Sazuna/UAT_keywords huggingface dataset:
ORIGIN: Laser Desorption Ionization Mass Spectrometry of Nucleobases for In Situ Space Exploration. The ORganics Information Gathering INstrument (ORIGIN) is a space-prototype laser desorption ionization mass spectrometer designed to analyze molecular biosignatures. Nucleobases, fundamental components of nucleic acids, have been found in carbonaceous meteorites and in returned samples from the asteroid Ryugu, which suggest their extraterrestrial origin and possibly their significance in prebiotic chemistry and the RNA world hypothesis. Therefore, future space missions should be equipped for the in situ detection of nucleobases at relevant concentrations. This study investigated six nucleobases—adenine, cytosine, 5-methylcytosine, guanine, thymine, and uracil—using the ORIGIN setup. All six are readily detected and identified, with the mass spectra showing parent ions and minimal fragmentation. Mixture analyses illustrate the instrument's quantitative potential. The detection limit for adenine was 52 fmol mm–2, and we show that sensitivity can be further improved by increasing detector voltage and sampling more positions. This study demonstrates ORIGIN's capability to detect nucleobases at trace abundance levels. The detection of nucleobases and other molecular biosignatures on other planetary objects might offer new insights into the origin of life on Earth and the possibility of discovering life beyond our planet.

Keywords: Space vehicle instruments, Time-of-flight mass spectrometry, Astrochemistry, Astrobiology, Biosignatures, Pre-biotic astrochemistry
Refined Mapping of Subsurface Water Ice on Mars to Support Future Missions. Mars has an extensive yet poorly understood cryosphere. Nevertheless, both direct and indirect evidence indicates extensive buried ice across the midlatitudes, including locations where it is presently unstable. While much progress has been made in exploring the processes responsible for ice deposition and preservation during recent climatic fluctuations, a global assessment of the multiple ice reservoirs remains elusive. Motivated by science and the need to find suitable human landing sites, the Mars Subsurface Water Ice Mapping (SWIM) project has developed techniques to map out buried ice. Through integration of all appropriate orbital data sets, the SWIM project produces ∼3 km pixel‑1 ice consistency maps over depth ranges of 0–1 m, 1–5 m, and &gt;5 m. In concert with other studies, prior SWIM phases have recognized the uncertainty in our understanding of the geographic and vertical distribution of ice, especially between depths of 1 m and 10 m, creating a push for new ice-prospecting orbital missions, such as the International Mars Ice Mapper mission concept. Here we document the latest SWIM phase, which provides notional targeting maps of the lowest-latitude ice for future missions via a significant improvement in the geomorphic component of our work. The new mapping incorporates both an enhancement in our mapping of geomorphic features and surveys of thermal contraction crack polygons. Our results demonstrate the highly variable nature of the spatial distribution of the shallowest ground ice, with the most equatorward excursions occurring below 30° latitude N/S, locations thought to be out of equilibrium with the current climate.

Keywords: Mars, Planetary climates
A Global Survey of Lunar Surface Thorium Anomalies Associated with Impact Basins. Radionuclides (e.g., thorium, uranium, and potassium) are the major sources of the Moon's endogenic heat. While their surface occurrence can be mapped from orbit by gamma-ray spectrometry, knowledge of their subsurface distribution is crucial in further understanding the Moon's thermal evolution. Here we have conducted a global survey of surface Th anomalies (regionally elevated Th content) to locate Th-bearing materials and deduce their origin in the subsurface. We find that the Th-bearing surface materials originated in the crust–mantle transition zone and that they were brought to the surface by either excavation by major basin-forming impacts or mare volcanism, and in some cases nonmare volcanisms in the basin rim structures. The anorthosite crust contains near-zero Th as evidenced by the fresh ejecta from recent major impacts on the highlands such as Tycho. This holds true globally. Therefore, the lateral variation of surface Th content is controlled mainly by the distribution of the large (≳400 km diameter) mare basins of impact origin. This first-order variation can be altered significantly by two types of processes that take place after the basin formation. The one is the gradual dilution of the Th content of the surface materials over time by subsequent impact gardening. The other is reworking/redistribution/re-excavation of the basin ejecta from depth by later, large impacts. Because the lateral variation of surface Th content is controlled primarily by impact-related processes, it probably does not have positive correlation with that of endogenic heat flow.

