Sazuna/UAT_keywords huggingface dataset:
Analyzing LDEX's Current Measurements in Lunar Orbit. The Lunar Dust Experiment (LDEX) on board the Lunar Atmosphere and Dust Environment Explorer mission orbited the Moon from 2014 September to 2015 April and observed a dynamic, permanently present dust cloud produced by continual meteoroid bombardment. In addition to measuring individual ejecta with radii &gt;0.3 μm, LDEX also recorded an integrated current of the collective signal generated by the impacts of smaller ejecta particles. From this signal, we explore the potential for electrostatic dust lofting via twilight craters through correlation with changes in lunar topography. As the integrated current can contain numerous background contributions, we start by isolating regions of transient enhancements of this signal. A consistent lunar dayside enhancement is identified, with solar wind ions reflected as energetic neutral atoms shown to be a feasible source. We do not detect any enhanced integrated current correlated with the antihelion meteoroid bombardment or discernible enhancement due to electrostatic lofting via twilight craters, suggesting that electrostatic dust lofting does not contribute to the lunar dust environment at high altitudes (≫1 km).

Keywords: Lunar surface, The Moon, Meteoroids
Highly Resolved Topography and Illumination at Mercury's South Pole from MESSENGER MDIS NAC. Mercury's south polar region is of particular interest since Arecibo radar measurements show many high-reflectance regions consistent with ice deposits. However, current elevation information in Mercury's southern hemisphere is not sufficient to perform detailed modeling of the illumination and thermal conditions at these radar-bright locations and to constrain properties of the volatiles potentially residing there. In this work, we leverage previously existing elevation maps of Mercury's surface from stereo-photogrammetry at 665 m pix-1, Mercury Dual Imaging System Narrow Angle Camera images, and Shape-from-Shading tools from the Ames Stereo Pipeline, to provide the first high-resolution topographic maps of the south pole with a resolution of 250 m pix-1 poleward of 75°S. We show that the increased resolution and level of detail provided by our new elevation model allow for a more realistic recovery of illumination conditions in Mercury's south polar region, thus opening the way to future thermal analyses and for the characterization of potential ice and volatile deposits. We compare both the old and new topographic models to the Mercury Dual Imaging System Narrow Angle Camera images to show the higher level of fidelity with our products, and we assess the improved consistency of derived permanently shadowed regions with reflectance measurements by Arecibo's antennas.

Keywords: Planetary surfaces, Planetary polar regions, Remote sensing, Surface ices, Mercury (planet)
Subsurface Science and Search for Life in Ocean Worlds. Several worlds in our solar system are thought to hold oceans of liquid water beneath their frozen surfaces. These subsurface ice and ocean environments are promising targets in the search for life beyond Earth, but they also present significant new technical challenges to planetary exploration. With a focus on Jupiter's moon Europa, here we (1) identify major benefits and challenges to subsurface ocean world science, (2) provide a multidisciplinary survey of relevant sample handling and life detection technologies, and (3) integrate those perspectives into the Subsurface Science and Search for Life in Ocean Worlds (SSSLOW) concept payload. We discuss scientific goals across three complementary categories: (1) search for life, (2) assess habitability, and (3) investigate geological processes. Major mission challenges considered include submerged operation in high-pressure environments, the need to sample fluids with a range of possible chemical conditions, and detection of biosignatures at low concentrations. The SSSLOW addresses these issues by tightly integrated instrumentation and sample handling systems to enable sequential, complementary measurements while prioritizing preservation of sample context. In this work, we leverage techniques and technologies across several fields to demonstrate a path toward future subsurface exploration and life detection in ice and ocean worlds.

