Sazuna/UAT_keywords huggingface dataset:
Spectral and Petrographic Properties of Inclusions in Carbonaceous Chondrites and Comparison with in Situ Images from Asteroid Ryugu. We imaged a set of carbonaceous chondrites from the CM2, CO3, CV3, and CK4 groups using the qualification model of MasCam, the camera on board the asteroid lander MASCOT, which touched down on asteroid Ryugu in 2018 October. A CI1 meteorite was also imaged but excluded from the analysis due to prominent terrestrial weathering. Following the methods used to image the rock on Ryugu, we placed a total of 14 meteorites approximately 20 cm in front of the camera to achieve a spatial resolution of about 0.2 mm per pixel and illuminated the samples with onboard light-emitting diodes of four different colors in the visible wavelength range. We mapped bright and dark inclusions within the meteorites and derived the inclusion brightness relative to the matrix in the red light, the relative spectral slope of each inclusion, the inclusion size frequency distribution and the matrix volume abundance. We find that the meteorite groups overlap within these parameters, but individual samples, as well as individual inclusions, can have deviating values. Terrestrial weathering appears to have no systematic influence on these parameters. Relating our analysis to the inclusions found in the rock on Ryugu, we find that the spectral parameters of Ryugu's inclusions fit well in the parameter space of the carbonaceous chondrites. Compared with the most common types of carbonaceous chondrites, Ryugu's rock has larger inclusions (mean diameter: 0.63 ± 0.91 mm) and a higher upper limit to the matrix abundance (92.4 vol%).

Keywords: Asteroids, Carbonaceous chondrites, Landers, Spectroscopy, Planetary science, Meteorites, Asteroid surfaces
Lunar Surface Composition Constraints from Maturity-corrected Far-ultraviolet Reflectance Maps. Far-ultraviolet (FUV) observations by the Lunar Reconnaissance Orbiter Lyman Alpha Mapping Project (LAMP) have shown that the lunar surface reflectance in the ultraviolet is sensitive to changes in both composition and maturity at wavelengths &gt;170 nm. This can lead to uncertainties in the interpretation of features that appear in maps created using LAMP data from this wavelength range. Here we utilize a correction based on the optical maturity parameter to remove large-scale immaturity features from LAMP spectral slope and band ratio maps. After performing the correction, the LAMP maps more accurately represent the FUV lunar surface in the context of composition. Corrected LAMP maps show good correlation with lunar FeO, plagioclase, and bulk silicate abundance maps for moderate- to high-iron regions, indicating a sensitivity in the LAMP data to differences in mineral composition in those regions. These maps represent a unique view into a relatively unexplored region of the spectrum and showcase the ability to perform compositional mapping and mineral identification using FUV remote-sensing measurements.

Keywords: The Moon, Lunar composition, Lunar science
Investigating the Relationship between (3200) Phaethon and (155140) 2005 UD through Telescopic and Laboratory Studies. The relationship between the near-Earth objects (3200) Phaethon and (155140) 2005 UD is unclear. While both are parents to meteor showers (the Geminids and Daytime Sextantids, respectively) and have similar visible-wavelength reflectance spectra and orbits, dynamical investigations have failed to find any likely method to link the two objects in the recent past. Here we present the first near-infrared reflectance spectrum of 2005 UD, which shows it to be consistently linear and red-sloped, unlike Phaethon's very blue and concave spectrum. Searching for a process that could alter some common starting material to both of these end states, we hypothesized that the two objects had been heated to different extents, motivated by their near-Sun orbits, the composition of Geminid meteoroids, and previous models of Phaethon's surface. We thus set about building a new laboratory apparatus to acquire reflectance spectra of meteoritic samples after heating to higher temperatures than available in the literature to test this hypothesis and were loaned a sample of the CI chondrite Orgueil from the Vatican Meteorite Collection for testing. We find that while Phaethon's spectrum shares many similarities with different CI chondrites, 2005 UD's does not. We thus conclude that the most likely relationship between the two objects is that their similar properties are only by coincidence as opposed to a parent-fragment scenario, though the ultimate test will be when JAXA's DESTINY+ mission visits one or both of the objects later this decade. We also discuss possible paths forward to understanding Phaethon's properties from dynamical and compositional grounds.

