Sazuna/UAT_keywords huggingface dataset:
Structure and Melting of Fe, MgO, SiO<SUB>2</SUB>, and MgSiO<SUB>3</SUB> in Planets: Database, Inversion, and Phase Diagram. We present globally inverted pressure─temperature (P─T) phase diagrams up to 5000 GPa for four fundamental planetary materials, Fe, MgO, SiO2, and MgSiO3, derived from logistic regression and supervised learning, together with an experimental phase equilibrium database. These new P─T phase diagrams provide a solution to long-standing disputes about their melting curves. Their implications extend to the melting and freezing of rocky materials in the interior of giant planets and super-Earth exoplanets, contributing to the refinement of their internal structure models.

Keywords: Exoplanets, Planetary mineralogy, Planetary structure, Solar system planets
Plume Particle Ejecta Can Trace Habitat-forming Gradients in Ocean Worlds: Insights from Planet Earth Geochemistry. Upcoming explorations for habitability in the ocean worlds of the solar system can greatly benefit from searching beyond parameters such as water, organics, nitrogen, phosphate, and silicate and being able to detect signs of metal catalysis. As metabolism needs metal clusters and nanoparticles, detecting them, disentangling how they form, and linking them to the functioning of Earth's analog habitats can help us explore the life-supporting processes in ocean worlds like Europa and Enceladus. Here, we present theoretical insights on how nanoparticles in general, and metal-bearing nanoparticles in particular, with their known mechanisms of formation across pH, temperature, and redox gradients and their superior stability and transportability, can serve as a habitability tracer. We outline an interdisciplinary oceanography-planetary science approach based on a case study of Earth analogs of pelagic and deep-sea hydrothermal redox gradients, as this is where the multi-element signatures of suspended marine nanoparticles began to emerge. This approach, incorporating new data sets from multiple sites under different gradients, will enable the linking of such "biogeosignatures" to their representative habitats. This interdisciplinary direction will enhance the interpretations of elemental compositions of ocean world plume ejecta, anticipated to emerge from current space missions like Europa Clipper and JUICE.

Keywords: Ocean planets, Astrobiology, Biosignatures, Habitable planets, Pre-biotic astrochemistry
Prospectivity Modeling of the NASA VIPER Landing Site at Mons Mouton near the Lunar South Pole. We use a high-resolution digital elevation model and a numerical thermal model to produce a variety of inputs for a water-ice prospectivity model for the Volatiles Investigating Polar Exploration Rover (VIPER) landing site. These input data are maps of topography, surface slope, surface aspect, surface curvature, maximum temperature, depth to ice stability, permanently shadowed regions (PSRs), distance to PSRs, and PSR density. This model predicts where water ice is most likely within the top meter of regolith, assuming plausible relationships between ice concentration and the various inputs. The model is designed to be adjusted in near-real time as data are collected during the VIPER mission. As such, it is a tool for both analyzing data from the mission as well as planning operations. Since the current model, at this point, relies only on orbital remote sensing, the final version will also be a tool to extrapolate the VIPER mission results across the lunar poles.

Keywords: Astrostatistics tools, Astronomy data modeling, Planetary polar regions, Astrostatistics techniques, The Moon, Astrostatistics, Lunar science, Lunar surface, Rovers, Comet volatiles , Craters
A Direct Simulation Monte Carlo–Driven Photochemical Model of Callisto's Ionosphere. Here we present a photochemical model of Callisto's ionosphere with inputs supplied by a direct simulation Monte Carlo model of its neutral atmosphere. We compare a model that considers interactions with photons as the sole external ionization mechanism to models also including magnetospheric electron impacts, where upstream electron densities and temperatures are varied over an order of magnitude to constrain the role that the highly variable electron population near Callisto has on the underlying ionospheric structure. Depending on the implemented upstream electron density, magnetospheric electron impacts dominate the production of Callisto's ionosphere or induce reactions at rates comparable to or less than those from solar photons. Furthermore, depending on the implemented upstream electron temperature, electron impacts either preferentially dissociate or ionize molecules. We show that ionization of an O2 component with a surface number density of 109 cm‑3, which is consistent with recent remote observations and models, is capable of producing the electron densities detected during Galileo radio occultations, from which an O2 surface density of ∼1010 cm‑3 was initially inferred. The modeled total plasma densities are also compared to those inferred from Galileo plasma-wave measurements and yield a reasonable agreement up to ∼1000 km, presenting the first model capable of simultaneously producing both Galileo radio occultations and plasma-wave observations. Finally, the implications of this work are discussed, highlighting several leads that need to be explored going forward to better constrain Callisto's atmosphere, ionosphere, and local plasma environment in anticipation of the eventual Jupiter Icy Moons Explorer observations.

