Sazuna/UAT_keywords huggingface dataset:
Evolution of Mercury's Volatile-bearing Crust within Raditladi Basin. Mercury's surface presents significant challenges for understanding planetary volatile distribution. Previous studies have identified features including hollows, flows, and chaotic terrains as associated with the presence of volatiles. Their formation and connection to Mercury's volatile inventory remain incompletely characterized. Using Hapke's radiative transfer model, we conducted detailed photometric analyses of three distinct regions within Mercury's Raditladi basin that display hollows and flow-like morphologies to quantify regolith properties and their relationship to volatile-driven processes, revealing three key findings. (1) The basin floor regolith exhibits distinct structural characteristics indicating a separate evolutionary pathway. (2) Hollows and surrounding halos demonstrate regolith properties (higher porosity, finer-grained) consistent with slow, low-energy sublimation processes that minimally disrupt intergrain relationships. (3) Areas within the peak ring display photometric signatures indicative of volatile-rich mass wasting flows. The hollows and halos exhibit significantly higher single-scattering albedos compared to other units, suggesting the presence of a unique residual material that remains after volatile sublimation that appears intimately mixed with common regolith components. Previously mapped flow-like features share regolith structural similarities with hollows supporting their derivation from a common volatile-rich layer (VRL). Regions along peak walls display distinctive photometric properties that likely represent remnants of VRL flow sources within the peak ring structure, suggesting that peak rings maintained their volatile composition throughout the flow process. The excavation of hollow-like regolith from impacts on the basin floor suggests either differentiation of the impact melt or burial of volatiles outgassed from the peak ring, deposited on the basin floor, and later buried.

Keywords: Mercury (planet)
Regionalized Formation and Recycling of New Venusian Crust at Chasmata. Venus and Earth are geologically active in ways distinct from each other. Earth exhibits plate tectonics, where the primary resurfacing mechanism is crust formation along a globe-girdling, extensional tectonic setting in mafic crust, the mid-ocean ridge (MOR). While Venus does not exhibit the key characteristics of plate tectonics, it also possesses a globe-girdling, extensional tectonic setting in mafic crust referred to here as the global rift network (GRN). Despite the macroscale similarities, the two rift systems feature disparate characteristics. Using numerical modeling compared against topographic models from Magellan, we test whether seafloor-spreading-like tectonics under Venusian conditions can reproduce the morphology of individual chasmata along the GRN. The results indicate that the MOR-like seafloor spreading does not occur along most of the GRN, only in unique tectonic environments like that within Artemis Corona. On the other hand, we find that rift-embedded coronae along the GRN have morphologies best explained by excess crustal formation and subsequent densification leading to lithospheric delamination like ephemeral subduction postulated for coronae in previous studies. This suggests that secondary hot spots form between the major plumes under Beta, Atla, Themis, and Phoebe Regios. These minor plumes follow the flow of the upwelling mantle to initiate the formation of rift-embedded coronae along the GRN before becoming inactive when the hot spot dies. Such regionalized formation and recycling of the crust under the influence of mantle plumes is consistent with active geodynamics with limited plate mobility, such as predicted by plutonic-squishy lid, deformable lid, and globally fragmented lid tectonic hypotheses.

Keywords: Venus, Lithosphere, Planetary geology, Plate tectonics, Tectonics, Volcanism
Holistic Mapping of the Present-day Martian Seasonal CO<SUB>2</SUB> Frost. I. Frost Detection within Global Visible, Thermal, and Spectral Data Sets. A dominant driver of Martian atmospheric, landscape, and landform activity is the annual cycle of CO2 and water, seasonally moving between atmospheric gases and surface frost. Orbital data set-based maps of the distribution of seasonal frost provide a broad look at how these volatiles move through time and space, as documented in past analyses. These past works typically take the form of a global study using a single, coarse-resolution, global data set or a spatially targeted site study combining data from multiple instruments. However, there does not yet exist a global map incorporating data sets from both the kilometer-resolution maps of the contiguous seasonal cap with landform-scale (about 10 m to hundreds of meters) patches of frost. Therefore, we produce a comprehensive, global map of the seasonal distribution of CO2 frost through a single Mars year, integrating the information contained in visible (HiRISE/Context Camera), thermal (Mars Climate Sounder/THEMIS), and spectral (CRISM) data sets so as to generate 2.4 billion frost probability estimates. Combining global instrument data across diverse spectral, spatial, and temporal regimes required the rigorous application of multiple data science methods and a multidisciplinary collaboration between data scientists and planetary scientists. We produce two papers: this first focuses on the analysis of the individual data sets, highlighting key data science techniques and metrics used to capture the underpinning physical science intuition within robust and efficient autonomous "frost detection" methods. We generate, for each data set, 36 frost probability maps showing the distribution of surface CO2 frost through a Mars year, with a temporal resolution of 10° Ls and a spatial resolution of 64 points-per-degree.

