Sazuna/UAT_keywords huggingface dataset:
The Population of Interstellar Objects Detectable with the LSST and Accessible for In Situ Rendezvous with Various Mission Designs. The recently discovered population of interstellar objects presents us with the opportunity to characterize material from extrasolar planetary and stellar systems up close. The forthcoming Vera C. Rubin Observatory Legacy Survey of Space and Time (LSST) will provide an unprecedented increase in sensitivity to these objects compared to the capabilities of currently operational observational facilities. We generate a synthetic population of 'Oumuamua-like objects drawn from their galactic kinematics and identify the distribution of impact parameters, eccentricities, hyperbolic velocities, and sky locations of objects detectable with the LSST, assuming no cometary activity. This population is characterized by a clustering of trajectories in the direction of the solar apex and antiapex, centered at orbital inclinations of ~90°. We identify the ecliptic or solar apex as the optimal sky location to search for future interstellar objects as a function of survey limiting magnitude. Moreover, we identify the trajectories of detectable objects that will be reachable for in situ rendezvous with a dedicated mission with the capabilities of the forthcoming Comet Interceptor or proposed Bridge concept. By scaling our fractional population statistics with the inferred spatial number density, we estimate that the LSST will detect of order ~15 interstellar objects over the course of its ~10 yr observational campaign. Furthermore, we find that there should be ~1-3 and ~0.0007-0.001 reachable targets for missions with propulsion capabilities comparable to Bridge and Comet Interceptor, respectively. These numbers are lower limits and will be readily updateable when the number density and size-frequency distribution of interstellar objects are better constrained.

Keywords: Interstellar objects
Compositional Mapping of Europa Using MCMC Modeling of Near-IR VLT/SPHERE and Galileo/NIMS Observations. We present maps of surface composition of Europa's anti-Jovian hemisphere acquired using high spatial resolution IFU multispectral data from the SPHERE instrument on the Very Large Telescope (0.95-1.65 μm) and the NIMS instrument on the Galileo orbiter (0.7-5.2 μm). Spectral modeling was performed using a Markov Chain Monte Carlo method to estimate endmember abundances and to quantify their associated uncertainties. Modeling results support the leading-trailing hemisphere difference in hydrated sulfuric acid abundances caused by exogenic plasma bombardment. Water-ice grains are found to be in the 100 μm-1 mm range, with larger grains present on the trailing hemisphere, consistent with radiation-driven sputtering destroying smaller grains. Modeling best estimates suggest a mixture of sulfate and chlorinated salts, although uncertainties derived from the MCMC modeling suggest that it is difficult to confidently detect individual salt abundances with low spectral resolution spectra from SPHERE and NIMS. The high spatial resolution offered by SPHERE allows the small-scale spatial distribution (&lt;150 km) of potential species to be mapped, including ground-based detection of lineae and impact features. This could be used in combination with other higher spectral resolution observations to confirm the presence of these species.

Keywords: Near infrared astronomy, Very Large Telescope, Europa
Winter Weakening of Titan's Stratospheric Polar Vortices. Polar vortices are a prominent feature in Titan's stratosphere. The Cassini mission has provided a detailed view of the breakdown of the northern polar vortex and formation of the southern vortex, but the mission did not observe the full annual cycle of the evolution of the vortices. Here we use a TitanWRF general circulation model simulation of an entire Titan year to examine the full annual cycle of the polar vortices. The simulation reveals a winter weakening of the vortices, with a clear minimum in polar potential vorticity and midlatitude zonal winds between winter solstice and spring equinox. The simulation also produces the observed postfall equinox cooling followed by rapid warming in the upper stratosphere. This warming is due to strong descent and adiabatic heating, which also leads to the formation of an annular potential vorticity structure. The seasonal evolution of the polar vortices is very similar in the two hemispheres, with only small quantitative differences that are much smaller than the seasonal variations, which can be related to Titan's orbital eccentricity. This suggests that any differences between observations of the northern hemisphere vortex in late northern winter and the southern hemisphere vortex in early winter are likely due to the different observation times with respect to solstice, rather than fundamental differences in the polar vortices.

