Sazuna/UAT_keywords huggingface dataset:
Sensitivity Testing of Stereophotoclinometry for the OSIRIS-REx Mission. II. Effective Observation Geometry for Digital Terrain Modeling. The OSIRIS-REx mission used stereophotoclinometry (SPC) to generate digital terrain models (DTMs) of its target asteroid, Bennu. Here we present a suite of preflight tests conducted to identify the observing geometry and number of images needed to create DTMs that would enable successful navigation around and to the surface of the asteroid. We demonstrate that high-quality DTMs can be generated by using only five images: four that are focused on topography, in which the spacecraft's viewing geometry brackets the target (north, south, east, and west), and a fifth that measures the target's albedo variation, taken from near local noon. We further show that the first 10 iterations of the SPC process can meaningfully improve DTM quality, including in the case of a suboptimal input image set, whereas after 10 iterations the DTM quality approaches an asymptotic maximum. We distill our findings into recommendations for observation planning that can be applied by other missions intending to use SPC to model the shape and terrain of their target.

Keywords: Near-Earth objects, Asteroids, Asteroid surfaces
The Secular Dynamical Evolution of Binary Asteroid System (65803) Didymos Post-DART. The successful impact of NASA's DART mission with Dimorphos, the secondary body of binary asteroid system (65803) Didymos, altered the attitude, shape, and orbit of Dimorphos. In addition to perturbing the immediate short-term dynamics of the system, these changes have major implications for the binary Yarkovsky–O'Keefe–Radzievskii–Paddack (BYORP) effect and resulting long-term secular evolution. In this study, we assess the range of possible reshaping-induced changes in BYORP. We produce high-fidelity numerical simulations of the orbit-attitude coupled tidal-BYORP dynamical evolution of the Didymos system to constrain how the secular evolution changed from its preimpact behavior. We find that the nature of the dynamics is highly dependent on a variety of initial conditions and assumptions, and it is difficult to fully predict how the system will secularly evolve following the impact. Rather, we provide a range of feasible possibilities within the bounds of observations and current best estimates of the Didymos system parameters. ESA's Hera mission will help reduce uncertainties surrounding the postimpact state and shape of Dimorphos in 2027, allowing our predictions of the secular evolutionary effects and long-term fate of the Didymos system to be better refined.

Keywords: Near-Earth objects, Asteroids, Asteroid dynamics, Small Solar System bodies, Asteroid satellites, Asteroid rotation, Asteroid surfaces
Achievement of the Planetary Defense Investigations of the Double Asteroid Redirection Test (DART) Mission. NASA's Double Asteroid Redirection Test (DART) mission was the first to demonstrate asteroid deflection, and the mission's Level 1 requirements guided its planetary defense investigations. Here, we summarize DART's achievement of those requirements. On 2022 September 26, the DART spacecraft impacted Dimorphos, the secondary member of the Didymos near-Earth asteroid binary system, demonstrating an autonomously navigated kinetic impact into an asteroid with limited prior knowledge for planetary defense. Months of subsequent Earth-based observations showed that the binary orbital period was changed by –33.24 minutes, with two independent analysis methods each reporting a 1σ uncertainty of 1.4 s. Dynamical models determined that the momentum enhancement factor, β, resulting from DART's kinetic impact test is between 2.4 and 4.9, depending on the mass of Dimorphos, which remains the largest source of uncertainty. Over five dozen telescopes across the globe and in space, along with the Light Italian CubeSat for Imaging of Asteroids, have contributed to DART's investigations. These combined investigations have addressed topics related to the ejecta, dynamics, impact event, and properties of both asteroids in the binary system. A year following DART's successful impact into Dimorphos, the mission has achieved its planetary defense requirements, although work to further understand DART's kinetic impact test and the Didymos system will continue. In particular, ESA's Hera mission is planned to perform extensive measurements in 2027 during its rendezvous with the Didymos–Dimorphos system, building on DART to advance our knowledge and continue the ongoing international collaboration for planetary defense.

