Sazuna/UAT_keywords huggingface dataset:
Shallow Crustal Density in the Lunar South Polar Region. Numerous space agencies are planning sustainable human presence at the lunar south pole. Understanding the nature of the lunar crust, particularly its three-dimensional density structure, is important, for example, for the search for water ice predicted to be present. The paucity of in situ measurements requires that we exploit the knowledge obtained through orbital measurements. Two data sets, gravity and topography, in combination with local geology, can provide constraints on the density of the crust. We analyzed the radial component of the gravity field to determine the density of the crust, which we relate to depth using a point-mass spherical harmonic approach. Our investigation provides estimates of density and density gradient at 20 sites in the south polar region: the original 13 Artemis sites, 5 permanently shadowed regions (PSRs), the south pole, and a site on the floor of the Amundsen crater. We find that the mean density in the top 2–10 km for the six PSRs (2475 ± 108 kg m‑3) is comparable to that (2483 ± 147 kg m‑3) for the 14 non-PSRs. The weighted mean gradient for the five PSRs and the Amundsen floor is 3 times greater than that for the 14 non-PSRs in the 2–4 km depth range; the average density increases with depth at 25 kg m‑3 km‑1. To investigate whether a relationship exists between inferred areal coverage of ice and our density results, we compared densities with results for reflectance in several common PSR localities. We find lower densities and higher gradients for areas characterized by greater areal coverage of ice.

Keywords: Lunar gravitational field
Spectral Properties of Ilmenite, Hematite, and Spinel: Implications for Upcoming Lunar Exploration Missions. Upcoming missions to the south polar region of the Moon will investigate this uncharted terrain. Investigations will include determining the bulk composition of the lunar crust to enhance our understanding of planetary processes. Lunar samples and remote-sensing data indicate that the lunar crust is mainly composed of silicate minerals such as pyroxene, plagioclase feldspar, and olivine. Oxide minerals such as ilmenite, hematite, and spinel, present in lower abundances, are valuable for in situ resource utilization, serving as sources of oxygen, hydrogen, or titanium. This study focuses on characterizing the spectral properties of ilmenite, hematite, and spinel and assessing their detectability using rover-based spectral instruments. We performed reflectance measurements of these minerals across the 350–15,385 nm range, for several grain sizes, viewing geometries, and abundances in mixtures with LHS-1 simulant. This resulted in a spectral library comprising over 1000 spectra. We modeled various mineral/LHS-1 spectral mixtures using the Hapke radiative transfer model and compared them to our laboratory spectra to assess the model's accuracy. The model yielded an average error of 4 wt% using the rms error and 5 wt% using the spectral angle. Finally, we explored the potential for detecting these minerals with multispectral sensors and identified band ratios that correlate with mineral abundance. Our findings suggest that the ratios BR_ILM_AIM1, BD_HEM_RMM, and BD_SPI_AIM are most strongly correlated with ilmenite, hematite, and spinel abundances and that the calculation of these ratios allows us to quickly evaluate the presence of these minerals within highlands material.

Keywords: Remote sensing, Radiative transfer, Lunar mineralogy, Infrared spectroscopy
On Dust Devil Diameters, Occurrence Rates, and Activity. As a phenomenon that occurs on Earth and on Mars, the diameter of a dust devil helps determine the amount of dust the devil injects into the atmosphere for both worlds—for a given dust flux density (dust lifted per area per time), a wider devil will lift more dust into the air. However, the factors that determine a dust devil's diameter D and how it might relate to the ambient conditions have remained unclear. Moreover, estimating the contribution to an atmospheric dust budget from a population of dust devils with a range of diameters requires an accurate assessment of the differential diameter distribution, but considerable work has yet to reveal the best representation or explain its physical basis. In this study, we propose that this distribution follows a power law ∝D‑5/3 and provide a simple physical explanation for why the distribution takes this form. By fitting diameter distributions of Martian dust devil diameters reported in several studies, we show that the data from several studies support this proposed form. Using a previous model that treats dust devils as thermodynamic heat engines, we also show that the areal density of dust devils (number per unit area) N0 scales with the product of their thermodynamic efficiency η and the sensible heat flux Fs as N0 ∝ ηFs.