Keywords: Polar caps, Surface ices, Atmospheric dynamics, Planetary polar regions
Parameter Space Exploration of Low-to-moderate-temperature Hydrothermal Systems on Ocean Worlds Using a Monte Carlo Framework. We explore the hydrogeologic and physical conditions necessary to sustain hydrothermal activity within the shallow subseafloors of ocean worlds, exploring wide ranges of multiple parameters using a Monte Carlo framework. We apply multiple analytical calculations to represent coupled fluid-thermal flow systems, as have been observed on Earth, using idealized representations that link lateral transport below a conductive boundary layer between sites of hydrothermal inflow (recharge) and outflow (discharge). These analytical calculations replicate outcomes and trends in results generated from more complex numerical simulations once we account for excess driving pressure that is consumed by secondary (local) convection during transport within the subseafloor. We investigate low heat flux scenarios that are expected to be limiting cases for sustaining hydrothermal flows (≤10 mW m‑2) for which there is modest heating from radiometric decay and/or tidal dissipation within the interior of an ocean world. We explore limiting conditions appropriate for Europa's deep subseafloor, and a subset of sustainable hydrothermal siphon calculations are identified that are especially efficient for mining interior heat. We identify parameters that can sustain a hydrothermal siphon for reaction temperatures of 80°C–120°C and water/rock mass ratios of ≤100 Gy–1. These conditions should result in discharging fluids that are altered relative to inflowing water and a silicate interior that is more likely to retain the potential for geochemical reactions over geologic time. These conditions are of particular interest because they could help create habitable conditions below or at the seafloor of an ocean world and can provide a foundation for linked reaction modeling.

Keywords: Ocean planets, Hydrosphere, Enceladus, Europa, Planetary science
The Surfaces of Small to Midsize Plutinos: Evidence of an Association between Inclination and Surface Type. Being one of the most populated mean motion resonances (MMRs) with Neptune and lying close to the inner boundary of the present-day cold classical disk, observations of the orbital and surface class distributions of the plutinos in the 3:2 MMR provide constraints on Neptune's migration and insight into the compositional structure of the premigration planetesimal disk. Here, we present observations of the surface reflectance of 43 small to midsize (HV ≳ 5) trans-Neptunian objects (TNOs) through the grz wavelength range, 14 of which are plutinos. We classify the surfaces of these TNOs using the two-surface class model (FaintIR and BrightIR surface classes) proposed by Fraser and collaborators, where the FaintIR surface class is dominated by cold classicals. Incorporating similar observations of plutinos from the literature for a total sample size of 43 plutinos, we find that the osculating inclination distributions (iosc) of the FaintIR and BrightIR plutinos are statistically distinguishable at 99.3% significance, where six out of seven of the plutinos with iosc &lt; 4 .° 5 have FaintIR surfaces. This is most easily explained if the FaintIR and BrightIR planetesimals were radially partitioned in the primordial planetesimal disk before being captured into the 3:2 resonance. While this could be evidence that the primordial cold classical disk with FaintIR surfaces was broader in the past by ∼3 au in the sunward direction, we cannot rule out the alternative explanation that these FaintIR plutinos were scattered from the ∼42.5–48 au region from the Sun and captured into the 3:2 resonance.

