Sazuna/UAT_keywords huggingface dataset:
A Technique for Retrieving the Exospheric Number Density Distribution from Pickup Ion Ring Distributions. Ion pickup by the solar wind is ubiquitous in space plasma. Because pickup ions are originally produced by ionization of an exospheric neutral atmosphere, their measurements contain information on the exospheric neutral abundance. Here we established a method to retrieve exospheric number densities, by analyzing the ion velocity distribution functions of pickup ions measured by the Mars Atmosphere and Volatile EvolutioN spacecraft. We successfully retrieved exospheric oxygen density distributions at altitudes ranging from 1000 to 10,000 km around Mars except for the vicinity of the bow shock. This method can be applied to other space missions to study the upper atmosphere of planets, moons, and other small bodies in our solar system, where pickup ions exist.

Keywords: Exosphere, Mars, Solar wind, Pickup ions, Planetary magnetospheres
Contribution of the Moon-forming Impactor to the Volatile Inventory in the Bulk Silicate Earth. The timing and mechanism by which the present-day inventory of life-essential volatiles hydrogen–carbon–nitrogen–sulfur (H–C–N–S) in the bulk silicate Earth (BSE) was established are debated. In this study we have modeled the equilibrium partitioning of H–C–N–S between core, magma ocean (MO), and atmosphere to determine whether the Moon-forming impactor (MFI) was the primary source of volatiles in the BSE. Our findings suggest that the MFI's core and MO-degassed atmosphere were its primary H–C–N–S reservoirs. Since the MFI likely lost its MO-degassed atmosphere before the giant impact, most of the BSE's volatiles must come from the small fraction of the MFI's core which reequilibrated with Earth's post-impact MO. This implies a high H–C–N–S inventory in the MFI (up to 50% of volatile-rich carbonaceous chondrites) to establish the BSE's volatile budget. Although isotopic compositions of nonvolatile elements do not rule out the possibility of substantial volatile-rich, carbonaceous material accretion, MFI's collisional growth from thermally metamorphosed/differentiated planetesimals makes it improbable that it contained ∼50% carbonaceous chondrite equivalent of H–C–N during its differentiation. Therefore, the MFI was unlikely the primary source of volatiles in the BSE. A significant portion of the BSE's volatile inventory (especially H and C) likely predates the Moon-forming event. To prevent loss to space and segregation into Earth's core, volatile-bearing materials must be delivered during the final accretion event(s) preceding the Moon-forming event. The substantial size of the proto-Earth at this stage, combined with limited metal–silicate equilibration during the Moon-forming event, facilitated the retention of these volatiles within the BSE.

Keywords: Cosmochemistry, Earth atmosphere, Earth (planet), Planetary science, Meteorites, Planet formation
The Dynamical State of the Didymos System before and after the DART Impact. NASA's Double Asteroid Redirection Test (DART) spacecraft impacted Dimorphos, the natural satellite of (65803) Didymos, on 2022 September 26, as a first successful test of kinetic impactor technology for deflecting a potentially hazardous object in space. The experiment resulted in a small change to the dynamical state of the Didymos system consistent with expectations and Level 1 mission requirements. In the preencounter paper, predictions were put forward regarding the pre- and postimpact dynamical state of the Didymos system. Here we assess these predictions, update preliminary findings published after the impact, report on new findings related to dynamics, and provide implications for ESA's Hera mission to Didymos, scheduled for launch in 2024 October with arrival in 2026 December. Preencounter predictions tested to date are largely in line with observations, despite the unexpected, flattened appearance of Didymos compared to the radar model and the apparent preimpact oblate shape of Dimorphos (with implications for the origin of the system that remain under investigation). New findings include that Dimorphos likely became prolate due to the impact and may have entered a tumbling rotation state. A possible detection of a postimpact transient secular decrease in the binary orbital period suggests possible dynamical coupling with persistent ejecta. Timescales for damping of any tumbling and clearing of any debris are uncertain. The largest uncertainty in the momentum transfer enhancement factor of the DART impact remains the mass of Dimorphos, which will be resolved by the Hera mission.

