Sazuna/UAT_keywords huggingface dataset:
The Increasingly Strange Polarimetric Behavior of the Barbarian Asteroids. Polarization phase-curve measurements provide a unique constraint on the surface properties of asteroids that are complementary to those from photometry and spectroscopy and have led to the identification of the "Barbarian" asteroids as a class of objects with highly unusual surfaces. We present new near-infrared polarimetric observations of six Barbarian asteroids obtained with the WIRC+Pol instrument on the Palomar Hale telescope. We find a dramatic change in polarimetric behavior from visible to near-infrared for these objects, including a change in the polarimetric inversion angle that is tied to the index of refraction of the surface material. Our observations support a two-phase surface composition consisting of high albedo and high index of refraction inclusions with a small optical size scale embedded in a dark matrix material more closely related to C-complex asteroids. These results are consistent with the interpretation that the Barbarians are remnants of a population of primitive bodies that formed shortly after calcium-aluminum-rich inclusion (CAIs). Near-infrared polarimetry provides a direct test of the constituent grains of asteroid surfaces.

Keywords: Polarimetry, Asteroids, Asteroid surfaces
A Radiative-convective Model for Terrestrial Planets with Self-consistent Patchy Clouds. Clouds are ubiquitous: they arise for every solar system planet that possesses an atmosphere and have also been suggested as a leading mechanism for obscuring spectral features in exoplanet observations. As exoplanet observations continue to improve, there is a need for efficient and general planetary climate models that appropriately handle the possible cloudy atmospheric environments that arise on these worlds. We generate a new 1D radiative-convective terrestrial planet climate model that self-consistently handles patchy clouds through a parameterized microphysical treatment of condensation and sedimentation processes. Our model is general enough to recreate Earth's atmospheric radiative environment without overparameterization, while also maintaining a simple implementation that is applicable to a wide range of atmospheric compositions and physical planetary properties. We first validate this new 1D patchy-cloud radiative-convective climate model by comparing it to Earth thermal structure data and to existing climate and radiative-transfer tools. We produce partially clouded Earth-like climates with cloud structures that are representative of deep tropospheric convection and are adequate 1D representations of clouds within rocky planet atmospheres. After validation against Earth, we then use our partially clouded climate model and explore the potential climates of super-Earth exoplanets with secondary nitrogen-dominated atmospheres which we assume are abiotic. We also couple the partially clouded climate model to a full-physics, line-by-line radiative-transfer model and generate high-resolution spectra of simulated climates. These self-consistent climate-to-spectral models bridge the gap between climate modeling efforts and observational studies of rocky worlds.

Keywords: Exoplanet atmospheric composition , Exoplanet atmospheric dynamics, Planetary atmospheres, Exoplanet atmospheric evolution, Exoplanet atmospheres, Exoplanet atmospheric structure
Relation of Gravity, Winds, and the Moment of Inertia of Jupiter and Saturn. We study the relationship of zonal gravity coefficients, J 2n , zonal winds, and axial moment of inertia (MoI) by constructing models for the interiors of giant planets. We employ the nonperturbative concentric Maclaurin spheroid method to construct both physical (realistic equation of state and barotropes) and abstract (small number of constant-density spheroids) interior models. We find that accurate gravity measurements of Jupiter's and Saturn's J 2, J 4, and J 6 by the Juno and Cassini spacecraft do not uniquely determine the MoI of either planet but do constrain it to better than 1%. Zonal winds (or differential rotation (DR)) then emerge as the leading source of uncertainty. For Saturn they are predicted to decrease the MoI by 0.4% because they reach a depth of ~9000 km, while on Jupiter they appear to reach only ~3000 km. We thus predict DR to affect Jupiter's MoI by only 0.01%, too small by one order of magnitude to be detectable by the Juno spacecraft. We find that winds primarily affect the MoI indirectly via the gravity harmonic J 6, while direct contributions are much smaller because the effects of pro- and retrograde winds cancel. DR contributes +6% and -0.8% to Saturn's and Jupiter's J 6 value, respectively. This changes the J 6 contribution that comes from the uniformly rotating bulk of the planet that correlates most strongly with the predicted MoI. With our physical models, we predict Jupiter's MoI to be 0.26393 ± 0.00001. For Saturn, we predict 0.2181 ± 0.0002, assuming a rotation period of 10:33:34 hr that matches the observed polar radius.

