Sazuna/UAT_keywords huggingface dataset:
Effects of Particle Shape and Size on Granular Mechanics in Vacuum and Microgravity Environments. Rubble pile asteroids and regolith-covered surfaces on small planetary bodies undergo evolution that is likely driven by particle–particle granular mechanics interactions. Interparticle interactions and porosity may regulate physical interactions as a result of shaking, impacts, and other disruptive behavior. The Strata-1 experiment, flown on the International Space Station (ISS), included four simulant tubes to characterize granular material behavior in microgravity and act as a bridge between simple spherical simulations and complex rubble pile asteroid observations. We analyze the behavior of the more idealized simulants, glass shards and spheres, in an effort to isolate the role of particle shape (spherical versus irregular) in the behavior of granular material sorting in microgravity. Additionally, ISS accelerometers are used to quantify experiment-level transient events (ISS SAMS) and the ISS quasi-steady acceleration environment (ISS MAMS). Long-duration forcing events such as reboosts, thruster events, and inversions are also identified. The median acceleration is small (&lt;1 μg, MAMS), indicating that forcing events dominate the acceleration environment. The shards were more active (showed higher variance) than the spheres, and the smallest particles were more active than the larger particles. We also find that areas of the tube with higher macroporosity show more activity. These results are consistent with the void-filling Brazil Nut Effect mechanism. Most, but not all, changes in particle packing can be explained by at least one concurrent ISS event, but not all events induce the same magnitude of change, indicating that granular bodies do have some capacity to resist disruption by external events.

Keywords: Space research, Microgravity, Lunar surface, Planetary science, International Space Station, Asteroid surfaces
Two Possible Orbital Histories of Phobos. The two moons of Mars, Phobos and Deimos, have orbits that are close to the Martian equator, indicating their formation from a circumplanetary disk. Phobos is currently migrating toward Mars due to tidal dissipation within the planet and may be disrupted into a ring in a few tens of Myr. The past evolution of Phobos is not fully understood, with one possibility being that Phobos formed in the early solar system just interior to the synchronous orbit and migrated inward over several Gyr. Alternatively, Phobos may be the most recent product of an ongoing Martian ring–moon cycle that lasted several Gyr but formed Phobos only 100 Myr ago at the fluid Roche limit. Here we use numerical integrations to simulate the past evolution of Phobos in both of these scenarios and test whether Phobos's small eccentricity and inclination are consistent with either of these hypotheses. During its tidal evolution, Phobos crossed multiple resonances with both the rotation of Mars and the apparent motion of the Sun, requiring detailed numerical modeling of these dynamical events. Furthermore, Phobos crossed resonances with Deimos, which can affect the orbit of Deimos. We find that both the ancient Phobos hypothesis and the ring–moon cycle are fully consistent with the present orbit of Phobos, with no currently available means of distinguishing between these very different dynamical histories. Furthermore, we find that Deimos is affected by weak chaos caused by secular resonances with the planetary system, making the eccentricity of Deimos an ineffective constraint on the past migration of Phobos.

Keywords: Celestial mechanics, Martian satellites, Orbital resonances, N-body simulations
Surface Deposition of Icy Dust Entrained in Europa's Plumes. Europa, an icy moon of Jupiter, features complex surface characteristics shaped by tidal forces and interactions with its subsurface ocean, making it a key target for astrobiology research. Outgassing plumes have been reported using Earth-based observations and in situ Galileo mission data, though the nature of plumes on Europa remains largely unknown. This study investigates the dynamics of dust entrained in Europa's water vapor plumes, which is crucial for understanding surface evolution and subsurface interactions. We employ the Direct Simulation Monte Carlo method to simulate these plumes considering various gas production rates and initial velocities. The Direct Simulation Monte Carlo results provide information for dust trajectory modeling to evaluate the effects of gas drag on particle transport during an idealized plume eruption. We explore how gas production rates, initial gas and dust velocities, and dust size distributions influence plume morphology and deposition patterns. Our findings reveal that gas drag plays a significant role in the behavior of dust, with smaller particles (0.001‑0.1 μm) becoming widely dispersed, while larger particles (0.1‑10 μm) tend to settle near the source. At the highest gas production rate of 1 × 1029 H2O s‑1 considered in this paper, gas drag becomes the dominant force and reduces the influence of initial ejection velocities. Our study also provides essential insights into surface‑subsurface interactions on Europa, aiding in interpreting the upcoming observational data from the missions of JUICE and Europa Clipper, which will further explore these intriguing phenomena.

