Sazuna/UAT_keywords huggingface dataset:
Length, Width, and Relative Age Analysis of Lineaments in the Galileo Regional Maps with LineaMapper. The Galileo regional mosaics ("RegMaps") show Europa's extensive regional-scale tectonic features under similar illumination conditions. Detailed lineament studies can help constrain resurfacing events and formation mechanisms, but most lineament maps only include a portion of the observed features. We gain statistical insights into lineament distributions of length, width, and relative age in different geological terrains contained within the RegMaps. We find evidence that only the most recently formed linear features remain discernible following the disruption by chaos terrain and hypothesize that younger features are stronger. Because mapping of lineaments is time-consuming and subjective, we employ the deep learning tool LineaMapper to make mapping faster and more consistent. Guided by LineaMapper, we produce a validated lineament map of the RegMaps southern leading hemisphere. The manually revised map is used as additional training data of 2140 lineaments, with which we train LineaMapper v1.1 and v2.0, using two different deep learning models. Based on this map, we find a lineament density (area) of 15% in chaos and 65% in ridged plains, which we use to fully automatically classify units of chaos and ridged plains in the full RegMaps. We find good agreement with a global geologic map. We conclude that LineaMapper can be employed for an objective assessment of Europa's previously unresolved regions with the Europa Imaging System on Europa Clipper. Finally, we make the full output of LineaMapper available and offer an interactive tool for testing LineaMapper v2.0, which utilizes the Segment Anything model by Meta.

Keywords: Galilean satellites, Jovian satellites, Europa
Comparing NASA Discovery and New Frontiers Class Mission Concepts for the Io Volcano Observer. Jupiter's moon Io is a highly compelling target for future exploration that offers critical insight into tidal dissipation processes and the geology of high heat flux worlds, including primitive planetary bodies, such as the early Earth, that are shaped by enhanced rates of volcanism. Io is important for understanding the development of volcanogenic atmospheres and mass exchange within the Jupiter system. However, fundamental questions remain about the state of Io's interior, surface, and atmosphere, as well as its role in the evolution of the Galilean satellites. The Io Volcano Observer (IVO) would advance answers to these questions by addressing three key goals: (A) determine how and where tidal heat is generated inside Io, (B) understand how tidal heat is transported to the surface of Io, and (C) understand how Io is evolving. IVO was selected for Phase A study through the NASA Discovery program in 2020, and, in anticipation of the next New Frontiers (NF) opportunity, an enhanced IVO-NF mission concept would increase the Baseline mission from 10 flybys to 20, with an improved radiation design; employ a Ka-band communication system to double IVO's total data downlink; add a wide-angle camera for color and stereo mapping; add a dust mass spectrometer; and lower the altitude of later flybys to enable new science. This study compares the architecture, instrument suite, and science objectives for Discovery (IVO) and NF (IVO-NF) missions to Io. IVO can achieve outstanding science results at the Discovery level, but we advocate for continued prioritization of Io for NF.

Keywords: Tidal interaction, Io, Galilean satellites, Space vehicles, Jovian satellites, Volcanism
Formation of Ammonium Nitrate Particles in CO<SUB>2</SUB>-rich Atmospheres. Aerosols play a crucial role in the study of exoplanet atmospheres, as they significantly impact a planet's climate, albedo, and observational spectra. Understanding aerosol formation and behavior may help in interpreting atmospheric compositions and conditions, providing insights into habitability and atmospheric dynamics. We construct a facility to simulate in the laboratory the effects of lightning discharge on gas mixtures in a controlled setup. In this study, we present experiments performed on gases composed predominantly of carbon dioxide with relatively low amounts of ammonia. Diagnostics using quadrupole mass spectrometry, ultraviolet, and infrared spectroscopy reveal the formation of nitrogen- and oxygen-containing compounds, including nitrates, as well as further oxidation of ammonia to produce solid ammonium nitrate on a cooled substrate. These results highlight the role of electrical discharges in driving atmospheric chemistry, offering insights into potential reaction pathways in exoplanets of similar atmospheric compositions.

