Sazuna/UAT_keywords huggingface dataset:
Roughness and Angularity of Fragments from Meteorite Disruption Experiments. In this study, we set out to explore the relationship between fracture roughness and sample strength. We analyze 45 fragments of Aba Panu, Allende, and Tamdakht, three meteorites that have been strength-tested to disruption, to determine whether their shape or texture is correlated with measured compressive strength. A primary goal is to understand whether these exterior properties correlate with more challenging strength-related measurements. We first scan the samples and construct high-fidelity 3D models. The gradient-based angularity index AI g  and the rms slope roughness metric θ rms are applied to all nine samples, and their validity and any correlation between them are analyzed. We find that different sample subsets show significant variation in both correlation strength and direction. We also find AI g  to be of questionable validity in its application to highly angular samples. Based on our methodology and results, we do not find sufficient separation between the roughness values of samples to allow distinct identification of the three meteorites based on roughness alone. Additionally, neither metric shows a strong correlation with the strength of individual fragments. We do find, however, that the spread of the fragment strength distribution within a given meteorite has some correlation with its average roughness metric. Increased fragment roughness may imply greater structural heterogeneity and therefore potentially weaker behavior at larger sizes. We only have significant data sets for two meteorites, however, which are insufficient to correlate meteorite fracture roughness to meteorite strength in any simple way.

Keywords: Chondrites, Small Solar System bodies, Carbonaceous chondrites, Computational methods, Meteorites
The Origin of Jupiter's Obliquity. The origin of the 3.°12 obliquity of Jupiter's spin axis to its orbit normal is unknown. Improved estimates of Jupiter's moment of inertia rule out a previously proposed explanation involving a resonance with the precession of the inclined orbit of Uranus. We find that a nonadiabatic crossing of the resonance between Jupiter's spin precession and the -f 5 + f 6 + g 6 mode could have tilted Jupiter to its present-day obliquity starting from a 0° primordial obliquity. This places constraints on the migration rates of the satellites Ganymede and Callisto.

Keywords: Spin-orbit resonances, Jupiter
Discovery of Seven Volcanic Outbursts on Io from an Infrared Telescope Facility Observation Campaign, 2016-2022. This study analyzes near-infrared measurements of Io, Jupiter's moon, observed over 170 nights from 2016 to early 2022 using the NASA Infrared Telescope Facility (IRTF). During this period, seven new volcanic outbursts-the most energetic volcanic events on Io-were discovered and characterized, increasing the total number of observed outburst events from 18 to 25. We also present simplified criteria for the thermal detection of an outburst, requiring it to be both confined to a specific location of Io and above a threshold intensity in the Lp band (3.8 μm).

Keywords: Infrared dark clouds, Lithosphere, Infrared Astronomical Satellite, Volcanoes, Infrared observatories, Io
Impact Crater Morphometry on Pluto: Implications for Surface Composition and Evolution. New Horizons showed that Pluto exhibits a wide range of geologic groups, with much of the surface modified by volatile ice processes. Impact craters are a valuable tool to investigate how these regions have evolved, as they record the effects of various modification mechanisms and retain information on the properties of the bedrock ice(s). In this work, we use Pluto's crater population to quantify the extent of surface modification and identify variations in surface properties on Pluto. In this study, we have measured the relative depth of Pluto's craters compared to minimally modified water-ice craters to interpret how the craters may have evolved and/or what the information tells us about the surface properties of the bedrock. We found a trend of increasing crater relative depth from southeast to northwest that may reflect the conditions of an ancient surface when a thicker layer of volatile ice may have existed, possibly changed by polar wander after the Sputnik impact. We have identified anomalously deep craters across Pluto's surface, with a concentration in Cthulhu Macula, suggesting different bedrock-ice properties in this region. Other deep craters may be influenced by extraneous factors, such as impactor speed. Overall, this study expands on our understanding of the evolution and composition of Pluto's surface and sets a road map for further investigations into Pluto's surface evolution.