Keywords: Planetary ionospheres, Photoionization, Callisto, Exosphere, Planetary atmospheres, Natural satellite atmospheres, Planetary science, Ionization, Electron impact ionization, Galilean satellites, Planetary magnetospheres, Jovian satellites
Improved Carbon and Nitrogen Isotopic Ratios for CH<SUB>3</SUB>CN in Titan's Atmosphere Using ALMA. Titan, Saturn's largest satellite, maintains an atmosphere composed primarily of nitrogen (N2) and methane (CH4) that leads to complex organic chemistry. Some of the nitriles (CN-bearing organics) on Titan are known to have substantially enhanced 15N abundances compared to Earth and Titan's dominant nitrogen (N2) reservoir. The 14N/15N isotopic ratio in Titan's nitriles can provide better constraints on the synthesis of nitrogen-bearing organics in planetary atmospheres as well as insights into the origin of Titan's large nitrogen abundance. Using high signal-to-noise ratio (&gt;13), disk-integrated observations obtained with the Atacama Large Millimeter/submillimeter Array Band 6 receiver (211─275 GHz), we measure the 14N/15N and 12C/13C isotopic ratios of acetonitrile (CH3CN) in Titan's stratosphere. Using the NEMESIS, we derived the CH3CN/13CH3CN ratio to be 89.2 ± 7.0 and the CH3CN/CH313CN ratio to be 91.2 ± 6.0, in agreement with the 12C/13C ratio in Titan's methane and other solar system species. We found the 14N/15N isotopic ratio to be 68.9 ± 4.2, consistent with previously derived values for HCN and HC3N, confirming an enhanced 15N abundance in Titan's nitriles compared with the bulk atmospheric N2 value of 14N/15N = 168, in agreement with chemical models incorporating isotope-selective photodissociation of N2 at high altitudes.

Keywords: Submillimeter astronomy, Remote sensing, Radio interferometry, Titan
Planetesimal Impact Vapor Plumes and Nebular Shocks Form Chondritic Mixtures. The origin of chondrules and the chondritic sedimentary rocks that dominate the meteoritic record is a long-standing problem in planetary science. Here, we develop a physical model for the formation of chondritic mixtures as an outcome of vaporizing collisions between planetesimals that were dynamically excited by the growth and migration of planets. We present calculations of nebular shock waves generated by impact vapor plumes and focus on aspects of the plume interaction with the nebular gas and dust that have been neglected in previous studies of impact ejecta. We find that when water dominates the vapor, the plumes are relatively cool. However, the plume expansion is supersonic and can drive strong shock waves in the dusty nebular gas. Portions of these nebular shock fronts initially melt nebular dust, forming chondrules that are coupled to the moving front. As the shock front expands and cools, the chondrules solidify, while the shock front entrains additional dust. Eventually, the plume expansion stalls and then hydrodynamically collapses, turbulently mixing variably processed dust and size-sorted chondrules. For probable impact parameters and nebular conditions during giant planet growth and migration, the impact-generated mixtures have characteristics that span the range observed in chondritic meteorites, providing an environment for rapid formation of chondritic assemblages after chondrule formation. Our impact vapor and nebular shocks model, named the IVANS model, links chondrule formation to the overall context of planet formation and provides a framework for interpreting the detailed chronological and geochemical record contained in chondritic meteorites.