Keywords: Near-Earth objects, Asteroids, Laboratory astrophysics, Meteor showers, Comets
FOSSIL. I. The Spin Rate Limit of Jupiter Trojans. Rotation periods of 53 small (diameters 2 km &lt; D &lt; 40 km) Jupiter Trojans (JTs) were derived using the high-cadence lightcurves obtained by the FOSSIL phase I survey, a Subaru/Hyper Suprime-Cam intensive program. These are the first reported periods measured for JTs with D &lt; 10 km. We found a lower limit of the rotation period near 4 hr, instead of the previously published result of 5 hr found for larger JTs. Assuming a rubble-pile structure for JTs, a bulk density of ≈0.9 g cm-3 is required to withstand this spin rate limit, consistent with the value ~0.8-1.0 g cm-3 derived from the binary JT system, (617) Patroclus-Menoetius system.

Keywords: Time domain astronomy, Asteroid rotation, Jupiter trojans, Time series analysis
Pluto and Charon Impact Crater Populations: Reconciling Different Results. The size-frequency distribution (SFD) of objects across the solar system is influenced by their formation and dynamic evolution. Bodies in different areas of the solar system-especially the inner versus outer-have likely experienced different histories, so measuring that SFD across orders of magnitude of solar distance can elucidate those different pasts. Accurate measurement of the SFD is greatly assisted by impact craters, formed from the smaller bodies that strike much larger ones, and it is often easier to measure impact craters' SFDs than the smaller impactors themselves. One of the main results from New Horizons' Pluto-Charon encounter was the crater SFD measurement, which illustrated an unexpected SFD with a distinct change in slope near ≈10-15 km diameter features. However, different methods of reporting these impact craters have resulted in some questions in the community about what the SFD actually is of Pluto's and Charon's crater population and therefore what the SFD is of the impactors that formed them. We have performed new crater population studies on both bodies, compared them with previously published work, and demonstrated that there is no ambiguity with respect to whether there is a transition to a shallower SFD population near ≈10-15 km. We find that this shallower slope is approximately -1.7 ± 0.2, while the steeper slope for larger craters is approximately -3.8 ± 0.6, though both of these uncertainties must be considered absolute minima based on fit sensitivity to the exact parameters and craters used. These values are consistent with previously reported results.

Keywords: Impact phenomena, Kuiper belt, Plutonian satellites, Solar system, Planetary science, Pluto, Trans-Neptunian objects
Threat from Within: Excitation of Venus's Co-orbital Asteroids to Earth-crossing Orbits. All five currently known asteroids in the 1:1 mean-motion resonance (co-orbital) with Venus cross Earth's orbit. We explore a scenario in which these near-Earth asteroids originate in a reservoir of asteroids co-orbiting with Venus on low-eccentricity orbits. Such an asteroid reservoir was proposed as the only viable source of Venus's co-orbital dust ring. So far, efforts to discover low-eccentricity Venus co-orbital (LEVCO) asteroids have been unsuccessful; however, their existence has not been ruled out. We show that LEVCO asteroids, stable for millions to billions of years, eventually evolve into Earth-crossing configurations, where they may pose a threat to Earth. We find that the orbits of these asteroids cross Earth's orbit for 22.5 million yr, on average, an order of magnitude longer than the corresponding Earth-crossing time of most asteroids escaping from the main belt. Using the results of the latest survey of LEVCO asteroids, we conclude that, given their absolute magnitudes, H, most of the observed Venus co-orbitals likely do not originate from the hypothetical population of LEVCO asteroids. However, we infer that there are up to ~500 asteroids originating from the LEVCO region with H &lt; 26.3 (10-40 m in diameter) that currently cross the orbit of Earth. Up to ~20 of those have H &lt; 24.1 (30-100 m in diameter), easily detectable by various near-Earth asteroid surveys. We estimate the current mass of the LEVCO reservoir as M ≈ 1013-1016 kg, 3-6 orders of magnitude lower than the current mass of the main belt, depending on their size-frequency distribution.