Keywords: Planetesimals, Resonant Kuiper belt objects, Kuiper belt, Trans-Neptunian objects
Impacts of Atmospheric Carbon Species and Stellar Type on Climates of Terrestrial Planets. The climates of terrestrial planets are largely determined by the composition of their atmospheres and the spectral types of their host stars. Previous studies suggest that a wide range of carbon species abundances (CO2, CO, and CH4) can result from variations in reducing fluxes and stellar spectral types that influence photochemistry. However, a systematic investigation of how varying carbon species, particularly CO, affect planetary climates across wide parameter spaces remains limited. Here, we employ a 1D radiative–convective equilibrium model to examine the dependence of planetary climate on the abundances of carbon species and host star type. We find that CO, due to weak absorption of stellar radiation, induces only moderate changes in stratospheric temperature, while its effect on surface temperature is negligible. Under Earth-like  pN2  (where pi is the partial pressure on the surface of species i), for cases with fixed  pCO2 , an increase in CO leads to surface cooling on planets orbiting Sun-like stars unless the sum of  pCO2  and  pCH4  exceeds ∼1 bar, whereas it results in surface warming for planets around M-type stars. When the total pressure of carbon species is fixed, converting CO2 or CH4 into CO always induces cooling. These effects arise from a combination of CO Rayleigh scattering, pressure broadening of greenhouse gas absorption lines, and varying water vapor levels. We further discuss how CO- and CH4-driven cooling (warming) can trigger positive (negative) climate-photochemistry feedback, influencing atmospheric evolution. Additionally, we suggest that CO-rich planets may be less susceptible to water loss and atmospheric oxidation due to lower stratospheric water vapor content.

Keywords: Atmospheric evolution, Planetary atmospheres, Planetary science, Planetary climates, Exoplanet atmospheres
Prospects of a New L<SUB>5</SUB> Trojan Flyby Target for the Lucy Mission. NASA's Lucy spacecraft is en route to conduct the first close encounter with Jupiter's Trojans. While most scheduled flybys lie in the L4 cloud, the only L5 target is the Patroclus–Menoetius binary. Since each flyby offers unique insights into target and population properties unattainable from Earth, we examine the feasibility of including an additional, yet unknown, L5 target while minimizing the impact on Lucy's primary mission. We use the background L5 Trojans brighter than the completeness limit to model their absolute magnitude, spatial, and orbital distributions. A semianalytical approach estimates the number of Trojans accessible to Lucy for a given Δv budget in both pre- and post-Patroclus scenarios. Our results indicate that, while it is unlikely that any suitable Trojan lies on Lucy's nominal path, a moderate Δv investment (35–50 m s‑1) could enable a subkilometer (500–700 m) flyby prior to the Patroclus encounter. Post-Patroclus, the likelihood of a similar flyby is ∼60% for Δv ∼ 50 m s‑1. Simulations with synthetic Trojans reveal that potential targets cluster near the node opposite the encounter window, producing an optimal search period in late 2026 for both scenarios. Surveying the densest 10% of this region would require under 5 nights with the Subaru Hyper Suprime-Cam or under 2 nights with Rubin, using shift-and-stack techniques. A successful subkilometric flyby would expand Lucy's Trojan target size range and provide new constraints on collisional evolution and the long-standing asymmetry in the L4/L5 clouds. This nodal-clustering strategy could guide target searches in future Lucy extensions or other planetary flyby missions.