Keywords: Galilean satellites, Europa
2020 BX<SUB>12</SUB>—The Last Binary Asteroid Discovered at Arecibo. Radar observations of 2020 BX12 conducted with the S-band planetary radar system (2380 MHz, 12.6 cm) at the Arecibo Observatory on 2020 February 4 and 5 revealed that this potentially hazardous asteroid is a binary system. Spectroscopic observations with the 10.4 m Gran Telescopio Canarias on 2024 February 16 indicate that 2020 BX12 is an S-complex asteroid (Bus–DeMeo taxonomy). We present the results of shape modeling and orbit fitting based on the radar observations. The system consists of a primary of a diameter ∼205 m and a ∼50 m secondary revolving around their common center of mass. This size places the system among the smallest 10% of known binary asteroid systems. The orbital period of the system is &gt;40 hr. The semimajor axis is &gt;375 m. This binary system, like many other binary near-Earth asteroids, features a spheroidal primary spinning near the breakup point, indicating likely formation through spin-up and fission and migration from the main belt. 2020 BX12 was the last binary asteroid discovered at Arecibo.

Keywords: Near-Earth objects, Asteroids, Small Solar System bodies, Radar telescopes, Asteroid satellites, Radar observations
Spatiotemporal Variations of Temperature in Jupiter's Upper Atmosphere. Global temperatures in Jupiter's upper atmosphere are poorly constrained. Other than an in situ measurement by the Galileo Probe, all temperature data come from remote-sensing methods that primarily rely on emissions from H , the dominant molecular ion in giant planet ionospheres. While H  temperature serves as a proxy for thermospheric temperature under specific conditions, the available H  observations at Jupiter have limited spatial coverage and a wide range of reported temperatures that complicate analysis of atmospheric temperatures. We present high-resolution H  temperature maps near local solar noon collected over 3 half-nights in 2022 and 2023. Pole-to-pole temperature structure is consistent across time spans of 1 month to 1 yr. Median equatorial (±25∘ latitude) temperature across all three nights is 762 ± 43 K, with night-to-night differences of &lt;75 K. Temperatures within the statistical locations of the northern and southern auroral ovals are 1200 ± 96 K and 1143 ± 120 K, respectively. A region ∼30 K cooler than its surroundings is found near 20° N, 90° W System III longitude, roughly coincident with a magnetic field anomaly, providing additional evidence for magnetic influence on Jupiter's upper atmosphere. Temperatures generally decrease smoothly from auroral to equatorial latitudes, consistent with the expected gradient if Jupiter's nonauroral latitudes are heated primarily by dynamical redistribution of auroral energy.

Keywords: Planetary ionospheres, Infrared spectroscopy, Ground-based astronomy, Jupiter
Characterization and Sensitivity Analysis of JIRAM Spectra for Optimizing CH<SUB>4</SUB> and <inline-formula> <mml:math><mml:msubsup><mml:mrow><mml:mi>H</mml:mi></mml:mrow><mml:mrow><mml:mn>3</mml:mn></mml:mrow><mml:mrow><mml:mo>+</mml:mo></mml:mrow></mml:msubsup></mml:math> </inline-formula> Retrieval. Since the Juno spacecraft started orbiting around Jupiter in 2016, our understanding of the planet has continued to expand. One of the mission's primary scientific objectives was to delve into the mechanisms governing the complex aurorae at Jupiter's poles, leading to significant progress. The Jovian InfraRed Auroral Mapper (JIRAM), on board the Juno mission and composed of an imager and a spectrometer, strongly contributed to advancing in the field. Throughout the mission, the imager has provided detailed monitoring of auroral morphology in the infrared, while the spectrometer has enabled us to derive the temperature and concentration of H 3+  and the distribution of CH4 across the planet. Despite the extended data volume provided by the spectrometer, only a small fraction of its observations have been analyzed so far, due to the intricate nature of JIRAM spectra, which pose challenges in modeling the observed signal. As new scientific goals have emerged, further investigation into these data is needed to enhance their characterization. In this study, we present several sensitivity tests on JIRAM spectra, with a specific emphasis on observations taken at nadir. Our aim is to characterize the criticalities of these data and assess the implications for further data analyses using inversion techniques. This research is intended as a valuable reference for future JIRAM spectra exploitation, outlining strategies used to address challenges arising from the nature of the data and identifying areas that still require further investigation.