Keywords: Mars, Planetary boundary layers, Land-atmosphere interactions
The Adjacency Effect at Kivu Lacus. Observations of high-contrast scenes through an atmosphere are subject to the adjacency effect—the artificial brightening from photons that have scattered in the atmosphere such that they appear to originate from the dark rather rather than the bright surface. In this work, we examine how the adjacency effect manifests in imaging of the surface of Titan, Saturn's largest moon, through the example case of a particularly high spatial resolution observation of a 100 km lake at Titan's north pole, Kivu Lacus. We find that the adjacency effect can increase the brightness of dark surfaces up to 10% at 5 μm, while observations at 2 μm may be brightened up to 1%. Shorter wavelengths are so dominated by multiple scattering that all directionality is lost; atmospheric scattering swamps any observable adjacency effect. The bidirectional reflectance distribution function modifies both the directionality and magnitude of the adjacency effect, maximizing the effect in the downsun direction for specular surfaces. High-resolution observations (∼1 km) of high-contrast scenes on Titan will need to take into account the adjacency effect at 2 μm, but the effects at longer wavelengths (or at lower atmospheric opacity) may be smaller than the pixel scale such that observed reflectance heterogeneities are more likely due to actual properties of the surface.

Keywords: Titan
JWST Spectroscopy of (142) Polana: Connection to NEAs (101955) Bennu and (162173) Ryugu. The new Polana collisional family is the hypothesized origin of the near-Earth asteroids (101955) Bennu, which was the target of the NASA OSIRIS-REx mission, and (162173) Ryugu, which was the target of the JAXA Hayabusa2 mission. We present JWST Near Infrared Spectrograph and Mid-Infrared Instrument spectroscopy of the parent body of the family, (142) Polana, and compare it with spacecraft and laboratory data of both near-Earth asteroids. We find that the near-infrared spectrum of Polana is similar to that of the returned sample from both Bennu and Ryugu but has a slope that differs from that of the global average spectra taken by both spacecraft. The mid-infrared Polana spectrum differs in shape from the global average spectrum of Bennu, possibly because of porosity, space weathering, or grain size. Spectral features at similar wavelengths in the spectra of Polana and those of Bennu and Ryugu support the hypothesis that both asteroids originated in the Polana family.

Keywords: Main belt asteroids, Asteroids, Infrared spectroscopy
Experimental Investigation of Soil Adsorption Effects on Water Migration in Simulated Lunar Conditions. Adsorption is a key mechanism governing water vapor diffusion in lunar regolith. To investigate this process, we conducted experiments under simulated lunar conditions—Knudsen diffusion conditions—using three soil types with varying water vapor adsorption heats and specific surface areas. Results show that soils with higher adsorption heat and larger surface area captured more water vapor. Lower temperatures enhanced water retention across all soil types. In samples with underlying ice, upward migration of water vapor was hindered by adsorption onto soil particles, reducing water loss. Montmorillonite, with its superior adsorption properties, retained the most water under all test conditions. These findings suggest that cold lunar regoliths with high adsorption capacity may act as a favorable reservoir for water accumulation.

Keywords: Lunar surface, Lunar atmosphere, Lunar mineralogy, Lunar science
The Mineralogical Connection between M- and K-type Asteroids as Indicated by Polarimetry. Polarimetry has the capacity to provide a unique probe of the surface properties of asteroids. Trends in polarization behavior as a function of wavelength trace asteroid regolith mineral properties that are difficult to probe without measurements in situ or on returned samples. We present recent results from our ongoing survey of near-infrared polarimetric properties of asteroids. Our data reveal a mineralogical link between asteroids in the broader M and K spectral classes. In particular, M-type objects (16) Psyche, (55) Pandora, (135) Hertha, and (216) Kleopatra show the same polarimetric-phase behavior as K-type objects (89) Julia, (221) Eos, and (233) Asterope from visible through near-infrared light. The near-infrared behavior for these objects is distinct from other classes observed to date, and shows a good match to the polarimetric properties of M-type asteroid (21) Lutetia from the visible to the near-infrared. The best link for these objects from laboratory polarimetric phase curve measurements is to a troilite-rich fine-grained regolith. Our observations indicate that the M- and K-type spectral classes are most likely part of a continuum, with the observed spectral differences due to heterogeneity from partial differentiation, shock darkening of the surface material, or other later evolution of the original parent population. We also provide incidental J- and H-band polarimetric observations of other main belt asteroids obtained during our survey.