Keywords: Impact phenomena, Near-Earth objects, Small Solar System bodies, Asteroids, Asteroid dynamics, Asteroid satellites, Planetary science, Asteroid surfaces, Solar system astronomy
The DECam Ecliptic Exploration Project (DEEP). V. The Absolute Magnitude Distribution of the Cold Classical Kuiper Belt. The DECam Ecliptic Exploration Project (DEEP) is a deep survey of the trans-Neptunian solar system being carried out on the 4 m Blanco telescope at the Cerro Tololo Inter-American Observatory in Chile using the Dark Energy Camera (DECam). By using a shift-and-stack technique to achieve a mean limiting magnitude of r ∼ 26.2, DEEP achieves an unprecedented combination of survey area and depth, enabling quantitative leaps forward in our understanding of the Kuiper Belt populations. This work reports results from an analysis of 20, 3 deg2 DECam fields along the invariable plane. We characterize the efficiency and false-positive rates for our moving-object detection pipeline, and use this information to construct a Bayesian signal probability for each detected source. This procedure allows us to treat all of our Kuiper Belt object (KBO) detections statistically, simultaneously accounting for efficiency and false positives. We detect approximately 2300 candidate sources with KBO-like motion with signal-to-noise ratios &gt; 6.5. We use a subset of these objects to compute the luminosity function of the Kuiper Belt as a whole, as well as the cold classical (CC) population. We also investigate the absolute magnitude (H) distribution of the CCs, and find consistency with both an exponentially tapered power law, which is predicted by streaming instability models of planetesimal formation, and a rolling power law. Finally, we provide an updated mass estimate for the CC Kuiper Belt of ${M}_{{CC}}({H}_{r}\lt 12)\,=\,{0.0017}_{-0.0004}^{+0.0010}{M}_{\oplus }$ , assuming albedo p = 0.15 and density ρ = 1 g cm‑3.

Keywords: Small Solar System bodies, Kuiper belt, Solar system, Planetary science, Solar system astronomy
Five Mars Years of Cloud Observations at Gale Crater: Opacities, Variability, and Ice Crystal Habits. We update the record of cloud opacity observations conducted by the Mars Science Laboratory (MSL) Curiosity rover to cover the first five Mars Years (MYs) of the mission (L s = 160° of MY 31 to L s = 160° of MY 36). Over the three MY period that we add to the previously analyzed two MY record, we achieve good diurnal coverage between 07:00 and 17:00 with nearly 1200 new observations. We derive a new scattering phase function for the clouds of the Aphelion Cloud Belt (ACB) using results from the Zenith and Suprahorizon movie data sets. Our phase function is generally smooth and featureless, which is consistent with the overall lack of atmospheric optical phenomena on Mars aside from a single instance of an observed halo. Applying our new phase function to the data, we find that there is very minimal variability in the ACB's opacity, either diurnally, intraseasonally, or interannually, noting that our observations are only sensitive to ice clouds and cannot detect any ice hazes that may be present over Gale. This contrasts with previous results, which observed a 57% difference in the opacity of morning and afternoon clouds in MY 33. The MY 33 results now appear to be an outlier, not replicated at any point during the MSL mission. We conclude that the higher morning opacities in MY 33 were a consequence of an incomplete understanding of the nature of the scattering phase function close to the Sun.

Keywords: Atmospheric clouds, Mars, Planetary atmospheres, Planetary science, Atmospheric variability, Atmospheric science
Mercury's Lobate Scarps Reveal that Polygonal Impact Craters Form on Contractional Structures. Analysis of polygonal impact craters (PICs) can be used to investigate the presence and orientations of subtle and/or buried faults and fractures across the solar system that may otherwise be unobservable in spacecraft images. Although this technique has been vetted for the analysis of extensional structures, no previous work has investigated if PICs also form on contractional thrust faults. This determination, which we investigated in this work, is critical for accurate tectonic setting interpretations from PICs. Mercury shows an abundance of thrust-fault-related landforms, making it an ideal laboratory to perform this investigation. In this work, we found that Mercury's thrust faults, and their overlying folds and fractures, cause some complex craters ∼20 km or larger to form PICs. However, in most cases, craters form as circular impact craters on these structures. When PIC straight rim segments do form, they parallel the lobate scarp thrust faults and fold hinges. Some PICs likely formed as a result of an impact's interaction with the thrust fault itself, while others may have interacted with fold hinge joints. The parallel relationship between PICs and shortening structures is consistent with the well-established relationship between PICs and extensional structures. Therefore, in addition to extensional fractures, contractional features should also be taken into consideration when utilizing PICs to interpret tectonic settings on bodies across the solar system.

