Sazuna/UAT_keywords huggingface dataset:
Inconsistencies in Simple Thermal Model Results for Near-Earth Asteroids between Infrared Telescope Facility SpeX and NEOWISE Data. Understanding the properties of near-Earth asteroids (NEAs) is key for many aspects of planetary science, particularly planetary defense. Our current knowledge of NEA sizes and regolith properties is heavily dependent on simple thermal models. These models are often used to analyze data from missions such as NEOWISE because they are well suited to deal with large volumes of data. However, simple model results based on NEOWISE data may be inconsistent with results based on other types of observation in some cases. In this work, we seek to better understand these potential inconsistencies, as well as the situations for which they are most prevalent. We do this by comparing simple model results based on Infrared Telescope Facility SpeX data to similar results based on NEOWISE data. This is carried out for six NEAs that represent a range of spectral types, shapes, and rotation states. We find that models based on SpeX and NEOWISE data for these six objects are inconsistent in some cases, even though the SpeX results are consistent with other methods and observations. We find that objects observed at fainter magnitudes and objects with more primitive compositions are more likely to produce inconsistent fits. These results highlight the importance of better understanding the limitations of simple models as applied to large survey data sets like NEOWISE. This is particularly true as we move into an era where our understanding of the NEA population will be dominated by future large surveys such as NEO Surveyor.

Keywords: Near-Earth objects, Astronomical models, Asteroids
A New Detailed Global Map of Lunar Light Plains. Lunar light plains (LPs) are globally distributed, smooth and flat geologic units occurring in crater floors and topographic lows, similar in morphology to mare basalts, but with moderate to high albedo. Despite numerous studies investigating LPs, their emplacement mechanism(s), ages, and origins remain highly debated. To aid in deciphering their origin(s), we produced a new independent global map of the extent of the LPs. Thus, we (1) evaluated the morphological and compositional definitions of LP; (2) tested the reproducibility of previous work; and (3) extended the previously mapped extents of LPs. We find morphological similarities between near- and farside LPs with regional variations in albedo and FeO contents. We were able to reproduce the majority of previous LP maps, with some notable exceptions. We find ∼13% of the lunar surface is covered by LPs, which is slightly higher than previous studies, likely due to our inclusion of smaller deposits. Overall, the distribution of LPs on the nearside appears to be denser around mare regions and exhibits more widely varying degrees of smoothness, size, albedo, and FeO contents compared to the farside highlands. In contrast, on the farside, we find a large number of LPs with similar morphologies and FeO contents, in ray-like patterns likely related to the Orientale impact event. Beyond Orientale's influence, the occurrences of LPs are of lower albedo and FeO contents are fewer and sparser, with similar morphologies to the nearside deposits. Thus, our study indicates that an impact-related origin for the majority of LP deposits is most likely.

Keywords: Lunar craters, Lunar science, Geological processes, Lunar impacts, Lunar surface, Lunar features, Craters
Visible Spectral Atlas of Geostationary Satellites from Tucson, AZ for Differentiating Between Natural and Artificial Objects. As near-Earth object (NEO) surveys continue to search for smaller NEOs, they will also detect an increasing number of temporarily captured objects, or minimoons, in geocentric orbital space. Derelict spacecraft and debris in Earth orbit and cislunar space can be mistaken for minimoons, but spectral characterization can distinguish between the two categories of objects. However, systematic noncompositional effects due to nightly and seasonal phase angle changes on artificial objects need to be quantified before such distinctions can be made. These effects have been studied on small solar system bodies, but very little on artificial bodies. We present the reduced data of our multiyear visible wavelength (450–950 nm) spectral campaign of the geostationary Earth-orbiting (GEO) satellite belt from Tucson, AZ, and include comparisons to relevant planetary materials. Although some bus types have steeper spectral slopes than planetary materials, certain bus type spectral features can be confused for planetary materials. One example is a rollover at red wavelengths in the Eurostar-3000 bus-type spectrum that appears similar to mineralogical absorption bands on S- and L-type asteroids. Observations include a total of 96 unique GEO satellites across 192 separate nights from 2020 to 2022. A select subset of GEO satellites is repeatedly observed to measure seasonal variations. Our methods for data acquisition, processing, and cleaning are outlined in this paper. A summary of the atlas shows the full night median spectrum with phase variations and a lightcurve of brightness versus phase angle for each of the 284 sets of data collected.