Keywords: Polarimetry, Asteroids, Asteroid surfaces
A Decrease in Slope Angles on Insolated Martian Slopes: Ground-based Experiments. Dry granular flow on Martian slopes can benefit from subsoil Knudsen compressors induced by thermal creep gas flow. The required temperature gradient for this natural compressor can be set by insolation. Here, we study the decrease of slope angles from the initial angles of repose on ambient pressure in ground-based laboratory experiments. At low pressure, we pour JSC Mars 1a particles with an average grain size of 75 μm as a Martian simulant to form a pile. Typical angles of repose are about 30°, with some variation. One side of the pile is then illuminated. We find that up to 100 mbar, the illumination of the slope induces erosion and decreases the slope angle systematically. For continuous illumination at high light flux, necessary under Earth gravity, the angle decreases by about 10°. If the light source is turned off, amplified emission of material is triggered, which can further lower the slope angle. This study complements low-gravity work and suggests that the effects are important for granular flows of sand-sized particles on Martian slopes throughout the planet's pressure range, i.e., independent of the specific location. A preliminary analysis shows that such a process could work for recurring slope lineae.

Keywords: Planetary surfaces, Planetary boundary layers, Surface processes, Mars, Solar-planetary interactions, Planetary science
Ejecta Mass Estimates from the DART Impact Plume Inferred from LICIACube Images. We report ejecta mass estimates produced by the Double Asteroid Redirection Test impact with Dimorphos, the secondary of the Didymos asteroid binary system. This first demonstration of an asteroid deflection technique was witnessed by the Light Italian Cubesat for Imaging of Asteroids (LICIACube). The LICIACube Unit Key Explorer (LUKE) RGB camera images are used to estimate the ejecta mass, critical to understanding the impact conditions and physical properties of the asteroid. This requires realistic scattering properties for the ejecta particles, which were obtained from model and laboratory scattering analog particles (sizes &lt;1 μm to ∼1 cm). The particle size distribution (PSD) of ejecta is constrained from a series of 18 images acquired at widely separated phase angles (50 .° 6 to 110 .° 2) using the size dependence of the analog scattering phase functions. Total plume radiance in the LUKE RGB channels is determined by spatially integrating over the field of view in each image. Plume radiances are then used to retrieve ejecta mass assuming an optically thin plume, giving lower limit estimates of 0.85 to 1.19 × 107 kg. Results indicate that the PSD of ejecta in the nascent plume follows a single power-law coefficient (k ≍ −2.5), rather than the broken power law inferred from later observations. Using a single, high signal-to-noise image, the observed areal mass-brightness relation is extrapolated inward, yielding an increase of ≍77% for ejecta mass in the optically thick inner region. Our ejecta mass estimates are consistent with Dimorphos having weak cohesive strength (&lt;5000 Pa but more likely ∼50 Pa).

Keywords: Impact phenomena, Near-Earth objects, Asteroids, Asteroid satellites, Radiative transfer
Crater Retention Timescales of Brain Coral Terrain Record Past Climatic Change on Mars. Glacial landforms on Mars offer an opportunity to decipher the planet's recent climate history. We used crater size frequency distributions of brain coral terrain on concentric crater fill, lobate debris aprons, and lineated valley fill, all of which have been previously interpreted to be glacial landforms, to make inferences about the evolution of these surfaces. We mapped brain coral terrain in Ismenius Lacus, Utopia Planitia, and Arcadia Planitia, and classified superposing impact craters by degradation state in order to derive detailed degradation histories across a broad area of the northern martian midlatitudes. Our data support a period of glacial landform deflation of ∼10 m beginning at some point after ∼25 Ma and ceasing at ∼3 Ma. The timing of the cessation of this deflationary period closely corresponds to a modeled shift in Mars' mean obliquity from mean 35° to mean 25°. Our results thus offer an important midlatitude geologic record of Mars' late-stage obliquity and climatic evolution during the Late Amazonian.