Keywords: Upper atmosphere, Infrared spectroscopy, Jupiter
In Search of the Potentially Hazardous Asteroids in the Taurid Resonant Swarm. The Taurid Complex is a large interplanetary system that contains comet 2P/Encke, several meteoroid streams, and possibly a number of near-Earth asteroids. The size and nature of the system have led to the speculation that it was formed through a large-scale cometary breakup. Numerical investigations have suggested that planetary dynamics can create a resonant region with a large number of objects concentrated in a small segment of the orbit, known as the Taurid swarm, which approaches the Earth in certain years and provides favorable conditions for studying the Taurid Complex. Recent meteor observations confirmed the existence of the swarm for millimeter- to meter-sized objects. Here we present a dedicated telescopic search for potentially hazardous asteroids and other macroscopic objects in the Taurid swarm using the Zwicky Transient Facility survey. We determine from our nondetection that there are no more than 9–14 H ≤ 24 (equivalent to a diameter of D ≳ 100 m) objects in the swarm, suggesting that the Encke–Taurid progenitor was ∼10 km in size. A progenitor of such a size is compatible with the prediction of state-of-the-art solar system dynamical models, which expects ∼0.1D &gt; 10 km objects on Encke-like orbits at any given time.

Keywords: Near-Earth objects
Unraveling the Water Sources in Comet 103P/Hartley 2 from Deep Impact Flyby Observations. The Deep Impact eXtended Mission flyby of comet 103P/Hartley 2 offered a rare opportunity to study a hyperactive comet with high-cadence and high-resolution observations from a fixed vantage point. Using the high signal-to-noise data from the HRI-IR instrument, the H2O and CO2 distributions in the comet's coma are mapped and quantified over one complete rotation period, revealing two major sources of water: direct sublimation from the nucleus, and sublimation of icy grains in the coma in the antisunward direction. These icy grains contributed 25%–40% of the total water production during the 2010 perihelion passage, quantifying the source of Hartley 2's hyperactivity. In addition, sublimation from slower-moving icy grains redeposited at the comet's gravitational low is detectable within 5.2 km of the nucleus, accounting for a few percent of the water production. CO2 production distinctly tracks with the nucleus's small lobe, which is seen to be active throughout Hartley 2's rotation even when not illuminated and thus is less dependent on instantaneous solar illumination than water. Differences in CO2 and H2O sources lead to spatially resolved CO2/H2O ratios ranging from 5% to 21% sampled at various times and locations in the coma throughout a single rotation, while the global abundance ratio varies by a factor of ∼2 throughout a single rotation (6%–12%). These observations highlight the complex interaction between solar insolation, comet rotation, and volatile outgassing and suggest that the lobes of Hartley 2 may have different formational or evolutionary origins, implying large-scale mixing in the protoplanetary disk.

Keywords: Comae, Short period comets, Infrared astronomy, Spectroscopy, Comets, Comet volatiles , Flyby missions
There's More to Life in Reflected Light: Simulating the Detectability of a Range of Molecules for High-contrast, High-resolution Observations of Nontransiting Terrestrial Exoplanets. The upcoming extremely large telescopes (ELTs) will provide the first opportunity to search for signs of habitability and life on nontransiting terrestrial exoplanets using high-contrast, high-resolution instrumentation. However, the suite of atmospheric gases in terrestrial exoplanet environments that are accessible to ground-based reflected light observations has not been thoroughly explored. In this work, we use an upgraded ELT detectability pipeline to simulate the detectability of gases that can serve as habitability markers, potential biosignatures, and false-positive discriminants in the atmospheres of Earth-sized and sub-Neptune planets. We calculate molecular detectability for five photochemically self-consistent atmosphere types, including the modern and Archean Earth, uninhabited biosignature "false-positive" environments, and a sub-Neptune, over a grid of observational configurations for nontransiting targets within 10 pc of Earth. For the most accessible nearby target, Proxima Centauri b, our results suggest that we may be able to rule out a sub-Neptune atmosphere in as little as a single hour of observing, and two biosignature disequilibrium pairs (O2/CH4 and CO2/CH4) may be accessible in ∼10 hr for the most optimistic scenario. It may also be possible to discriminate uninhabited worlds and rule out biosignature false positives by identifying contextual indicators (CO and H2O) of abiotic O2 and/or CH4 buildup on similar timescales. In the near term, ELT reflected light observations will likely allow us to characterize multiple nearby terrestrial atmospheres and ultimately search for signs of habitability and life.