Keywords: Laboratory astrophysics, Planetary atmospheres
A New Saturn Model of Ionospheric Transport and Electrodynamics (SMITE). We introduce the Saturn Model of Ionospheric Transport and Electrodynamics (SMITE), a new model that incorporates interhemispheric plasma transport using a dipole magnetic field aligned grid, and a range of dynamic processes that influence Saturn's ionosphere. SMITE includes tunable parameters for the inflow of exogenous material, seasonal and local time atmospheric variations, the ring shadow, and plasma transport driven by neutral winds and low-latitude electrodynamics. SMITE is an adaptation of the terrestrial SAMI2 model, which has successfully reproduced numerous ionospheric phenomena at Earth. Preliminary results show that SMITE can reproduce latitudinal trends in the total electron content and altitudinal electron density distributions observed by the Cassini spacecraft. Model–data comparisons also show that diurnally variable low-latitude electrodynamics may intermittently be active at Saturn. SMITE is also the first model to show that strong plasma density gradients, such as those caused by Saturn's ring shadow in the winter hemisphere, drive interhemispheric field-aligned transport from the sunlit hemisphere to the winter hemisphere, which has previously been hypothesized from Cassini spacecraft measurements. Future applications will use SMITE to analyze data from the Cassini mission in detail and investigate the influence of Saturn's magnetic field on the structure of its ionosphere. These investigations will provide the first insights into the role of nonauroral electrodynamics at a giant planet, thus advancing our broader understanding of giant planet ionospheres.

Keywords: Astronomical models, Saturn, Planetary ionospheres, Astronomy data modeling, Planetary atmospheres, Solar system gas giant planets, Atmospheric dynamics
Characterization of the DART Ejecta Using Computer Modeling of the Ground-based and HST Photopolarimetric Data. Among the published observations of the DART ejecta, we have identified a set of quasi-simultaneous data acquired on 2022 October 4─5, using different but complementary techniques: polarimetry (FORS2 at the Very Large Telescope (VLT)), spectroscopy (MUSE at the VLT), and imaging (WFC3 at the Hubble Space Telescope (HST)). These data offer a unique opportunity to carry out a novel, detailed analysis of the ejecta particles. At that time, the ejecta exhibited a well-developed tail with the g − r color and B and R polarization remaining unchanged along its length. The observed color and polarization of the ejecta are best explained by a model consisting of agglomerated particles formed from 10 to 20 μm monomers. The model was refined using dynamic modeling, which simulates the motion of ejecta particles from Dimorphos through the observed tail. The best-fit model corresponds to an ensemble of agglomerates with sizes ranging from 10 to 200─5000 μm (depending on the distance from the asteroid), following a power-law size distribution with an index of −3.2. Using the derived particle properties and HST imaging of the tail, we reconstruct the column density and mass distribution of the dust along the tail as well as the total mass of material within the tail as of 2022 October 5.

Keywords: Impact phenomena, Near-Earth objects, CCD photometry, Astronomy data modeling, HST photometry, Polarimetry
Conditions for Accretion Favoring an Unmelted Callisto and a Differentiated Ganymede. Analysis of Callisto's moments of inertia, derived from Galileo's gravity data, suggests that its structure is not fully differentiated. This possibly undifferentiated state contrasts sharply with the globally molten state inferred in its counterpart, Ganymede, and poses unique challenges to theories of the formation and evolution of the Galilean moons. During their formation, both moons experienced multiple heating mechanisms, including tidal heating, radiogenic heating from short-lived radionuclides, accretional heating from impacts, and heat from the surrounding circumplanetary disk (CPD). Our study investigates the optimal conditions required to account for Callisto's partially differentiated state in contrast to Ganymede's complete differentiation. We investigate crucial accretion parameters, such as the timing of accretion onset, the duration of accretion, and the impactor size distribution. We find that the observed dichotomy between Ganymede and Callisto can be attributed to similar formation conditions, assuming an identical impactor size distribution and composition in the Jovian CPD. The key differences in the formation of Ganymede and Callisto are the disk temperature at their respective formation locations and their final radii. Our results indicate that both moons accreted gradually over more than 2 Myr, concluding at least 5.5 Myr after the formation of calcium–aluminum-rich inclusions in the protosolar nebula. Our model demonstrates that Callisto can remain undifferentiated despite accreting a substantial influx of kilometer-sized impactors—potentially contributing up to 30% of the total mass inflow—while still allowing for the complete differentiation of Ganymede.