Keywords: Saturn, Planetary interior, Jupiter
Determining the Pyroxene Mineralogies of Vestoids. Bulk pyroxene compositions were calculated for a number of V-type asteroid spectra using formulae derived by Burbine et al. These formulae were derived by analyzing HED (howardite, eucrite, and diogenite) meteorites and calculate bulk Fs (mol%) and Wo (mol%) contents using derived band centers. Using HEDs with known bulk pyroxene compositions, the uncertainty in the predicted Fs contents was determined to be ±3 mol%, and the uncertainty in the predicted Wo contents was ±2 mol%. V-type asteroids tend to have interpreted pyroxene mineralogies consistent primarily with eucrites and howardites. We investigate why diogenitic mineralogies appear so rare among ~5-10 km V-type asteroids but are much more commonly present among HED meteorites. One possibility is that diogenitic intrusions are extremely "thin" but widespread in Vesta's eucritic crust. In this scenario, Vestoids (V-type asteroids thought to be derived from Vesta) would be expected to be solid fragments of Vesta. Another possibility is that Vesta's upper crust has been significantly shattered and diogenitic material would be much less common than the eucritic material in the crust. Vestoids would then be expected to be rubble piles. The belief that most asteroid families were shattered at least twice would argue that Vesta's crust is also shattered and that Vestoids are rubble piles.

Keywords: Meteorites, Vesta, Asteroids, Main belt asteroids
Depletion of <SUP>13</SUP>C in CO in the Atmosphere of Mars Suggested by ExoMars-TGO/NOMAD Observations. The atmosphere of Mars is mainly composed by carbon dioxide (CO2). It has been predicted that photodissociation of CO2 depletes 13C in carbon monoxide (CO). We present the carbon 13C/12C isotopic ratio in CO at 30-50 km altitude from the analysis of the solar occultation measurements taken by the instrument Nadir and Occultation for Mars Discovery on board the ExoMars Trace Gas Orbiter (ExoMars-TGO). We retrieve 12C16O, 13C16O, and 12C18O volume mixing ratios from the spectra taken at 4112-4213 cm-1, where multiple CO isotope lines with similar intensities are available. The intensities of the 12C16O lines in this spectral range are particularly sensitive to temperature, thus we derive the atmospheric temperature by retrieving CO2 density with simultaneously measured spectra at 2966-2990 cm-1. The mean δ 13C value obtained from the 13C16O/12C16O ratios is -263‰, and the standard deviation and standard error of the mean are 132‰ and 4‰, respectively. The relatively large standard deviation is due to the strong temperature dependences in the 12C16O lines. We also examine the 13C16O/12C18O ratio, whose lines are less sensitive to temperature. The mean δ value obtained with 12C18O instead of 12C16O is -82‰ with smaller standard deviation, 60‰. These results suggest that CO is depleted in 13C when compared to CO2 in the Martian atmosphere as measured by the Curiosity rover. This depletion of 13C in CO is consistent with the CO2 photolysis-induced fractionation, which might support a CO-based photochemical origin of organics in Martian sediments.

Keywords: Planetary atmospheres
Space Weathering of Genesis Mission Solar-wind Collectors with Inferences for Weathering on Airless Bodies. Samples from the Genesis Solar Wind Sample Return (NASA Discovery 5) are a unique opportunity to study the initial stages of space weathering, i.e., the physical and chemical effects of solar-wind irradiation. Arrays of collectors containing multiple materials were each exposed to a different solar-wind regime (fast, slow, bulk, or coronal mass ejection) at the L1 point for long durations (years). Materials exposed to the solar wind included metals, semiconductors, and insulators. Although the time of exposure was obviously short relative to samples having extraterrestrial origins, optical properties, surface chemical properties, and matrix structure have changed in many collectors due to exposure to solar wind. The thickness of amorphous zones, where present, appears to correspond with the depth of the peak of the solar-wind H distribution in each regime. Damage from high-energy particles was negligible because the collectors were 700 μm or less in thickness and shielded from the back by the spacecraft. Micrometeorite impacts and sputtering were also negligible because of the short exposure times. Our current results are preliminary: We hope future workers will extend this study both to support Genesis characterization efforts and to further understand space-weathering processes on a geologic timescale.