Keywords: Impact phenomena, Chondrites, Chondrules, Planetesimals, Planetary migration, Shocks
Wind Shear and the Role of Eddy Vapor Transport in Driving Water Convection on Jupiter. Recent observations of convection in the Jovian atmosphere have demonstrated that convection is strongly concentrated at specific locations on the planet. For instance, observations of lightning show that the cyclonic features (e.g., belts and folded filamentary regions) show increased convective activity compared to anticyclonic regions. Meanwhile, the distribution of ammonia and water vapor shows a large enrichment near the equator, which is also suggestive of strong upwelling and convective activity. Marrying these different observations is challenging owing to a lack of data concerning the characteristics of the deep Jovian atmosphere and a resulting inability to observe the true deep source of the various convective phenomena. To understand the nature of these convective events and the role of the structure of the deep atmosphere in driving convective events, we run simulations of cloud formation and convection using the Explicit Planetary hybrid-Isentropic Coordinate General Circulation Model. We vary the dynamics of the atmosphere by parameterizing the deep wind shear and studying the resulting effect on the strength, frequency, and distribution of convective storms. We find that convection in our model is strongly tied to the local dynamics and the deep wind shear. We further decompose the generation of convective available potential energy into three components (thermal, mechanical, and moist/chemical) and find that the chemical mechanism is the strongest component, working to advect water vapor from moisture-rich regions to moisture-poor regions and to drive convection along a "moisture front."

Keywords: Water vapor, Atmospheric clouds, Solar system gas giant planets, Jupiter, Atmospheric dynamics
An Analytical Model of Wavelength-dependent Opposition Surge in Emittance and Reflectance Spectroscopy of Airless Rocky Exoplanets. Theoretical frameworks for reflection and emission spectroscopy of exoplanet surfaces are becoming increasingly important for the characterization of rocky exoplanets, especially with the rapid growth of the detected exoplanet population and observational capabilities. The Hapke theory of reflectance and emittance spectroscopy has been widely adopted in the exoplanet community, yet a key physical effect—the opposition surge enhancement at small phase angles—remains largely neglected. This phenomenon, driven by shadow hiding and coherent backscattering, introduces a significant brightening that depends on wavelength, particle size, and surface morphology. In this paper, I propose an alternative formulation for opposition surge modeling, ensuring a smooth-to-sharp transition at small phase angles, dictated by wavelength-dependent scattering properties. I evaluate the impact of opposition surge on phase curves and surface spectra, comparing a family of models with increasing simplifications, ranging from a full wavelength-dependent opposition effect to its complete omission. My results indicate that neglecting opposition effects can introduce systematic deviations in retrieved albedos, spectral features, and phase curves, with errors reaching up to 20%–30% in certain spectral bands. Upcoming JWST observations will probe phase angles below ∼10° for rocky exoplanets around M dwarfs; thus, accounting for opposition effects is crucial for accurate surface characterization. Proper treatment of this effect will lead to improved retrievals of surface albedo, mineralogical composition, and roughness properties. This study establishes a physically consistent framework for exoplanet phase-curve modeling and provides a foundation for future retrieval algorithms aimed at interpreting exoplanet surfaces.

Keywords: Extrasolar rocky planets, Radiative transfer, Spectroscopy
Continental Orientation and the Climate of Land-dominated, Arid Planets. The climate and habitability of exoplanets are particularly difficult to constrain due to a lack of planetary information (e.g., obliquity and rotation rate) alongside current observational limitations. Surface water content is one of the most highly sought variables given its connections to the origins of life on Earth. Unfortunately, surface water is impossible to constrain due to uncertainties in (i) water content observations and (ii) surface–mantle water differentiation. Global ocean scenarios are prevalent in the literature, but it is vital to investigate the alternative arid scenarios with varied continental orientations and surface water abundances. Here, we use an ensemble of ROCKE-3D global climate model simulations to investigate the potential habitability of single-continent, land-dominated planets. This ensemble simulates climate over a range of water surface areas (WSAs; global ocean coverage) and continental orientations (pole- and equator-centered continents). We find that pole-centered orientations are 2°C–5°C warmer than equator-centered orientations across most WSAs due to the lack of highlands in the northern pole preventing snow and ice accumulation. These differences between continental orientations are completely diminished under the most arid scenarios. This is due to water limitation that results in a breakdown of the ice-albedo feedback, causing warming. Our results show that both WSA and continental orientation play roles in the global mean surface temperature of exoplanets. Future direct imaging missions, such as the Habitable Worlds Observatory, will play a crucial role in constraining the climate of exoplanets due to their ability to assess surface water and land dichotomies.