Keywords: Ice physics, Planetary surfaces, Craters, Pluto
Are NH<SUB>3</SUB> and CO<SUB>2</SUB> Ice Present on Miranda?. Published near-IR spectra of the four largest classical Uranian satellites display the presence of discrete deposits of CO2 ice, along with subtle absorption features around 2.2 μm. The two innermost satellites, Miranda and Ariel, also possess surfaces heavily modified by past endogenic activity. Previous observations of the smallest satellite, Miranda, have not detected the presence of CO2 ice, and a report of an absorption feature at 2.2 μm has not been confirmed. An absorption feature at 2.2 μm could result from exposed or emplaced NH3- or NH4-bearing species, which have a limited lifetime on Miranda's surface, and therefore may imply that Miranda's internal activity was relatively recent. In this work, we analyzed near-IR spectra of Miranda to determine whether CO2 ice and the 2.2 μm feature are present. We measured the band area and depth of the CO2 ice triplet (1.966, 2.012, and 2.070 μm), a weak 2.13 μm band attributed to CO2 ice mixed with H2O ice, and the 2.2 μm band. We confirmed a prior detection of a 2.2 μm band on Miranda, but we found no evidence for CO2 ice, either as discrete deposits or mixed with H2O ice. We compared a high signal-to-noise-ratio spectrum of Miranda to synthetic and laboratory spectra of various candidate compounds to shed light on what species may be responsible for the 2.2 μm band. We conclude that the 2.2 μm absorption is best matched by a combination of NH3 ice with NH3 hydrates or NH3-H2O mixtures. NH4-bearing salts like NH4Cl are also promising candidates that warrant further investigation.

Keywords: Planetary surfaces, Uranian satellites, Surface processes, Surface composition, Surface ices
The Feasibility of Detecting Biosignatures in the TRAPPIST-1 Planetary System with JWST. The James Webb Space Telescope (JWST) provides the first opportunity to detect gases in the atmospheres of M-dwarf terrestrial planets and search for signs of life. Here we determine the detectability of a comprehensive suite of biosignature gases that may have been episodically prevalent across Earth's history. We used coupled 1D climate-photochemical models to generate synthetic inhabited terrestrial planetary environments for TRAPPIST-1 d and e. These encompass cloudy and/or hazy Archean-Earth-like environments with either a dominant sulfur- or methane-producing biosphere, as well as clear and cloudy modern-Earth-like environments with photosynthetic oxygen-producing biospheres. We generate transmission spectra and assess the likely detectability of different biosignatures with JWST. Our simulations suggest that biogenically generated O2 and its photosynthetic by-product O3 will likely be extremely difficult to detect. We explored the detectability of methyl chloride (CH3Cl) as an alternative indicator for a photosynthetic biosphere but find that it will likely require significantly higher global surface fluxes than Earth's. We find that the CH4 and CO2 disequilibrium pair is potentially detectable in ~10 transits for both the methanogen-dominated Archean-like environment and the modern photosynthetic-dominated biosphere-even in cloudy atmospheres. Organic haze and methyl mercaptan are other potential biosignatures for the Archean. Given the likely difficulties in observing an oxygenic-photosynthetic biosphere with JWST, we conclude that the methanogenic biosphere revealed by the combination of outgassed CO2 in the presence of methanogenically generated CH4 may be the most persistent detectable biosignature for an Earth-like planet.

Keywords: Biosignatures, Astrobiology, Exoplanet atmospheres, Transmission spectroscopy
Masses and Densities of Dwarf Planet Satellites Measured with ALMA. We have used the Atacama Large Millimeter/submillimeter Array to measure precise absolute astrometric positions and detect the astrometric wobble of dwarf planet Orcus and its satellite Vanth over a complete orbit. We also place upper limits to the astrometric wobble induced by Dysnomia on dwarf planet Eris around its orbit. From the Vanth-Orcus barycentric motion, we find a Vanth-Orcus mass ratio of 0.16 ± 0.02-the highest of any known planet or dwarf planet. This large ratio is consistent with the hypothesis that Vanth is a largely intact impactor from a giant collision in the system and that the system has likely evolved to a double synchronous state. We find only an upper limit of the barycenter motion of Eris, which implies a 1σ upper limit to the Dysnomia-Eris mass ratio of 0.0085, close to the modeled transition region between giant impact generated satellites, which are largely intact remnants of the original impactor and those which form out of reaccreted disk material left over postimpact. The low albedo of Dysnomia leads us to marginally favor the intact impactor scenario. We find that Dysnomia has a density of &lt;1.2 g cm-3, significantly lower than the 2.4 g cm-3 of Eris.