Keywords: Near-Earth objects, Phase angle, Space research, Spectroscopy, Geostationary satellites
Numerical Investigation of the Cohesive Strength Regime of the Bilobated Arrokoth after the Sky-crater-forming Impact Event. In 2019, NASA's New Horizons mission, using the Long Range Reconnaissance Imager, revealed Arrokoth's bilobated shape and a large impact-crater-like region ("Sky") on the small lobe, which is ∼7 km wide and ∼1 km deep. Given that this depression takes up ∼7% of the entire volume of the small lobe, Arrokoth's neck, the most structurally sensitive area to failure, might have been subject to substantial structural modification if the Sky-crater-forming event occurred after the bilobate shape had formed. Using the π-scaling law, we quantified the linear momentum imparted to the small lobe by the Sky-crater-forming event, which was in the range of (2.4–4.0) × 1013 kg m s‑1, depending on Arrokoth's bulk density of 250–500 kg m‑3 and impact speeds of 100 m s‑1, 300 m s‑1, and 1 km s‑1. If the linear momentum was fully transferred to Arrokoth's small lobe, it would have given the small lobe an impulse velocity of approximately 0.1 m s‑1 relative to the large lobe. To assess the structural impact of this event, we used a finite-element modeling approach to simulate post-impact stress fields driven by the estimated impulse velocity on the small lobe and constrained the critical cohesive strength required to prevent structural failure. Based on the current parameter space, our results suggest that the Sky-crater-forming event could have required the critical cohesive strength of up to ∼20 kPa for Arrokoth's neck to avoid structural failure, which is higher than the typical cohesive strength estimated for small bodies (usually less than 1 kPa for asteroids and comets).

Keywords: Small Solar System bodies, Asteroid dynamics, Classical Kuiper belt objects, Computational methods, Craters
How Meteor Showers Can Guide the Search for Long-period Comets. With orbital periods longer than 200 yr, most long-period comets (LPCs) remain undiscovered until they are in-bound toward perihelion. The comets that pass close to Earth's orbit are potentially hazardous objects. Those with orbital periods up to ∼4000 yr tend to have passed close to Earth's orbit in a previous orbit and produced a meteoroid stream dense enough to be detected at Earth as a meteor shower. In anticipation of Rubin Observatory's Legacy Survey of Space and Time (LSST), we investigate how these meteor showers can guide dedicated searches for their parent comets. Assuming search parameters informed by LSST, we calculated where the 17 known parent bodies of LPC meteor showers would have been discovered based on a cloud of synthetic comets generated from the shower properties as measured at Earth. We find that the synthetic comets predict the on-sky location of the parent comets at the time of their discovery. The parent comet's location on average would have been 1.°51 ± 1.°19 from a line fit through the synthetic comet cloud. The difference between the heliocentric distance of the parent and mean heliocentric distance of synthetic comets on the line was 2.09 ± 1.89 au for comets with unknown absolute nuclear magnitudes and 0.96 ± 0.80 au for comets with known absolute nuclear magnitudes. We applied this method to the σ-Hydrids, the proposed meteor shower of comet Nishimura, and found that it successfully matched the pre-covery location of this comet 8 months prior to Nishimura's discovery.

Keywords: Long period comets, Meteor showers
On the Early Thermal Processing of Planetesimals during and after the Giant Planet Instability. Born as ice-rich planetesimals, cometary nuclei were gravitationally scattered onto their current orbits in the Kuiper Belt and the Oort Cloud during the giant planets' dynamical instability in the early stages of our solar system's history. Here, we model the thermal evolution of planetesimals during and after the giant planet instability. We couple an adapted thermal evolution model to orbital trajectories provided by N-body simulations to account for the planetesimals' orbital evolution, a parameter so far neglected by previous thermal evolution studies. Our simulations demonstrate intense thermal processing in all planetesimal populations, mainly concerning the hypervolatile ice content. Unlike previous predictions, we show that hypervolatile survival was possible in a significant number of planetesimals of the Kuiper Belt and the Oort Cloud. Planetesimals ejected into interstellar space proved to be the most processed, while planetesimals ending in the Oort Cloud were the least processed population. We show that processing differences between populations are a direct consequence of their orbital evolution patterns, and that they provide a natural explanation for the observed variability in the abundance ratios of CO on cometary populations and on the recent observations of long-distance CO-driven activity on inbound long-period comets.