Keywords: Impact phenomena, Planetary science, Mercury (planet), Tectonics, Craters
Large Carbonaceous Chondrite Parent Bodies Favored by Abundance–Volatility Modeling: A Possible Chemical Signature of Pebble Accretion. Primitive meteorite groups such as the Vigarano, Mighei, and Karoonda carbonaceous chondrites have enigmatic patterns of elemental abundances, with moderately volatile elements—those that transition from vapor to condensate between ∼400 and ∼900 K—defining plateaus of subequal abundances despite a wide range in volatility. In detail, each group defines a plateau with distinctive nonmonotonic "chemical fingerprints" that have been attributed to combinations of mixing, vaporization/condensation, and fluid-mediated metasomatism—but the extent to which these processes can reproduce the observed variability has not been quantified. Starting with primitive Ivuna chondrite, a two-stage, two-component equilibrium condensation–vaporization model—with gravity implemented as Jeans escape—can explain large-scale plateaus in these chondrite groups, as well as more complex, nonmonotonic small-scale variations. For all three chondritic meteorite groups, models favor earlier high-temperature fractionation under low-gravity conditions followed by a low-temperature fractionation event that took place on a protoplanet at least as large as Ceres. The second fractionation event may represent the fractionation of incoming materials to the planetesimal during protracted pebble accretion. Models with only thermally driven volatile loss, gravity, and mixing can explain more than 80% of the observed compositional variability in these meteorite groups. In our five-parameter model, using only five randomly selected elements yields uselessly large ranges of planet sizes and temperatures, ranges that converge with increasing numbers of elements. These results suggest that even simple models are prone to generating inaccurate conclusions when constrained by too few observations, a fault likely held by more complex models as well.

Keywords: Meteorite composition, Chondrites, Carbonaceous chondrites, Planetesimals, Meteorites, Planet formation
Direct N-body Simulations of Satellite Formation around Small Asteroids: Insights from DART's Encounter with the Didymos System. We explore binary asteroid formation by spin-up and rotational disruption considering the NASA DART mission's encounter with the Didymos–Dimorphos binary, which was the first small binary visited by a spacecraft. Using a suite of N-body simulations, we follow the gravitational accumulation of a satellite from meter-sized particles following a mass-shedding event from a rapidly rotating primary. The satellite's formation is chaotic, as it undergoes a series of collisions, mergers, and close gravitational encounters with other moonlets, leading to a wide range of outcomes in terms of the satellite's mass, shape, orbit, and rotation state. We find that a Dimorphos-like satellite can form rapidly, in a matter of days, following a realistic mass-shedding event in which only ∼2%–3% of the primary's mass is shed. Satellites can form in synchronous rotation due to their formation near the Roche limit. There is a strong preference for forming prolate (elongated) satellites, although some simulations result in oblate spheroids like Dimorphos. The distribution of simulated secondary shapes is broadly consistent with other binary systems measured through radar or lightcurves. Unless Dimorphos's shape is an outlier, and considering the observational bias against lightcurve-based determination of secondary elongations for oblate bodies, we suggest there could be a significant population of oblate secondaries. If these satellites initially form with elongated shapes, a yet-unidentified pathway is needed to explain how they become oblate. Finally, we show that this chaotic formation pathway occasionally forms asteroid pairs and stable triples, including coorbital satellites and satellites in mean-motion resonances.

Keywords: Near-Earth objects, Small Solar System bodies, Asteroid dynamics, Asteroids, Asteroid satellites, Asteroid rotation
A Solution for the Density Dichotomy Problem of Kuiper Belt Objects with Multispecies Streaming Instability and Pebble Accretion. Kuiper Belt objects (KBOs) show an unexpected trend, whereby large bodies have increasingly higher densities, up to five times greater than their smaller counterparts. Current explanations for this trend assume formation at constant composition, with the increasing density resulting from gravitational compaction. However, this scenario poses a timing problem to avoid early melting by decay of 26Al. We aim to explain the density trend in the context of streaming instability and pebble accretion. Small pebbles experience lofting into the atmosphere of the disk, being exposed to UV and partially losing their ice via desorption. Conversely, larger pebbles are shielded and remain icier. We use a shearing box model including gas and solids, the latter split into ices and silicate pebbles. Self-gravity is included, allowing dense clumps to collapse into planetesimals. We find that the streaming instability leads to the formation of mostly icy planetesimals, albeit with an unexpected trend that the lighter ones are more silicate-rich than the heavier ones. We feed the resulting planetesimals into a pebble accretion integrator with a continuous size distribution, finding that they undergo drastic changes in composition as they preferentially accrete silicate pebbles. The density and masses of large KBOs are best reproduced if they form between 15 and 22 au. Our solution avoids the timing problem because the first planetesimals are primarily icy and 26Al is mostly incorporated in the slow phase of silicate pebble accretion. Our results lend further credibility to the streaming instability and pebble accretion as formation and growth mechanisms.

