Sazuna/UAT_keywords huggingface dataset:
Imaging Lunar Craters with the Lucy Long Range Reconnaissance Imager (L'LORRI): A Resolution Test for NASA's Lucy Mission. NASA's Lucy mission is designed to better understand the unique population of Trojan asteroids. Trojans were probably captured in Jupiter's L4 and L5 points early in the solar system's evolution and little altered since then. A critical investigation of Lucy is to use its highest-resolution camera, the Lucy Long Range Reconnaissance Imager (L'LORRI), to image Trojans' surfaces to understand their geology and impact crater populations. Through crater statistics, the population of smaller bodies that produced those impacts, relative age differences across the bodies, and other comparative investigations between bodies can be studied. Mapping the crater population to the minimum diameters needed to achieve Lucy's objectives might require image subsampling and deconvolution ("processing") to improve the spatial resolution, a process whereby multiple, slightly offset images are merged to create a single, better-sampled image and deconvolved with L'LORRI's point-spread function. Lucy's first Earth Gravity Assist (EGA1) provided an opportunity to test this process's accuracy using L'LORRI images of the Moon, whose crater population is well characterized and therefore provides ground-truth testing. Specifically, the lunar crater imaging by L'LORRI during EGA1 allowed us to compare crater statistics derived from raw and processed L'LORRI images with ground-truth statistics derived from higher-resolution lunar imaging from other missions. The results indicate the processing can improve impact crater statistics such that features can be identified and measured to ≈70% the diameter that they can otherwise be reliably mapped on native L'LORRI images. This test's results will be used in the observation designs for the Lucy flyby targets.

Keywords: Observational astronomy, Lunar craters, The Moon, Jupiter trojans, Craters, Astronomy image processing
Unraveling the Geologic History of Miranda's Inverness Corona. Miranda is the only icy body whose surface is known to contain the enigmatic features called corona-ovoid to trapezoidal areas of deformation. In this work, we seek to constrain potential formation mechanisms for Inverness Corona, the youngest known region on Miranda. To do this, we created the first detailed geologic map of Inverness, enabling the creation of a stratigraphic column of the order of events that formed this region. We employed a previously published Digital Elevation Model of the northern region of Inverness Corona to analyze the spacing of features in the region, which we propose to be extensional in origin. From this, we estimate an approximate brittle ice shell thickness of 2.5-3.8 km at the time of the region's formation, indicating that Miranda's brittle ice shell may have been relatively thin in the geologically recent past. We propose that Inverness formed from extension driven by a rising diapir or ice-shell thickening from a recent orbital resonance with Umbriel. The Uranus Orbiter and Probe mission is the highest priority flagship mission recommendation of the 2023-2032 Planetary Science and Astrobiology Decadal Survey. As such, we suggest measurements related to imaging, composition, gravity, and ice-shell thickness to gain an understanding of the geologic and orbital histories of the Uranian satellites, which would have implications for the evolution of the system as a whole.

Keywords: Planetary geology, Uranian satellites
Optical Monitoring of the Didymos-Dimorphos Asteroid System with the Danish Telescope around the DART Mission Impact. The NASA's Double-Asteroid Redirection Test (DART) was a unique planetary defence and technology test mission, the first of its kind. The main spacecraft of the DART mission impacted the target asteroid Dimorphos, a small moon orbiting the asteroid Didymos (65803), on 2022 September 26. The impact brought up a mass of ejecta which, together with the direct momentum transfer from the collision, caused an orbital period change of 33 ± 1 minutes, as measured by ground-based observations. We report here the outcome of the optical monitoring campaign of the Didymos system from the Danish 1.54 m telescope at La Silla around the time of impact. The observations contributed to the determination of the changes in the orbital parameters of the Didymos-Dimorphos system, as reported by Thomas et al., but in this paper we focus on the ejecta produced by the DART impact. We present photometric measurements from which we remove the contribution from the Didymos-Dimorphos system using an H-G photometric model. Using two photometric apertures we determine the fading rate of the ejecta to be 0.115 ± 0.003 mag day-1 (in a 2″ aperture) and 0.086 ± 0.003 mag day-1 (5″) over the first week postimpact. After about 8 days postimpact we note the fading slows down to 0.057 ± 0.003 mag day-1 (2″ aperture) and 0.068 ± 0.002 mag day-1 (5″). We include deep-stacked images of the system to illustrate the ejecta evolution during the first 18 days, noting the emergence of dust tails formed from ejecta pushed in the antisolar direction, and measuring the extent of the particles ejected Sunward to be at least 4000 km.