Keywords: Dwarf planets, Radio astrometry, Natural satellite formation
Atmospheric Interactions of Ejecta on Earth and Mars Including the Effect of Vaporization. Atmospheres play an important role in ejecta deposition after an impact event. Many impact experiments and simulations neglect the effect of atmospheres. We simulate ejecta plumes created by craters with transient diameters of 2 and 20 km on Mars and Earth, to show the effect atmospheric density and crater size have on the strength of the interaction. The interaction of ejecta with an atmosphere is explored in this study using a two-fluid hydrocode that simultaneously simulates ejecta and atmospheres as coupled, continuum fields to correctly capture the transfer of mass, energy, and momentum between the two. Here, we study the effect of vaporization of plume material as well as the effect of the bow shock. We find that only the fastest ejecta is vaporized with a peak vaporized mass of 2.5 × 105 kg, 3.5 s after the impact in our 2 km diameter terrestrial crater. Terrestrial meteorites are preferentially formed from the fastest ejecta. However, that fastest ejecta is mostly vaporized in our simulations, so to form a terrestrial meteorite, there must be a sufficiently large impact for solid material to be ejected and not vaporize. Thus, we place a lower limit of 33 km on the size of crater needed to generate terrestrial meteorites, but the crater size needed could be substantially larger. The bow shocks in our simulations result in lofting of ejecta, especially vaporized material, in the wake of the impactor.

Keywords: Atmospheric effects
Composition and Sticking of Hot Chondritic Dust in a Protoplanetary Hydrogen Atmosphere. The sticking properties of dust in early phases of planet formation depend on the thermal history and ambient atmosphere. Therefore, dust will change its ability to build larger aggregates in collisions, depending on its location in protoplanetary disks. We aim at quantifying the change in sticking properties as chondritic dust is heated under various atmospheric conditions. In laboratory experiments, we milled two different meteorites (Sayh al Uhaymir 001 and Allende) to dust and formed millimeter-size cylinders. These cylindrical aggregates were sequentially heated from 600 to 1400 K in vacuum and in a hydrogen atmosphere, with compositional changes being tracked via Mössbauer spectroscopy. Using a Brazilian splitting test, the splitting tensile strength was determined. At higher temperatures, iron in silicates is reduced to metallic Fe(Ni) within the hydrogen atmosphere. In any case, adhesive forces are strongly increased by orders of magnitude from 1000 to 1400 K with minimum variations, depending on the atmospheric conditions. The dust in protoplanetary disks becomes ever more sticky, approaching a sublimation line upon exposure to temperatures of about 1400 K.

Keywords: Protoplanetary disks, Planet formation
Fitting Thermal Evolution Models to the Chronological Record of Erg Chech 002 and Modeling the Ejection Conditions of the Meteorite. The history of accretion and differentiation processes in the planetesimals is provided by various groups of meteorites. Sampling different parent body layers, they reveal the circumstances of the metal-silicate segregation and the internal structures of the protoplanets. The ungrouped achondrite Erg Chech 002 (EC 002) added to the suite of samples from primitive igneous crusts. Here we present models that utilize thermochronological data for EC 002 and fit the accretion time and size of its parent body to these data. The U-corrected Pb-Pb pyroxene, Pb-Pb phosphate, and Ar-Ar ages used imply a best-fit planetesimal with a radius of 20-30 km that formed at 0.1 Ma after calcium-aluminum-rich inclusions. Its interior melted early and differentiated by 0.5 Ma, allowing core and mantle formation with a transient lower mantle magma ocean and a melt fraction of &lt;25% at the meteorite layering depth. EC 002 formed from this melt at a depth of 0.8 km in a partially differentiated region covered by an undifferentiated crust. By simulating collisions with impactors of different sizes and velocities, we analyzed the minimum ejection conditions of EC 002 from its original parent body and the surface composition of the impact site. The magma ocean region distinct from the layering depth of EC 002 implies that it was not involved in the EC 002 genesis. Our models estimate closure temperatures for the Al-Mg ages as 1030-1200 K. A fast parent body cooling attributes the late Ar-Ar age to a local reheating by another, late impact.