Keywords: The Moon, Lunar composition
Long-term Spectral Monitoring of Active Asteroid (6478) Gault: Implications for the H Chondrite Parent Body. Active asteroid (6478) Gault underwent outbursts between late 2018 and early 2019 with tails morphologically similar to the ejecta from Dimorphous following the Double Asteroid Redirection Test impact. Multiple studies investigated the dust properties, confirmed that Gault is an S-type Phocaea-family asteroid, and obtained a ∼2.5 hr rotation period consistent with being near the critical rotation period for breakup. We present results from near-infrared spectral monitoring of Gault on one night during a period of activity and five nights across 3 yr after activity ceased in order to understand the evolution of surface mineralogy over time. Spectral band parameters show an average Band I center of 0.920 ± 0.005 μm, Band II center of 2.04 ± 0.13 μm, and band area ratio of 1.33 ± 0.04. These values correspond to an olivine–pyroxene ratio of 0.40, 18.7 mol% fayalite, and 17.2 mol% ferrosilite—all of which are consistent with an H chondrite that has low levels of thermal metamorphism. Three meteorite analogs were identified that are H chondrites with petrologic types between H3.4 and H4. The low-level thermal metamorphism interpretation of Gault's surface suggests that it formed from the outermost portion of the progenitor of the Phocaea family, assuming an "onion shell' structure, which was catastrophically disrupted 1.2 Gyr ago. We discuss implications of Gault's surface composition to better understand this H chondrite parent body, with the suggestion that more dynamical and spectral analyses be performed for members of the Phocaea family.

Keywords: Solar system formation, Chondrites, Infrared spectroscopy, Main belt asteroids, Meteorites, Asteroid surfaces
Ariel's Medial Grooves: Spreading Centers on a Candidate Ocean World. We present evidence that Ariel's massive chasma-medial groove systems formed via spreading, where internally sourced material ascended and formed new crust. Evidence for this interpretation includes close alignment of offset faults and chasma margins during reconstruction, axial troughs bounded by raised rims, bowed-up chasma floors with marginal valleys, subparallel chasma floor ridges, and relatively young medial groove–bounding terrain. Ariel's medial grooves are among the youngest known Uranian moon geologic features and might be conduits to the interior and the source of NH-bearing species, CO, CO2, and other potential internally derived volatiles detected on the surface. While medial grooves are observable in Brownie and Kewpie Chasmata, our results indicate that these features are also present below Voyager 2 Imaging Science System image resolutions in Korrigan, Pixie, and Sylph Chasmata. Close flybys of Ariel with a Uranus orbiter are imperative to uncover the nature of these curious features and to gain insight into this moon's most recent geologic events.

Keywords: Uranian satellites, Natural satellite surfaces, Natural satellites (Solar system), Planetary science, Tectonics
A Laboratory Study of Plasma Charging Inside Lava Tubes on the Lunar Surface. The electrostatic charging environment inside lunar lava tubes was investigated in laboratory experiments using a glass tube exposed to a simulated solar wind flow. A conducting surface was attached at the entrance of the tube and biased to various negative potentials to study the electron shielding effect on the charging conditions inside the tube. The electrical potential at the bottom of the glass tube was measured using a planar probe. It is shown that the bottom surface potential is positive and increases with the increasing ion beam energy, as well as with the increasing depth inside the tube, as a result of electron Debye shielding at the entrance and along the length of the tube due to the electron thermal motion. It is found that the bottom tube potential does not approach the ion kinetic energy even when the solar wind electrons are nearly fully shielded from entering the tube. We show that ion-generated secondary electrons from the sidewall of the tube partially neutralize the buildup of positive charges at the bottom of the tube. Our results provide insights into the plasma charging environment inside lunar lava tubes that may be used as natural habitats for future human exploration on the surface of the Moon.