Keywords: Planetary surfaces, Surface processes, Glaciers, Geological processes, Surface ices, Planetary climates, Planetary geology, Glaciation, Regolith, Craters
Asteroid Companions in the Visible: WFPC 2 Images. We report the observation of six asteroidal companions in direct images of five asteroids from Hubble Space Telescope (HST). These are (45) Eugenia, (87) Sylvia, (93) Minerva, (107) Camilla (the discovery observation for this companion), and (121) Hermione. Images of the companions are barely above the threshold detectability and appear to have the same colors as the primary body. The primary asteroids are all resolved in the HST images, and their shapes and sizes can be clearly seen after reconstruction. These asteroids generally appear to be darker than expected from data in the literature, which is generally derived from ground-based adaptive optics observations and from IR radiometry (the SIMPS). The asteroids average about 5% smaller than their radiometric diameters, which is an effect of the image reconstruction process used here.

Keywords: Asteroid satellites
Simulating the (99942) Apophis Earth Flyby Using a Contact Binary Model. This paper investigates the mass shifts of asteroid (99942) Apophis during its 2029 close encounter with Earth, using the contact dynamics method, a type of discrete element method. Unlike previous analyses, we model the asteroid as a contact binary body with the addition of granules between the body's components. To account for uncertainties in Apophis' shape, we create eight multibody models, with a particular focus on a contact binary asteroid model featuring boulders concentrated in its neck region. Our simulations show that the inclusion of boulders, whether distributed across the surface or concentrated in the neck region, facilitates internal mass shifts, with minimal differences between models, indicating that boulder placement has little effect on the magnitude of the mass shifts. In polyhedral models, angularity dominates over friction and orientation. Spherical models are more sensitive to friction and orientation than shape. Both show minimal sensitivity to tensile strength. While we can find considerable shifts in the system for some parameter values, for values we consider more realistic, we find only modest deformation of the components and motion of surface material, on par with previous simulations. A critical stability threshold is identified at a neck size ratio of α ≈ 0.4, below which contact binary asteroids become highly vulnerable to external perturbations and tend to reconfigure into more stable shapes.

Keywords: Asteroids, Asteroid dynamics, Asteroid surfaces
X-Ray-induced Photochemistry of Hydrocarbons: Implications for the Formation of Organic Haze in (Exo)Planetary Atmospheres. We present a laboratory study of X-ray-induced chemistry of organic molecules (CH4, C2H4, and C2H6) irradiated with synchrotron X-rays in the 200–1000 eV range from the Advanced Light Source beamline 9.3.2 at the Lawrence Berkeley National Laboratory. Broadband nonmonochromated X-rays beams used in this study partially simulate X-rays emitted from low-mass young stellar objects (0.2–2 keV). The experiment is conducted by irradiating a vacuum chamber prefilled with the selected hydrocarbon at a pressure of 100 mTorr at room temperature during predefined exposure times of 5, 10, 20, and 30 minutes and 1 hr. After each exposure, the chemical photoproducts deposited on Si substrates are analyzed in situ using X-ray photoelectron spectroscopy (XPS). Secondary-ion mass spectrometry is also performed ex situ to determine the hydrogen content of the deposited samples. Our analysis indicates that the photoproducts formed from X-ray irradiation of C2H4 undergo more extensive photoprocessing than those derived from CH4 and C2H6. XPS results show that sp2- and sp3-fitted XPS bands correspond to amorphous carbon particles with hybridization that depends on the parent precursor molecules. When irradiating pure CH4, a fully sp3-hybridized molecule, we found that X-ray photons induce photochemical reactions leading to the formation of heavier organics with sp2 C=C bonds. Possible chemical pathways and astrophysical implications are discussed.