Keywords: Asteroid satellites, Asteroids, Asteroid dynamics
Estimate of Water and Hydroxyl Abundance on Asteroid (16) Psyche from JWST Data. Our understanding of solar system evolution is closely tied to interpretations of asteroid composition, particularly the M-class asteroids. These asteroids were initially thought to be the exposed cores of differentiated planetesimals, a hypothesis based on their spectral similarity to iron meteorites. However, recent astronomical observations have revealed hydration on their surface through the detection of 3 μm absorption features associated with OH and potentially H2O. We present evidence of hydration due mainly to OH on asteroid (16) Psyche, the largest M-class asteroid, using data from the James Webb Space Telescope (JWST) spanning 1.1–6.63 μm. Our observations include two detections of the full 3 μm feature associated with OH and H2O resembling those found in CY-, CH-, and CB-type carbonaceous chondrites, and no 6 μm feature uniquely associated with H2O across two observations. We observe 3 μm depths of between 4.3% and 6% across two observations, values consistent with hydrogen abundance estimates on other airless bodies of 250–400 ppm. We place an upper limit of 39 ppm on the water abundance from the standard deviation around the 6 μm feature region. The presence of hydrated minerals suggests a complex history for Psyche. Exogenous sources of OH-bearing minerals could come from hydrated impactors. Endogenous OH-bearing minerals would indicate a composition more similar to E- or P-class asteroids. If the hydration is endogenous, it supports the theory that Psyche originated beyond the snow line and later migrated to the outer main belt.

Keywords: Surface composition, Asteroids, Infrared spectroscopy
On the Sensitivity of Apophis's 2029 Earth Approach to Small Asteroid Impacts. Apophis's current trajectory takes it safely past our planet at a distance of several Earth radii on 2029 April 13. Here the possibility is considered that Apophis could collide with a small asteroid, like the ones that frequently and unpredictably strike Earth, and the resulting perturbation of its trajectory. The probability of an impact that could significantly displace Apophis relative to its keyholes is found to be less than one in 106, requiring a Δv ≳ 0.3 mm s‑1, while for an impact that could significantly displace Apophis compared to its miss distance in 2029, it is less than one in 109, requiring a Δv ≳ 5 cm s‑1. These probabilities are below the usual thresholds considered by asteroid impact warning systems. Apophis is in the daytime sky and unobservable from mid-2021 to 2027. It will be challenging to determine from single-night observations in 2027 if Apophis has moved on the target plane enough to enter a dangerous keyhole, as the deviation from the nominal ephemeris might be only a few tenths of an arcsecond. An impending Earth impact would, however, be signaled clearly in most cases by deviations of tens of arcseconds of Apophis from its nominal ephemeris in 2027. Thus, most of the impact risk could be retired by a single observation of Apophis in 2027, though a minority of cases present some ambiguity and are discussed in more detail. Charts of the on-sky position of Apophis under different scenarios are presented for quick assessment by observers.

Keywords: Near-Earth objects, Close encounters, Small Solar System bodies, Asteroids
Temporal Variations of <SUP>222</SUP>Rn Density Distributions in the Lunar Exosphere. Because of radiogenic processes, the lunar interior is a source of rare gases like helium (4He), argon (40Ar), and radon (222Rn) that might be released continuously, or impulsively during moonquakes. The detection of radon is therefore important in the sense that it can help trace the crustal dynamics on the Moon. In this study, we will introduce a Monte Carlo–based model designed to investigate the time-dependent transient dynamics of the lunar 222Rn exosphere. Our model accounts for the background emission and transient ejection of gas molecules from the lunar surface, encompassing loss processes such as radioactive decay, photoionization, and the cold trapping in permanently shadowed regions near the poles. Additionally, it incorporates the diurnal temperature fluctuations of the lunar surface, which significantly influence the condensation duration of the radon atoms and their subsequent release near the sunrise. This model also can support future observations in missions such as Chang'E 6 or other lunar explorations.