Keywords: Comet nuclei, Short period comets, Comet dynamics, Long period comets, Interstellar objects, Planetesimals, Comets, Comet volatiles
Statistical Analysis of Near-surface Structure and Material Properties on Momentum Transfer in Rubble Pile Targets Impacted by Kinetic Impactors. Rubble pile asteroids consist of reassembled fragments of once larger monolithic asteroid parent bodies. Recent spacecraft missions to asteroids like Itokawa, Ryugu, Bennu, and Dimorphos suggest that rubble pile asteroids are common in the asteroid population, and rubble piles could be a likely structure among potentially hazardous objects. Therefore, it is important to understand the response of rubble pile targets to kinetic impacts for potential future deflection needs. The recent Double Asteroid Redirection Test (DART) mission motivates an investigation of kinetic impacts into rubble pile targets to understand their effects on deflection. Here, we simulate kinetic impacts into Dimorphos-sized asteroid targets to understand the effect of the impact site structure on the deflection efficiency of relevant sizes for planetary defense. We perform 52 two-dimensional simulations where we vary the impact site structure of the impact site, the target porosity, and the material behavior/strength model to understand their relative effects on crater size and the momentum enhancement factor (β). We find that the effects of the impact site on both crater size and β are greatest for impacts into weaker targets, where impact sites rich in matrix material result in statistically larger craters and higher βs compared to impact sites rich in boulder material. Further, impact site structures that promote increased boulder ejection result in larger β values. These results provide important intuition to understand the DART impact and to extrapolate results to future potential missions.

Keywords: Impact phenomena, Near-Earth objects, Hydrodynamical simulations, Asteroids, Small Solar System bodies
Analysis of Enceladus's Time-variable Space Environment to Magnetically Sound its Interior. We provide a comprehensive study of Enceladus's time-variable magnetic field environment and identify in measurements of the Cassini spacecraft signatures that appear to be consistent with induced fields from the moon's interior. Therefore, we first analyze the background field Enceladus is exposed to within 21 flybys and 50 crossings of the moon's orbit by the Cassini spacecraft. Considering magnetic field variability due to Enceladus's eccentric orbit, Saturn's planetary period oscillations, and local time effects within the magnetospheric current sheet, we construct predictive, time-variable background fields near Enceladus with a correlation coefficient of 0.75 and larger compared to the measured background fields. Subsequently, we build a geophysically based electrical conductivity model of Enceladus's ocean from the equation of state for saline water and mixing laws for a porous core permeated by water. Using this conductivity model and the derived time-variable fields, we calculate expected induced fields. For close flybys, we identify within mostly plume-dominated magnetic field perturbations of 10–30 nT much smaller perturbations of 1–3 nT, which could be consistent with induction. The flybys over Enceladus's north pole are best suited for induction studies, and the associated measurements suggest that a conductivity of the ocean with 1–3 S m–1 is not sufficient to produce an adequate induction response, but they support a highly conductive, porous core of 20–30 S m–1 and/or a more conductive ocean. Our study also provides strategies for future magnetic sounding of Enceladus.

Keywords: Enceladus, Magnetic fields
Artificial Impacts on the Moon: Modeling 3D Seismic Propagation Effects with AxiSEM3D. During the Apollo missions, used spacecraft were deliberately crashed into the Moon to provide large signals for the seismic experiments. We use AxiSEM3D and a variety of 1D and 3D models to model these impacts and propagate seismic waves across the Moon in 3D. Simulations using a smoothly varying background model, which include scattering heterogeneities to 50 km depth, reproduced some of the observations, especially farther from the source. These simulations have an emergent onset and an increase and decay in the seismic envelope. However, close to the source (&lt;15°), the simulations include a large-amplitude surface wave, which is inconsistent with the observations. Traditionally, artificial and meteoroid impacts on the Moon have been considered to have P and S phases. However, a true S phase may be absent. Previous authors have treated artificial or meteoroid impacts on airless bodies as explosions. A shear wave traveling directly from the source is not expected from an explosion. Instead, the small change of the slope of the seismic envelope may be explained by either a PS phase or scattered phases of P-to-SV conversions that start to dominate the seismogram. The locations of the artificial impacts are well known in comparison with other types of events. Due to their shallow paths, they are also ideal for constraining the near-surface layers. Understanding how the seismic waves propagate within the highly complex near-surface layers will also lead to a better understanding of how the waves propagate beneath them, as well as better results from future missions.

Keywords: Lunar interior, Lunar seismology
The Upper Atmosphere of Uranus from Stellar Occultations. II. Revised Temperatures in the Upper Stratosphere and Lower Thermosphere. Measurements made by Voyager 2 during its flyby of Uranus in 1986 found warm stratospheric and hot thermospheric temperatures that cannot be explained by solar energy alone. This contributes to what is 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 the coldest stratosphere temperatures, the hottest thermospheric temperatures, and the weakest internal heat flux of all four giant planets. Moreover, the Voyager 2 temperature measurements are at odds with many contemporaneous Earth-based stellar occultations. In Paper I, we introduced two updated techniques for reanalyzing these 26 occultations—forward modeling and inversion—and demonstrated them on the 1977 Uranus occultation. This work (Paper II) presents the results of applying these techniques to 26 total Uranus stellar occultations, observed between 1977 and 1996. We find that the lower thermosphere of Uranus is much cooler than the Voyager 2 profiles but slightly warmer than the originally published occultations. We find that the stratosphere of Uranus is nearly isothermal and the stratosphere–thermosphere boundary is much higher in altitude than previously believed. Furthermore, we present a family of new, one-dimensional atmospheric models for Uranus fit to our results. The models suggest that there is a significant source of heat transport or dissipation away from the stratosphere, which we discuss as resulting from gravity-wave activity. We offer our models as new representative profiles and discuss how they improve the understanding of the energy balance of Uranus.

