Sazuna/UAT_keywords huggingface dataset:
A Lab-scale Investigation of the Mars Kieffer Model. The Kieffer model is a widely accepted explanation for seasonal modification of the Martian surface by CO2 ice sublimation and the formation of a "zoo" of intriguing surface features. However, the lack of in situ observations and empirical laboratory measurements of Martian winter conditions hampers model validation and refinement. We present the first experiments to investigate all three main stages of the Kieffer model within a single experiment: (i) CO2 condensation on a thick layer of Mars regolith simulant; (ii) sublimation of CO2 ice and plume, spot, and halo formation; and (iii) the resultant formation of surface features. We find that the full Kieffer model is supported on the laboratory scale as (i) CO2 diffuses into the regolith pore spaces and forms a thin overlying conformal layer of translucent ice. When a buried heater is activated, (ii) a plume and dark spot develop as dust is ejected with pressurized gas, and the falling dust creates a bright halo. During plume activity, (iii) thermal stress cracks form in a network similar in morphology to certain types of spiders, dendritic troughs, furrows, and patterned ground in the Martian high south polar latitudes. These cracks appear to form owing to sublimation of CO2 within the substrate, instead of surface scouring. We discuss the potential for this process to be an alternative formation mechanism for "cracked" spider-like morphologies on Mars. Leveraging our laboratory observations, we also provide guidance for future laboratory or in situ investigations of the three stages of the Kieffer model.

Keywords: Mars, Experimental techniques, Planetary science
The New Horizons Extended Mission Target: Arrokoth Search and Discovery. Following the Pluto flyby of the New Horizons spacecraft, the mission provided a unique opportunity to explore the Kuiper Belt in situ. The possibility existed to fly by a Kuiper Belt object (KBO), as well as to observe additional objects at distances closer than are feasible from Earth-orbit facilities. However, at the time of launch no KBOs were known about that were accessible by the spacecraft. In this paper we present the results of 10 yr of observations and three uniquely dedicated efforts—two ground-based using the Subaru Suprime Camera, the Magellan MegaCam and IMACS Cameras, and one with the Hubble Space Telescope—to find such KBOs for study. In this paper we overview the search criteria and strategies employed in our work and detail the analysis efforts to locate and track faint objects in the Galactic plane. We also present a summary of all of the KBOs that were discovered as part of our efforts and how spacecraft targetability was assessed, including a detailed description of our astrometric analysis, which included development of an extensive secondary calibration network. Overall, these efforts resulted in the discovery of 85 KBOs, including 11 that became objects for distant observation by New Horizons and (486958) Arrokoth, which became the first post-Pluto flyby destination.

Keywords: Astrometry, Trans-Neptunian objects
The Pale Blue Dot: Using the Planetary Spectrum Generator to Simulate Signals from Hyperrealistic Exo-Earths. The atmospheres and surfaces of planets show a tremendous amount of spatial variation, which has a direct effect on the spectrum of the object, even if this may not be spatially resolved. Here, we apply hyperrealistic radiative simulations of Earth as an exoplanet comprising thousands of simulations and study the unresolved spectrum. The GlobES module on the Planetary Spectrum Generator was used, and we parameterized the atmosphere as described in the modern-Earth retrospective analysis for research and applications (MERRA-2) database. The simulations were made into high spatial resolution images and compared to space-based observations from the DSCOVR/EPIC (L1) and Himawari-8 (geostationary) satellites, confirming spatial variations and the spectral intensities of the simulations. The DISCOVR/EPIC camera only functions in narrow wavelength bands, but strong agreement is demonstrated. It is shown that aerosols and small particles play an important role in defining Earth's reflectance spectra, contributing significantly to its characteristic blue color. Subsequently, a comprehensive noise model is employed to constrain the exposure time required to detect O2, O3, and H2O as a function of varying ground and cloud cover for several concept observatories, including the Habitable Worlds Observatory (HWO). Cloud coverage enhances the detectability of planets in reflected light, with important consequences for the design of the future HWO. The HWO concept would require between 3 and 10 times longer to observe the studied features than LUVOIR A but performs better than the HabEx without a starshade. The codes, routines, and noise models are made publicly available.