Keywords: Asteroid satellites, Light curves, Apollo group, Planetary probes
Investigation of Titan's South Polar HCN Cloud during Southern Fall Using Microphysical Modeling. Ice clouds in Titan's polar stratosphere are implicated in radiative heating and cooling and in transporting volatile organic compounds from where they form in the upper atmosphere to the surface of the moon. In early southern fall, Cassini detected a large, unexpected cloud at an altitude of 300 km over Titan's south pole. The cloud, which was found to contain HCN ice, was inconsistent with the most recent measurements of temperature in the same location and suggested that the atmosphere had to be 100 K cooler than expected. However, changes to Cassini's orbit shortly after the cloud's appearance precluded further observations, and, consequently, the atmospheric conditions and the details of the formation and evolution of the cloud remain unknown. We address this gap in the observational record by using microphysical cloud modeling to estimate the parameter space consistent with published measurements. Based on the nearest available temperature profile retrievals and other observations, we hypothesize that the cloud forms around 300 km and then descends until it reaches the cold lower stratosphere by late southern fall. The observations can be simulated using a cloud microphysical model by introducing a descending cold layer with temperatures near 100 K. In simulations of this scenario, the precipitation from this cloud rapidly removes over 70% of the HCN vapor from the stratosphere. This result suggests that vapor descending into the polar stratosphere during early fall is mostly removed from the stratosphere before the onset of winter and does not circulate to lower latitudes.

Keywords: Planetary atmospheres, Titan, Atmospheric clouds
VLT/MUSE Characterization of Dimorphos Ejecta from the DART Impact. We have observed the Didymos-Dimorphos binary system with the MUSE integral field unit spectrograph mounted at the Very Large Telescope before and after DART impact and captured the ensuing ejecta cone, debris cloud, and tails at subarcsecond resolutions. We targeted the Didymos system over 11 nights from 2022 September 26 to October 25 and utilized both narrow- and wide-field observations with and without adaptive optics, respectively. We took advantage of the spectral-spatial coupled measurements and produced both white-light images and spectral maps of the dust reflectance. We identified and characterized numerous dust features, such as the ejecta cone, spirals, wings, clumps, and tails. We found that the base of the sunward edge of the wings, from October 3 to 19, is consistent with maximum grain sizes on the order of 0.05-0.2 mm and that the earliest detected clumps have the highest velocities, on the order of ;10 m s-1. We also see that three clumps in narrow-field mode (8″ × 8″) exhibit redder colors and slower speeds, around 0.09 m s-1, than the surrounding ejecta, likely indicating that the clump is composed of larger, slower grains. We measured the properties of the primary tail and resolved and measured the properties of the secondary tail earlier than any other published study, with first retrieval on October 3. Both tails exhibit similarities in curvature and relative flux; however, the secondary tail appears thinner, which may be caused by lower-energy ejecta and possibly a low-energy formation mechanism such as secondary impacts.

Keywords: Impact phenomena, Optical astronomy, Asteroid satellites, Apollo group, Ground telescopes
The Challenge of Measuring Asteroid Masses with Gaia DR2 Astrometry. The Gaia second data release (DR2) contains high-accuracy astrometric measurements of thousands of solar system bodies. These measurements raise the possibility of determining asteroid masses by modeling scattering events between massive objects observed by Gaia. In this paper, we identify promising encounters between small asteroids that occur during DR2 and quantify the various errors involved in mass determination. We argue that, in the best case, Gaia astrometry can provide constraints as tight as ≈1 km on the positions of asteroids. Further, we find that even with general relativistic corrections, integrations of the solar system accumulate 1 km errors after 700 days. While not a problem for modeling DR2 astrometry, future Gaia data releases may require models accounting for additional effects such as gravitational harmonics of the sun and planets. Additionally, due to suboptimal astrometric uncertainty, the geometry of the observations, and the Gaia observing pattern there are much looser constraints as a result in most cases, with constraints being several orders of magnitude weaker in some cases. This suggests that accurate mass determination for the smallest asteroids will require additional observations, either from future Gaia data releases or from other sources. We provide a list of encounters that are most promising for further investigation.