Keywords: High resolution spectroscopy, Astrobiology, Exoplanet atmospheres
Saturnian Irregular Satellites as a Probe of Kuiper Belt Surface Evolution. We present the JWST NIRSpec PRISM 0.7–5.3 μm spectra of Albiorix and Siarnaq and the NIRSpec G235H/G395M 1.7–5.3 μm spectra of Phoebe, the three largest Saturnian irregular satellites. The irregular satellites of the giant planets are thought to be captured planetesimals from the same population as Kuiper Belt objects (KBOs). They are emplaced inside Saturn's Hill sphere during the giant-planet instability described by the Nice model and are thus valuable tracers of Kuiper Belt surface evolution. Phoebe's JWST spectrum matches the global average from Cassini VIMS, and by comparing the spectrum to the library of KBO spectra from JWST, we demonstrate Phoebe's compositional similarity to water-rich KBOs. On the smaller Albiorix and Siarnaq, we observe a broad 3 μm O–H band but do not see a Fresnel peak or the 1.5/2.0 μm features characteristic of H2O ice. We posit that after capture, the frequent high-velocity collisions between smaller irregular satellites sublimate the water ice, while the much larger Phoebe is resistant to disruption and retains its water ice. We suggest that the presence of CO2 on the smaller satellites, despite the lack of water ice, indicates later formation of CO2 on these surfaces through irradiation of organic compounds.

Keywords: Kuiper belt, Irregular satellites, Infrared spectroscopy
Jupiter's Interior with an Inverted Helium Gradient. Jupiter's gravity field observed by NASA's Juno spacecraft indicates that the density in the 10–100 GPa region is lower than one would expect from a H/He adiabat with 0.5–5× solar water abundance, as has been observationally inferred in Jupiter's atmosphere, supported by the 2–4× solar enrichment in the heavy noble gases and other volatiles observed by the Galileo entry probe. Here, we assume that Jupiter's envelope harbors a radiative window at ∼0.975–0.99RJ. This outer stable layer (OSL) delays particle exchange and accelerates the cooling of the deep interior. Consequently, the He depletion at the Mbar level, where H/He phase separation occurs, would be stronger than seen in the atmosphere. We find that the inverted He gradient across the OSL leads to atmospheric heavy element abundances that are up to ΔZatm = 0.03(+2× solar) higher than for adiabatic models. With an additional inverted Z gradient, Zatm up to 3× solar is possible. Models with 1× solar Zatm have a dilute core confined to the inner 0.2–0.3MJ (0.4–0.5RJ), smaller than in adiabatic models. Models with 3× solar Zatm have a largely homogeneous Z interior at 1× solar. The low observed atmospheric Ne/He ratio suggests that Ne is transported through the OSL as efficiently as He is, and at an enhanced diffusivity, as is characteristic of double-diffusive convection. Better knowledge of the H/He equation of state in the 10–100 GPa region and of the H/He phase diagram is needed to understand Jupiter's interior structure.

Keywords: Planetary interior, Solar system gas giant planets, Jupiter
Charged Clouds of Ionized Gas Emerge from Tribocharging Grains. If two solid particles collide, charge is exchanged. However, this transfer is not restricted to the surface of the particle. Ions are also dispersed into the environment. They form a charge cloud around the particle. In this way, all particle-laden atmospheres from volcanic plumes on Earth over exoplanet atmospheres to protoplanetary disks might be subject to gas-phase ionization by means of particle collisions. In laboratory experiments, we quantify the amount of ions produced in a collision of glass beads with 2.8 mm diameter. We extract the ions by applying an external electrostatic field and measuring the generated current. The ions are detected at all the pressures studied, i.e., from 0.3 mbar to 100 mbar. However, the ionization rate peaks at about 1 mbar. Scaled to individual bouncing collisions, charge as high as ∼1 pC of each polarity was detected. This implies collisions of grains can be a significant source of ions in various atmospheres.