Keywords: Space plasmas, Surface processes, The Moon, Surface composition, Solar wind, Lunar surface
Surface Energy of Insoluble Organic Matter Simulant: Evaluation Based on Adhesive Force Measured by Centrifugal and Impact Separation Methods. In protoplanetary disks, organic mantle is regarded as promoting the collisional sticking of rocky dust grains. However, the surface energy, which is one of the primary factors determining collisional sticking, has not been well quantified. Here, we evaluated it by measuring the adhesive forces of synthetic insoluble organic matter, which is a realistic, chemically synthesized simulant of the organic matter found in meteorites, comets, and interplanetary dust particles. The simulant was prepared by repeated decantation of the reaction products of small reactive molecules, which are observed abundantly in protoplanetary disks. The adhesive force was measured at room temperature using both centrifugal and impact separation methods. For the latter, we developed a new apparatus that may enable measurements under varied conditions in the future as the organic matter is sensitive to temperature. We demonstrated that the measurements obtained with the new apparatus worked well as they closely matched those obtained using the centrifugal method. The measurements show that the surface energy of the simulant is ∼10 mJ m‑2, which is comparable to or even lower than that of silica, depending on disk conditions. Therefore, assuming that the simulant is similar to protoplanetary organic matter, the surface energy of the organic matter would not promote the collisional sticking of rocky dust grains. Other factors, such as the viscosity of organic matter, the role of water-soluble organic matter, and the environmental conditions in protoplanetary disks, may help us better assess the true effects of organic matter on collisional sticking.

Keywords: Dust physics, Experimental techniques, Protoplanetary disks
Application of Machine Learning Techniques to Distinguish between Mare, Cryptomare, and Light Plains in Central Lunar South Pole‑Aitken Basin. We apply machine learning techniques to identify and map resurfacing units in the central South Pole‑Aitken (SPA) basin using three Lunar Reconnaissance Orbiter (LRO) mission data sets: 321/415 nm and 566/689 nm band reflectance ratios from Hapke photometrically standardized albedo maps and a Terrain Ruggedness Index map using the Wilson et al. method. Other data were considered, but albedo and topography data were key in distinguishing between maria, cryptomaria, and light plains. A two-step image classification approach was applied to the data sets, an unsupervised K-Means algorithm followed by a supervised Maximum Likelihood Classification (MLC) algorithm. K-Means identified four units, one associated with dark smooth maria, two not associated with any particular features, and a fourth associated with edge effects. To further discriminate between the two nonassociated units, the K-Means unit map and an LRO morphologic basemap were used to select multiple training areas for three defined units in the MLC algorithm: mare, cryptomare, and cryptomare/light plains. From the training area values, the MLC unit map showed a distinction between the two prior indistinguishable K-Means units. Our results show (1) that the cryptomare from the MLC algorithm is in good agreement with cryptomaria mapped by J. L. Whitten &amp; J. W. Head, (2) that the presence of scattered maria within large patches of cryptomaria indicates possible incomplete and/or uneven ejecta deposits or sheet flows covering cryptomare surfaces, and (3) a 79% increase in the total extent of cryptomaria compared to that by J. L. Whitten &amp; J. W. Head for the same given study area in central SPA.