Keywords: Atmospheric circulation, Titan, Planetary atmospheres, Stratosphere, Saturnian satellites, Atmospheric science
Mixing of Condensable Constituents with H-He during the Formation and Evolution of Jupiter. Simulations of Jupiter's formation are presented that incorporate mixing of H-He with denser material entering the planet as solids. Heavy compounds and gas mix substantially when the planet becomes roughly as massive as Earth, because incoming planetesimals can fully vaporize. Supersaturation of vaporized silicates causes the excess to sink as droplets, but water remains at higher altitudes. Because the mean molecular weight decreases rapidly outward, some of the compositional inhomogeneities produced during formation can survive for billions of years. After 4.57 Gyr, our Jupiter model retains compositional gradients; proceeding outward, one finds (i) an inner heavy-element core, the outer part derived from hot supersaturated rain-out; (ii) a composition-gradient region, containing most of the heavy elements, where H-He abundance increases outward, reaching about 0.9 mass fraction at 0.3 of the radius, with silicates enhanced relative to water in the lower parts and depleted in the upper parts; (iii) a uniform-composition region (neglecting He immiscibility) that is enriched over protosolar and contains most of the planet's mass; and (iv) an outer region where cloud formation (condensation) of heavy constituents occurs. This radial compositional profile has heavy elements more broadly distributed than predicted by classical formation models but less diluted than suggested by Juno-constrained gravity models. The compositional gradients in the region containing the bulk of the heavy elements prevent convection, in both our models and those fitting current gravity, resulting in a hot interior where much of the accretion energy remains trapped.

Keywords: Accretion, Planet formation, Jupiter
Geologic Context of the OSIRIS-REx Sample Site from High-resolution Topography and Imaging. The OSIRIS-REx spacecraft collected a surface sample from Hokioi crater (55.8° N, 42.3° E; diameter ~20 m) on the asteroid Bennu in 2020 October. We explore the geology of the sample collection site, known as Nightingale, by using digital terrain models, relative albedo maps, and images collected by the OSIRIS-REx spacecraft. Hokioi crater sits at the northwest edge of an older, larger (120 m diameter) crater between two north-south ridges respectively located at roughly 0° and 90° longitude, between which unconsolidated material generally migrates from the geopotential high at the north (+Z) pole to the geopotential low at the equator. The impact that formed Hokioi crater exposed relatively unweathered, fine-grained dark material that we observe within and ejected beyond the crater. The regional slope and steep crater walls to the north of the Nightingale site have enabled a mix of the dark debris and brighter material (which may include carbonates and/or exogenic basalts) surrounding Hokioi crater to migrate onto the crater floor, where the sample was collected; some of this material may be old ejecta excavated from up to 10 m depth when the 120 m diameter crater formed. We therefore expect the OSIRIS-REx sample to include materials of varying brightnesses, compositions, and exposure ages, derived primarily from the 0°-90° longitude quadrant and from as deep as 10 m. The sample may also include material derived from the impactor that formed Hokioi crater. We expect it to have low cohesion (≪0.6 Pa) and a friction angle between 32° and 39°.

Keywords: Asteroids, Asteroid surfaces
Neptune's Pole-on Magnetosphere: Dayside Reconnection Observations by Voyager 2. The "pole-on" configuration occurs when the polar magnetosphere of a planet is directed into the solar wind velocity vector. Such magnetospheric configurations are unique to the ice giant planets. This means that magnetic reconnection, a process that couples a magnetosphere to the solar wind, will be different at the ice giants when they are pole-on compared to other planets. The only available in situ measurements of a pole-on magnetosphere are from the Neptune flyby by Voyager 2, which we analyze in this paper. We show that dayside magnetopause conditions were conducive to magnetic reconnection. A plasma depletion layer in the magnetosheath adjacent to the magnetopause was observed. Plasma measurements inside the magnetospheric cusp show evidence of multiple reconnection taking place at the magnetopause before the spacecraft crossed the open-closed field line boundary. A possible traveling compression region from a nearby passing flux rope was also observed, providing further supporting evidence that multiple X-line reconnection occurred during the flyby. During a perfectly pole-on configuration, reconnection will not depend on the orientation of the interplanetary magnetic field, as is the case at other planetary magnetospheres. The rate of reconnection will not vary because the area of the dayside magnetopause where antiparallel shears occur will be approximately equal for all interplanetary magnetic field orientations. Therefore, we suggest that rotating into and out of the pole-on configuration will likely drive the "on-off"/"switch-like" dynamics observed in simulations. Consequently, the pole-on configuration is most likely an important rotational phase for driving ice giant magnetospheric dynamics.