Keywords: Space research, Solar wind, Planetary science
Dual-band Fourier-transform Millimeter-wave Spectrometry for In Situ Gas Sensing. The exploration of icy body composition in the solar system has often involved spectroscopic measurements of volatiles detected with remote sensing, such measurements portray materials naturally expelled from the surface that enter the exosphere and potentially escape into space. Variations in the ratio of deuterium and hydrogen in these measurements have led to inconclusive hypotheses regarding potential cometary origins of Earth's ocean water and/or organics. Observational biases regarding unknown previous processing of the observable ejected materials necessitates studies of more dormant, less-processed bodies. Landed missions on comets have brought focus onto the development of small, sensitive instrumentation capable of similar composition measurements of the nascent surface and near-surface materials. We present an evolution of our compact Fourier-transform millimeter-wave cavity spectrometer that is tuned for sensitivity at 80.6 and 183 GHz where HDO and H2O exhibit resonance features. We discuss both a low-SWaP (size-weight and power) architecture that uses custom microchip transceiver elements as well as a modular configuration using traditional GaAs-based millimeter-wave hardware. New design features for these systems including quartz-based coupling elements, system thermal management, and a separable clocking board are discussed in addition to sensitivity studies and applications in potential mission scenarios.

Keywords: High resolution spectroscopy, Space vehicle instruments, Molecular spectroscopy, Millimeter-wave spectroscopy, Comet surfaces
Aerodynamic Roughness Height of Gravel-covered Plains in the Puna of Argentina. Plains covered by gravel-dominated desert pavement in the Puna of Argentina have an aerodynamic roughness height (or length) z 0 of ~1 cm, likely representing a skimming flow regime above the closely spaced gravel particles. Aerodynamic roughness height locally may transition from that of skimming flow over the gravels to a z 0 that includes the effects of obstacles considerably larger than those of the gravel particles alone. Among large (&gt;60 cm tall) megaripples, z 0 is elevated beyond that of the gravels alone to values of 2-4 cm. These results represent an analog for an improved understanding of the aerodynamics of gravel-dominated desert pavement and megaripples documented by multiple rovers on Mars.

Keywords: Geological processes, Surface processes, Earth (planet)
Preatmospheric Detection of a Meter-sized Earth Impactor. On 2020 September 18 U.S. Government (USG) sensors detected a bolide with peak bolometric magnitude of -19 over the Western Pacific. The impact was also detected by the Geostationary Lightning Mapper instrument on the GOES-17 satellite and infrasound sensors in Hawaii. The USG measurements reported a steep entry angle of 67° from horizontal from a radiant 13° east of north and an impact speed of 11.7 km s-1. Interpretation of all energy yields produces a preferred energy estimate of 0.4 kt TNT, corresponding to a 23,000 kg, 3 m diameter meteoroid. A postimpact search of telescopic images found that the Asteroid Terrestrial-impact Last Alert System survey captured the object just 10 minutes prior to impact at an Earth-centered distance of nearly 11,900 km with apparent magnitude m = 12.5. The object appears as a 0.44° streak originating on the eastern edge of the image, extending one-third of the USG state-vector-based prediction of 1.26° over the 30 s exposure. The streak shows brightness variability consistent with small asteroid rotation. The position of Earth's shadow, the object's size, and its consistency with the reported USG state vector confirm the object is likely natural. This is the eighth preatmospheric detection of a near-Earth asteroid (NEA) impactor and the closest initial telescopic detection prior to impact. The high altitude of peak fireball brightness suggests it was a weak object comparable in many respects with 2008 TC3 (the Almahata Sitta meteorite), with an absolute magnitude H = 32.5 and likely low albedo. Therefore, we suggest the NEA was a C-complex asteroid.