Keywords: Planetary probes, Astrobiology, Europa
Thin-shell Tidal Dynamics of Ocean Worlds. Several solar system moons harbor subsurface water oceans; extreme internal heating or solar irradiation can form magma oceans in terrestrial bodies. Tidal forces drive ocean currents, producing tidal heating that affects the thermal-orbital evolution of these worlds. If the outermost layers (ocean and overlying shell) are thin, tidal dynamics can be described using thin-shell theory. Previous work assumed that the ocean and shell's thickness and density are uniform. We present a formulation of thin-shell dynamics that relaxes these assumptions and apply it to several cases of interest. The tidal response of unstratified oceans of constant thickness is given by surface gravity and Rossby waves, which can resonate with the tidal force. The oceans of the outer solar system are too thick for gravity wave resonances, but high-amplitude Rossby waves can be excited in moons with high orbital obliquity. We find that meridional ocean thickness variations hinder the excitation of Rossby waves, decreasing tidal dissipation and increasing the inclination damping timescale, which allows us to reconcile the present inclination of the Moon with the existence of a past long-lived magma ocean and to explain the inclination of Titan and Callisto without invoking a recent excitation. Stratified oceans can support internal gravity waves. We show that dissipation due to internal waves can exceed that resulting from surface gravity waves. For Enceladus, it can be close to the moon's thermal output, even if the ocean is weakly stratified. Shear due to internal waves can result in Kelvin-Helmholtz instabilities and induce ocean mixing.

Keywords: Enceladus, Natural satellites (Solar system), Ocean tides, Io, Earth-moon system
Optical Characterization of the DART Impact Plume: Importance of Realistic Ejecta Scattering Properties. The Double Asteroid Redirection Test (DART) mission will impact the moon Dimorphos of the (65803) Didymos binary and demonstrate the kinetic impactor technique for planetary defense. Observations from the ride-along CubeSat companion, LICIACube, of the spatial structure and temporal evolution of the resulting ejecta plume will help determine the vector momentum transfer and constrain physical properties such as strength and porosity. The optical scattering properties of the ejecta particles used in plume simulations will dictate the critical relation between observed brightness and inferred ejecta mass (and momentum). Here we examine the scattering behavior of plausible analogs for Dimorphos ejecta particles, including laboratory-measured "millimeter grains" selected based on a comparison with Bennu particle photometry. Over the range of phase angles observable by LICIACube (≲120°), brightness simulations for optical depths ranging from 0.01 to 10 show that scattering from these analogs is considerably dimmer than from grains scattering isotropically. Therefore, adopting realistic scattering properties for ejecta particles is critical for accurately interpreting and understanding observations of the DART impact.

Keywords: Impact phenomena, Near-Earth objects, Asteroids, Asteroid satellites, Radiative transfer, Radiative transfer simulations
Ammonia Abundance Derived from Juno MWR and VLA Observations of Jupiter. The vertical distribution of trace gases in planetary atmospheres can be obtained with observations of the atmosphere's thermal emission. Inverting radio observations to recover the atmospheric structure, however, is nontrivial, and the solutions are degenerate. We propose a modeling framework to prescribe a vertical distribution of trace gases that combines a thermochemical equilibrium model with a vertical temperature structure and compare these results to models where ammonia can vary between predefined pressure nodes. We compare these model to nadir brightness temperatures and limb-darkening parameters, together with their uncertainties, which we reduced from the raw Juno Microwave Radiometer (MWR) data set. We then apply this framework to MWR observations during Juno's first years of operation (perijove passes 1-12) and to longitudinally averaged latitude scans taken with the upgraded Very Large Array. We use the model to constrain the distribution of ammonia between -60° and 60° latitude and down to 100 bars. We constrain the ammonia abundance to be ${340.5}_{-21.2}^{+34.8}$ ppm ( ${2.66}_{-0.17}^{+0.27}\times $ solar abundance) and find a depletion of ammonia down to a depth of ~20 bars, which supports the existence of processes that deplete the atmosphere below the ammonia and water cloud layers. At the equator we find an increase of ammonia with altitude, while the zones and belts in the midlatitudes can be traced down to levels where the atmosphere is well mixed. The latitudinal variation in the ammonia abundance appears to be opposite to that shown at higher altitudes, which supports the existence of a stacked-cell circulation model.