Keywords: Planetary magnetospheres, Neptune, Planetary polar regions, Space plasmas
Optical Properties of Cyanoacetylene Ices in the Far- to Near-infrared with Direct Relevance to Titan's Stratospheric Ice Clouds. Cyanoacetylene (HC3N) ice has been observed in Titan's stratosphere by both Voyager 1's InfraRed Interferometer Spectrometer (IRIS) and Cassini's Composite InfraRed Spectrometer (CIRS), and it is likely prevalent in other objects in our solar system and exoplanetary systems as well. While previous experimental studies targeting Titan's stratospheric clouds have determined the optical properties of HC3N ice in the infrared (IR) spectral range, those thin ice films were formed by annealing processes, which contradicts the formation mechanism of Titan's stratospheric ice clouds. As a result, optical constants of HC3N ices, experimentally created in a similar manner to the way they are formed in Titan's stratosphere, are crucial. Here we experimentally measured absorbance spectra of HC3N thin ice films from the near- to far-IR spectral region (50-8000 cm-1; 200-1.25 μm) formed via direct vapor deposition at 30, 50, 70, 90, 110, and 113 K. The corresponding optical constants at all temperatures were also computed, resulting in the largest continuous IR spectral range available for HC3N ice. New tentative peak assignments for spectral features in the near-IR are also reported, thereby further enhancing the inventory of optical constants available for HC3N ice spanning the near- to far-IR spectral range.

Keywords: Titan, Planetary atmospheres, Radiative transfer, Atmospheric clouds
Subseasonal Variation in Neptune's Mid-infrared Emission. We present an analysis of all currently available ground-based imaging of Neptune in the mid-infrared. Dating between 2003 and 2020, the images reveal changes in Neptune's mid-infrared (~8-25 μm) emission over time in the years surrounding Neptune's 2005 southern summer solstice. Images sensitive to stratospheric ethane (~12 μm), methane (~8 μm), and CH3D (~9 μm) display significant subseasonal temporal variation on regional and global scales. Comparison with H2 S(1) hydrogen quadrupole (~17.035 μm) spectra suggests that these changes are primarily related to stratospheric temperature changes. The stratosphere appears to have cooled between 2003 and 2009 across multiple filtered wavelengths, followed by a dramatic warming of the south pole between 2018 and 2020. Conversely, upper-tropospheric temperatures-inferred from ~17 to 25 μm imaging-appear invariant during this period, except for the south pole, which appeared warmest between 2003 and 2006. We discuss the observed variability in the context of seasonal forcing, tropospheric meteorology, and the solar cycle. Collectively, these data provide the strongest evidence to date that processes produce subseasonal variation on both global and regional scales in Neptune's stratosphere.

Keywords: Neptune, Atmospheric clouds, Atmospheric circulation, Planetary atmospheres, Atmospheric science, Planetary science, Atmospheric variability, Atmospheric composition, Solar system astronomy
Comparison of Two Analytic Energy Balance Models Shows Stable Partial Ice Cover Possible for Any Obliquity. In this study, we compare two analytic energy balance models with an explicit dependence on obliquity to study the likelihood of different stable ice configurations. We compare the results of models with different methods of heat transport and different insolation distributions. We show that stable partial ice cover is possible for any obliquity, provided the insolation distribution is sufficiently accurate. Additionally, we quantify the severity of the transition to the snowball state as different model parameters are varied. In accordance with an earlier study, transitions to the snowball state are more severe for higher values of the albedo contrast and energy transport across latitudes in both models; however, we find that the snowball transition is not equally likely across both models. This work is general enough to apply to any rapidly rotating planet and could be used to study the likelihood of snowball transitions on planets within the habitable region of other stars.