Keywords: Exoplanet atmospheric composition , Planetary atmospheres, Habitable planets
The Global Distribution of Water and Hydroxyl on the Moon as Seen by the Moon Mineralogy Mapper (M<SUP>3</SUP>). The Moon Mineralogy Mapper (M3) on the Chandrayaan-1 spacecraft provided nearly global 0.5–3 μm imaging-spectroscopy data at 140 m pixel–1 in 85 spectral bands. Targeted locations were imaged at 70 m pixel–1 and higher spectral resolution. These data enable a detailed look at the mineralogy, hydroxyl, and water signatures exposed on the lunar surface. We find evidence for multiple processes, including probable solar wind implantation, excavation of hydroxyl-poor and water-poor material in cratering events, excavation of hydroxyl and water-rich materials from depth and global trends with rock type and latitude. Some water-rich areas display sharp boundaries with water-poor rocks but have a diffuse halo of hydroxyl surrounding the water-rich rocks indicating a weathering process of destruction of water, probably due to a regolith gardening process. Mapping for specific mineralogy shows evidence for absorptions near 2.2 μm, probably associated with smectites, and near 1.9 μm due to water. Lunar swirls are confirmed to be OH-poor, but we also find evidence that swirls are water-poor based on a weak 1.9 μm water band. Some swirls show enhanced pyroxene absorption. "Diurnal" signatures are found with stable minerals. Pyroxene is shown to exhibit strong band depth changes with the diurnal cycle, which directly tracks the solar incidence angle and is consistent with changing composition and/or grain size with depth. Mapping of M3 data for the presence of iron oxides (e.g., hematite and goethite) is found to be a false signature in the M3 data due to scattered light in the instrument.

Keywords: Lunar composition, Infrared spectroscopy, Lunar regolith, Lunar maria, The Moon, Lunar highlands, Spectroscopy
Enhancement of the Cerean Exosphere by Sublimation from Complex Craters. On icy bodies like the dwarf planet Ceres, impacts excavate volatile-rich material from beneath a dessicated lag layer and deposit it in the near-surface environment where higher temperatures drive sublimation. Ice has been detected in the upper meter of the ejecta blanket and interior of Occator crater, suggesting that large craters could be a significant source of exospheric water vapor. We assess the present-day exospheric contribution of a complex crater by first estimating the extent of volatile-rich deposits associated with a crater of a given size. We use a vapor diffusion model to calculate sublimation rates from the deposits, taking into account constraints on the thermophysical parameters of icy regolith from the Dawn mission. Extrapolating this model to craters formed throughout Ceres' history, we find that the cumulative present-day sublimation rate from all complex crater deposits is ∼0.01 kg s‑1, a factor of a few times greater than the outgassing rate from the global ice table. The dominant source of sublimation is not the conspicuous faculae but rather the volatile-rich ejecta blankets, which cover a significantly larger area than deposits in the crater interior. Because large impacts can blanket a significant fraction of the surface with ice-rich ejecta, complex craters are crucial for understanding the background present-day exosphere and the history of sublimation on icy bodies.

Keywords: Ceres, Thermal properties (Ice), Craters, Exosphere
Triton's Captured Youth: Tidal Heating Kept Triton Warm and Active for Billions of Years. Neptune's moon Triton has two remarkable attributes: its retrograde orbit suggests that it was captured from the Kuiper Belt, and Triton has one of the youngest surfaces of all the icy satellites in the solar system. Soon after capture, Triton experienced strong diurnal tides raised by Neptune, which caused intense deformation, heating, and melting of its ice shell as its highly eccentric initial orbit was circularized. While previous studies have suggested that Triton's orbit would have circularized early in solar system history, we show that internal feedbacks between tidal heating and ice shell melting significantly reduce the orbital evolution rate, causing strong tidal heating to persist for billions of years. We simulate Triton's post-capture evolution over a range of initial semimajor axes and ice shell properties. We find that Triton's ice shell would have been extremely thin (1–10 km) for a period of 1–4 billion years, with tidal stresses strong enough to fracture the entire ice shell down to the subsurface ocean. A final phase of intense geologic activity may have occurred after tidal dissipation waned, in which late-stage ice shell thickening caused ocean pressurization potentially sufficient to refracture the ice shell and push water to the surface. Such overpressurization could have caused recent massive cryovolcanic resurfacing, perhaps explaining Triton's geologically young surface. It is therefore possible that Triton's youthful surface and its origin as a captured satellite may in fact be related. A long-lived subsurface ocean and extended thin ice shell period also greatly increase Triton's astrobiological potential.

