Sazuna/UAT_keywords huggingface dataset:
Comprehensive Analyses of the Strongly Carbon-chain Depleted Comets in Lowell Observatory's Narrowband Photometry Database. We present measurements, analyses, and results for the 17 strongly carbon-chain depleted comets in Lowell Observatory's narrowband photometry database. The majority of comets exhibit a very similar, i.e., typical, composition in optical wavelengths, though the existence of anomalous comets with lower abundances of carbon-chain molecules relative to CN has long been known. M. F. A'Hearn et al. identified an entire class of these carbon-chain depleted comets, and the most recent full analysis of our database reveals that there are varying degrees of carbon-chain depletion. Here we focus on the most depleted comets, the strongly carbon-chain depleted class, which is the largest nontypical compositional class to emerge from our taxonomic analyses. All comets in this class are strongly depleted in both C2 and C3 with respect to OH and CN, with depletions for these ratios being 3─27× below the mean abundance ratios for comets with typical composition. Several comets in this class additionally exhibit depletion in NH, with the largest depletions being 11× below mean typical values. A number of these comets exhibit asymmetry in production rates as a function of time and heliocentric distance, and one exhibits evidence of small secular changes. Almost all of the strongly depleted comets are Jupiter-family comets, indicating a Kuiper Belt origin for this compositional class. Multiple lines of evidence from our full database indicate that this composition is due to primordial conditions when and where these comets were formed and is not due to thermal heating after their arrival in the inner solar system.

Keywords: Comets, Short period comets, Comet volatiles , Comae
Analysis of Surface Age Dating Techniques and Uncertainties through Comparison of Independently Determined Crater Size─Frequency Distributions at Two Lunar Landing Sites. This study compares differences in crater-count-based measurement techniques and determines lava flow ages for geologic context at two NASA Commercial Lunar Payloads Services (CLPS) landing sites. Using the same software tools, two researchers independently performed crater size─frequency measurements using identical images with the same illumination conditions for Reiner Gamma and opposing illumination for Mare Crisium. The uniform nature of the analysis environment allowed the researchers to use accepted crater size─frequency distribution (aka ''crater-counting'') techniques to determine absolute model ages (AMAs) while subsequently allowing the examination of the variations in the personal approaches used by the researchers. Comparisons revealed variations in researcher methodology that ultimately affected the AMA results. Count areas were defined within geochemically uniform units of mare basalts near the CLPS landing sites. Our results indicate that both sites have Imbrian age basalts that were emplaced during the most volcanically active period (3.6─3.7 Ga) in the Moon's history. Variations in AMAs between the researchers arose due to multiple factors that affected identification of secondary and degraded craters (e.g., lighting geometry and the decision to list a crater as secondary or primary or as a crater at all). To improve on the legacy work of the crater-counting community, we recommend rigorous and consensus-based secondary crater identification and exclusion, as well as making improvements in identifying crater rim crests and diameter measurements. We find that the judicious use of digital terrain models and high-resolution orbital images can improve researcher crater measurements.

Keywords: Lunar craters, Lunar maria, The Moon, Lunar impacts, Planetary science, Craters, Volcanism
Surface Changes on Io Observed by Large Binocular Telescope/SHARK in Early 2025. High spatial resolution images of the volcanic moon Io at visible and near-infrared wavelengths were obtained by the SHARK-VIS and SHARK-NIR instruments on the Large Binocular Telescope on UT 2025 February 18 and 23. Large-scale changes on Io's surface are identified in these data and provide vital context for infrared observations from other telescopes and spacecraft. SHARK-VIS imaged part of the plume deposit from a large eruption close to Io's south pole at Illyrikon that was first observed by NASA's Juno spacecraft in 2024 December, detecting significant deposit modification. Examples of other significant surface changes detected include at Seth, identifying a new pyroclastic deposit in addition to the new lava flows previously detected in Juno infrared observations; at Amirani, confirming that volcanic activity was now confined to the southern half of the Galileo-epoch lava flow field; new red sulphur-rich deposits at Mixcoatl; and changes in the plume deposits around Prometheus. Plume deposits at Prometheus and at other volcanoes show evidence of complex interplay between different plumes issuing from the same volcano. The combination of SHARK-VIS and Juno JunoCam data moves closer to near-global, near-contemporaneous, visible-wavelength coverage of Io. SHARK-VIS lives up to its promise of a new era of planetary imaging at visible wavelengths and filling the temporal coverage gap between Juno and the arrival of the Europa Clipper and JUICE spacecraft in the Jovian system in 2030 and 2031, respectively.

