Sazuna/UAT_keywords huggingface dataset:
The Perturbed Full Two-body Problem: Application to Post-DART Didymos. With the successful impact of the NASA Double Asteroid Redirection Test (DART) spacecraft in the Didymos-Dimorphos binary asteroid system, we provide an initial analysis of the post-impact perturbed binary asteroid dynamics. To compare our simulation results with observations, we introduce a set of "observable elements" calculated using only the physical separation of the binary asteroid, rather than traditional Keplerian elements. Using numerical methods that treat the fully spin-orbit-coupled dynamics, we estimate the system's mass and the impact-induced changes in orbital velocity, semimajor axis, and eccentricity. We find that the changes to the mutual orbit depend strongly on the separation distance between Didymos and Dimorphos at the time of impact. If Dimorphos enters a tumbling state after the impact, this may be observable through changes in the system's eccentricity and orbit period. We also find that any DART-induced reshaping of Dimorphos would generally reduce the required change in orbital velocity to achieve the measured post-impact orbit period, and will be assessed by the ESA Hera mission in 2027.

Keywords: Near-Earth objects, Small Solar System bodies, Asteroid dynamics, Gravitational interaction, Asteroid satellites
Thermal Properties of the Leading Hemisphere of Callisto Inferred from ALMA Observations. We present a thermal observation of Callisto's leading hemisphere obtained using the Atacama Large Millimeter/submillimeter Array at 0.87 mm (343 GHz). The angular resolution achieved for this observation was ~0.″16, which for Callisto at the time of this observation (D ~ 1.″05) was equivalent to ~six elements across the surface. Our disk-integrated brightness temperature of 116 ± 5 K (8.03 ± 0.40 Jy) is consistent with prior disk-integrated observations. Global surface properties were derived from the observation using a thermophysical model constrained by spacecraft data. We find that models parameterized by two thermal inertia components more accurately fit the data than single thermal inertia models. Our best-fit global parameters adopt a lower thermal inertia of 15-50 J m-2 K-1 s-1/2 and a higher thermal inertia component of 1200-2000 J m-2 K-1 s-1/2, with retrieved millimeter emissivities of 0.89-0.91. We identify several thermally anomalous regions, including spots ~3 K colder than model predictions colocated with the Valhalla impact basin and a complex of craters in the southern hemisphere; this indicates the presence of materials possessing either a higher thermal inertia or a lower emissivity. A warm region confined to the midlatitudes in these leading hemisphere data may be indicative of regolith property changes due to exogenic sculpting.

Keywords: Planetary surfaces, Callisto, Surface processes, Galilean satellites, Radio interferometry, Jovian satellites
Regolith Inhibits Salt and Ice Crystallization in Mg(ClO<SUB>4</SUB>)<SUB>2</SUB> Brine, Implying More Persistent and Potentially Habitable Brines on Mars. On Mars, liquid water may form in regolith when perchlorate salts absorb water vapor and dissolve into brine, or when ice-salt mixtures reach their melting temperature and thaw. Brines created in this way can chemically react with minerals, alter the mechanical properties of regolith, mobilize salts in the soil, and potentially create habitable environments. Although Martian brines would exist in contact with regolith, few studies have investigated how regolith alters the formation and stability of brines at Mars-relevant conditions. To fill this gap, we studied magnesium perchlorate brine in a Martian regolith simulant at salt concentrations up to 5.8 wt.%. We measured the water mass fraction and water activity between 3 and 98% relative humidity at 25 °C using the isopiestic method, and monitored salt and ice crystallization between -150 °C and 20 °C with differential scanning calorimetry. Results show that regolith inhibits salt and ice crystallization, allowing water to form and persist at much colder and drier conditions than pure brine. Remarkably, in several samples, neither salt nor ice crystallized at any conditions. These results suggest that brines could exist in regolith for longer periods of the Martian year than previously thought, and could persist indefinitely under certain conditions. By retaining water, inhibiting salt and ice crystallization, and maintaining habitable water activity, briny regolith may be a more favorable environment for life than pure brine alone. These findings indicate the critical importance of brine-regolith interactions for understanding the properties, evolution, and potential habitability of Mars's surface.