Keywords: Solar radiation, Theoretical models, Exoplanets
An Open-source Bayesian Atmospheric Radiative Transfer (BART) Code. I. Design, Tests, and Application to Exoplanet HD 189733b. We present the open-source Bayesian Atmospheric Radiative Transfer (BART) retrieval package, which produces estimates and uncertainties for an atmosphere's thermal profile and chemical abundances from observations. Several BART components are also stand-alone packages, including the parallel Multi-Core Markov-chain Monte Carlo (MC3), which implements several Bayesian samplers; a line-by-line radiative-transfer model, transit; a code that calculates Thermochemical Equilibrium Abundances (TEA), and a test suite for verifying radiative-transfer and retrieval codes, BARTTEST. The codes are in Python and C. BART and TEA are under a Reproducible Research (RR) license, which requires reviewed-paper authors to publish a compendium of all inputs, codes, and outputs supporting the paper's scientific claims. BART and TEA produce the compendium's content. Otherwise, these codes are under permissive open-source terms, as are MC3 and BARTTEST, for any purpose. This paper presents an overview of the code, BARTTEST, and an application to eclipse data for exoplanet HD 189733b. Appendices address RR methodology for accelerating science, a reporting checklist for retrieval papers, the spectral resolution required for synthetic tests, and a derivation of the effective sample size required to estimate any Bayesian posterior distribution to a given precision, which determines how many iterations to run. Paper II, by Cubillos et al., presents the underlying radiative-transfer scheme and an application to transit data for exoplanet HAT-P-11b. Paper III, by Blecic et al., discusses the initialization and post-processing routines, with an application to eclipse data for exoplanet WASP-43b. We invite the community to use and improve BART and its components at http://GitHub.com/ExOSPORTS/BART/.

Keywords: Exoplanet atmospheric composition , Open source software, Astrostatistics techniques, Uncertainty bounds, Planetary atmospheres, Exoplanet systems
An Open-source Bayesian Atmospheric Radiative Transfer (BART) Code. II. The TRANSIT Radiative Transfer Module and Retrieval of HAT-P-11b. This and companion papers by Harrington et al. and Blecic et al. present the Bayesian Atmospheric Radiative Transfer (BART) code, an open-source, open-development package to characterize extrasolar planet atmospheres. BART combines a thermochemical equilibrium abundance (TEA), a radiative transfer (TRANSIT), and a Bayesian statistical (MC3) module to constrain atmospheric temperatures and molecular abundances for given spectroscopic observations. Here we describe the TRANSIT radiative transfer package, an efficient line-by-line radiative transfer C code for one-dimensional atmospheres, developed by P. Rojo and further modified by the UCF exoplanet group. This code produces transmission and hemisphere-integrated emission spectra. TRANSIT handles line-by-line opacities from HITRAN, Partridge &amp; Schwenke (H2O), Schwenke (TiO), and Plez (VO) and collision-induced absorption from Borysow, HITRAN, and ExoMol. TRANSIT emission spectra models agree with models from C. Morley (private communication) within a few percent. We applied BART to the Spitzer and Hubble transit observations of the Neptune-sized planet HAT-P-11b. Our analysis of the combined HST and Spitzer data generally agrees with those from previous studies, finding atmospheric models with enhanced metallicity (≳100× solar) and high-altitude clouds (≲1 mbar level). When analyzing only the HST data, our models favor high-metallicity atmospheres, in contrast with the previous analysis by Chachan et al. We suspect that this discrepancy arises from the different choice of chemistry modeling (free constant-with-altitude versus thermochemical equilibrium) and the enhanced parameter correlations found when neglecting the Spitzer observations. The BART source code and documentation are available at https://github.com/exosports/BART.

