteroid impacts that transiently reduced the entire atmosphere, allowing nitriles to form in subsequent photochemistry. Here we investigate impact-generated reducing atmospheres using new time-dependent, coupled atmospheric chemistry and climate models that account for gas-phase reactions and surface catalysis. The resulting H2-, CH4-, and NH3-rich atmospheres persist for millions of years, until the hydrogen escapes to space. The HCN and HCCCN production and rainout to the surface can reach 109 molecules cm-2 s-1 in hazy atmospheres with a mole ratio of CH4/CO2 &gt; 0.1. Smaller CH4/CO2 ratios produce HCN rainout rates of &lt;105 molecules cm-2 s-1 and negligible HCCCN. The minimum impactor mass that creates atmospheric CH4/CO2 &gt; 0.1 is 4 × 1020-5 × 1021 kg (570-1330 km diameter), depending on how efficiently iron reacts with a steam atmosphere, the extent of atmospheric equilibration with an impact-induced melt pond, and the surface area of nickel that catalyzes CH4 production. Alternatively, if steam permeates and deeply oxidizes the crust, impactors of ~1020 kg could be effective. Atmospheres with copious nitriles have &gt;360 K surface temperatures, perhaps posing a challenge for RNA longevity, although cloud albedo can produce cooler climates. Regardless, postimpact cyanide can be stockpiled and used in prebiotic schemes after hydrogen has escaped to space.

Keywords: Earth atmosphere, Earth (planet), Astrobiology, Atmospheric composition, Pre-biotic astrochemistry
Earth as a Transiting Exoplanet: A Validation of Transmission Spectroscopy and Atmospheric Retrieval Methodologies for Terrestrial Exoplanets. The James Webb Space Telescope (JWST) will enable the search for and characterization of terrestrial exoplanet atmospheres in the habitable zone via transmission spectroscopy. However, relatively little work has been done to use solar system data, where ground truth is known, to validate spectroscopic retrieval codes intended for exoplanet studies, particularly in the limit of high resolution and high signal-to-noise ratio (S/N). In this work, we perform such a validation by analyzing a high-S/N empirical transmission spectrum of Earth using a new terrestrial exoplanet atmospheric retrieval model with heritage in solar system remote sensing and gaseous exoplanet retrievals. We fit the Earth's 2-14 μm transmission spectrum in low resolution (R = 250 at 5 μm) and high resolution (R = 100,000 at 5 μm) under a variety of assumptions about the 1D vertical atmospheric structure. In the limit of noiseless transmission spectra, we find excellent agreement between model and data (deviations &lt;10%) that enable the robust detection of H2O, CO2, O3, CH4, N2, N2O, NO2, HNO3, CFC-11, and CFC-12 thereby providing compelling support for the detection of habitability, biosignature, and technosignature gases in the atmosphere of the planet using an exoplanet-analog transmission spectrum. Our retrievals at high spectral resolution show a marked sensitivity to the thermal structure of the atmosphere, trace gas abundances, density-dependent effects, such as collision-induced absorption and refraction, and even hint at 3D spatial effects. However, we used synthetic observations of TRAPPIST-1e to verify that the use of simple 1D vertically homogeneous atmospheric models will likely suffice for JWST observations of terrestrial exoplanets transiting M dwarfs.

Keywords: Extrasolar rocky planets, Exoplanet atmospheric composition , Exoplanets, Earth (planet), Transmission spectroscopy, Exoplanet astronomy, James Webb Space Telescope, Exoplanet atmospheres, Exoplanet atmospheric structure
Libration- and Precession-driven Dissipation in the Fluid Cores of the TRAPPIST-1 Planets. The seven planets orbiting TRAPPIST-1 have sizes and masses similar to Earth and mean densities that suggest that their interior structures are comprised of a fluid iron core and rocky mantle. Here we use idealized analytical models to compute estimates of the viscous dissipation in the fluid cores of the TRAPPIST-1 planets induced by mantle libration and precession. The dissipation induced by the libration at orbital periods is largest for TRAPPIST-1b, of the order of 600 MW, and decreases with orbital distance, to values of 5-500 W for TRAPPIST-1h, depending on its triaxial shape. Extrapolating these results to the larger libration amplitudes expected at longer periods, dissipation may perhaps be as high as 1 TW in TRAPPIST-1b. Orbital precession induces a misalignment between the spin axes of the fluid core and mantle of a planet, the amplitude of which depends on the resonant amplification of its free precession and free core nutation. Assuming Cassini states, we show that the dissipation from this misalignment can reach a few TW for planets e and f. Our dissipation estimates are lower bounds, as we neglect ohmic dissipation, which may dominate if the fluid cores of the TRAPPIST-1 planets sustain magnetic fields. Our results suggest that dissipation induced by precession can be of the same order as tidal dissipation for the outermost planets, may perhaps be sufficient to supply the power to a generate a magnetic field in their liquid cores, and likely played an important role in the evolution of the TRAPPIST-1 system.

Keywords: Extrasolar rocky planets, Exoplanet dynamics, Libration, Planetary cores, Planetary interior