Keywords: Orbits, Flyby missions, Sky surveys, Jupiter trojans
The Visibility of the Ōtautahi–Oxford Interstellar Object Population Model in LSST. With a new probabilistic technique for sampling interstellar object (ISO) orbits with high efficiency, we assess the observability of ISOs under a realistic cadence for the upcoming Vera C. Rubin Observatory's Legacy Survey of Space and Time (LSST). Using the Ōtautahi–Oxford population model, we show that there will be complex on-sky structure in the pattern of direction and velocity revealed by the detected ISO population, with the expected enhanced northern flux complicating efforts to derive population parameters from the LSST's predominately southern footprint. For reasonable luminosity functions with slopes of 2.5 ≤ qs ≤ 4.0, the most discoverable ISOs have Hr ≃ 14.6‑20.7. The slope of the luminosity function of ISOs will be relatively quickly constrained by the characteristics of the LSST detected population, such as the distributions of perihelia, velocity at infinity, and discovery circumstances. Discoveries are evenly split around their perihelion passage and are biased to lower velocities. After their discovery by LSST, it will be rare for ISOs to be visible for less than a month; most will have mr ≤ 23 for months, and the window for spectroscopic characterization could be as long as 2 yr. While these probabilistic assessments are robust against model or spatial density refinements that change the absolute numbers of ISO discoveries, our simulations predict a yield of 6–51 asteroidal ISOs, which is similar to previous works and demonstrates the validity of our new methods.

Keywords: Interdisciplinary astronomy, Small Solar System bodies, Interstellar objects
Survivability of Amino Acids in Lunar Soil. We present a laboratory investigation on the survivability of amino acids in lunar simulant soil under conditions similar to the lunar surface. Survival rates of various amino acids are quantified using ultra-high-performance liquid chromatography in conjunction with AccQ·Tag derivitization and fluorescence detection. Results show that vacuum and hydrogen gas exposure have relatively minor effects on amino acid survivability compared to hydrogen plasma and ultraviolet radiation. After the equivalent of 20 yr of irradiation at the Moon, a small amount (∼4%–7%) of amino acids continues to survive in the soil. This study also highlights the importance of shielding by lunar dust: amino acids buried as little as 8 mm below the surface have a ≳95% survival rate after 2.5 yr of equivalent radiation.

Keywords: Space plasmas, Lunar regolith, The Moon, Solar radiation, Complex organic molecules
Absorption Coefficients of Condensed O<SUB>2</SUB>: Application to Ganymede. Two absorption features in the visible reflectance spectra of the icy Galilean satellites are associated with dense phase molecular oxygen (O2). These were identified from ground-based and Hubble Space Telescope data on Ganymede, Europa, and Callisto. Molecular oxygen is the radiolytic product of energetic particle bombardment and breakdown of water ice. The oxygen features are strongest near the equator on the trailing hemisphere of Ganymede. We review previous laboratory measurements of high-pressure gas, liquid, and solid phases of O2, noting differences that arise with increased density and phase changes. We measure transmission spectra of condensed liquid and solid-γ phase O2 from 455 to 5000 nm (22,000─2000 cm−1) using a Fourier transform infrared spectrometer at 1 cm−1 spectral resolution. This spectral range includes the strongest visible and near-infrared absorption features. The measured absorption is dependent on both phase and temperature increasing with colder temperatures and in the solid form. We use these data to determine the absorption coefficients of the liquid and solid phases. These are then compared with absorption by water ice, the dominant constituent of Ganymede's surface. O2 has an absorption coefficient that is ∼2 orders of magnitude stronger than water ice in the visible. Using simple reflectance models we estimate that a fractional abundance of 4%─5% over the path length in the surface is needed to create the observed visible absorptions, and this fraction does not contribute noticeable features in the infrared.

Keywords: Ice spectroscopy, Surface composition, Ganymede, Radiation interactions (Ice)
Topographic Relaxation of Complex Impact Craters in a Clathrate Crust on Titan. Titan's impact craters are significantly shallower than fresh craters on Ganymede, which are often used as templates for fresh craters on Titan. The presence of a clathrate crust on Titan, which would insulate the ice shell and maintain warmer ice near the surface, may contribute to the shallowness of its craters. Research into the effects of a clathrate crust on the topographic relaxation of craters found that a 5–10 km thick clathrate crust may explain their shallowness. That previous study simulated simple, bowl-shaped craters with Ganymede-derived depths. However, if craters are initially like Ganymede's, they will exhibit complex rather than simple morphologies. Therefore, we model the relaxation of more realistic shapes incorporating short-wavelength features (central peaks, pits, and pit-rims), floor widths, and rimwall slopes derived from Ganymede's fresh complex craters. We simulate topographic relaxation of craters 40–100 km in diameter in ice shells with 5–20 km thick clathrate crusts. We find that most crater depths can be reproduced in 5–15 km thick clathrate crusts. Notably, simulated short-wavelength central features remain or grow during relaxation. Evidence of central features is rare, suggesting that additional processes modify Titan's craters. To fill the remaining flexural moats, 300–1000 m of infill is required, while 200–400 m may need to erode from elevated central features to flatten the relief. We conclude that topographic relaxation may be partially responsible for the shallowness and that erosion and infill are responsible for the dearth of central features in Titan's craters.