Keywords: Atmospheric composition, Radio astronomy, Planetary atmospheres
Leto Mission Concept for Green Reconnaissance of the Marius Hills Lunar Pit. Lava tubes are potentially important sites for the long-term human presence on the Moon because they provide shelter from surface hazards, including micrometeorites, radiation, extreme temperatures, and dust. The discovery of a lava tube opening or pit at Marius Hills in Oceanus Procellarum is compelling motivation for robotic and eventually human exploration missions to these sites for in situ investigations and site assessments to determine viability for habitation and utilization of lunar resources. We make the case for Marius Hills to be a high-priority landing site and present elements of lunar data analysis, instrument/payload concepts, science justification for robotic missions, and thematic geologic reconnaissance and remote sensing that should be conducted prior to any construction or emplacement of infrastructure. This is described as a "green reconnaissance" approach to lunar exploration and exploitation, which seeks to address such contamination factors as sprayed rocket exhaust and sublimating water in order to preserve science fidelity. We are developing a concept of operations called the Leto mission for a green reconnaissance approach to robotically access the Marius Hills sublunarean void.

Keywords: The Moon, Lunar science, Lunar features
Spectral Analysis of Clay-bearing Outcrops in Northern Xanthe Terra, Mars: Comparison with Oxia Planum, the Landing Site for the ExoMars Rover Mission. Clay minerals detected on Mars are valuable targets to seek traces of life on the planet, where biosignatures might be preserved. Here, we report an in-depth spectral analysis of clay-rich outcrops identified in northern Xanthe Terra (300°-320° E, 10°-20° N). We focused particularly on the absorptions centered in the 1.0-2.6 μm spectral range to (1) constrain the mineralogy of the clay outcrops, (2) map their strength and distribution throughout the region, and thus (3) develop a better understanding of the geologic environment at circum-Chryse Planitia. We then compared the infrared signatures in Xanthe Terra and Oxia Planum. Like in Oxia Planum, Xanthe's clays are consistent with either Fe-bearing saponites or vermiculites. However, the spectral signatures in Xanthe are weaker relative to Oxia Planum, perhaps due to significant dust cover in the region. Besides the spectral signatures, northern Xanthe Terra displays several morphological features similar to Oxia Planum, indicating long-lasting aqueous activity (fluvial channels and fan deltas). Clays found at the fan deltas could be detrital (fluvial transport) or authigenic (lacustrine or deltaic sedimentation), while the origin of clays seen elsewhere on the surrounding plateaus remains undetermined. Oxia Planum has been selected as the landing site for ESA's ExoMars "Rosalind Franklin" rover, where its instruments will search for signs of life and constrain the nature and origin of the clays. This exploration will indubitably provide new clues on the clays found in the circum-Chryse basin.

Keywords: Mars
Analysis of CN Coma Morphology Features of Comet 21P/Giacobini-Zinner. We analyze jet features found in the coma of comet 21P/Giacobini-Zinner (21P/GZ) during its 2018 perihelion passage using narrowband CN photometric imaging in order to determine the comet's rotational period, and we constrain the CN gas outflow velocity and rotational state through the analysis of azimuthally enhanced morphological features. We find that 21P/GZ has a period of either 7.39 ± 0.01 hr or 10.66 ± 0.01 hr. We measure a lower limit to the outflow velocity for the northern jet of 730 ± 30 m s-1 and for the southern jet of 740 ± 30 m s-1. We analyze the morphologies of the jet features and determine that the northern jet possesses a corkscrew pattern, and we utilize that knowledge to determine a rotational pole position at an R.A. of ${169}_{-23}^{+{28}^{}}$ deg and a decl. of ${73}_{-11}^{+5}$ deg, with an undetermined sense of rotation.