Keywords: Accretion, Impact phenomena, Asteroids, Achondrites, Planetesimals, Meteorites, Cosmochronology, Planetary interior
Effects of Airless Bodies' Regolith Structures and of the Solar Wind's Properties on the Backscattered Energetic Neutral Atoms Flux. The surfaces of airless planetary bodies, such as the Moon or Mercury, are covered with regoliths, which interact with the solar wind. The solar protons can either be absorbed by the surface or neutralized and reflected as hydrogen energetic neutral atoms (ENAs). The ENA flux is thought to depend mostly on the structure of the upper regolith layer. By using a model combining a Monte Carlo approach to describe a solar proton's journey through the lunar surface with molecular dynamics to characterize its interactions with the regolith's grains, we highlight the surface roughness as a key parameter that influences the backscattered H ENA flux. By considering spherical silica grains, the lunar regolith's structure is described using the open-source code Large-scale Atomic/Molecular Massively Parallel Simulator (or LAMMPS), which allows a realistic description of grain-on-grain contacts. The roughness of the modeled regolith, characterized by the roughness ratio, is shown to be dictated by the surface energy and the grain-size distribution. This work shows that a rougher surface favors deeper penetration of the protons inside the regolith, which increases the number of collisions and thus decreases their reflected fraction. The angular distribution of the backscattered H ENAs is influenced by both the surface roughness and the solar zenith angle. We show that the angular distribution of the backscattered ENAs is anisotropic and is influenced by the regolith's structure, which is consistent with Chandrayaan-1 measurements. This work aims for a better understanding of the interactions ongoing at this interface and intends to look into the possibility of deducing information on the surface structure solely from ENA flux measurements. Highlighting the key structural parameters influencing the ENA backscattering will also help the development of models of surface-bounded exospheres.

Keywords: Regolith, Planetary surfaces
OSIRIS-APEX: An OSIRIS-REx Extended Mission to Asteroid Apophis. The Origins, Spectral Interpretation, Resource Identification, and Security-Regolith Explorer (OSIRIS-REx) spacecraft mission characterized and collected a sample from asteroid (101955) Bennu. After the OSIRIS-REx Sample Return Capsule released to Earth's surface in 2023 September, the spacecraft diverted into a new orbit that encounters asteroid (99942) Apophis in 2029, enabling a second mission with the same unique capabilities: OSIRIS-Apophis Explorer (APEX). On 2029 April 13, the 340 m diameter Apophis will draw within ~32,000 km of Earth's surface, less than 1/10 the lunar distance. Apophis will be the largest object to approach Earth this closely in recorded history. This rare planetary encounter will alter Apophis's orbit, will subject it to tidal forces that change its spin state, and may seismically disturb its surface. APEX will distantly observe Apophis during the Earth encounter and capture its evolution in real time, revealing the consequences of an asteroid undergoing tidal disturbance by a major planet. Beginning in 2029 July, the spacecraft's instrument suite will begin providing high-resolution data of this "stony" asteroid-advancing knowledge of these objects and their connection to meteorites. Near the mission's end, APEX will use its thrusters to excavate regolith, a technique demonstrated at Bennu. Observations before, during, and after excavation will provide insight into the subsurface and material properties of stony asteroids. Furthermore, Apophis's material and structure have critical implications for planetary defense.