Keywords: Lunar maria, The Moon, Lunar science, Lunar features
Evaluating the Depth–Age Hypothesis for the Evolution of the Lunar Regolith. Lunar regolith is the fractured rock layer covering most of the lunar surface. This rock is fractured into regolith primarily by repeated meteorite impacts over eons. The depth of the regolith is determined by the maximum depth reworked by impactors. Older surfaces are expected to have thicker regoliths because they have been exposed to longer periods of bombardment than younger surfaces—a concept I refer to as the Depth–Age Hypothesis. To test the hypothesis, I compare published, measured regolith depths on mare basalts with published, measured surface ages of those mare. If the Depth–Age Hypothesis is correct, older mare surfaces should have thicker regoliths than younger surfaces. Contrary to the hypothesis, published data show that both younger and older lunar surfaces have median regolith depths ranging from about 3 to 9 m. Possible reasons for this finding include variations among measurement methods, reporting regolith depths with too great precision, and the inherent variability of the lunar regolith.

Keywords: Lunar craters, Lunar regolith, Lunar maria, The Moon, Lunar surface, Lunar evolution, Regolith, Craters
Crater Dimensions on the Dwarf Planets. The icy dwarf planets of Pluto, Charon, and Ceres provide important geologic comparisons for each other as they possess similar gravities and experience impacts of similar velocities compared to larger planets and moons. Differences in their impact craters can therefore be attributed to differences in the impactor and/or target compositions. Craters on Ceres show taller rims than craters on Charon, but comparable internal crater dimensions (depth, wall slope, and peak size). It is possible that the non-ice component of the Ceres crust provides additional strength to this outer portion of the crater, maintaining less rim collapse during the modification stage of crater formation, while the warmer central crater region is controlled by the weakness of the icy component. The spreads in depth-to-diameter ratio and wall-slope values for the Pluto data set are not clearly related to preservation state, suggesting that fresh craters on Pluto possess a large variance in these crater dimensions compared to Charon. This could be due to the geologically diverse terrains and depositional histories at different latitudes and longitudes of Pluto. These provide different target properties for each impact, so that even pristine impact craters on Pluto could display a wide range in depths and wall slopes based on the different strength of the target in each area.

Keywords: Ceres, Pluto, Craters, Plutonian satellites
Dimorphos's Material Properties and Estimates of Crater Size from the DART Impact. On 2022 September 26, the Double Asteroid Redirection Test (DART) spacecraft intentionally collided with Dimorphos, the moon of the binary asteroid system 65803 Didymos. This collision provided the first full-scale test of a kinetic impactor for planetary defense. Images from DART's DRACO camera revealed Dimorphos to be an oblate spheroid covered in boulders of varying sizes and shapes. Very little was known about Dimorphos prior to DART's impact, including its shape, structure, and material properties. Approach observations and those following the DART impact have provided crucial knowledge that narrows the parameter space relevant to modeling the impact into Dimorphos. Here we present the results of a suite of hydrocode simulations of the DART impact on Dimorphos. Despite remaining uncertainties, initial models of DART's kinetic impact provide important information about the results of DART (e.g., potential crater size and morphology, ejecta mass) and the properties of Dimorphos. Simulations here suggest that Dimorphos has near-surface strength ranging from a few Pascals to tens of kPa, which corresponds to crater sizes of ∼40–60 m. Simulated crater sizes provide a crucial comparison metric for the European Space Agency Hera mission when it arrives at the Didymos system. Hera's measurement of crater size in combination with measurement of Dimorphos's mass will allow us to assess our simulations and provide the information needed to make the DART impact experiment both the first test of a planetary defense mitigation mission and the first full-scale planetary defense simulation validation exercise.