Keywords: Main belt asteroids, Asteroids, Asteroid dynamics
Spectrophotometric and Topographic Correlations within the Mare Ingenii Swirl Region: Evidence for a Highly Mobile Lunar Regolith. The spectrophotometric properties of two study areas in the Ingenii swirl region show that the combined effects of multiple processes are required to explain the regolith's mineralogical and physical properties. Production of the swirl regions requires mobilization of the regolith in addition to preferential radiation shielding of subareas. The discovery of topographic correlations between on- and off-swirl (dark lanes) clearly shows that the on-swirl regions are statistically lower than the off-swirl dark lanes by 2-3 m. Photometric analyses show no microscale roughness differences between on- and off-swirl, suggesting no differences in the regolith's fairy-castle structure between the two swirl regions. The photometric properties of one of the study areas suggest that off-swirl dark lanes may have a more complicated grain structure than on-swirl areas. Enhanced abundances of plagioclase are observed on-swirl in both study areas. Enhanced abundances of FeO and orthopyroxene are observed off-swirl in both areas. No variations in olivine or clinopyroxene abundance were observed for either study area. The discovery of topographic correlations coupled with the similarities in structural properties provides new constraints on the types of processes acting on lunar swirl surfaces.

Keywords: The Moon
Strong Tidal Dissipation at Uranus?. Geophysical estimates of paleo heat fluxes on the Uranian moons Miranda and Ariel are in the range of 25-75 mW m-2. For a canonical Uranus dissipation factor Q = 18,000, expected equilibrium tidal heating rates for these satellites are less than 6 mW m-2. At least for Ariel, this order-of-magnitude discrepancy can be resolved by positing a low Uranus Q ≈ 103 in the recent past and at the present day. Such a low Q (high dissipation) can be reconciled with an ancient origin of the Uranian satellites if Q is time-dependent, as exemplified by the "resonance-locking" hypothesis, and provides an additional constraint on the interior structure of the planet. A Q of 103 implies present-day migration rates for Miranda and Ariel of 5 and 11 cm yr-1, respectively, potentially detectable via astrometry.

Keywords: Uranus, Uranian satellites
Dust Properties of Comets Observed by Spitzer. As comets journey into the inner solar system, they deliver particulates and volatile gases into their comae that reveal the most primitive materials in the solar system. Cometary dust particles provide crucial information for assessing the physicochemical conditions in the outer disk from which they formed. Compared to the volatiles and soluble organics, the refractory dust particles are more robust and may be traceable to other small bodies. Using data from the Spitzer Heritage Archive, we present thermal dust models of 57 observations of 33 comets observed spectroscopically with the NASA Spitzer Space Telescope. This comet spectral survey offers the opportunity to study comets with data from the same instrument, reduced by the same methods, and fitted by the same thermal model using the same optical constants. The submicron dust tends to be dominated by amorphous carbon, and the submicron silicate mass tends to be dominated by amorphous silicate materials. We discuss the implications of these findings as they relate to Mg-rich crystalline silicates, which are high-temperature condensates, as well as to potential ion irradiation of amorphous Mg:Fe silicates prior to their incorporation into comets. These results impact our understanding of the protoplanetary disk conditions of planetesimal formation. Lastly, we cannot definitively conclude that a distinct difference exists in the dust composition between the Oort cloud and Jupiter-family comet dynamical population as a whole.