Keywords: Monte Carlo methods, Lunar science, Lunar atmosphere
Light Scattering Measurements of KCl Particles as an Exoplanet Cloud Analog. Salt clouds are predicted to be common on warm exoplanets, but their optical properties are uncertain. The Exoplanet Cloud Ensemble Scattering System (ExCESS), a new apparatus to measure the scattering intensity and degree of linear polarization for an ensemble of particles, is introduced here and used to study the light scattering properties of KCl cloud analogs. ExCESS illuminates particles with a polarized laser beam (532 nm) and uses a photomultiplier tube detector to sweep the plane of illumination. Scattering measurements for KCl particles were collected for three size distributions representative of modeled clouds for the warm exoplanet GJ 1214b. Our measurements show that Lorenz–Mie calculations, commonly used to estimate the light scattering properties of assumedly spherical cloud particles, offer an inaccurate depiction of cubic and cuboid KCl particles. All of our measurements indicate that Lorenz–Mie scattering overestimates the backscattering intensity of our cloud analogs and incorrectly predicts the scattering at mid-phase angles (∼90°) and the preferential polarization state of KCl scattered light. Our results align with the general scattering properties of nonspherical particles and underscore the importance of further understanding the effects that such particles will have on radiative transfer models of exoplanet atmospheres and reflected light observations of exoplanets by the upcoming Nancy Grace Roman Space Telescope and Habitable Worlds Observatory.

Keywords: Atmospheric clouds, Laboratory astrophysics, Mini Neptunes, Interdisciplinary astronomy, Exoplanet atmospheres
Validation Experiments for In Situ Ne Isotope Analysis on Mars: Gas Separation Flange Assembly Using Polyimide Membrane and Metal Seal. The Martian atmospheric Ne may reflect recent gas supply from its mantle via volcanic degassing, due to its short (∼100 Myr) escape timescale. The isotopic ratio of the Martian atmospheric Ne would therefore provide insights into that of the Martian mantle, further suggesting the origin of Mars volatiles during planetary formation. Mass spectrometric analysis of the Martian atmospheric Ne, however, has faced challenges from interference between 20Ne+ and 40Ar++. Previous studies using a polyimide membrane for 20Ne/40Ar separation were limited by the drawbacks of elastomeric O-rings to support the membrane, such as low-temperature intolerance, outgassing, and the need to endure environmental conditions during the launch and before/after landing on Mars. This study proposes a new method employing a metal C-ring to secure a 100 μm polyimide sheet within vacuum flanges. Environmental tests, including vibration, shock, extreme temperatures, and radiation exposure, were conducted on the gas separation flanges. Pre- and post-test analyses for He, Ne, and Ar demonstrated the membrane-flange system's resilience. Gas permeation measurements using terrestrial air effectively permeated 4He and 20Ne, while reducing 40Ar by more than six orders of magnitude. This study achieved a &lt;3% accuracy in determining the 20Ne/22Ne ratio, sufficient for assessing the origins of Ne in the Martian mantle. Furthermore, experiments with a 590 Pa gas mixture simulating the Martian atmosphere achieved a 10% accuracy for the 20Ne/22Ne isotope ratio, with gas abundances consistent with numerical predictions based on individual partial pressures. These results validate the suitability of the developed polyimide membrane assembly for in situ Martian Ne analyses.

Keywords: Space vehicle instruments, Planetary atmospheres, Planetary science
Crater Morphometry on Callisto. Impact crater formation is affected by the physical properties of planetary crusts, allowing comparison of crater dimensions to serve as a proxy for comparing the crustal properties of different planetary bodies. New topographic profiles of Callisto craters, derived from Galileo-based digital terrain models, are presented, and the crater dimensions recorded. These data were used to derive crater morphometry scaling trends, which were then compared to the established trends of Ganymede and the Moon. Our comparative study suggests that the upper brittle portion of Callisto's ice crust allows for the retention of steep-sided and elevated rim scarps, while subsurface warmer ice leads to an enhanced uplift and shallowing of the crater bowl. Crater dimensions are similar between Callisto and Ganymede, suggesting that the bulk properties of their near-surface crusts are comparable. The most notable difference between craters on these two Galilean moons were the smaller central pit diameters on Callisto. This difference can be explained if the pit formation on these bodies is controlled by the presence and movement (drainage and/or volatile loss) of impact melt water: the lower impact velocity and/or lower expected crustal heat flow on Callisto will result in less impact melt generation, and thus smaller central pits.