Keywords: Near-Earth objects, Asteroid dynamics, Space observatories, Close encounters, Asteroid surfaces
The Upper Atmosphere of Uranus from Stellar Occultations. I. Methods and Validation. Measurements made by the Voyager 2 spacecraft during its flybys of Uranus in 1986 found warm stratospheric and hot thermospheric temperatures that cannot be explained by solar energy alone. It contributes to what has become known as the "giant planet energy crisis"; there is a fundamental lack of understanding of the energy balance of giant planets in the solar system. Uranus, in particular, has both the hottest thermospheric temperatures and the weakest internal heat flux of all four giant planets. Moreover, the Voyager 2 UV temperature measurements are at odds with the many contemporaneous Earth-based stellar occultation observations. In this work, we examine the 1977 Uranus stellar occultation (U0) and compare the observed light curve to reported Voyager 2 temperature profiles by simulating the latter into stellar occultation light curves. In this investigation, we find that the observed light curves are in tension with the simulated light curves to a high degree of statistical confidence. Next, we reprocess the U0 light curves using a modern approach, with some significant adjustments described herein, and report updated profiles. We find that the lower thermosphere of Uranus is much cooler than the Voyager 2 profiles suggest but slightly warmer than those originally published from the U0 occultation. In Paper II, we will present the results of applying these methods to many of the dozens of archival Uranus stellar occultations.

Keywords: Planetary atmospheres, Thermosphere, Stellar occultation, Stratosphere, Uranus
Col-OSSOS: The Distribution of Surface Classes in Neptune's Resonances. The distribution of surface classes of resonant trans-Neptunian objects (TNOs) provides constraints on the protoplanetesimal disk and giant planet migration. To better understand the surfaces of TNOs, the Colours of the Outer Solar System Origins Survey acquired multiband photometry of 102 TNOs and found that the surfaces of TNOs can be well described by two surface classifications: BrightIR and FaintIR. These classifications both include optically red members and are differentiated predominantly based on whether their near-infrared spectral slope is similar to their optical spectral slope. The vast majority of cold classical TNOs, with dynamically quiescent orbits, have the FaintIR surface classification, and we infer that TNOs in other dynamical classifications with FaintIR surfaces share a common origin with the cold classical TNOs. Comparison between the resonant populations and the possible parent populations of cold classical and dynamically excited TNOs reveal that the 3:2 has minimal contributions from the FaintIR class, which could be explained by the ν 8 secular resonance clearing the region near the 3:2 before any sweeping capture occurred. Conversely, the fraction of FaintIR objects in the 4:3 resonance, 2:1 resonance, and the resonances within the cold classical belt suggest that the FaintIR surface formed in the protoplanetary disk between ≳34.6 and ≲47 au, though the outer bound depends on the degree of resonance sweeping during migration. The presence and absence of the FaintIR surfaces in Neptune's resonances provides critical constraints for the history of Neptune's migration, the evolution of the ν 8, and the surface class distribution in the initial planetesimal disk.

Keywords: Resonant Kuiper belt objects, Trans-Neptunian objects
Earth-based Stellar Occultation Predictions for Jupiter, Saturn, Uranus, Neptune, Titan, and Triton: 2023─2050. In support of studies of decadal-timescale evolution of outer solar system atmospheres and ring systems, we present detailed Earth-based stellar occultation predictions for Jupiter, Saturn, Uranus, Neptune, Titan, and Triton for 2023─2050, based on the Gaia Data Release 3 star catalog and near-IR K-band photometry from the Two Micron All Sky Survey catalog. We tabulate the number of observable events by year and magnitude interval, reflecting the highly variable frequency of high-signal-to-noise ratio (S/N) events depending on the target's path relative to the star-rich regions of the Milky Way. We identify regions on Earth where each event is potentially observable, and for atmospheric occultations we determine the latitude of the ingress and egress events. For Saturn, Uranus, and Neptune, we also compute the predicted ring occultation event times. We present representative subsets of the predicted events and highlight particularly promising events. Jupiter occultations with K ≤ 7 occur at a cadence of about one per year, with bright events at higher frequency in 2031 and 2043. Saturn occultations are much rarer, with only two predicted events with K ≤ 5 in 2032 and 2047. Ten Uranus ring occultations are predicted with K ≤ 10 for the period 2023─2050. Neptune traverses star-poor regions of the sky until 2068, resulting in only 13 predicted occultations for K ≤ 12 between 2023 and 2050. Titan has several high-S/N events between 2029 and 2031, whereas Triton is limited to a total of 22 occultations with K ≤ 15 between 2023 and 2050. Details of all predicted events are included in the Supplementary Online Material.

Keywords: Neptune, Saturn, Titan, Planetary rings, Jupiter, Triton, Uranus