Keywords: Kuiper belt, Hydrodynamics, Dwarf planets, Pluto, Planet formation
Subsurface Thermophysical Properties of Europa's Leading and Trailing Hemispheres as Revealed by ALMA. We present best-fit values of porosity—and the corresponding effective thermal inertiae—determined from three different depths in Europa's near-subsurface (∼1–20 cm). The porosity of the upper ∼20 cm of Europa's subsurface varies between 75% and 50% (Γeff ≈ 50–140 J m‑2 K‑1 s‑1/2) on the leading hemisphere and 50%–40% (Γeff ≈ 140–180 J m‑2 K‑1 s‑1/2) on the trailing hemisphere. Residual maps produced by comparison with these models reveal thermally anomalous features that cannot be reproduced by globally homogeneous porosity models. These regions are compared to Europa's surface terrain and known compositional variations. We find that some instances of warm thermal anomalies are co-located with known geographical or compositional features on both the leading and trailing hemisphere; cool temperature anomalies are well correlated with surfaces previously observed to contain pure, crystalline water ice and the expansive rays of Pwyll crater. Anomalous regions correspond to locations with subsurface properties different from those of our best-fit models, such as potentially elevated thermal inertia, decreased emissivity, or more porous regolith. We also find that ALMA observations at ∼3 mm sound below the thermal skin depth of Europa (∼10–15 cm) for a range of porosity values, and thus do not exhibit features indicative of diurnal variability or residuals similar to other frequency bands. Future observations of Europa at higher angular resolution may reveal additional locations of variable subsurface thermophysical properties, while those at other wavelengths will inform our understanding of the regolith compaction length and the effects of external processes on the shallow subsurface.

Keywords: Planetary surfaces, Millimeter astronomy, Natural satellite surfaces, Radio astrometry, Europa, Remote sensing, Planetary science, Submillimeter astronomy, Galilean satellites, Ice porosity, Thermal properties (Ice)
One-dimensional Microphysics Model of Venusian Clouds from 40 to 100 km: Impact of the Middle-atmosphere Eddy Transport and SOIR Temperature Profile on the Cloud Structure. We conducted a simulation of H2SO4 vapor, H2O vapor, and H2SO4–H2O liquid aerosols from 40 to 100 km, using a 1D Venus cloud microphysics model based on the one detailed in Imamura &amp; Hashimoto. The cloud distribution obtained is in good agreement with in situ observations by Pioneer Venus and remote-sensing observations from Venus Express (VEx). Case studies were conducted to investigate sensitivities to atmospheric parameters, including eddy diffusion and temperature profiles. We find that efficient eddy transport is important for determining upper haze population and its microphysical properties. Using the recently updated eddy diffusion coefficient profile by Mahieux et al., our model replicates the observed upper haze distribution. The H2O vapor distribution is highly sensitive to the eddy diffusion coefficient in the 60–70 km region. This indicates that updating the eddy diffusion coefficient is crucial for understanding the H2O vapor transport through the cloud layer. The H2SO4 vapor abundance varies by several orders of magnitude above 85 km, depending on the temperature profile. However, its maximum value aligns well with observational upper limits found by Sandor et al., pointing to potential sources other than H2SO4 aerosols in the upper haze layer that contribute to the SO2 inversion layer. The best-fit eddy diffusion profile is determined to be ∼2 m2 s‑1 between 60 and 70 km and ∼360 m2 s‑1 above 85 km. Furthermore, the observed increase of H2O vapor concentration above 85 km is reproduced by using the temperature profile from the VEx/SOIR instrument.