Keywords: Galilean satellites, Craters
Reflectance Spectroscopy of 27 Fine-particulate Mineral Samples from Far-ultraviolet through Mid-infrared (0.12─20 μm). This paper presents far-ultraviolet through mid-infrared (0.12─20 μm) reflectance spectra of 27 fine-particulate (&lt;10 μm) terrestrial mineral samples, providing continuous spectra that cover an unusually broad spectral range and are of unusually fine particle size relative to most existing spectral libraries. These spectra of common geologic materials are useful for future applications that study the dust on various planetary bodies. Reflectance spectra were acquired of the samples at multiple laboratories at multiple wavelengths. All of the spectra were compared to one another to observe the general, common spectral characteristics (e.g., slope, band shape, and band depth), and the best segments of the spectra representing the mineral reflectance were scaled and spliced together to form a "Frankenspectrum" for each mineral that best represents the full wavelength range of far-ultraviolet, visible, near-infrared, and middle-infrared wavelengths. These scaled and spliced Frankenspectra, as well as the entire set of individual "original" reflectance spectra from each laboratory, are available in the Planetary Data System Geosciences Node.

Keywords: Vibrational spectroscopy, Infrared spectroscopy, Spectroscopy, Ultraviolet spectroscopy
Constraints on the Long-term Existence of Dilute Cores in Giant Planets. Post-Cassini ring seismology analysis suggests the existence of a stable stratification inside Saturn that extends from the center to ∼60% of its radius, in what is recognized today as Saturn's dilute core. Similarly, gravity measurements on Jupiter suggest the existence of a dilute core of weekly constrained radial extent. These cores are likely in a double-diffusive regime, which prompts the question of their long-term stability. Indeed, previous direct numerical simulation (DNS) studies in triply periodic domains have shown that, in some regimes, double-diffusive convection tends to spontaneously form shallow convective layers, which coarsen until the region becomes fully convective. In this paper, we study the conditions for layering in double-diffusive convection using different boundary conditions, in which temperature and composition fluxes are fixed at the domain boundaries. We run a suite of DNSs varying microscopic diffusivities of the fluid and the strength of the initial stratification. We find that convective layers still form as a result of the previously discovered γ-instability, which takes place whenever the local stratification drops below a critical threshold that only depends on the fluid diffusivities. We also find that the layers grow once formed, eventually occupying the entire domain. Our work thus recovers the results of previous studies, despite the new boundary conditions, suggesting that this behavior is universal. The existence of Saturn's stably stratified core, today, therefore suggests that this threshold has never been reached, which places a new constraint on scenarios for the planet's formation and evolution.

Keywords: Hydrodynamical simulations, Saturn, Solar system gas giant planets, Exoplanet evolution
Observations of Igneous Subsurface Stratigraphy during the Jezero Crater Floor Rapid Traverse from the RIMFAX Ground-penetrating Radar. Perseverance traversed the eastern, northern, and western margins of the Séítah formation inlier on the rover's western fan front approach. Mapping the stratigraphy and extent of the Máaz and Séítah formations is key to understanding the depositional history and timing of crater floor resurfacing events. Perseverance's rapid progress across the Jezero crater floor between the Octavia E. Butler landing site and the western fan front resulted in limited contextual images of the deposits from the Navigation Camera and Mast Camera Zoom. By combining the limited surface images with continuous subsurface sounding by the Radar Imager for Mars' Subsurface Experiment (RIMFAX) ground-penetrating radar, Jezero crater floor stratigraphy was inferred along this rapid traverse. We produced the first subsurface map of the Máaz formation thickness and elevation of the buried Séítah formation for 2.3 km of the rapid traverse. Three distinct reflector packets were observed in RIMFAX profiles interspersed with regions of low-radar reflectivity. We interpret these reflector packets with increasing depth to be the Roubion member of the Máaz formation (covered in places with regolith), the Rochette member, and the Séítah formation. We found a median permittivity of 9.0 and bulk density of 3.2 g cm‑3 from hyperbola fits to RIMFAX profiles, which suggests a mafic composition for Máaz and Séítah. The low-radar reflectivity regions within each reflector packet could indicate potential depositional hiatuses where low-density material like sediment or regolith could have accumulated between successive Máaz formation lava flows and the Séítah formation at depth.