Keywords: Near-Earth objects, Asteroids, Asteroid dynamics, Atira group, Venus, Orbital resonances, Orbital evolution, Aten group, Dynamical evolution
New Constraints on Pluto's Sputnik Planitia Ice Sheet from a Coupled Reorientation-Climate Model. We present a coupled reorientation and climate model, to understand how true polar wander (TPW) and atmospheric condensation worked together to create the Sputnik Planitia (SP) ice sheet and reorient it to its present-day location on Pluto. SP is located at 18°N, 178°E, very close to the anti-Charon point, and it has been previously shown that this location can be explained by TPW reorientation of an impact basin as it fills with N2 ice. We readdress that hypothesis while including a more accurate treatment of Pluto's climate and orbital obliquity cycle. Our model again finds that TPW is a viable mechanism for the formation and present-day location of SP. We find that the initial impact basin could have been located north of the present-day location, at latitudes between 35°N and 50°N. The empty basin is constrained to be 2.5-3 km deep, with enough N2 available to form at most a 1-2 km thick ice sheet. Larger N2 inventories reorient too close to the anti-Charon point. After reaching the final location, the ice sheet undergoes short periods of sublimation and recondensation on the order of 10 m of ice, due to Pluto's variable obliquity cycle, which drives short periods of reorientation of a few kilometers. The obliquity cycle also has a role in the onset of infilling; some initial basin locations are only able to begin accumulating N2 ice at certain points during the obliquity cycle. We also explore the sensitivity of the coupled model to albedo, initial obliquity, and Pluto's orbit.

Keywords: Surface ices, Planetary interior, Planetary climates, Pluto
Tiger: Concept Study for a New Frontiers Enceladus Habitability Mission. Data returned from the Cassini-Huygens mission have strengthened Enceladus, a small icy moon of Saturn, as an important target in the search for life in our solar system. Information gathered from Cassini to support this includes the presence of a subsurface liquid water ocean, vapor plumes and ice grains emanating from its south polar region, and the detection of essential elements and organic material that could potentially support life. However, several outstanding questions remain regarding the connectivity of plume material to the ocean and the composition of the complex organic material. Herein we introduce Tiger, a mission concept developed during the 2020 Planetary Science Summer School at NASA's Jet Propulsion Laboratory. Tiger is a flyby mission that would help further constrain the habitability of Enceladus through two science objectives: (1) determine whether Enceladus's volatile inventory undergoes synthesis of complex organic species that are evidence for a habitable ocean, and (2) determine whether Enceladus's plume material is supplied directly from the ocean or if it interfaces with other reservoirs within the ice shell. To address the science goals in a total of eight flybys, Tiger would carry a four-instrument payload, including a mass spectrometer, a single-band ice-penetrating radar, an ultraviolet imaging spectrograph, and an imaging camera. We discuss Tiger's instrument and mission architecture, as well as the trades and challenges associated with a habitability-focused New Frontiers-class flyby mission to Enceladus.

Keywords: Ocean planets, Astrobiology, Interdisciplinary astronomy, Saturnian satellites, Habitable planets
A Model to Predict the Size of Regolith Clumps on Planetary Bodies. Prior investigations of the behavior of regolith on the surface of planetary bodies has considered the motion and interactions of individual grains. Recent work has shown the significance of cohesion in understanding the behavior of planetary regolith, especially on small, airless bodies. Surficial regolith grains may detach from a planetary body due to a variety of phenomena, including aeolian effects, spacecraft operations, micrometeoroid bombardment, and electrostatic lofting. It is well known in terrestrial powder handling that cohesive powders tend to form clumps. We present a theory for the size of regolith clumps that are likely to form and be easier to detach from a surface than their constituent grains, assuming monodisperse, spherical grains. The model predictions are significant for our interpretation of the surface of asteroids, as well as understanding a variety of phenomena on planetary bodies and designing of sampling spacecraft.