Keywords: Io, Remote sensing, Jovian satellites, Volcanism
Differentiation, the Exception, Not the Rule: Evidence for Full Miscibility in Sub-Neptune Interiors. We investigate the consequences of nonideal mixing between silicate, iron metal, and hydrogen for the structures of the cores of sub-Neptunes with implications for super-Earths and perhaps other planets formed by mixtures of silicate melt, iron metal, and significant mass fractions of hydrogen. A method of extrapolating what we know about the miscibility in the three bounding binary systems MgSiO3─H2, MgSiO3─Fe, and Fe─H2 to the ternary composition space is used to deduce the phase equilibria of this system at relevant temperature and pressure conditions. We find that while separate silicate and metal phases can exist at shallow depths, the phases become entirely miscible deeper in the cores, thus altering the density structure of the cores. The assumption that the interiors of large rocky planets, either with extant magma oceans beneath H2-rich envelopes or evolved from such bodies, are composed of a differentiated metal core overlaid by a silicate mantle is inconsistent with our understanding of the phase equilibria of these bodies.

Keywords: Exoplanets
A High-precision, Differentiable Code for Solar System Ephemerides. We present jorbit, a python/JAX library designed to enable modern data-driven numerical studies of the solar system. Written entirely in JAX, an autodifferentiable and optionally GPU accelerated language behind many current large-scale machine learning efforts, jorbit includes an independent implementation of REBOUND's IAS15 integrator and the ability to parse precomputed ephemerides such as the JPL DE series. In its default behavior, jorbit maintains ∼1 mas agreement with JPL Horizons on ∼decade timescales for typical main-belt asteroids, enabling it to fully capitalize on high-precision astrometry and ranging data. We include details of the code's implementation and several worked examples, including illustrations of jorbit's ability to simulate N-body systems, forward model astrometric data, fit orbits, replicate the Minor Planet Center's "MPChecker" service, and contribute to modeling the effect of minor planets on stellar light curves.

Keywords: Bayesian statistics, Solar system, Orbit determination, Astronomy software
The Caltech Mission to Apophis: Accelerating Planetary Science and Planetary Defense. The close approach of asteroid (99942) Apophis in 2029 offers a rare opportunity to observe the reaction of a small, suspected rubble-pile body to planetary tidal forces, providing insight into its surface and interior properties and contributing valuable knowledge for planetary defense. The California Institute of Technology (Caltech) is pioneering a mission to rendezvous with Apophis before and escort it through its Earth closest approach (ECA). The mission consists of a Mothership and two radar-equipped CubeSats. Mission science objectives include observing potential resurfacing due to ECA and studying the asteroid's interior using low-frequency radar, producing three-dimensional maps of Apophis's internal composition and porosity and providing unprecedented insight into the interiors of rubble piles. Here, we compile and summarize Apophis modeling and data, focusing on knowns, unknowns, current science knowledge gaps, and how Caltech's mission can fill those gaps. We discuss current knowledge regarding the surface dynamics and interior structure of rubble-pile asteroids, implications for asteroid formation and evolution, predicted responses to Earth encounters via numerical modeling, and how these predictions inform mission requirements. We outline how Caltech's mission aligns with the landscape of other Apophis missions, such as OSIRIS-APEX and RAMSES, and how its unique bistatic radar data set complements the data returned by other missions.