Keywords: Period determination, Short period comets, Comet dynamics, Lomb-Scargle periodogram, Comets
(523599) 2003 RM: The Asteroid that Wanted to be a Comet. We report a statistically significant detection of nongravitational acceleration on the subkilometer near-Earth asteroid (523599) 2003 RM. Due to its orbit, 2003 RM experiences favorable observing apparitions every 5 yr. Thus, since its discovery, 2003 RM has been extensively tracked with ground-based optical facilities in 2003, 2008, 2013, and 2018. We find that the observed plane-of-sky positions cannot be explained with a purely gravity-driven trajectory. Including a transverse nongravitational acceleration allows us to match all observational data, but its magnitude is inconsistent with perturbations typical of asteroids such as the Yarkovsky effect or solar radiation pressure. After ruling out that the orbital deviations are due to a close approach or collision with another asteroid, we hypothesize that this anomalous acceleration is caused by unseen cometary outgassing. A detailed search for evidence of cometary activity with archival and deep observations from the Panoramic Survey Telescope and Rapid Response System and the Very Large Telescope does not reveal any detectable dust production. However, the best-fitting H2O sublimation model allows for brightening due to activity consistent with the scatter of the data. We estimate the production rate required for H2O outgassing to power the acceleration and find that, assuming a diameter of 300 m, 2003 RM would require Q(H2O) ~ 1023 molec s-1 at perihelion. We investigate the recent dynamical history of 2003 RM and find that the object most likely originated in the mid-to-outer main belt (~86% probability) as opposed to from the Jupiter-family comet region (~11% probability). Further observations, especially in the infrared, could shed light on the nature of this anomalous acceleration.

Keywords: Near-Earth objects, Comet dynamics, Asteroid dynamics
Reaction between Hydrogen and Ferrous/Ferric Oxides at High Pressures and High Temperatures-Implications for Sub-Neptunes and Super-Earths. Sub-Neptune exoplanets may have thick hydrogen envelopes and therefore develop a high-pressure interface between hydrogen and the underlying silicates/metals. Some sub-Neptunes may convert to super-Earths via massive gas loss. If hydrogen chemically reacts with oxides and metals at high pressures and temperatures (P-T), it could impact the structure and composition of the cores and atmospheres of sub-Neptunes and super-Earths. While H2 gas is a strong reducing agent at low pressures, the behavior of hydrogen is unknown at the P-T expected for sub-Neptunes' interiors, where hydrogen is a dense supercritical fluid. Here we report experimental results of reactions between ferrous/ferric oxides and hydrogen at 20-40 GPa and 1000-4000 K utilizing the pulsed laser-heated diamond-anvil cell combined with synchrotron X-ray diffraction. Under these conditions, hydrogen spontaneously strips iron off the oxides, forming Fe-H alloys and releasing oxygen to the hydrogen medium. In a planetary context where this reaction may occur, the Fe-H alloy may sink to the metallic part of the core, while released oxygen may stabilize as water in the silicate layer, providing a mechanism to ingas hydrogen to the deep interiors of sub-Neptunes. Water produced from the redox reaction can also partition to the atmosphere of sub-Neptunes, which has important implications for understanding the composition of their atmospheres. In addition, super-Earths converted from sub-Neptunes may contain a large amount of hydrogen and water in their interiors (at least a few wt% H2O). This is distinct from smaller rocky planets, which were formed relatively dry (likely a few hundredths wt% H2O).

Keywords: Exoplanets, Exoplanet evolution, Planetary science, Exoplanet formation, Planetary interior, Planet formation
RETRACTED: Redox Evolution of the Crystallizing Terrestrial Magma Ocean and Its Influence on the Outgassed Atmosphere. Magma oceans (MOs) are episodes of large-scale melting of the mantle of terrestrial planets. The energy delivered by the Moon-forming impact induced a deep MO on the young Earth, corresponding to the last episode of core-mantle equilibration. The crystallization of this MO led to the outgassing of volatiles initially present in the Earth's mantle, resulting in the formation of a secondary atmosphere. During outgassing, the MO acts as a chemical buffer for the atmosphere via the oxygen fugacity, set by the equilibrium between ferrous- and ferric-iron oxides in the silicate melts. By tracking the evolution of the oxygen fugacity during MO solidification, we model the evolving composition of a C-O-H atmosphere. We use the atmospheric composition to calculate its thermal structure and radiative flux. This allows us to calculate the lifetime of the terrestrial MO. We find that, upon crystallizing, the MO evolves from a mildly reducing to a highly oxidized redox state, thereby transiting from a CO- and H2-dominated atmosphere to a CO2- and H2O-dominated one. We find the overall duration of the MO crystallization to depend mostly on the bulk H content of the mantle, and to remain below 1.5 millions yr for up to nine Earth's water oceans' worth of H. Our model also suggests that reduced atmospheres emit lower infrared radiation than oxidized ones, despite of the lower greenhouse effect of reduced species, resulting in a longer MO lifetime in the former case. Although developed for a deep MO on Earth, the framework applies to all terrestrial planet and exoplanet MOs, depending on their volatile budgets.