Keywords: Atmospheric evolution, Atmospheric clouds, Planetary atmospheres, Venus, Atmospheric composition
Signatures of X-Ray-dominated Chemistry in the Spectra of Exoplanetary Atmospheres. High-energy radiation from stars impacts planetary atmospheres, deeply affecting their chemistry and providing departures from chemical equilibrium. While the upper atmospheric layers are dominated by ionizations induced by extreme-ultraviolet radiation, deeper into the atmosphere, molecular abundances are controlled by a characteristic X-ray-dominated chemistry, mainly driven by an energetic secondary electron cascade. In this work, we aim at identifying molecular photochemically induced fingerprints in the transmission spectra of a giant planet atmosphere. We have developed a numerical code capable of synthesizing transmission spectra with arbitrary spectral resolution, exploiting updated infrared photoabsorption cross sections. Chemical mixing ratios are computed using a photochemical model tailored to investigate high-energy ionization processes. We find that in the case of high levels of stellar activity, synthetic spectra in both low and high resolutions show significant, potentially observable out-of-equilibrium signatures arising mainly from CO, CH4, C2H2, and HCN.

Keywords: Exoplanet atmospheric composition , Exoplanet atmospheres, Star-planet interactions
A New Database of Giant Impacts over a Wide Range of Masses and with Material Strength: A First Analysis of Outcomes. In the late stage of terrestrial planet formation, planets are predicted to undergo pairwise collisions known as giant impacts. Here, we present a high-resolution database of giant impacts for differentiated colliding bodies of iron–silicate composition, with target masses ranging from 1 × 10‑4 M ⊕ up to super-Earths (5 M ⊕). We vary the impactor-to-target mass ratio, core–mantle (iron–silicate) fraction, impact velocity, and impact angle. Strength in the form of friction is included in all simulations. We find that, due to strength, the collisions with bodies smaller than about 2 ×10‑3 M ⊕ can result in irregular shapes, compound-core structures, and captured binaries. We observe that the characteristic escaping velocity of smaller remnants (debris) is approximately half of the impact velocity, significantly faster than currently assumed in N-body simulations of planet formation. Incorporating these results in N-body planet formation studies would provide more realistic debris–debris and debris–planet interactions.

Keywords: Extrasolar rocky planets, Solar system terrestrial planets, Planet formation
Revealing Callisto's Carbon-rich Surface and CO<SUB>2</SUB> Atmosphere with JWST. We analyzed spectral cubes of Callisto's leading and trailing hemispheres, collected with the NIRSpec Integrated Field Unit (G395H) on the James Webb Space Telescope. These spatially resolved data show strong 4.25 μm absorption bands resulting from solid-state 12CO2, with the strongest spectral features at low latitudes near the center of its trailing hemisphere, consistent with radiolytic production spurred by magnetospheric plasma interacting with native H2O mixed with carbonaceous compounds. We detected CO2 rovibrational emission lines between 4.2 and 4.3 μm over both hemispheres, confirming the global presence of CO2 gas in Callisto's tenuous atmosphere. These results represent the first detection of CO2 gas over Callisto's trailing side. The distribution of CO2 gas is offset from the subsolar region on either hemisphere, suggesting that sputtering, radiolysis, and geologic processes help sustain Callisto's atmosphere. We detected a 4.38 μm absorption band that likely results from solid-state 13CO2. A prominent 4.57 μm absorption band that might result from CN-bearing organics is present and significantly stronger on Callisto's leading hemisphere, unlike 12CO2, suggesting these two spectral features are spatially antiassociated. The distribution of the 4.57 μm band is more consistent with a native origin and/or accumulation of dust from Jupiter's irregular satellites. Other, more subtle absorption features could result from CH-bearing organics, CO, carbonyl sulfide, and Na-bearing minerals. These results highlight the need for preparatory laboratory work and improved surface–atmosphere interaction models to better understand carbon chemistry on the icy Galilean moons before the arrival of NASA's Europa Clipper and ESA's JUICE spacecraft.

Keywords: Infrared spectroscopy, Callisto, Natural satellite surfaces, Carbon dioxide, Natural satellite atmospheres, James Webb Space Telescope, Irregular satellites, Galilean satellites, Complex organic molecules