Keywords: Surface processes, Regolith, Planetary surfaces, Mars
The Oxygen Isotopic Composition of Samples Returned from Asteroid Ryugu with Implications for the Nature of the Parent Planetesimal. We present oxygen isotopic analyses of fragments of the near-Earth Cb-type asteroid Ryugu returned by the Hayabusa2 spacecraft that reinforce the close correspondence between Ryugu and CI chondrites. Small differences between Ryugu samples and CI chondrites in ${{\rm{\Delta }}}^{{\prime} 17}{\rm{O}}$ can be explained at least in part by contamination of the latter by terrestrial water. The discovery that a randomly sampled C-complex asteroid is composed of CI-chondrite-like rock, combined with thermal models for formation prior to significant decay of the short-lived radioisotope 26Al, suggests that if lithified at the time of alteration, the parent body was small (≪50 km radius). If the parent planetesimal was large (&gt;50 km in radius), it was likely composed of high-permeability, poorly lithified sediment rather than consolidated rock.

Keywords: Carbonaceous chondrites, Asteroids, Planetary thermal histories
OSSOS. XXIX. The Population and Perihelion Distribution of the Detached Kuiper Belt. The detached trans-Neptunian objects (TNOs) are those with semimajor axes beyond the 2:1 resonance with Neptune that are neither resonant nor scattering. Using the detached sample from the Outer Solar System Origins Survey (OSSOS) telescopic survey, we produce the first studies of their orbital distribution based on matching the orbits and numbers of the known TNOs after accounting for survey biases. We show that the detached TNO perihelion (q) distribution cannot be uniform but is instead better matched by two uniform components with a break near q ≈ 40 au. We produce parametric two-component models that are not rejectable by the OSSOS data set and estimate that there are 36,000 ${}_{-9000}^{+12,000}$ detached TNOs with absolute magnitudes H  r  &lt; 8.66 (D ≳ 100 km) and semimajor axes 48 au &lt; a &lt; 250 au (95% confidence limits). Although we believe that these heuristic two-parameter models yield a correct population estimate, we then use the same methods to show that the perihelion distribution of a detached disk created by a simulated rogue planet matches the q distribution even better, suggesting that the temporary presence of other planets in the early solar system is a promising model to create today's large semimajor axis TNO population. This cosmogonic simulation results in a detached TNO population estimate of 48,000 ${}_{-12,000}^{+15,000}$ . Because this illustrates how difficult-to-detect q &gt; 50 au objects are likely present, we conclude that there are (5 ± 2) × 104 dynamically detached TNOs, roughly twice as many as in the entire trans-Neptunian hot main belt.

Keywords: Kuiper belt, Trans-Neptunian objects, Small Solar System bodies, Detached objects
Sample-based Spectral Mapping around Landing Sites on the Moon-Lunar Timescale Part 1. Studying the geology of a terrestrial body and its evolution requires being able to set up a chronology. Crater statistics is a powerful tool to do so. However, calibration of this method, which is derived on the Moon, requires properly defined geological units, large enough for reliable crater statistics, and dated samples representative of these geological units. Yet, little effort has been put into choosing a representative set of lunar mission units and samples based on spectral information. Therefore, accuracy and precision of so-called cratering-chronology models remain limited. Here, we analyzed near-infrared orbital data to suggest a geological unit as a reference unit for Apollo 11, 12, 14-17 and Luna 16, 20, and 24 landing sites. We used near-infrared spectral information from orbital data and laboratory measurements to identify the set of samples that is the most representative of the landing-site reference units. We now provide spectrally constrained reference units, for which crater frequencies can be derived, and our sample recommendation will assign the reference age for updating the currently existing cratering-chronology models. We highlight that determining a reference geological unit in the highlands of the Moon is challenging because of the very nature of the terrain, while it is more straightforward for mare units. However, ejecta presence on these mare units comprises solvable challenges.