Keywords: Impact phenomena, Planetary science, Asteroids, Craters
Thermally Driven Atmospheric Escape: Transition from Diffusion-limited to Drag-off Escape. We examine the transition from diffusion-limited to drag-off escape using a direct simulation Monte Carlo (DSMC) model developed to simulate planetary atmospheres, referred to as Harrah. A 1D spherically symmetric DSMC model is used to simulate two-component atmospheres to focus on the impact of rarefaction on thermal diffusion. The results for the escape rates and thermal structure are characterized using a mass-averaged Jeans parameter, λavg,0, and Knudsen number, Kna,0, defined at a reference radial distance r0. As a test of the model, we simulated the escape of N2 and H2 self-consistently for conditions of Pluto's upper atmosphere observed during the New Horizons mission. As expected, the DSMC result for H2 escape is consistent with the diffusion-limited approximation, and H2 escape has little effect on the background N2 atmosphere. Then we examined the transition from diffusion-limited to drag-off escape for two-component atmospheres characterized by mass-averaged Knudsen numbers and Jeans parameters of Kna,0 ≈ 0.01–0.1 and λavg,0 ≈ 0.5–13, respectively. We found that escape transitioned from hydrodynamic escape to an enhanced Jeans-like escape at λavg,0 ≈ 3.0–3.6. For values of λavg,0 &lt; 3.0–3.6, escape was hydrodynamic and in the blow-off regime. For values of λavg,0 &gt;≈ 3.6, the DSMC results indicated that using the diffusion-limited and drag-off approximations can lead to inaccurate estimates of the escape rate.

Keywords: Pluto, Atmospheric evolution, Exosphere
Can Well-sampled Phase Curves Be Used to Infer Asteroid Spectral Features?. The relationship of an asteroid's reduced magnitude to its phase has a long history of study. Included in this history have been efforts to study the correlation between these parameters and spectral type. However, these efforts often suffer from the inclusion of only a few asteroids, missing phase curve data, uncorrected rotational or apparitional aberrations, and other issues. In this paper, we build upon previous approaches and address these issues. Broadly, this paper is split into two parts. The first is primarily concerned with carefully deriving phase curve parameters using a combined data set from several different sources, including observations from Gaia, the Transiting Exoplanet Survey Satellite, Palomar Transient Factory, Asteroid Terrestrial-impact Last Alert System, and Asteroid Lightcurve Data Exchange Format database using an ellipsoidal model that can correct for rotational and apparitional effects. The second concerns itself with making predictions on that data set and quantifying what can and cannot be inferred from phase parameters, both as a function of the phase curve parameterization chosen and as a function of the chosen model. We find that, while individual spectral classes remain hard to infer from the phase curves, broader statements on the presence of absorption features can dependably be made.

Keywords: Phase angle, Asteroids, Phase effect
Informed Design of a Gravity Science Experiment for the Future Geophysical Investigation of the Uranian Moons. The outer solar system beyond Saturn remains unexplored by dedicated orbital missions. With a launch window opening in 2029, the Uranus Orbiter and Probe (UOP) mission has been prioritized as a NASA Flagship mission for the next decade (2023–2032) to comprehensively study Uranus and its major moons—Miranda, Ariel, Umbriel, Titania, and Oberon. We define and apply novel mission design principles centered on scientific objectives to UOP's gravity science (GS) experiment. Using a combination of Bayesian and Precise Orbit Determination inversions, it is possible to determine mission requirements ensuring the achievement of scientific goals. Our methodology involves building measurement-to-interior parameter maps via extensive Markov Chain Monte Carlo simulations, linking geodetic measurements' precisions to uncertainties in key interior parameters of the Uranian moons. We show how this mapping approach allows for the rapid evaluation of the ability of a GS experiment design to constrain interior parameters. We conduct a covariance analysis of two orbital tours, multiple measurement strategies, and inversion settings. The tested cases enable the satisfactory determination of Ariel's ice shell thickness (to about 16%), as well as its rock-to-ice mass ratio (≈28%). None of the solutions were able to constrain its ocean thickness. This reverse approach allows for the rapid and scientifically informed adjustment of mission design, thereby demonstrating its potential applicability to other planetary science experiments.

Keywords: Deep space probes, Uranian satellites, Gravitational fields, Tides, Remote sensing, Libration, Markov chain Monte Carlo, Planetary interior