Keywords: Near-Earth objects, Sky surveys, Bolides
Examining Uranus' ζ Ring in Voyager 2 Wide-angle Camera Observations: Quantifying the Ring's Structure in 1986 and Its Modifications Prior to the Year 2007. The ζ ring is the innermost component of the Uranian ring system. It is of scientific interest because its morphology changed significantly between the Voyager 2 encounter in 1986 and subsequent Earth-based observations around 2007. It is also of practical interest because some Uranus mission concepts have the spacecraft pass through the inner flank of this ring. Recent reexaminations of the Voyager 2 images have revealed additional information about this ring that provide a more complete picture of the ring's radial brightness profile and phase function. These data reveal that this ring's brightness varies with phase angle in a manner similar to other tenuous rings, consistent with it being composed primarily of submillimeter-sized particles. The total cross section of particles within this ring can also be estimated from these data, but translating that number into the actual risk to a spacecraft flying through this region depends on a number of model-dependent parameters. Fortunately, comparisons with Saturn's G and D rings allows the ζ ring's particle number density to be compared with regions previously encountered by the Voyager and Cassini spacecraft. Finally, these data indicate that the observed changes in the ζ ring's structure between 1986 and 2007 are primarily due to a substantial increase in the amount of dust at distances between 38,000 and 40,000 km from Uranus' center.

Keywords: Dust physics, Planetary rings, Uranus
Simulating Secondary Electron and Ion Emission from the Cassini Spacecraft in Saturn's Ionosphere. The Cassini spacecraft's Grand Finale flybys through Saturn's ionosphere provided unprecedented insight into the composition and dynamics of the gas giant's upper atmosphere and a novel and complex spacecraft-plasma interaction. In this article, we further study Cassini's interaction with Saturn's ionosphere using three-dimensional particle-in-cell simulations. We focus on how electrons and ions, emitted from spacecraft surfaces due to the high-velocity impact of atmospheric water molecules, could have affected the spacecraft potential and low-energy plasma measurements. The simulations show emitted electrons extend upstream along the magnetic field, and for sufficiently high emission rates, charge the spacecraft to positive potentials. The lack of accurate emission rates and characteristics, however, makes differentiation between the prominence of secondary electron emission and ionospheric charged dust populations, which induce similar charging effects, difficult for Cassini. These results provide further context for Cassini's final measurements and highlight the need for future laboratory studies to support high-velocity flyby missions through planetary and cometary ionospheres.

Keywords: Space plasmas, Saturn, Planetary ionospheres, Planetary atmospheres, Planetary rings, Astrophysical dust processes
A Shallow-water Model Exploration of Atmospheric Circulation on Sub-Neptunes: Effects of Radiative Forcing and Rotation Period. Sub-Neptune-type exoplanets are abundant in our Galaxy yet have no solar system analogs. They exist in a broad range of stellar forcing and rotational regimes that are distinctly different from solar system planets and more commonly studied hot Jupiters. Here we present simulations that explore global atmospheric circulation of sub-Neptunes generated with a two-dimensional shallow-water model, SWAMPE. We explore the circulation regimes of synchronously rotating sub-Neptunes with a focus on the interaction of planetary rotation rate and radiative timescale in a variety of stellar insolations. In highly irradiated, short-timescale regimes, our models exhibit high day-night geopotential contrasts. As the timescales become longer, the geopotential contrasts and longitudinal variability decrease, while temporal variability increases. The transition from day-to-night flow to jet-dominated flow is primarily driven by the radiative timescale. Strong- and medium-forcing regimes exhibit transitions between day-to-night flow and jet-dominated flow at similar points in the parameter space. The weak-forcing regime differs owing to comparatively stronger rotational effects. Planetary rotation period dominates in determining equator-to-pole geopotential contrast. Our simulations exhibit higher time variability when either radiative timescale or rotation period is long.