Keywords: Planetary atmospheres, Habitable planets, Exoplanet surface composition
Architecture and Field Operation of a Portable Digital Holographic Microscope for In Situ Measurements of Bacterial Motility. The development of a next-generation, portable, digital holographic microscope enables the real-time volumetric characterization of bacterial behavior in extreme environments. This microscope is designed to observe bacteria in their native habitats, minimizing the experimental bias introduced by the extraction of samples for laboratory studies. The instrument, which operates at a wavelength of 405 nm and offers a spatial resolution of 1 μm, is fully self-contained with onboard computing and power, allowing hours of uninterrupted operation in the field. This digital holographic microscope is 180 mm × 300 mm × 135 mm and is less than 16 pounds, allowing easy transport to brine pools at the field sites described in this investigation. The instrument was field tested at the Boulby Underground Research Laboratory in the UK, where bacterial motility was observed and characterized in brine pockets undisturbed by human contamination. The holographic architecture of the microscope captures volumetric data at a video rate without moving parts, providing a stable long-term platform for field operation. This technology, identical to the proposed design for spaceflight instruments, will aid in the search for life on icy moons by improving our understanding of bacterial behavior in extreme conditions. Future developments of this platform will focus on refining data reduction algorithms and operational methodologies for Earth-based and space-based applications.

Keywords: Interdisciplinary astronomy, Biosignatures, Holographic interferometry, Direct imaging
A Catalytic Pathway for the Formation of Cyanobenzene in Nitrogen-rich Environments and the Spectroscopy of the Reactive Intermediates. The catalytic reaction of isocyanobenzene (C6H5NC) with NCN‑ produces cyanobenzene (C6H5CN) through various highly stable reactive intermediate species. Nitrogen-rich environments such as Titan's atmosphere serve as favorable locations to study reaction pathways involving nitrogenated species contributing to organic growth. Formation pathways of cyanobenzene have been characterized, but none with the contribution of anions or phenyl groups. In regions with a high abundance of nitrogen anions, such as Titan's atmosphere, reactions with species such as NCN‑ may play a role in the formation of cyanobenzene. Highly accurate computational methods are used to compute the rotational and vibrational spectroscopic properties of five thermodynamically stable reactive intermediate anions. Further, immense permanent dipole moments (∼10 D) make these five intermediates, and INT1 (phenyl–NCNCN‑) in particular, highly detectable with radio astronomy, and searches with facilities such as the Atacama Large Millimeter/submillimeter Array and the Green Bank Telescope may lead to their discovery. Four of the reactive intermediates possess intense CN stretching transitions in the 2100–2200 cm‑1 region that may produce a uniquely identifiable signal in high spatial and spectral resolution JWST spectra. Based on these reaction pathways, a future nondetection of isocyanobenzene in the atmosphere of Titan may point to cyanobenzene as a possible reservoir for this isomeric family of molecules.

Keywords: Infrared spectroscopy, Rotational spectroscopy, Molecular spectroscopy, Titan, Planetary atmospheres, Astrochemistry
Seasonal Evolution of Titan's Stratospheric Tilt and Temperature Field at High Resolution from Cassini/CIRS. The Cassini spacecraft observed Titan from 2004 to 2017, capturing key atmospheric features, including the tilt of the middle atmosphere and the formation and breakup of winter polar vortices. We analyze low spectral resolution infrared observations from Cassini's Composite Infrared Spectrometer (CIRS), which provide excellent spatial and temporal coverage and the best horizontal spatial resolution of any of the CIRS observations. With approximately 4 times higher meridional resolution than previous studies, we map the stratospheric temperature for almost half a Titan year. We determine the evolution of Titan's stratospheric tilt, finding that it is most constant in the inertial frame, directed 120° ± 6° west of the Titan–Sun vector at the northern spring equinox, with seasonal oscillations in the tilt magnitude between around 2 .° 5 and 8°. Using the high meridional resolution temperature field, we reveal finer details in the zonal wind and potential vorticity. In addition to the strong winter zonal jet, a weaker zonal jet in Titan's summer hemisphere is observed, and there is a suggestion that the main winter hemisphere jet briefly splits into two. We also present the strongest evidence yet that Titan's polar vortex is annular for part of its life cycle.