Keywords: Ocean planets, Natural satellite formation, Natural satellite surfaces, Neptunian satellites, Orbital evolution, Planetary thermal histories, Planetary science, Planetary geology, Tides, Planetary interior, Triton
Mid-infrared Measurements of Ion-irradiated Carbonaceous Meteorites: How to Better Detect Space Weathering Effects. Remote sensing study of asteroids will soon enter a new era with an increasing amount of data available thanks to the JWST, especially in the mid-infrared (MIR) range that allows identification of mineral species. It will then be possible to establish a taxonomy, as is currently available in the visible–near-infrared range, based on MIR spectral parameters. It had been previously shown that the MIR range is very sensitive to space weathering (SpWe) effects. Thus, it is crucial to determine which spectral changes are involved to disentangle initial composition from surface aging and provide tools to interpret future remote sensing data of asteroids. We present here MIR measurements of a wide variety of ion-irradiated carbonaceous chondrites as a simulation of the solar wind SpWe component. We evaluate several parameters (the Christiansen feature and Reststrahlen band positions, the width of the main Si–O band) and test different measurement conditions (ion energy and geometry of observation). We highlight a dependency of the spectral changes with the initial composition, as hydrated samples are more affected than anhydrous ones. We confirm the role of the geometry in the detection of SpWe effects as already shown in the near-infrared, with a competition effect between the depth probed by photons and the implantation depth of ions (function of the energy used). We will discuss the results in the framework of future observations and Ryugu's and Bennu's samples studied in the laboratory.

Keywords: Carbonaceous chondrites, Infrared spectroscopy, Asteroid surfaces
Experimental Method for Measuring Cohesion of Regolith via Electrostatic Lofting. The hypothesized electrostatic lofting of individual regolith grains on the Moon and asteroids has been investigated extensively in laboratory studies. Cohesion may dominate how regolith behaves on these small, airless bodies, yet the magnitude of this force remains uncertain. We induce the electrostatic detachment of dust as a mechanism to break cohesive bonds between individual zirconia-silica microspheres in order to measure the interparticle cohesive force between them, likely dominated by capillary bridges. A high-speed camera imaged centroid positions of the lofted microspheres over time. Using the centroids from the initial detachment, we numerically calculated initial accelerations to solve for the cohesion that had been restraining the microspheres. Unexpectedly, the electrostatic lofting of clumps of particles was observed and experimental results showed that clumps were a nonnegligible portion of the lofted object population.

Keywords: Dust physics, Silicate grains, Asteroids, Very small grains, Experimental data, Lunar regolith, The Moon, Experimental techniques, Lunar science, Regolith, Particle physics, Asteroid surfaces
Jovian Vortex Hunter: A Citizen Science Project to Study Jupiter's Vortices. The Jovian atmosphere contains a wide diversity of vortices, which have a large range of sizes, colors, and forms in different dynamical regimes. The formation processes for these vortices are poorly understood, and aside from a few known, long-lived ovals, such as the Great Red Spot and Oval BA, vortex stability and their temporal evolution are currently largely unknown. In this study, we use JunoCam data and a citizen science project on Zooniverse to derive a catalog of vortices, some with repeated observations, from 2018 May to 2021 September, and we analyze their associated properties, such as size, location, and color. We find that different-colored vortices (binned as white, red, brown, and dark) follow vastly different distributions in terms of their sizes and where they are found on the planet. We employ a simplified stability criterion using these vortices as a proxy, to derive a minimum Rossby deformation length for the planet of ∼1800 km. We find that this value of L  d  is largely constant throughout the atmosphere and does not have an appreciable meridional gradient.