Keywords: Asteroids, Surface processes, Radar observations, Close encounters, Tidal interaction, Asteroid surfaces
Space Weathering on Carbon-rich Surfaces: Spectral Characterization of Fe-poor Mercury and Carbonaceous Asteroid Analogs. Experimental space weathering efforts and recent sample return analyses have proven that the composition of an airless body plays a distinct role in how its spectra will be altered by space weathering processes. Space weathering on Fe-poor bodies, such as Mercury and a subset of the carbonaceous asteroid population, is not well understood. In an aim to characterize how space weathering may impact the spectra of highly reduced, C-rich regoliths, we simulated aspects of micrometeorite bombardment on 12 analog mixtures featuring low-Fe or Fe-free silicates and carbonaceous opaques with varying levels of graphitization. We present spectral analyses from 0.3─2.5 μm, 4─8 μm, and 8─50 μm (200─1250 cm−1) before and after simulated space weathering. Our investigation shows that carbon-rich materials can darken and redden in the visible-to-near infrared without the presence of nanophase iron, implying that opaques like carbon play a significant role in space weathering of carbon-bearing bodies. The graphitization state of carbon also has clear impacts on spectral features and albedo, which may aid in interpreting what forms of carbon could be present on airless bodies.

Keywords: Small Solar System bodies, Asteroids, Infrared spectroscopy, Space weather, Carbonaceous chondrites, Solar system terrestrial planets, Regolith, Solar system evolution, Spectroscopy, Mercury (planet), Micrometeorites
Detection of an NH<SUB>3</SUB> Absorption Band at 2.2 μm on Europa. The presence of NH3-bearing components on icy planetary bodies has important implications for their geology and potential habitability. Here, I report the detection of a characteristic NH3 absorption feature at 2.20 ± 0.02 μm on Europa, identified in an observation from the Galileo Near Infrared Mapping Spectrometer. Spectral modeling and band position indicate that NH3 hydrate and NH4 chloride are the most plausible candidates. Spatial correlation between detected ammonia signatures and Europa's microchaos, linear, and band geologic units suggests emplacement from the underground or shallow subsurface. I posit that NH3-bearing materials were transported to the surface via effusive cryovolcanism or similar mechanisms during Europa's recent geological past. The presence of ammoniated compounds implies a thinner ice shell and a thicker, chemically reduced, high-pH subsurface ocean on Europa. With the detection of NH3-bearing components, this study presents the first evidence of a nitrogen-bearing species on Europa—an observation of astrobiological significance given nitrogen's essential role in the chemistry of life.

Keywords: Small Solar System bodies, Surface composition, Europa, Planetary science, Galilean satellites
The Open-source Photochem Code: A General Chemical and Climate Model for Interpreting (Exo)Planet Observations. With the launch of the James Webb Space Telescope, we are firmly in the era of exoplanet atmosphere characterization. Understanding exoplanet spectra requires atmospheric simulations that span the diversity of planetary atmospheres. Here we present Photochem, a more general chemical and climate model developed for this purpose. We benchmark the open-source, 1D code against the observed compositions and climates of Venus, Earth, Mars, Jupiter, and Titan with a single set of kinetics, thermodynamics and opacities. We also model the chemistry of the hot Jupiter exoplanet WASP-39b. All simulations are open-source and reproducible. To first order, Photochem broadly reproduces the gas-phase chemistry and pressure−temperature profiles of all six planets. The largest model−data discrepancies are found in Venus's sulfur chemistry, motivating future experimental work on sulfur kinetics and spacecraft missions to Venus. We also find that clouds and hazes are important for the energy balance of Venus, Earth, Mars, and Titan and that accurately predicting aerosols with Photochem is challenging. Finally, we benchmark Photochem against the popular VULCAN and HELIOS photochemistry and climate models, finding excellent agreement for the same inputs; we also find that Photochem simulates atmospheres from 2× to ∼102× more efficiently. These results show that Photochem provides a comparatively general description of atmospheric chemistry and physics that can be leveraged to study solar system worlds or interpret telescope observations of exoplanets.