Keywords: The Moon, Infrared spectroscopy, Craters
Review and Revision of the Lunar Cratering Chronology-Lunar Timescale Part 2. Times and rates of planetary surface-modifying processes are crucial for the sequence and correlation of events on planetary bodies. For most planetary surfaces, superposition principles and crater densities are commonly used methods to collect relative age information. Lunar-based cratering-chronology models, which pair crater densities and sample ages from several lunar landing and sampling sites, calibrate the relative age information in absolute time. Here, we propose calibration pairs based on new crater statistics and spectrally supported sample-age assignments for the lunar cratering-chronology model. The resulting model reflects modern high-precision, radiometric ages, compositional and spectral information, and an up-to-date crater-production function. This revision supports a crater-forming projectile flux with monotonic decay, similar to previous standard models, but of distinctively lower flux. This originates from lower crater densities identified in spectrally and morphologically defined reference units, and from assigning more precise sample ages accounting for spectral resemblance between reference unit and sample. The observed maximal values for crater densities and ages provide the oldest and most densely cratered calibration pair. Because of the nature of highland samples, age constraints for the Luna 20 and Apollo 16 sampling sites remain challenging, which restricts the confidence in times for individual basin-formation events older than Orientale Basin. The new cratering-chronology model, when transferred to other planetary bodies, would cause aging of the surfaces, because of the lower overall flux.

Keywords: Selenology, Lunar science, Lunar geochronology, Lunar impacts, Lunar surface
The Spatial Distribution of the Unidentified 2.07 μm Absorption Feature on Europa and Implications for its Origin. A weak absorption feature at 2.07 μm on Europa's trailing hemisphere has been suggested to arise from radiolytic processing of an endogenic salt, possibly sourced from the interior ocean. However, if the genesis of this feature requires endogenic material to be present, one might expect to find a correlation between its spatial distribution and the recently disrupted chaos terrains. Using archived near-infrared observations from the Very Large Telescope/SINFONI with a ~1 nm spectral resolution and a linear spatial resolution ~130 km, we examine the spatial distribution of this feature in an effort to explore this endogenic formation hypothesis. We find that, while the presence of the 2.07 μm feature is strongly associated with the irradiation pattern on Europa's trailing hemisphere, there is no apparent association between the presence or depth of the absorption feature and Europa's large-scale chaos terrain. This spatial distribution suggests that the formation pathway of the 2.07 μm feature on Europa is independent of any endogenous salts within the recent geology. Instead, we propose that the source of this feature may simply be a product of the radiolytic sulfur cycle or arise from some unidentified parallel irradiation process. Notably, the 2.07 μm absorption band is absent from the Pwyll crater ejecta blanket, suggesting that radiolytic processing has not had enough time to form the species responsible and placing a lower limit on the irradiation timescale. We are unable to find a plausible spectral match to the 2.07 μm feature within the available laboratory data.

Keywords: Very Large Telescope, Planetary surfaces, Infrared spectroscopy, Surface composition, Europa, Surface ices, Galilean satellites
Equatorial Waves and Superrotation in the Stratosphere of a Titan General Circulation Model. We investigate the characteristics of equatorial waves associated with the maintenance of superrotation in the stratosphere of a Titan general circulation model. A variety of equatorial waves are present in the model atmosphere, including equatorial Kelvin waves, equatorial Rossby waves, and mixed Rossby-gravity waves. In the upper stratosphere, acceleration of superrotation is strongest around solstice and is due to interaction between equatorial Kelvin waves and Rossby-type waves in winter hemisphere midlatitudes. The existence of this "Rossby-Kelvin"-type wave appears to depend on strong meridional shear of the background zonal wind that occurs in the upper stratosphere at times away from the equinoxes. In the lower stratosphere, acceleration of superrotation occurs throughout the year and is partially induced by equatorial Rossby waves, which we speculate are generated by quasigeostrophic barotropic instability. Acceleration of superrotation is generally due to waves with phase speeds close to the zonal velocity of the mean flow. Consequently, they have short vertical wavelengths that are close to the model's vertical grid scale and therefore likely to be not properly represented. We suggest that this may be a common issue among Titan general circulation models that should be addressed by future model development.