Keywords: Planetary atmospheres, Thermosphere, Stellar occultation, Stratosphere, Uranus
Understanding the Effects of Micrometeoroid Bombardment on Graphite-rich Mercury Analogs through Laboratory Experiments and Electron Microscopy Analysis. Space weathering alters the spectral, microstructural, and chemical characteristics of the surface of Mercury, and an effective way to understand it is in the laboratory. To simulate energetic micrometeoroid impacts on the surface of Mercury, we irradiated pellets containing forsteritic olivine and graphite with a pulsed laser. Our analysis with scanning electron microscopy showed two morphological textures: one that is melt-rich and one consisting of fluffy, C-rich globules. Performing transmission electron microscopy on these textures, we identified the presence of new microstructural and chemical features resulting from simulated space weathering, including C-rich inclusions in the melt and vesiculated textures in the C-rich globules. Separate analysis of Si wafers, which were suspended near the target to collect the vapor and melt ejected during irradiation, show a variety of ejected material, including forsterite grains, melt splash, and C-rich particles. These observations suggest the possibility that space weathering products on the surface of Mercury may be different than on other airless bodies, which will be further explored by the BepiColombo mission.

Keywords: Regolith, Planetary surfaces, Micrometeoroids, Mercury (planet)
Orientale Basin as a Guide for Identifying Lunar Basin Datable Impact Melt and Assessing Impact Melt Differentiation. Two fundamental questions face lunar scientists: (1) What is the absolute age of each lunar impact basin and thus the early impact flux curve? (2) To what degree did basin impact melt seas undergo differentiation? We compiled a 1:200,000-scale geological map of the lunar Orientale basin, focusing on identifying the most widespread and accessible occurrences of impact melt deposits from the basin-forming impact to help guide sample-return missions to Orientale and especially to other undated lunar basins using the identification and interpretation strategies for Orientale. We assess the size of craters excavating through basalt cap rock that may have exhumed datable basin impact melt, and we assess the possibility of impact melt sampling and melt differentiation for the large complex crater Maunder. We also provide guidance for distinguishing impact melt produced by larger complex craters from excavated basin melt and determining whether such craters may have also sampled through the entire melt deposit. Our analysis finds six such sites that are predicted to have the same age—that of the Orientale-forming event—and provides guidance for assessing possible melt differentiation. Future missions could collect samples from these sites for in situ age dating and petrologic assessment and/or for return to Earth and subsequent age dating and analysis. By sampling and dating impact melt of known provenance from the Moon's dozens of large basins, future work can anchor the chronostratigraphy of the Moon's formative years. Such information could be scaled to infer Earth's large impactor flux around the time of life's first emergence.

Keywords: Impact phenomena, Lunar craters, Lunar maria, Lunar science, Lunar geochronology, Lunar impacts, Lunar surface
Crater Equilibrium State Characterization given Crater Production from a Single Power Law. We generalize the crater equilibrium concept, a terminal state on a cratered surface where the balance of crater production and erasure apparently limits the crater population from further growth. Assuming the crater production consists of a single power law, our model identifies four classes of crater equilibrium. The first class is the most common state, where the power-law slope for the equilibrium size–frequency distribution is independent of the crater production slope power. The second class arises when there is efficient degradation of larger craters by smaller crater production, which results in dependence of the crater equilibrium slope power on the crater production slope power. The third class is another common state when a shallow production function causes a crater equilibrium state with a similarly shallow slope. This class results from the enhanced degradation of smaller craters by larger crater production. The fourth class is a combination of the second and third classes. We further compare the concept of geometric saturation, which has been widely used to quantify the level of crater equilibrium, and that of cookie-cutter saturation. We present a crucial update to the cookie-cutter saturation concept that brings models closer to the reality of crater accumulation over a range of sizes than the geometric saturation concept. Our model offers simpler analytical formulae for cookie-cutter saturation and proposes this concept as a more meaningful reference to argue the crater equilibrium level. Our work and earlier studies confirm the consistency of the crater equilibrium concepts, enabling deeper interpretations of crater equilibrium.

Keywords: Impact phenomena, Planetary surfaces, Impact gardening, Craters