Keywords: Exoplanet atmospheres, Planetary atmospheres, Planetary climates
Calculating Occultation Light Curves Using Wavelets: Exponential Atmospheres and the Constraints of Static Stability. The signatures of waves are seen during many high-quality ground-based refractive stellar occultations by solar system atmospheres. We present a new forward-modeling technique for ground-based stellar occultations based on wavelet decomposition. If profiles of refractivity are written as the product of an exponential and a wavelet decomposition, then we can analytically write the profiles of the bending angles and the bending angle derivatives that are needed to calculate occultation light curves. Requiring that the atmosphere is statically stable places limits on the amplitudes of atmospheric waves and their effect on the observed light curve.

Keywords: Computational methods, Stellar occultation, Atmospheric structure
Lithological Controls on Aqueous Phosphorus on Ocean-covered Exoplanets. On Earth, weathering of subaerial continental crust is necessary for the delivery of phosphorus (P)—a critical nutrient for life—to the oceans. However, P inputs, and therefore the potential for nutrient limitation on biological productivity, must be different on terrestrial planets completely covered in oceans. Absent subaerial continents, the sole source of P can only be the submarine weathering of oceanic crust. Because nonvolatile dissolved species in the ocean must ultimately be sourced from reactions between seawater and the seafloor, the chemical composition of the oceanic crust is necessarily a primary control on ocean chemistry. Here we use geochemical modeling to explore the relationship between seafloor lithology and aqueous P availability. We find that the concentration of dissolved inorganic phosphorus (DIP) is coupled to the amount of calcium (Ca) in the submarine weathering system. More specifically, higher Ca decreases the solubility of the calcium phosphate mineral fluorapatite, which decreases DIP upon precipitation. Calcium also affects fluorapatite solubility via the precipitation of Ca-bearing carbonate minerals. For example, a decrease in calcite formation—and consequent increase in fluorapatite formation—leads to lower DIP. Because ocean crust Ca abundance controls aqueous Ca, we demonstrate the importance of considering lithological controls on ocean chemistry when assessing the habitability of ocean-covered planets. Lastly, we make first-order predictions that suggest that the range in metallicity of nearby stars—and the inferred resulting exoplanet compositions—could strongly modulate the potential for these stars to host planets with P-rich oceans.

Keywords: Ocean planets, Hydrosphere, Exoplanets, Planetary mineralogy, Astrobiology, Habitable planets
Surface Properties of Sediments at the 2014─2015 Holuhraun Lava Flow-field: Insights from Multiwavelength Radar. Redistribution of sediments can lead to mantling of geologic features. This can obscure the original texture of lava flows, making it difficult to understand their emplacement conditions based on remote sensing data alone. In situ data acquired in planetary-analog environments can be used with remote sensing data to estimate radar attenuation due to mantling and improve interpretations of planetary data sets. We use remote sensing data of the 2014─2015 Holuhraun lava flow-field in Iceland to quantify how sediment mantling impacts radar returns. Specifically, we (1) examine changes between 2015 and 2022 in Sentinel-1 C-band (5.405 GHz) synthetic aperture radar data due to sediment mantling over the flow-field, (2) use in situ ground-penetrating radar (GPR) measurements to estimate sediment thickness, and (3) incorporate radar modeling work to estimate attenuation for both C- and L-band radar and surface scattering. Our results show that lava mantled by sediment exhibits a reduction in radar backscatter on the order of ∼4 dB from 2015 to 2022 for VH and VV polarizations. Field work in 2022 July using GPR resolved average sediment layer thicknesses of 37─62 cm for two locations along the northern margin of the 2014─2015 Holuhraun lava flow-field. We suggest that damp sediment impedes radar penetration and that radar loss from 2015 to 2022 is due to surface scattering differences between rough lava and a smooth sediment-mantled surface. This highlights the importance of constraining surface dielectric properties for interpretation of future planetary radar data sets and modeling work.