Keywords: Planetary atmospheres, Titan, Planetary science
Predicting the Effect of Surface Properties on Enceladus for Landing. The prospect of landing on the surface of Enceladus comes with the question of whether the surface conditions permit selection and certification of one or more safe landing sites in an area of high science value. On Enceladus, the search for biosignatures in plume materials is a high science value objective that correlates with proximity to the south polar terrain, where the plume deposition rate is highest; however, such areas may be unsafe if unsintered particles make the landing site unstable. To investigate this, the surface of Enceladus was modeled using the level set discrete element method. This method models the kinetics and kinematics of large groups of individual ice particles both in contact and sintered together. Using the model, a rigid footpad was initialized at a 1 m s-1 descent just above the ice surface under Enceladus gravity. Parameters studied were the sintering amount, particle size distribution, footpad geometry, and surface slope. The model predicted that some sintering is required for the surface to support a lander; however, too much sintering can cause a lander to bounce. For tests on sloped surfaces, landing could be possible on slopes as steep as 20° for certain conditions, but it is safest to land in areas with a slope angle of 15° or less. While slope angle and sintering level were much more important than footpad geometry, the hemisphere footpad had the best performance (lowest slipping) in most cases compared to the cone or disk.

Keywords: Interdisciplinary astronomy, Enceladus, Surface ices, Landers
Implications for Chondrule Formation Regions and Solar Nebula Magnetism from Statistical Reanalysis of Chondrule Paleomagnetism. Converging lines of evidence show that protoplanetary disks are complex environments hosting spatial and temporal variability at multiple scales. Here we reanalyze paleomagnetic estimates of solar nebula magnetic field strengths using a Bayesian framework that tests for recording bias due to chondrule motion and explicitly accounts for time-varying ambient fields. We find that LL and CO group chondrule paleointensities likely rotated during cooling (p = 0.79-0.99), validating assumptions in previous paleomagnetic studies. Chondrule rotation also suggests low gas density formation environments beyond 2 and 4 au for LL and CO chondrules, respectively. Our recomputed paleointensities for LL and CO chondrules imply either: (1) temporally constant magnetic fields of ${34}_{-14}^{+36}$ μT and ${106}_{-18}^{+88}$ μT, respectively; or (2) time-varying magnetic fields with peak amplitudes between ${49}_{-21}^{+97}$ μT and ${128}_{-11}^{+307}$ μT. Considering the known mechanisms for sustaining magnetic field gradients and high-amplitude temporal magnetic fluctuations in the solar nebula, we find that magnetic field flux concentrations in disk gaps or time-varying magnetic fields, for example due to the Hall shear instability, are most compatible with the existing data. Using this statistical framework, future paleointensity studies of chondrules can be used to directly test for the variability of magnetic fields in the solar system protoplanetary disk and to distinguish between these scenarios.

Keywords: Chondrites, Asteroid dynamics, Chondrules, Planetary system formation, Protoplanetary disks, Magnetic fields
The Case for Future Gravity Science Investigations at Saturn with a Planetary Orbiter. The next phase in the robotic exploration of the Saturnian system will target unresolved questions about the gas giant's atmosphere, interior, magnetosphere, and rings that were left open by investigations on board the Cassini mission. Among these, we find gravity science objectives, which relate mainly to explaining the origin of the large wind-induced gravity signal and reconciling existing incongruities regarding the internal density distribution. Here we attempt to identify which future observations may yield additional information about Saturn's internal mechanisms. We report on the results of precise numerical simulations of a gravity science experiment carried out with a planetary orbiter in the 2040s and characterized by varying periapsis altitude over the 1 bar planetary surface. The goal is to identify achievable measurement requirements that can advance the current understanding of Saturn's interior and atmospheric dynamics. We find that inclined, elliptical orbits with low-altitude closest approaches over the northern hemisphere can improve the present determination of the gravity field coefficients by up to 1 order of magnitude, provided that at least a dozen pericenters are devoted to gravity science. Furthermore, if future observations are combined with the available Cassini Grand Finale data in the southern hemisphere, a significant improvement in terms of maximum measurable gravity field degree is observed.