Keywords: Planetary surfaces, Surface processes, Mars, Geological processes, Radar observations, Planetary geology, Rovers, Volcanism
The Stability of a Dense Crust Situated on Small Bodies. Small planetary bodies in the solar system, including Io, Ganymede, and Callisto, may have a crust denser than their underlying mantle. Despite the inherent gravitational instability of such structures, we show that the growth timescale of the Rayleigh–Taylor (RT) instability can be as long as the age of the solar system, owing to the strong temperature dependence of viscosity. Even in cases where the instability timescale is shorter, the instability is confined to a thin layer at the base of the crust, making the foundering of the entire crust improbable in many scenarios. This study delineates the onset and aftermath of the RT instability, applying a quantitative framework to assess the stability of (i) rock-contaminated crust on icy satellites, and (ii) silicate crust floating on top of a subsurface magma ocean on Io. Notably, for Io the RT instability peels off only 10–100 m from the crust's base, and thermal diffusion rapidly recovers the crustal thickness through solidification of a magma ocean. Despite recurrent delamination of the crustal base, the initial crustal thickness is maintained by thermal diffusion, virtually stabilizing a floating dense crust. Cracking of the crust also is unlikely to result in the foundering of the crust. A dense crust on a small body is therefore difficult to be overturned, suggesting the potential ubiquity of dense surface layers throughout the solar system.

Keywords: Io, Galilean satellites, Ganymede, Callisto
The Trojan-like Colors of Low-perihelion Kuiper Belt Objects. An important testable prediction of dynamical instability models for the early evolution of the solar system is that Jupiter Trojans share a source population with the Kuiper Belt. Concrete evidence of this prediction remains elusive, as Kuiper Belt objects (KBOs) and Jupiter Trojans appear to have different surface compositions. We address the long-standing question of Trojan origin by finding a dynamical subpopulation in the Kuiper Belt with Trojan-like colors. Combining existing photometric data with our own surveys on Keck I and Palomar P200, we find that the low-perihelion (q &lt; 30 au, a &gt; 30 au) component of the Kuiper Belt has colors that bifurcate similarly to the Jupiter Trojans, unlike Centaurs (a &lt; 30 au), which have redder, Kuiper Belt-like colors. To connect the Jupiter Trojans to the Kuiper Belt, we test whether the distinct Trojan-like colors of low-perihelion KBOs result from surface processing or are sourced from a specific population in the Kuiper Belt. By simulating the evolution of the Canada–France Ecliptic Plane Survey synthetic population of KBOs for four billion years, we find that differences in heating timescales cannot result in a significant depletion of very red low-perihelion KBOs as compared to the Centaurs. We find that the neutrally colored scattered disk objects (e &gt; 0.6 KBOs) contribute more to the low-perihelion KBO population than to Centaurs, resulting in their different colors.

Keywords: Centaur group, Kuiper belt, Jupiter trojans, Solar system evolution, Photometry
Testing the Bus–DeMeo Asteroid Taxonomy Using Meteorite Spectra. The most widely used method to spectrally classify asteroids is the Bus–DeMeo taxonomy. To test how well the Bus–DeMeo taxonomy groups asteroids on the basis of their mineralogy, we have classified ∼1500 meteorite spectra using this Bus–DeMeo system. Some asteroid classes group together meteorites with similar compositions better than others. Howardite, eucrite, and diogenite spectra tend to be classified as V-types, while ordinary chondrite spectra tend to be classified as S-complex or Q-type bodies. The relatively featureless D- and X-types tend to be dominated by CM carbonaceous chondrites but with a substantial number of matches also with iron meteorites. The large proportion of CM chondrite matches for the D- and X-classes is most likely due to the large number of CM chondrite spectra and the rarity of spectra of more fragile carbonaceous chondrites in our data set. A number of relatively featureless asteroid classes like the C-, B-, L-, and Xc-types group meteorite types together with a wide variety of mineralogies and thermal histories. Visual albedos are vital for distinguishing between many of these assemblages. The Bus–DeMeo taxonomy does have trouble classifying olivine-dominated meteorites that do not have red-sloped spectra because this type of spectrum is rare among asteroids. For many asteroid classes, care must be used when making mineralogical interpretations based solely on spectral type.

Keywords: Meteorites, Asteroid belt