Keywords: Impact phenomena, Methane, Titan, Surface ices, Planetary science, Planetary interior, Saturnian satellites, Craters
The Role of Tectonic Luck in Long-term Habitability of Abiotic Earth-like Planets. Carbonate-silicate weathering feedback is thought to stabilize Earth's climate on geologic timescales. If climate warms, faster mineral dissolution and increased rainfall speed up weathering, increasing CO2 drawdown and opposing the initial warming. Limits to where this feedback might operate on terrestrial exoplanets with N2–O2–CO2–H2O atmospheres are used to define the "habitable zone"—the range of orbits around a star where liquid water can be stable on a planet's surface. However, the impacts on long-term habitability of randomly varying volcanic outgassing, tectonic collisions, and tectonic parameters (e.g., number of continental plates, size of plates, plate velocity) remain poorly understood. In this work, we present an idealized and broadly applicable quasi-2D model of the long-term climate stability of abiotic Earth twins. The model tracks atmospheric CO2 as "disks" collide, promoting uplift and supplying new weatherable minerals through erosion. Without resupply, soils become less weatherable and the feedback's strength wanes, making a planet susceptible to catastrophic warming events or hard snowballs where the surface becomes frozen over. We find that tectonic uplift spurred by continental collisions cannot be the sole supplier of weatherable minerals within our model framework, as such climates either become uninhabitably hot (for complex life) as soils become leached of weatherable minerals or experience extreme swings in temperature over short timescales. This conclusion is strengthened when taking into account the destabilizing effects of outgassing variability and increasing stellar luminosity. In addition to frequent collisions, other resupply mechanisms for weatherable minerals, such as wind-driven dust transport, glacial erosion, and/or seafloor weathering, are likely required for long-term stability on Earth-like terrestrial exoplanets.

Keywords: Atmospheric evolution, Earth atmosphere, Ocean-atmosphere interactions, Planetary atmospheres, Planetary climates, Habitable planets, Land-atmosphere interactions, Exoplanet atmospheric evolution
Solar Wind Sputtering of Secondary Ions from Water-ice-covered Regolith Analogs. The surfaces of airless bodies in space are constantly bombarded by solar wind and magnetospheric ions that sputter regolith grains and eject secondary particles into the exosphere. Refractory elements, water, and other volatile species can potentially be detected using secondary ion mass spectrometry (SIMS). This manuscript characterizes the sputtered secondary ions produced by solar wind energy ions from (i) silica, (ii) iron oxide, and (iii) pyrite. The samples were exposed to 5 keV H 2+  primary ions, and SIMS spectra were collected (i) from bare samples at room temperature, (ii) after cooling to 100 K and depositing ∼20–50 monolayers of D2O, and (iii) after rewarming to room temperature. Sputtering the bare samples produced abundant refractory ions that were representative of the measured sample compositions but whose relative intensities differed from the bulk. Depositing water completely obscured the mineral substrates, and the observed intensity of water-group ions passed through a maximum as the substrate was exposed. This behavior was observed for all three samples and can be understood by changes in the surface structure or morphology for thin (&lt;10 monolayers) ice coverages. Additionally, the deposited D2O was seen to chemically react with the substrate surfaces, and deuterated molecular ions were seen in several of the postdeposition room-temperature spectra. Future work will determine the total secondary ion yields for water in contact with various regolith materials and their dependence on the underlying substrate composition, temperature, and incident ion type and energy.

Keywords: Planetary surfaces, Water vapor, Exosphere, Solar wind, Regolith