Keywords: Mini Neptunes, Exoplanet atmospheres, Atmospheric circulation
Investigating the Stability and Distribution of Surface Ice in Mercury's Northernmost Craters. Observations made by Earth-based radar telescopes and the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft provided compelling evidence for water ice in Mercury's polar craters. In our investigation, we constructed higher-resolution (125 m pixel-1) digital elevation models (DEMs) for four of the largest northernmost craters, Kandinsky, Tolkien, Chesterton, and Tryggvadóttir. The DEMs were leveraged to model solar illumination and the thermal environment, products that were used to identify permanently shadowed regions and simulate surface temperatures. From these models, we predicted the regions of surface stability for ice and volatile organic compounds. These predictions were then compared against the Arecibo radar, Mercury Laser Altimeter (MLA), and Mercury Dual Imaging System (MDIS) data. Our radar analysis shows that areas of high radar backscatter are correlated with areas predicted to host surface ice. Additionally, we identify radar backscatter heterogeneities within the deposits that could be associated with variations in ice purity, mantling of the ice, or ice abundances. The MDIS analysis did not reveal conclusive evidence for ice or volatiles at the surface, while MLA results support the presence of water ice at the surface in these craters. However, evidence for boundaries between the surface ice and low-reflectance volatile organic compounds, as suggested could be present by our models, was inconclusive owing to the limited MESSENGER data in these regions. BepiColombo's upcoming orbital mission at Mercury has the opportunity to obtain new measurements of these high-latitude craters and test our predictions for the distribution of surface volatiles in these environments.

Keywords: Planetary surfaces, Surface ices, Planetary polar regions, Mercury (planet)
New Insights into Variations in Enceladus Plume Particle Launch Velocities from Cassini-VIMS Spectral Data. Enceladus's plume consists mainly of a mixture of water vapor and solid ice particles that may originate from a subsurface ocean. The physical processes underlying Enceladus's plume particle dynamics are still being debated, and quantifying the particles' size distribution and launch velocities can help constrain these processes. Cassini's Visual and Infrared Mapping Spectrometer observed the Enceladus plume over a wavelength range of 0.9-5.0 μm for a significant fraction of Enceladus's orbital period on three dates in the summer of 2017. We find that the relative brightness of the plume on these different dates varies with wavelength, implying that the particle size distribution in the plume changes over time. These observations also enable us to study how the particles' launch velocities vary with time and observed wavelength. We find that the typical launch velocity of particles remains between 140 and 148 m s-1 at wavelengths between 1.2 and 3.7 μm. This may not be consistent with prior models where particles are only accelerated by interactions with the vent walls and gas and could imply that mutual particle collisions close to the vent are more important than previously recognized.

Keywords: Dust physics, Enceladus, Infrared spectroscopy, Volcanism
Formation, Structure, and Detectability of the Geminids Meteoroid Stream. The Geminids meteoroid stream produces one of the most intense meteor showers at Earth. It is an unusual stream in that its parent body is understood to be an asteroid, (3200) Phaethon, unlike most streams, which are formed via ongoing cometary activity. Until recently, our primary understanding of this stream came from Earth-based measurements of the Geminids meteor shower. However, the Parker Solar Probe (PSP) spacecraft has transited near the core of the stream close to its perihelion and provides a new platform to better understand this unique stream. Here, we create a dynamical model of the Geminids meteoroid stream, calibrate its total density to Earth-based measurements, and compare this model to recent observations of the dust environment near the Sun by PSP. For the formation mechanisms considered, we find with the exception of very near perihelion the core of the meteoroid stream predominantly lies interior to the orbit of its parent body and we expect grains in the stream to be ≳10 μm in radius. Data-model comparisons of the location of the stream relative to Phaethon's orbit near perihelion are more consistent with a catastrophic formation scenario, with the core stream residing near or outside the orbit of its parent body consistent with PSP observations. This is in contrast to a cometary formation mechanism, where even near the Sun the meteoroid stream is interior to the orbit of its parent body. Finally, while PSP transits very near the core of the stream, the impact rate expected from Geminids meteoroids is orders of magnitude below the impact rates observed by PSP, and hence undetectable in situ. We similarly expect the upcoming DESTINY+ mission to be unable to detect appreciable quantities of Geminids grains far from (3200) Phaethon.

Keywords: Meteoroid dust clouds, Interplanetary dust, Zodiacal cloud