Keywords: Ganymede, Callisto, Natural satellite formation, Solar system, Planetesimals
A JWST Study of the Remarkable Oort Cloud Comet C/2017 K2 (PanSTARRS). Comets, during their journeys into the inner solar system, deliver volatile gases, organics, and particulates into their comae that provide crucial information for assessing the physicochemical conditions in the outer disk from which they formed. Here we present observational and modeling results of a JWST NIRSpec and MIRI MRS integral field unit spatial-spectral study of the inner coma of the Oort Cloud comet C/2017 K2 (PanSTARRS) at a heliocentric distance of 2.35 au. We find that the comet is hyperactive (water-ice active fraction ≳86%), with a nucleus radius of &lt;4.2 km, exhibiting strong emission from H2O, 12CO, 13CO, and CO2, as well as CN, H2CO, CH3OH, CH4, C2H6, HCN, NH2, and OH prompt emission. The water ortho-to-para ratio is ≳2.75. The modeled dust composition (relative mass fraction of the submicron grains) in the coma is dominated by amorphous carbon (≃25%), amorphous Mg:Fe olivine (≃19%), amorphous Mg:Fe pyroxene (≃16%), and Mg-rich crystalline olivine (≃39%), and the crystalline mass fraction of the submicron grains in the coma is fcryst ≃ 0.384 ± 0.065. Analysis of residuals in the 3–8 μm region of the spectral energy distribution strongly suggests the presence of polycyclic aromatic hydrocarbon species in the coma.

Keywords: Long period comets, Dust composition, Comet origins, Infrared spectroscopy
SHARAD Illuminates Deeper Martian Subsurface Structures with a Boost from Very Large Rolls of the MRO Spacecraft. Throughout its mission, the Mars Reconnaissance Orbiter (MRO) has often rolled about its along-track axis by up to 28° to partially compensate for the suboptimal location of the Shallow Radar (SHARAD) antenna along an edge of the spacecraft that is opposite the imaging payload deck, thereby enhancing the signal-to-noise ratio (S/N) of echoes returned from the surface. After recent modeling work predicted that a much larger roll would improve the S/N by ~10 dB relative to nadir-pointed observing, MRO began a limited series of 120° roll maneuvers to test the effects on radar sounding. Three such SHARAD very-large-roll (VLR) observations were acquired between 2023 May and 2024 September, and they show dramatic improvements in signal clarity and depth of penetration, with S/N increasing by 9, 11, and 14 dB over that of nearly coincident observations at 0° roll angle. In low dielectric terrains, the first and second VLR observations enabled basal detections at depths previously unachievable, reaching depths of 800 m in Medusae Fossae materials and 1500 m through the ice of Ultimi Scopuli, respectively. The second VLR observation also obtained enhanced reflections throughout the ice stack. In the higher dielectric terrain of Amazonis Planitia, the third VLR observation improved continuity of a dipping subsurface interface, but it revealed neither an extension of the interface to greater depths nor any deeper interfaces. The MRO mission intends to obtain more SHARAD VLR observations of polar terrains and of midlatitude glacial and ground ices, sediments, and volcanics.