Keywords: Asteroid surfaces
An Improved Method to Measure Head Echoes Using a Meteor Radar. We present an improved methodology to obtain absolute position and velocity of meteor head echoes, which can yield orbital information, generally limited to the use of High-Power, Large-Aperture radars, using an advanced-designed specular meteor radar. The observations, which were performed during a period when an outburst of the β-Taurid meteor shower was expected, were performed with the Southern Argentine Agile MEteor Radar. Three different methodologies are utilized to confirm our results: an improved interferometric solver building on previous work, and two different target localization techniques using remote receiving stations. In addition, we performed simultaneous optical observations during the meteor shower period. Overall, 71 radar head echo events were detected and analyzed using interferometry, while 12 of those events have detected signals strong enough to be analyzed using localization methods at the remote sites. Due to poor weather, however, the optical cameras only observed two events simultaneously with the radar. Results from these events are in agreement with the radar results. We find that interferometry methods from both radar and optical data resulted in the most accurate estimation of meteor properties, while target localization techniques derived similar results, albeit with larger uncertainty. We also computed heliocentric meteoroid orbits, and while a fraction was hyperbolic, we believe these to be due to uncertainty. Two events are suspected to be β-Taurid shower members.

Keywords: Radio interferometry, Radar telescopes, Meteor showers
Constraining Saturn's Interior with Ring Seismology: Effects of Differential Rotation and Stable Stratification. Normal mode oscillations in Saturn excite density and bending waves in the C ring, providing a valuable window into the planet's interior. Saturn's fundamental modes (f-modes) excite the majority of the observed waves, while gravito-inertial modes (rotationally modified g-modes) associated with stable stratification in the deep interior provide a compelling explanation for additional density waves with low azimuthal wavenumbers m. However, multiplets of density waves with nearly degenerate frequencies, including an m = 3 triplet, still lack a definitive explanation. We investigate the effects of rapid and differential rotation on Saturn's oscillations, calculating normal modes for independently constrained interior models. We use a non-perturbative treatment of rotation that captures the full effects of the Coriolis and centrifugal forces, and consequently the mixing of sectoral f-modes with g-modes characterized by very different spherical harmonic degrees. Realistic profiles for differential rotation associated with Saturn's zonal winds can enhance these mode interactions, producing detectable oscillations with frequencies separated by less than 1%. Our calculations demonstrate that a three-mode interaction involving an f-mode and two g-modes can feasibly explain the finely split m = 3 triplet, although the fine-tuning required to produce such an interaction generally worsens agreement with seismological constraints provided by m = 2 density waves. Our calculations additionally demonstrate that sectoral f-mode frequencies are measurably sensitive to differential rotation in Saturn's convective envelope. Finally, we find that including realistic equatorial antisymmetry in Saturn's differential rotation profile couples modes with even and odd equatorial parity, producing oscillations that could in principle excite both density and bending waves simultaneously.

Keywords: Saturn, Hydrodynamics, Solar system, Pulsation modes, Planetary science, Planetary structure
Collision Chains among the Terrestrial Planets. II. An Asymmetry between Earth and Venus. During the late stage of terrestrial planet formation, hit-and-run collisions are about as common as accretionary mergers, for expected velocities and angles of giant impacts. Average hit-and-runs leave two major remnants plus debris: the target and impactor, somewhat modified through erosion, escaping at lower relative velocity. Here we continue our study of the dynamical effects of such collisions. We compare the dynamical fates of intact runners that start from hit-and-runs with proto-Venus at 0.7 au and proto-Earth at 1.0 au. We follow the orbital evolutions of the runners, including the other terrestrial planets, Jupiter, and Saturn, in an N-body code. We find that the accretion of these runners can take ≳10 Myr (depending on the egress velocity of the first collision) and can involve successive collisions with the original target planet or with other planets. We treat successive collisions that the runner experiences using surrogate models from machine learning, as in previous work, and evolve subsequent hit-and-runs in a similar fashion. We identify asymmetries in the capture, loss, and interchange of runners in the growth of Venus and Earth. Hit-and-run is a more probable outcome at proto-Venus, being smaller and faster orbiting than proto-Earth. But Venus acts as a sink, eventually accreting most of its runners, assuming typical events, whereas proto-Earth loses about half, many of those continuing to Venus. This leads to a disparity in the style of late-stage accretion that could have led to significant differences in geology, composition, and satellite formation at Earth and Venus.