Keywords: Planetary theory, Planetary atmospheres, Planetary thermal histories, Planetary science, Planetary structure, Atmospheric science
Early Water Delivery to Terrestrial Planet Regions during the Stages of Jupiter's Formation and Migration in the Grand Tack Model. The formation and subsequent migration of gas giants could significantly affect the material mixing in the solar system. In this study, we use N-body simulations to investigate how much water is transported into the region of the terrestrial planet formation during the growth and migration phases of Jupiter in the Grand Tack model. We found that Jupiter's growth was accompanied by significant mass transport and that a substantial amount of water (about 10 times Earth's ocean mass for the initial planetesimal distribution based on the minimum-mass solar nebula) was transported into the terrestrial planet region. The total amount delivered increased further during Jupiter's migration phase (totaling about 10-40 times Earth's ocean mass), which was less dependent on simulation parameters. In addition, at these stages, terrestrial planets were not fully grown. Therefore, water supplied during these early stages could interact with metallic iron during the core formation of protoplanets and/or growing Earth. Since hydrogen in water molecules can dissolve into their cores, this could explain the density deficit observed in the current Earth core. Notably, Jupiter could play an important role as a "barrier" in explaining the dichotomy of the isotopic compositions between noncarbonaceous (NC) and carbonaceous (CC) meteorites. This study's results show that Jupiter's growth necessitates some mixing of NC and CC materials.

Keywords: Solar system, Planetary dynamics, Planet formation
Mercury's Circumsolar Dust Ring as an Imprint of a Recent Impact. A circumsolar dust ring has been recently discovered close to the orbit of Mercury. There are currently no hypotheses for the origin of this ring in the literature, so we explore four different origin scenarios here: the dust originated from (1) the sporadic meteoroid complex that comprises the major portion of the Zodiacal Cloud, (2) recent asteroidal/cometary activity, (3) hypothetical dust-generating bodies locked in mean-motion resonances beyond Mercury, and (4) bodies co-orbiting with Mercury. We find that only scenario (4) reproduces the observed structure and location of Mercury's dust ring. However, the lifetimes of Mercury's co-orbitals (&lt;20 Ma) preclude a primordial origin of the co-orbiting source population due to dynamical instabilities and meteoroid bombardment, demanding a recent event feeding the observed dust ring. We find that an impact on Mercury can eject debris into the co-orbital resonance. We estimate the ages of six candidate impacts that formed craters larger than 40 km in diameter using high-resolution spacecraft data from MESSENGER and find two craters with estimated surface ages younger than 50 Ma. We find that the amount of mass transported from Mercury's surface into the co-orbital resonance from these two impacts is several orders of magnitude smaller than what is needed to explain the magnitude of Mercury's ring inferred from remote sensing. Therefore we suggest that numerous younger, smaller impacts collectively contributed to the origin of the ring. We conclude that the recent impact hypothesis for the origin of Mercury's dust ring is a viable scenario, whose validity can be constrained by future inner solar system missions.

Keywords: Impact phenomena, Planetary surfaces, Asteroids, Orbital resonances, Meteoroid dust clouds, Mercury (planet), Zodiacal cloud, Interplanetary dust, Craters