Keywords: Gravitational fields, Orbiters, Saturn, Planetary atmospheres
MIR Spectra and Analysis of Jovian Trojan Asteroids. Jovian Trojan asteroids make up a large group of primitive bodies that populate Jupiter's L4 and L5 Lagrange points. The Trojans' dynamics and composition carry insight into the formation mechanisms that shaped our solar system. Mid-infrared (MIR; 5-35 μm) spectra of Trojans exhibit puzzling silicate emission features, like spectra of optically thin comet comae, which may be interpreted as "fluffy" regoliths. By understanding the physical properties of the regolith (e.g., particle size and regolith porosity), more accurate compositional interpretations can be made. Here we show 14 Spitzer Space Telescope MIR spectra of Trojans and their compositional makeup. Through parameterization of spectral features and comparison to laboratory and remote-sensing spectra, the results show that the Trojans have highly porous regoliths of fine-particulate crystalline (forsterite, enstatite, and possibly a small amount of fayalite and diopside) and amorphous silicates. These results are consistent with a primordial Kuiper Belt origin.

Keywords: Small Solar System bodies, Asteroids, Infrared spectroscopy, Trojan asteroids, Spectral energy distribution, Spectroscopy, Asteroid surfaces
Microwave Observations of Venus with CLASS. We report on the disk-averaged absolute brightness temperatures of Venus measured at four microwave frequency bands with the Cosmology Large Angular Scale Surveyor. We measure temperatures of 432.3 ± 2.8, 355.6 ± 1.3, 317.9 ± 1.7, and 294.7 ± 1.9 K for frequency bands centered at 38.8, 93.7, 147.9, and 217.5 GHz, respectively. We do not observe any dependence of the measured brightness temperatures on solar illumination for all four frequency bands. A joint analysis of our measurements with lower-frequency Very Large Array observations suggests relatively warmer (~7 K higher) mean atmospheric temperatures and lower abundances of microwave continuum absorbers than those inferred from prior radio occultation measurements.

Keywords: Atmospheric composition, Brightness temperature, Venus
Exploring Martian Magnetic Fields with a Helicopter. The era of helicopter-based surveys on Mars has already begun, creating opportunities for future aerial science investigations with a range of instruments. We argue that magnetometer-based studies can make use of aerial technology to answer some of the key questions regarding early Mars evolution. As such, we discuss mission concepts for a helicopter equipped with a magnetometer on Mars, measurements it would provide, and survey designs that could be implemented. For a range of scenarios, we build magnetization models and test how well structures can be resolved using a range of different inversion approaches. With this work, we provide modeling ground work and recommendations to plan the future of aerial Mars exploration.

Keywords: Mars, Solar system terrestrial planets, Planetary science, Planetary magnetospheres, Planetary interior, Planetary structure
Spatial Distribution of Glycine and Aspartic Acid in Rapidly Frozen Brines Relevant to Enceladus. Saturn's moon Enceladus harbors a global, subsurface liquid ocean beneath an icy crust that actively erupts water jets from fissures in its south pole. Data returned from the Cassini mission have identified salts and organic matter within these ejected plume particles. Such combinations of water, organics, and salts present rather complex chemical environments that may hold direct implications for habitability. The fundamental behavior of organics in frozen brine systems upon exposure to relevant Enceladus surface conditions is an important aspect that has not been explored to date (e.g., how they organize and partition relative to the salt minerals within the ice matrix). The present work investigates this topic by characterizing the spatial distribution of two amino acids with different side chains (glycine and aspartic acid) in a putative frozen Enceladus brine, containing sodium, chloride, and carbonate ions, via micro-Raman imaging. The results show that both organic-salt solutions likely undergo some degree of vitrification upon flash freezing, especially for the chloride-bearing species. The subsequent annealing of the vitreous samples reveals a preferential association of the amino acids with crystalline salt hydrates, while minimal negative to no correlation is found between them and water ice. In particular, both amino acids exhibit stronger affinities for natron (Na2CO3•10H2O) than hydrohalite (NaCl•2H2O). This suggests that solute-solute interaction likely dominates in these frozen systems, especially when charged species are present. The results imply that salt-rich ice particles can serve as concentrators of organic biomarkers, enhancing their potential for detection from remote sensing or in situ analysis.

Keywords: Enceladus, Ice spectroscopy, Experimental techniques, Astrochemistry, Planetary science