Keywords: Exoplanet atmospheric composition , Astrostatistics techniques, Open source software, Planetary atmospheres
An Open-source Bayesian Atmospheric Radiative Transfer (BART) Code. III. Initialization, Atmospheric Profile Generator, Post-processing Routines. This and companion papers by Harrington et al. and Cubillos et al. describe an open-source retrieval framework, Bayesian Atmospheric Radiative Transfer (BART), available to the community under the reproducible-research license via https://github.com/exosports/BART. BART is a radiative transfer code (transit; https://github.com/exosports/transit; Rojo et al.), initialized by the Thermochemical Equilibrium Abundances (TEA; https://github.com/dzesmin/TEA) code (Blecic et al.), and driven through the parameter phase space by a differential-evolution Markov Chain Monte Carlo (MC3; https://github.com/pcubillos/mc3) sampler (Cubillos et al.). In this paper we give a brief description of the framework and its modules that can be used separately for other scientific purposes; outline the retrieval analysis flow; present the initialization routines, describing in detail the atmospheric profile generator and the temperature and species parameterizations; and specify the post-processing routines and outputs, concentrating on the spectrum band integrator, the best-fit model selection, and the contribution functions. We also present an atmospheric analysis of WASP-43b secondary eclipse data obtained from space- and ground-based observations. We compare our results with the results from the literature and investigate how the inclusion of additional opacity sources influences the best-fit model.

Keywords: Exoplanet atmospheric composition , Open source software, Astrostatistics techniques, Uncertainty bounds, Planetary atmospheres, Exoplanet systems
Did Earth Eat Its Leftovers? Impact Ejecta as a Component of the Late Veneer. The presence of highly siderophile elements in Earth's mantle indicates that a small percentage of Earth's mass was delivered after the last giant impact in a stage of "late accretion." There is ongoing debate about the nature of late-accreted material and the sizes of late-accreted bodies. Earth appears isotopically most similar to enstatite chondrites and achondrites. It has been suggested that late accretion must have been dominated by enstatite-like bodies that originated in the inner disk, rather than ordinary or carbonaceous chondrites. Here we examine the provenances of "leftover" planetesimals present in the inner disk in the late stages of accretion simulations. Dynamically excited planet formation produces planets and embryos with similar provenances, suggesting that the Moon-forming impactor may have had a stable isotope composition very similar to the proto-Earth. Commonly, some planetesimal-sized bodies with similar provenances to the Earth-like planets are left at the end of the main stage of growth. The most chemically similar planetesimals are typically fragments of protoplanets ejected millions of years earlier. If these similar-provenance bodies are later accreted by the planet, they will represent late-accreted mass that naturally matches Earth's composition. The planetesimal-sized bodies that exist during the giant impact phase can have large core mass fractions, with core provenances similar to the proto-Earth. These bodies are an important potential source for highly siderophile elements. The range of core fractions in leftover planetesimals complicates simple inferences as to the mass and origin of late accretion based on the highly siderophile elements in the mantle.

Keywords: Impact phenomena, Solar system formation, Cosmochemistry, Earth (planet), Planetary science, Planetesimals, Meteorites, Planet formation
Neptune's Moon Triton: Continuing Surface Seasonal Volatile Transport. Observations of Triton's rotational light curve from Table Mountain Observatory in 2017 show that volatile transport is continuing on its surface. Changes in the light curve are consistent with sustained increases in albedo in two patches near the equator at longitudes of ~120° and ~280°, as first reported by Bauer et al. based on observations obtained with the Hubble Space Telescope. An early observation of Triton's visual albedo shows a substantially lower albedo in the past, when the northern polar region was visible. This result confirms the hypothesis of Moore &amp; Spencer and Spencer &amp; Moore of a net flux of volatile material into the southern hemisphere of Triton over much of the satellite's history and up to the present. The averaged V-band geometric albedo of Triton has been stable over the past three decades. The color of Triton has also been stable during the past decade.

Keywords: Neptune, Small Solar System bodies, Neptunian satellites, Trans-Neptunian objects, Triton