Keywords: Dust composition, Infrared spectroscopy, Short period comets, Long period comets, Comet origins
X-Ray Energy Deposition Model for Simulating Asteroid Response to a Nuclear Planetary Defense Mitigation Mission. In the event of a potentially catastrophic asteroid impact, with sufficient warning time, deploying a nuclear device remains a powerful option for planetary defense if a kinetic impactor or other means of deflection proves insufficient. Predicting the effectiveness of a potential nuclear deflection or disruption mission depends on accurate multiphysics simulations of the device's X-ray energy deposition into the asteroid and the resulting material ablation. The relevant physics in these simulations span many orders of magnitude, require a variety of different complex physics packages, and are computationally expensive. Having an efficient and accurate way of modeling this system is necessary for exploring a mission's sensitivity to the asteroid's range of physical properties. To expedite future simulations, we present a completed X-ray energy deposition model developed using the radiation-hydrodynamics code Kull that can be used to initiate a nuclear mitigation mission calculation. The model spans a wide variety of possible mission initial conditions: four different asteroid-like materials at a range of porosities, two different source spectra, and a broad range of radiation fluences, source durations, and angles of incidence. Using blowoff momentum as the primary metric, the model-initiated simulation results match the full radiation-hydrodynamics results to within 10%.

Keywords: Near-Earth objects, Hydrodynamical simulations, Asteroids, Radiative transfer simulations, Comets
The Variability of Lunar Mare Basalt Properties from Surface Rock Abundance. We use the Lunar Reconnaissance Orbiter Diviner Lunar Radiometer Experiment surface rock abundance data set to investigate how rock content changes with surface age in the maria. We find that surface rock abundance decreases with unit age as expected for a thickening regolith, but age alone cannot explain most of the observed regional variability in rock abundance. We propose that this additional variability is primarily caused by differences in the initial mare basalt properties such that some flows break down more readily than others. We calculate the best-fit relationship between the surface rock abundance and unit age and investigate the regional variability in the residual errors of this fit. Relative to this best-fit relationship, we find that Mare Humorum and parts of Oceanus Procellarum are anomalously rocky, and Mare Australe is rock-poor for its age. These regional differences, which cannot be explained by unit age, are likely due to variability in the initial properties of mare basalts.

Keywords: Planetary surfaces, Lunar regolith, Lunar maria, Surface processes, Regolith, Volcanism
An Efficient Numerical Approach to Modeling the Effects of Particle Shape on Rubble-pile Dynamics. We present an approach for the inclusion of nonspherical constituents in high-resolution N-body discrete element method (DEM) simulations. We use aggregates composed of bonded spheres to model nonspherical components. Though the method may be applied more generally, we detail our implementation in the existing N-body code pkdgrav. It has long been acknowledged that nonspherical grains confer additional shear strength and resistance to flow when compared with spheres. As a result, we expect that rubble-pile asteroids will also exhibit these properties and may behave differently than comparable rubble piles composed of idealized spheres. Since spherical particles avoid some significant technical challenges, most DEM gravity codes have used only spherical particles or have been confined to relatively low resolutions. We also discuss the work that has gone into improving performance with nonspherical grains, building on pkdgrav's existing leading-edge computational efficiency among DEM gravity codes. This allows for the addition of nonspherical shapes while maintaining the efficiencies afforded by pkdgrav's tree implementation and parallelization. As a test, we simulated the gravitational collapse of 25,000 nonspherical bodies in parallel. In this case, the efficiency improvements allowed for an increase in speed by nearly a factor of 3 when compared with the naive implementation. Without these enhancements, large runs with nonspherical components would remain prohibitively expensive. Finally, we present the results of several small-scale tests: spin-up due to the YORP effect, tidal encounters, and the Brazil nut effect. In all cases, we find that the inclusion of nonspherical constituents has a measurable impact on simulation outcomes.

Keywords: Near-Earth objects, Theoretical models, Asteroids, Asteroid dynamics, Asteroid rotation, Planetary science, Trans-Neptunian objects, N-body simulations, Astronomical simulations, Asteroid surfaces
Deep Dielectric Breakdown of Silicates: Microstructural Damage and Implications for Lunar Space Weathering. Solar energetic particle events electrically charge the lunar surface and may produce electric fields sufficient to induce dielectric breakdown in regolith grains. We irradiated series of silicate minerals with electrons to determine their physical and chemical response to deep dielectric charging and subsequent breakdown. Two electrical phenomena, flashovers and subsurface dielectric breakdown, produced damage including erosional and eruptive channels, surface pits, comminuted grains, and melt and vapor deposits. Iron abundances strongly affected the scale of damage and the minimum fluence required to reach dielectric breakdown; higher iron abundances required higher fluences to reach the breakdown threshold and produced more areally dense damage with each event. If dielectric breakdown is a prominent space-weathering process on the Moon, it should contribute to differential weathering signatures across the lunar surface as a function of target composition.