Keywords: Astrochemistry
Spectral Trends across the Rings and Inner Moons of Uranus and Neptune from JWST NIRCam Images. JWST NIRCam images provide low-resolution spectra of the rings and inner moons orbiting Uranus and Neptune. These data reveal systematic variations in spectral parameters like the strength of the strong OH absorption band around 3 μm and the spectral slopes at continuum wavelengths. Neptune's rings show an extremely weak 3 μm band, which is likely due to the small particle sizes in these dusty rings. Neptune's small inner moons also have weaker 3 μm bands and redder continua than Uranus' small inner moons, indicating that Neptune's moons have a lower water-ice fraction. There are also clear spectral trends across the inner Uranian system. The strength of the 3 μm band clearly increases with distance from Uranus, with the rings having a noticeably weaker 3 μm band than most of the small inner moons, which have a weaker 3 μm band than the larger moons like Miranda. While the rings and most of the small moons have neutral spectra between 1.4 and 2.1 μm, the outermost small moon Mab exhibits a blue spectral slope comparable to Miranda, indicating that Mab's surface may also be relatively water ice rich. The next moon interior to Mab, Puck, exhibits a stronger 3 μm band and bluer continuum slope than any of the moons orbiting interior to it, perhaps indicating that it is being covered by water-ice-rich material derived from Mab via the μ ring. Finally, the small moon Rosalind has a redder spectral slope than its neighbors, possibly due to being coated with material from the dusty ν ring.

Keywords: Neptune, Uranian satellites, Ice spectroscopy, Neptunian satellites, Planetary rings, Uranus
Atomic-scale Insights into the Effects of Diffusion on the Binding of Adsorbed Sodium on the Surfaces of the Moon and Mercury. The collisionless atmospheres of the Moon and Mercury allow for different space weathering processes to occur on their surfaces. During these processes, atoms can be ejected ballistically into the exosphere, a portion of which will eventually return to the surface. These returning atoms can then adsorb on the surface with a binding energy (BE) different than that of the mineral. However, it is unknown how adsorbates sample the different possible binding sites on the surface, or how diffusion can dynamically affect the BEs and eventual desorption process. Here, we conduct molecular dynamics simulations of the adsorption, diffusion, and desorption of sodium (Na) atoms on different silicates relevant to the Moon and Mercury. We consider the effect of crystallinity and temperature on the BE and diffusion behavior of adsorbed Na over time. Results show that Na adsorption strongly depends on the surface mineral composition and the presence of bridging and nonbridging oxygen. Na on silica surfaces had the highest adsorption energy compared to albite and anorthite due to the higher proportion of exposed nonbridging oxygens on the surface. We also observe that the BE increases as the Na atoms are allowed to diffuse and desorb. This suggests that while adsorbates may initially randomly sample different binding sites, with time they will diffuse toward high-BE sites. Finally, our simulations show that with an increase in temperature, there is an increased probability of desorption.

Keywords: Planetary surfaces, Exosphere, Surface processes, The Moon, Mercury (planet)
A Novel Metric for Assessing Climatological Surface Habitability. Planetary surface habitability has so far been considered, in the main, on a global scale. The increasing number of 3D modelling studies of (exo)planetary climate has highlighted the need for a more nuanced understanding of surface habitability. Using satellite-derived data of photosynthetic life to represent the observed surface habitability of modern Earth, we validate a set of climatologically defined metrics previously used in habitability studies. The comparison finds that the metrics defined by surface temperature alone show spatial patterns of habitability distinct to those defined by aridity or water availability, with no metric able to completely replicate the observed habitability. We build upon these results to introduce a new metric defined by the observed thermal limits of modern Earth-based life, along with surface water fluxes as an analog for water and nutrient availability. Furthermore, we pay attention to not only the thermal bounds of macroscopic complex life, but additionally the limits of microbial life which have been vital to the generation of Earth's biosignatures, thus expanding considerations of climatic habitability out of a historically binary definition. Repeating the validation for our metric, along with another that uses a similar definition that incorporates conditions for both temperature and water availability, shows a significant improvement in capturing the broad patterns of surface habitability, laying the groundwork for more comprehensive assessments of potential life-supporting climates upon other planets.

Keywords: Planetary atmospheres, Earth (planet), Astrobiology, Planetary climates, Habitable planets