Keywords: Mars, Geological processes, Polar caps, Remote sensing, Radar observations, Planetary science, Planetary geology
Insights into the Lunar Imbrium Basin Mare Units by Characterizing Their Regolith Property, Chronology, and Composition. Mare basalts are volcanic products that filled the large topographic depressions on the Moon. Investigating volcanic activity aids in deeply understanding the lunar endogenic geological processes and thermal evolution over time. Previous studies on lunar volcanism mainly focused on using optical, spectral, and topographical data, which are good at analyzing lunar surface morphology and composition, but detection of its subsurface regolith property has been greatly restricted. Chang'E-2 microwave radiometer data can reveal the thermal and dielectric properties of mare deposits to variable depths and identify potential lava flows, providing a new perspective for delineating volcanic units. This work presents a comprehensive analysis of the regolith properties, chronology, and composition of mare basalts in the Imbrium basin, aiming to reveal the details of the basin's volcanic history and thermal evolution. Trend surface analysis was applied to remove latitude effects, generating detrended brightness temperature difference (dTB) maps that distinctly highlight major mare deposits. We identified Imbrium mare units using detrended dTB maps, which effectively capture the diurnal temperature variations. Results show at least three major episodes of lava filling events in the basin, approximately occurring at 3.51 Ga, 3.26 Ga, and 2.76 Ga, respectively. Although the range of compositions varied in each eruption, the general trend suggests an increasingly highly evolved composition for the mare deposits emplaced in the Imbrium basin over time. The updated geological map provides detailed regional background information for understanding the evolution of the Imbrium basin.

Keywords: Lunar maria, The Moon, Remote sensing, Planetary science, Volcanism
Potential Landing Sites: A Comprehensive Reconnaissance Assessment of the Europa Clipper Trajectory. NASA's Europa Clipper mission will explore Jupiter's icy moon via multiple flybys in the early 2030s. The ocean world Europa is one of the most promising locations to search for life elsewhere in the solar system, and thus Europa Clipper's main goal is to characterize Europa's habitability. In the future, especially if Europa Clipper finds that Europa is habitable, a follow-on landed mission may explore Europa's surface to search for evidence of life. Here we show that 12 of the 49 prime-mission Europa Clipper flybys are "reconable," meaning they contain at least one portion of the ground track where the requirements for collecting data necessary for terrain relative navigation (TRN) are fulfilled. TRN would be used by a future mission to navigate to a landing site. Using data from the prior Galileo mission, we study what is currently known about these reconable areas and rank them. Three reconable flybys are ranked highest because of their particular scientific potential, which we discuss based on existing studies. We also identify and rank supporting flybys, which are not themselves reconable but provide data for additional characterization of reconable areas. These current rankings demonstrate the process for assessing reconable areas and reflect present-day knowledge. Future decisions on landing site location(s) would be based on new knowledge from Europa Clipper and would likely yield different priorities than the current rankings. We conclude that there are areas on Europa with particular scientific interest that Europa Clipper will be able to fully characterize for potential future in situ exploration.

Keywords: Planetary geology, Europa
Formation and Evolution Simulations of Saturn, Including Composition Gradients and Helium Immiscibility. In this paper, the formation of Saturn is modeled by detailed numerical simulations according to the core-nucleated accretion scenario. Previous models are enhanced to include the dissolution of accreting planetesimals, composed of water ice, rock, and iron, in the gaseous envelope of the planet, leading to a nonuniform composition with depth. The immiscibility of helium in metallic hydrogen layers is also considered. The calculations start at a mass of 0.5 Earth masses and are extended to the present day. At 4.57 Gyr, the model, proceeding outward, has the following structure: (i) a central core composed of 100% heavy elements and molecules, (ii) a region with a decreasing heavy-element mass fraction, down to a value of 0.1, (iii) a layer of uniform composition with the helium mass fraction Y enhanced over the primordial value, (iv) a helium rain region with a gradient in Y, (v) an outer convective, adiabatic region with uniform composition in which Y is reduced from the primordial value, and (vi) the very outer layers where cloud condensation of the heavy elements occurs. Models of the distribution of heavy elements as a function of radius are compared with those derived to fit the observations of the Cassini mission, with rough qualitative agreement. The helium mass fraction in Saturn's outer layers is estimated to be around 20%. Models are found that provide good agreement with Saturn's intrinsic luminosity and radius.