Keywords: Planetary atmospheres, Titan, Radiative transfer, Infrared spectroscopy
Multiwavelength JWST Observations of (3200) Phaethon Show a Dehydrated Object with an Aqueously Altered Origin. We present JWST observations of the near-Earth asteroid (3200) Phaethon using NIRCam, NIRSpec, and MIRI to further investigate the composition of Phaethon's surface. Our NIRSpec data confirms that Phaethon's surface is dehydrated, showing no evidence of hydrated minerals in the 3 μm region. We estimate an upper limit on the hydrogen content in phyllosilicates of 0.06 wt%. Comparisons with laboratory spectra of carbonaceous chondrites suggest that Phaethon's surface composition is best matched by thermally metamorphosed samples of the CM chondrite Murchison (heated to 1000 °C), rather than CY meteorites as previous work suggested. We find no evidence of ongoing surface evolution due to recent perihelion passages. A comparison of the mid-infrared spectra of Phaethon and Bennu shows distinct spectral differences that are consistent with their different thermal histories. Our findings further refine our understanding of Phaethon's current surface composition and evolution and provide additional insights for the upcoming DESTINY+ mission.

Keywords: Near-Earth objects, Asteroids, Infrared spectroscopy, James Webb Space Telescope, Spectroscopy
Effects of the 2018 Martian Global Dust Storm on Boundary Positions in the Induced Magnetosphere. Global dust storms at Mars have a significant impact on the atmosphere and ionosphere, but only recently has their impact on the magnetosphere been investigated. The 2018 global dust storm at Mars was the first global event following the arrival of the Mars Atmosphere and Volatile EvolutioN mission at Mars, providing additional data to that of Mars Express observing how plasma boundaries (the bow shock and induced magnetospheric boundary (IMB)) varied over the storm duration. Applying 2D boundary models to spacecraft crossings, we find that the variability of both boundaries increases due to the storm onset and continues after surface conditions have returned to normal. While the bow shock shows no influence from the crustal magnetic fields in the southern hemisphere of Mars, the IMB dips here, the opposite of its normal bulging behavior. This is consistent with the signature found during the 2007 global dust storm. We suggest this signature is due to a decrease in ionospheric pressure in this area from the transport of ionized particles down crustal magnetic field lines toward the surface of Mars.

Keywords: Planetary magnetospheres, Mars
Origin of Phobos and Deimos: Orbital Evolution Shortly after Formation from a Potential Dislocation. This paper deals with the formation and evolution of Mars' moons, Phobos and Deimos, assuming the dislocation of a larger progenitor as the origin of these moons. The study by R. Hyodo et al. argues that under somewhat simplistic modeling, the postdislocation orbits of Phobos and Deimos inevitably collide within 10,000 yr, leading to their mutual annihilation. These findings are based on  N -body simulations, accounting for Mars' J2 and J4 gravitational perturbations and mutual perturbations between the moons. In this paper, we challenge these findings by extending their work. We incorporate important perturbations such as solar perturbations, Mars' axial precession and nutation, and its deformation along three axes. We also extend some of the hypotheses made by R. Hyodo et al. concerning the initial distribution of Phobos and Deimos after the dislocation. Our analysis reveals that including these additional perturbations, as well as the possibility of having more than two fragments after the dislocation, does not alter the ultimate fate of Phobos and Deimos. The moons still converge towards collision within comparable timescales, supporting R. Hyodo et al.'s conclusions that the dislocation hypothesis under the dynamical scenario developed by A. Bagheri et al. has, in the best conditions, about a 10% chance of surviving after the first 100,000 yr following their formation.

Keywords: Martian satellites, Natural satellite formation, Planetary system formation, Celestial mechanics, N-body simulations