Keywords: Mars, Radar observations, Earth (planet)
Revisiting Electronic and Nuclear Sputtering from Ions at Mercury Using Linear Cascade Theory. This study revisits calculations using linear cascade theory (LCT) to estimate the relative importance of the ion-induced collisional sputtering yield (also referred to as knock-on, nuclear, or kinetic sputtering) and the ion-induced electronic sputtering yield. We focus on sputtering of Na from Mercury's surface using data from the Mercury Surface, Space Environment, Geochemistry and Ranging (MESSENGER) mission. The updated nuclear and electronic sputtering yields for H and He solar wind ions at 1 keV amu−1, respectively, are approximately an order of magnitude larger than the values calculated using LCT in M. A. McGrath et al. Compared to this earlier work, our study uses a factor of 10 larger Na surface fraction and a factor of 3 lower total atom surface density based on MESSENGER data that were not available when the McGrath et al. study was carried out. Additional differences are the use of new data more relevant to Mercury's surface minerals for the nuclear and electronic stopping-power cross sections and the surface binding energies. For the conditions considered in this study, the nuclear sputtering yields calculated using LCT show good agreement with the values calculated using recent binary collision approximation models. We qualitatively compare estimates of the Na sputtering source rate to other source processes for Mercury's exosphere, considering recent studies of the precipitating ion flux based on MESSENGER data. Future experiments that measure the yield and ejecta energy spectra for simulated Mercury surface conditions, along with advanced modeling of ion─surface interactions, are required to reduce uncertainties and support exospheric studies.

Keywords: Space weather, Exosphere, Mercury (planet)
Detection of OH Maser Emission in the 71 yr Periodic Comet 12P/Pons-Brooks Using the 40 m Thai National Radio Telescope. Although the optical cometary database is extensive, the radio database is limited. The 18 cm OH maser observations of comets allow us to determine (i) the production rate of OH (QOH) and (ii) the water expansion velocity, for each comet. To reveal the physical properties of the periodic comet 12P/Pons-Brooks, we conducted the OH maser observations of the comet using the 40 m Thai National Radio Telescope on 2024 March 22, 27, and 29, before the perihelion passage on 2024 April 21. We successfully detected 1665 and 1667 MHz OH maser emissions from the comet. The average OH production rates of 12P/Pons-Brooks were determined as 4.28 ± 0.30 × 1029 s−1, 5.21 ± 0.42 × 1029 s−1, and 3.36 ± 0.43 × 1029 s−1 for March 22, 27, and 29, respectively. Combining our results with previous estimates, we find that the OH production rate of 12P/Pons-Brooks shows some fluctuations on timescales of a few days, but gradually increases on longer timescales as the comet approaches the last perihelion. The water expansion velocities of the comet were determined to be 1.55 ± 0.14, 1.55 ± 0.35, and 2.02 −0.45+0.47  km s−1 for the observations on March 22, 27, and 29, respectively. The reason why the errors are different is because the signal-to-noise ratio is different for each OH maser emission. All expansion velocities are consistent with the individual results of the heuristic law within errors.

Keywords: Radio spectroscopy, Comets, Short period comets, Hydroxyl masers
Seasonal Effects of the Changing Photon Scattering Rates on Mercury's Exospheric Structure. Emission in Mercury's exosphere observed from the ground and by spacecraft is produced by resonant scattering of sunlight. The process of resonant scattering changes the structure of the exosphere owing to the transfer of momentum between the incident photons and the scattering atoms, resulting in a net antisunward-directed force known as radiation pressure. The photon scattering rate (the so-called g-value) and the magnitude of radiation pressure depend strongly on both Mercury's distance from the Sun and the radial velocities of the scattering atoms relative to the Sun. We discuss four effects of the changing g-value over a Mercury year that require a model capable of tracking the positions and speeds of exospheric constituents in order to properly interpret emission data: (1) variations in the escape flux of atoms, (2) variations in the ratio of atoms that escape Mercury in neutral versus ionized form, (3) difficulties in determining where material was ejected from the surface based on the locations of the emitting atoms in the exosphere, and (4) systematic uncertainties in interpreting the column density of emitting gas using a constant g-value versus a variable g-value that takes into account the radial motion of the atoms relative to the Sun.

Keywords: Astronomy data modeling, Exosphere, Solar-planetary interactions, Planetary atmospheres, Mercury (planet)