Keywords: Saturn, Solar system gas giant planets, Planetesimals, Planetary interior, Planet formation
On Error Estimates for Hapke Photometric Model Parameters from Disk-integrated Phase Curves of Airless Planetary Bodies. The Hapke bidirectional reflectance model is widely used to analyze photometric observations of planetary surfaces. When fitting disk-integrated data, nonuniqueness concerns arise if observations lack sufficient phase angle coverage to constrain the model's numerous parameters. Sparsity and nonuniformity of observational phase angle coverage especially challenge the goal of obtaining reliable parameter values and error estimates. The obstacles include the relatively small number and phase angle spread of observations in comparison to the sizable number of model parameters, coupling of model parameters and their ability to mimic one another, and systematic differences in measurement uncertainties between data collected from different instruments and observing environments. In these cases, meaningful error analysis is especially critical. We lay a strategic foundation for obtaining uncertainty estimates for Hapke model parameters retrieved from fits to disk-integrated phase curves of airless planetary bodies. We develop and demonstrate analysis tools for treating the separate contributions of goodness-of-fit errors, uncertainties due to the absence of critical phase angle coverage, and absolute calibration errors. Our approach suggests a parameter retrieval methodology that leverages the intricate coupling among Hapke parameters to provide constraints that would not be possible were they strictly independent variables. We apply this new strategy to fits of the Hapke model to phase curves of Kuiper Belt objects and dwarf planets observed by New Horizons.

Keywords: Planetary surfaces, Classical Kuiper belt objects, Plutonian satellites, Uncertainty bounds, HST photometry, Chi-squared statistic, Surface ices, Trans-Neptunian objects, Broad band photometry, Pluto, Triton
Effects of Ultraviolet Radiation on Sub-Neptune Exoplanet Hazes through Laboratory Experiments. Temperate sub-Neptune exoplanets could contain large inventories of water in various phases, such as water worlds with water-rich atmospheres or even oceans. Both space-based and ground-based observations have shown that many exoplanets likely also contain photochemically generated hazes. Haze particles are a key source of organic matter and may impact the evolution or origin of life. In addition, haze layers could provide a mechanism for lower-atmospheric shielding and ultimately atmospheric retention. Often orbiting close to M dwarf stars, these planets receive large amounts of radiation, especially during flaring events, which may strip away their atmospheres. M dwarf stars are known to have higher stellar activity than other types of stars, and stellar flares have the potential to accelerate atmospheric escape. In this work, we present the results from laboratory investigations of UV radiation effects simulating two different stellar flare energies on laboratory-produced exoplanet hazes made under conditions analogous to water-world atmospheres. We find that both simulated flares altered the overall transmittance and reflectance of the hazes, and higher-energy "flares" make those alterations more pronounced. On a larger scale, these laboratory-made hazes show potential signs of degradation over the simulated flaring period. Our results provide insight into the effects that stellar flaring events have on potential exoplanet haze composition and the ability for water-world-like exoplanets to retain their atmospheres.

Keywords: Exoplanet atmospheric composition , Infrared spectroscopy, Exoplanets, Experimental data, Super Earths, Laboratory astrophysics, Ultraviolet spectroscopy, Experimental techniques, Stellar flares, Mini Neptunes, Exoplanet atmospheres, Exoplanet atmospheric evolution
Constraints on Quaoar's Rings and Atmosphere from JWST/NIRCam Observations of a Stellar Occultation. Observations of stellar occultations have revealed that small bodies are capable of hosting ring systems. The trans-Neptunian object Quaoar is the host of an enigmatic ring system, with two rings located well outside the Roche limit. To better understand these structures, we observed a stellar occultation by Quaoar and its rings using the James Webb Space Telescope's NIRCam instrument. Our observations detect both known rings, although Q2R—the inner known ring—is not detected on both sides of Quaoar, showing that it has substantial azimuthal variations similar to Q1R, the outer ring. We also fit a model of the ring radii and pole orientation of the ring system, which confirms that Quaoar's spin–orbit and Weywot's mean-motion resonances (especially Weywot's 6:1) may play a role in the rings' confinement and stability. In addition to examination of Quaoar's ring system, we also use our observations to place upper limits on a putative CH4 atmosphere around Quaoar, finding that no global atmosphere with surface pressure &gt; 1 nbar can exist (at 3σ significance). The lack of atmosphere supports the hypothesis that atmospheric processes are not the source of Quaoar's recently discovered inventory of light hydrocarbons.

Keywords: James Webb Space Telescope, Stellar occultation, Planetary rings, Trans-Neptunian objects