Keywords: Atmospheric dynamics, Jupiter, Atmospheric structure
Ocean Circulation on Tide-locked Lava Worlds. I. An Idealized 2D Numerical Model. A magma ocean is expected to exist on the dayside of tide-locked planets if surface temperature exceeds the melting temperature of typical crust. As highly prioritized targets for the James Webb Space Telescope, more information about the surface and atmosphere of lava planets will soon be available. In most previous studies of lava planets, the system is typically assumed to be vigorously convecting and isentropic. This implies a magma ocean depth reaching  (104–105) m, determined by the adiabats and melting curves. In this study, we aim to simulate ocean circulation and ocean depth on tidally locked lava worlds using an idealized 2D (x–z) model developed by the authors. Our simulation results show that under zero or a small internal source, the maximum zonal current speed ranges from 0.1 to 1.0 m s‑1 and the magma ocean depth remains  (100) m, being more than 100 times shallower than that predicted in a fully convecting system. We demonstrate that the ocean heat transport divergence is consistently smaller than the stellar insolation by 1–2 orders of magnitude. Consequently, the impact of ocean circulation on the thermal phase curve of tidally locked lava worlds is minimal in observations.

Keywords: Exoplanet dynamics, Habitable planets, Exoplanets
Ocean Circulation on Tide-locked Lava Worlds. II. Scalings. On tidally locked lava planets, a magma ocean can form on the permanent dayside. The circulation of the magma ocean can be driven by stellar radiation and atmospheric winds. The strength of ocean circulation and the depth of the magma ocean depend on external forcings and the dominant balance of the momentum equation. In this study, we develop scaling laws for the magma ocean depth, oceanic current speed, and ocean heat transport convergence driven by stellar and wind forcings in three different dynamic regimes: nonrotating viscosity-dominant Regime I, nonrotating inviscid limit Regime II, and rotation-dominant Regime III. Scaling laws suggest that magma ocean depth, current speed, and ocean heat transport convergence are controlled by various parameters, including vertical diffusivity/viscosity, substellar temperature, planetary rotation rate, and wind stress. In general, scaling laws predict that magma ocean depth ranges from a few meters to a few hundred meters. For Regime I, results from scaling laws are further confirmed by numerical simulations. Considering the parameters of a typical lava super-Earth, we found that the magma ocean is most likely in the rotation-dominant Regime III.

Keywords: Exoplanet dynamics, Habitable planets, Exoplanets
Delivery of DART Impact Ejecta to Mars and Earth: Opportunity for Meteor Observations. NASA's Double Asteroid Redirection Test (DART) and ESA's Hera missions offer a unique opportunity to investigate the delivery of impact ejecta to other celestial bodies. We performed ejecta dynamical simulations using 3 million particles categorized into three size populations (10 cm, 0.5 cm, and 30 μm) and constrained by early postimpact LICIACube observations. The main simulation explored ejecta velocities ranging from 1 to 1000 m s‑1, while a secondary simulation focused on faster ejecta with velocities from 1 to 2 km s‑1. We identified DART ejecta orbits compatible with the delivery of meteor-producing particles to Mars and Earth. Our results indicate the possibility of ejecta reaching the Mars Hill sphere in 13 yr for launch velocities around 450 m s‑1, which is within the observed range. Some ejecta particles launched at 770 m s‑1 could reach Mars's vicinity in 7 yr. Faster ejecta resulted in a higher flux delivery toward Mars and particles impacting the Earth Hill sphere above 1.5 km s‑1. The delivery process is slightly sensitive to the initial observed cone range and driven by synodic periods. The launch locations for material delivery to Mars were predominantly north of the DART impact site, while they displayed a southwestern tendency for the Earth–Moon system. Larger particles exhibit a marginally greater likelihood of reaching Mars, while smaller particles favor delivery to Earth–Moon, although this effect is insignificant. To support observational campaigns for DART-created meteors, we provide comprehensive information on the encounter characteristics (orbital elements and radiants) and quantify the orbital decoherence degree of the released meteoroids.