Keywords: Solar system formation, Solar system terrestrial planets
Collision Chains among the Terrestrial Planets. III. Formation of the Moon. In the canonical model of Moon formation, a Mars-sized protoplanet "Theia" collides with proto-Earth at close to their mutual escape velocity vesc and a common impact angle ~45°. The "graze-and-merge" collision strands a fraction of Theia's mantle into orbit, while Earth accretes most of Theia and its momentum. Simulations show that this produces a hot, high angular momentum, silicate-dominated protolunar system, in substantial agreement with lunar geology, geochemistry, and dynamics. However, a Moon that derives mostly from Theia's mantle, as angular momentum dictates, is challenged by the fact that O, Ti, Cr, radiogenic W, and other elements are indistinguishable in Earth and lunar rocks. Moreover, the model requires an improbably low initial velocity. Here we develop a scenario for Moon formation that begins with a somewhat faster collision, when proto-Theia impacts proto-Earth at ~ 1.2vesc, also around ~45°. Instead of merging, the bodies come into violent contact for a half hour and their major components escape, a "hit-and-run" collision. N-body evolutions show that the "runner" often returns ~0.1-1 Myr later for a second giant impact, closer to vesc; this produces a postimpact disk of ~2-3 lunar masses in smoothed particle hydrodynamics simulations, with angular momentum comparable to canonical scenarios. The disk ends up substantially inclined, in most cases, because the terminal collision is randomly oriented to the first. Moreover, proto-Earth contributions to the protolunar disk are enhanced by the compounded mixing and greater energy of a collision chain.

Keywords: Planet formation, Lunar origin, Earth-moon system
Multiple Moist Climate Equilibrium States on Arid Rocky M-dwarf Planets: A Last-saturation Tracer Analysis. Terrestrial-type exoplanets orbiting nearby red dwarf stars (M dwarfs) are the first potentially habitable exoplanets suitable for atmospheric characterization in the near future. Understanding the stability of water in cold-trap regions on such planets is critical because it directly impacts transmission spectroscopy observations, the global energy budget, and long-term surface water evolution. Here we diagnose the humidity distribution in idealized general circulation model simulations of terrestrial-type exoplanets. We use the "tracer of last saturation" technique to study the saturation statistics of air parcels. We find that on synchronously rotating planets the water vapor abundance in the nightside upper troposphere depends weakly on planetary rotation, while more water vapor builds up in the nightside lower troposphere on fast-rotating planets. We then discuss how last-saturation statistics can elucidate the multiple moist climate equilibrium states on synchronously and asynchronously rotating arid planets. We show that the multiple moist climate states arise from the cold-trapping competition between the substellar upper atmosphere and cold surface regions. We find that fast synchronously rotating planets tend to trap surface water on the nightside as a result of their weak atmospheric and strong surface cold traps compared to the slow-rotating case. These results elucidate the nature of the water cycle on arid rocky exoplanets and will aid interpretation of atmospheric observations in the future.

Keywords: Extrasolar rocky planets, Water vapor, Atmospheric circulation, Computational methods, Astrobiology, Exoplanet atmospheres
Size and Shape of (11351) Leucus from Five Occultations. We present observations of five stellar occultations for (11351) Leucus and reports from two efforts on (21900) Orus. Both objects are prime mission candidate targets for the Lucy Discovery mission. Combined results for Leucus indicate a very dark surface with pV = 0.037 ± 0.001, which is derived from the average of the multichord occultations. Our estimate of the triaxial ellipsoidal shape is for axial diameters of 63.8 × 36.6 × 29.6 km assuming that the spin pole is normal to the line of sight. The actual shape of the object is only roughly elliptical in profile at each epoch. Significant topography is seen with horizontal scales up to 30 km and vertical scales up to 5 km. The most significant feature is a large depression on the southern end of the object as seen from a terrestrial viewpoint. For this work we developed a method to correct for differential refraction, accounting for the difference in color between the target object and the reference stars for astrometry derived from ground-based images.

Keywords: Astrometry, Stellar occultation, Jupiter trojans