Keywords: Collisional processes, Charge transfer, Planetary atmospheres, Planetary science, Charge exchange ionization, Planetary dynamics, Atmospheric science
LiDO: Exploring the Stable Plutino Parameter Space. We present a publicly available, high-resolution, filled-parameter-space synthetic distribution of the plutinos, trans-Neptunian objects (TNOs) librating in the 3:2 mean-motion resonance with Neptune, with particular focus on the plutinos simultaneously Kozai librating. This synthetic distribution was built in preparation for results from the Large inclination Distant Objects (LiDO) survey, which pointed at locations on the sky where Kozai plutinos are predicted to come to pericenter and are thus most easily detected in magnitude-limited surveys. Although we do not expect the full stable parameter space presented here to be populated with real TNOs, it provides a useful starting point for comparison with Neptune migration simulations and debiased observational results. Our new stable parameter-space synthetic distribution of fictitious plutinos is consistent with previous works, and we build on past results by focusing on the behavior of Kozai plutinos over 4 Gyr integrations. We find that 95% of 4 Gyr stable Kozai plutinos remain in the same ω-libration island for the entire integration. This provides an interesting diagnostic opportunity: any asymmetry in the true number of 4 Gyr stable Kozai plutinos in the two ω-libration islands must be caused by the details of emplacement during giant planet migration. Through analysis of previously published Neptune migration models, we show that the intrinsic fraction of plutinos captured into Kozai depends on Neptune's migration speed and mode. Combining the filled-parameter-space synthetic distribution with future migration simulations and the results of the carefully characterized LiDO survey will enable interpretation of the intrinsic orbital distribution of the Kozai and non-Kozai plutinos.

Keywords: Small Solar System bodies, Kuiper belt, Plutoids, Resonant Kuiper belt objects, Trans-Neptunian objects
Fully Coherent Model of Dynamics around Binary Asteroids: Application to Didymos and the DART Impact. The dynamical environment around binary asteroids has been studied in depth, but these models typically make assumptions about the eccentricity, shapes, or rotational stability of the asteroids. In this work, we develop a fully coherent dynamical model accounting for the gravitational influence of two arbitrarily shaped asteroids and the Sun, allowing for eccentricity and irregular spin states within the binary asteroid. We apply this model to Didymos after the DART impact to determine the stability of orbits in the perturbed system. We then study the behavior of ejecta and identify regions in which ejecta may be long-lived, a concern for the Hera mission. It is likely debris from the DART impact will survive in the system throughout the duration of the Hera mission, and these particles are generally at least 10 cm in diameter and found in wide, eccentric, and inclined orbits. The most likely region for Hera to encounter these particles is just outside the orbit of Dimorphos.

Keywords: Astrodynamics, Ejecta, Asteroid dynamics, Asteroid satellites, N-body simulations
Equatorial CO<SUB>2</SUB> Distribution Suggests Active CO<SUB>2</SUB> Supply on Europa. The James Webb Space Telescope's (JWST) observation of Europa recently revealed CO2 accumulation around geologically young chaos terrains Tara Regio and Powys Regio. The spatial heterogeneity in CO2 distribution suggests an endogenic source of CO2 in these terrains, although the timescale of CO2 supply remains uncertain. Here, we investigate CO2 distribution on Europa by conducting Monte Carlo simulations considering sublimation, ballistic transport, and loss via photoionization. With a hypothetical CO2 source at the equator, a CO2 molecule is transported to the polar regions over a timescale of ∼10 days before being lost via photoionization. Accordingly, CO2 accumulates around the poles, with minimal CO2 around the hypothetical source under steady-state conditions. To achieve a CO2 distribution similar to that observed by the JWST, an unknown effective loss process of CO2 on Europa, &gt;100 times faster than photoionization, would be required. Such a process may include CO2 dissociation/ionization by irradiation of high-energy particles. Since CO2 at the equatorial regions would be lost via either transport to the polar regions or dissociation/ionization within tens of days after CO2 supply, CO2 at around the equatorial regions observed by the JWST suggests its ongoing supply to the surface. Further continuous observations of Europa provide insights into the chemistry and dynamics of CO2.

Keywords: James Webb Space Telescope, Carbon dioxide, Europa