Keywords: Impact phenomena, Ejecta, Meteors, Orbital evolution
Imaging in Shadows: A Comparison of Craters Observed in Primary and Secondary Illumination with the Lunar Reconnaissance Orbiter Camera. By definition, permanently shadowed regions (PSRs) never receive primary illumination from the Sun. However, most receive secondary illumination reflected from crater walls and nearby massifs. The nature of that secondary illumination, diffuse lighting that can vary significantly across small distances, complicates interpretations of geologic features. To better understand secondary illumination and aid in interpreting images of PSRs, we analyzed a collection of long-exposure Lunar Reconnaissance Orbiter Camera (LROC) Narrow Angle Camera (NAC) images of five equatorial craters collected when the crater interiors were mainly in shadow, using these as analog images for PSR illumination conditions but enabling comparisons with LROC NAC images of the same features under direct primary illumination. Using illumination models, we quantified the range of secondary photometric angles contributing to illuminating each pixel in the shadowed terrain and measured reflectance under secondary illumination. The phase angles of secondary illumination (secondary phase angles) contributing to a pixel can be well represented by the median value of contributing illumination weighted by magnitude. We show that features observed to have approximately constant albedo in primary illumination show substantial variations in reflectance across the scene in secondary illumination depending on the median secondary phase angle. Approximately 30% of craters with high-reflectance ejecta deposits are detectable in secondary illumination; only when the reflectance contrast is high (&gt;1.3 times higher than the background reflectance in primary illumination) are a majority (&gt;70%) of these deposits detectable in secondary illumination, meaning that small albedo differences will be hard to detect in images of PSRs.

Keywords: Surface photometry, Lunar craters, The Moon
Forming Massive Terrestrial Satellites through Binary-exchange Capture. The number of planetary satellites around solid objects in the inner solar system is small either because they are difficult or unlikely to form or because they do not survive for astronomical timescales. Here we conduct a pilot study on the possibility of satellite capture from the process of collision-less binary exchange and show that massive satellites in the range 0.01–0.1 M ⊕ can be captured by Earth-sized terrestrial planets in a way already demonstrated for larger planets in the solar system and possibly beyond. In this process, one of the binary objects is ejected, leaving the other object as a satellite in orbit around the planet. We specifically consider satellite capture by an "Earth" in an assortment of hypothetical encounters with large terrestrial binaries at 1 au around the Sun. In addition, we examine the tidal evolution of captured objects and show that orbit circularization and long-term stability are possible for cases resembling the Earth–Moon system.

Keywords: Natural satellite dynamics, Solid body tides, Planet formation, Natural satellite formation, Natural satellites (Solar system), Earth-moon system, Natural satellite evolution
The Faustini Permanently Shadowed Region on the Moon. Faustini crater (41 km diameter) hosts a large (664 km2) permanently shadowed region (PSR) with a high potential to harbor water-ice deposits. One of the 13 candidate Artemis III landing areas contains a portion of the crater rim and proximal ejecta. The ShadowCam instrument aboard the Korea Pathfinder Lunar Orbiter provides detailed images of the PSR within Faustini. We characterize the terrain and thermal environment within the Faustini PSR from ShadowCam images, Lunar Reconnaissance Orbiter thermal measurements and laser ranging, and thermal modeling. Our mapping revealed three distinct areas of the floor of Faustini based on elevations, slopes, and surface roughness. These units broadly correlate with temperatures; thus, they may be influenced by variations in volatile sublimation. Crater retention and topographic diffusion rates appear to be asymmetric across the floor, likely due to differences in maximum and average temperatures. Several irregular depressions and a pronounced lobate-rim crater are consistent with subsurface ice. However, differences in the thicknesses of deposited materials on the floor may also explain the asymmetry. Additionally, zones of elevated surface roughness across Faustini appear to result from overprinted crater ray segments, possibly from Tycho and Jackson craters. Mass wasting deposits and pitting on opposite sides of the crater wall may have resulted from the low-angle delivery of material ejected by the Shackleton crater impact event, suggesting that the Artemis III candidate landing region named "Faustini Rim A" will contain material from Shackleton.

Keywords: Lunar regolith, The Moon, Lunar science, Lunar surface, Lunar features