Keywords: Solar energetic particles, Lunar regolith
Discovery of Extensive [O III] Emission Near M31. We report the discovery of a broad, 1.°5 long filamentary [O III] emission nebulosity some 1.°2 southeast of the M31 nucleus. This nebulosity is not detected in Hα and has no obvious emission counterparts in X-ray, UV, optical, infrared, and radio surveys. To our knowledge, this emission feature has not been previously reported in the literature. We briefly discuss its possible origin.

Keywords: Galaxy stellar halos, Interstellar filaments
20 s Cadence TESS Photometry of HR 8799. We analyzed 20 s cadence Transiting Exoplanet Survey Satellite time-series photometry of the exoplanet host star HR 8799 collected in Sector 56. The amplitude spectrum shows Gamma Doradus (γ Dor) pulsations consistent with previous space-based photometry from MOST. Assuming that HR 8799 is a representative of γ Dor stars in the Kepler sample, the dominant dipole mode at 1.98 cycles day-1 implies a core rotation period of ~0.7 day, which combined with $v\sin i$ and stellar radius measurements would result in a preliminary stellar inclination of ~28° assuming rigid rotation. We find no significant residual photometric variation after removing the pulsation signal aside from a ~9 days trend that is likely a systematic effect or an artifact from performing aggressive frequency subtraction in the presence of red noise.

Keywords: Stellar pulsations, Exoplanet systems, Variable stars, Planet hosting stars, Gamma Doradus variable stars
The Behavior of HgMn Stars in the Far-UV-Paper 24: HD 159975 (μ Oph). The analysis of two high resolution spectra of the Hg Mn star HD 159975 recorded by the SWP camera on board the International Ultraviolet Explorer does not reveal variations of the far-ultraviolet flux over a 18 yr time interval. From its effective temperature and surface gravity, HD 155975 appears to have evolved away from the Main Sequence in a theoretical Hertzsprung Russell diagram. It is one of the rare subgiant HgMn stars. Several Si II resonance or low excitation lines are strong absorbers in the mean high resolution SWP spectrum of HD 159975. The Al II resonance line at 1670.79 Å is a strong absorber too. There is no evidence of real variations of the low excitation Si II lines.

Keywords: Mercury-manganese stars, Chemically peculiar stars
The Abundances of Helium, Magnesium and Phosphorus in the Atmosphere of HD144844. Abundances of helium and magnesium are derived in LTE for the B9 Mn P Ga star HD 144844 using the group of He I lines near 4470.40 Å and the Mg II triplet at 4481.22 Å. Both elements are found to be very underabundant, about 2% of the solar helium and magnesium abundances. The profile of the Mg II line at 4481.22 Å clearly shows two components and confirms that this star is a double-lined spectroscopic binary. The synthesis of three P II lines at 6024.18, 6034.04 and 6043.88 Å yields phosphorus abundances from 150 up to 200 times the solar phosphorus abundance. A NLTE synthesis is necessary to derive more accurate abundances.

Keywords: Mercury-manganese stars, Chemically peculiar stars
No Compact Radio Emission from the Proposed Blazar Candidate Counterpart for the Fermi Source 4FGL J1848.7-0129. By assessing available radio data, we argue that the recently proposed new counterpart for the Fermi γ-ray source 4FGL J1848.7-0129 is unlikely to be a blazar. The radio source coincident with a Chandra X-ray point source is extended on ~10″ angular scale, has no detected compact component (3 GHz flux density ≲1 mJy), and its radio spectrum is steep. These properties contradict to what is expected for blazars with relativistically beamed radio jet emission.

Keywords: Gamma-ray sources, Blazars, Radio jets