Sazuna/UAT_keywords huggingface dataset:
Atmospheric Overturning Circulation on Dry, Tidally Locked Rocky Planets Is Mainly Driven by Radiative Cooling. In this study, we examine the driving mechanism for the atmospheric overturning circulation on dry, tidally locked rocky planets without the condensation of water vapor or other species. We find that the main driving process is the radiative cooling of CO2 (or other noncondensable greenhouse gases) rather than CO2 greenhouse warming or stellar radiation. Stellar radiation is the ultimate mechanism but not the direct mechanism. Due to the combination of the uneven distribution in the stellar radiation and effective horizontal energy transports in the free troposphere, there is strong temperature inversion in the area away from the substellar region. This inversion makes CO2 have a radiative cooling effect rather than a radiative warming effect for the atmosphere, the same as that in the stratosphere of Earth's atmosphere. This cooling effect produces negative buoyancy and drives large-scale downwelling, supporting the formation of a global-scale overturning circulation. If CO2 is excluded from the atmosphere, the overturning circulation becomes very weak, regardless of the level of stellar radiation. This mechanism is completely different from that for the atmospheric overturning circulation on Earth or on moist, tidally locked rocky planets, where latent heat release and/or baroclinic instability are the dominated mechanisms. Our study improves the understanding of the atmospheric circulation on tidally locked exoplanets and also on other dry planets, such as Venus and Mars in the solar system.

Keywords: Exoplanet atmospheres, Planetary atmospheres, Planetary science, Atmospheric circulation
Identifying Interstellar Object Impact Craters. The discoveries of two interstellar objects (ISOs) in recent years have generated significant interest in constraining their physical properties and the mechanisms behind their formation. However, their ephemeral passages through our solar system permitted only incomplete characterization. We investigate avenues for identifying craters that may have been produced by ISOs impacting terrestrial solar system bodies, with particular attention toward the Moon. A distinctive feature of ISOs is their relatively high encounter velocity compared to asteroids and comets. Local stellar kinematics indicate that terrestrial solar system bodies should have experienced of order unity ISO impacts exceeding 100 km s-1. By running hydrodynamical simulations for projectiles of different masses and impact velocities up to 100 km s-1, we show how late-stage equivalence dictates that transient crater dimensions alone are insufficient for inferring the projectile's velocity. On the other hand, the melt volume within craters of a fixed diameter may be a potential route for identifying ISO craters, as faster impacts produce more melt. This method requires that the melt volume scales with the energy of the projectile while the crater diameter scales with the point-source limit (subenergy). Given that there are probably only a few ISO craters in the solar system at best, and that transient crater dimensions are not a distinguishing feature for impact velocities, at least up to 100 km s-1, identification of an ISO crater proves a challenging task. Melt volume and high-pressure petrology may be diagnostic features once large volumes of material can be analyzed in situ.

Keywords: Impact phenomena, Hydrodynamical simulations, Interstellar objects
The LCO Outbursting Objects Key Project: Overview and Year 1 Status. The LCO Outbursting Objects Key (LOOK) Project uses the telescopes of the Las Cumbres Observatory (LCO) Network to (1) systematically monitor a sample of previously discovered over the whole sky, to assess the evolutionary state of these distant remnants from the early solar system, and (2) use alerts from existing sky surveys to rapidly respond to and characterize detected outburst activity in all small bodies. The data gathered on outbursts helps to characterize each outburst's evolution with time, helps to assess the frequency and magnitude distribution of outbursts in general, and contributes to the understanding of outburst processes and volatile distribution in the solar system. The LOOK Project exploits the synergy between current and future wide-field surveys such as ZTF, Pan-STARRS, and LSST, as well as rapid-response telescope networks such as LCO, and serves as an excellent test bed for what will be needed for the much larger number of objects coming from Rubin Observatory. We will describe the LOOK Project goals, the planning and target selection (including the use of NEOexchange as a Target and Observation Manager or "TOM"), and results from the first phase of observations, including the detection of activity and outbursts on the giant comet C/2014 UN271 (Bernardinelli-Bernstein) and the discovery and follow-up of 28 outbursts on 14 comets. Within these outburst discoveries, we present a high-cadence light curve of 7P/Pons-Winnecke with 10 outbursts observed over 90 days, a large outburst on 57P/duToit-Neujmin-Delporte, and evidence that comet P/2020 X1 (ATLAS) was in outburst when discovered.

Keywords: Optical observation, Asteroids, Centaur group, Narrow band photometry, Short period comets, Long period comets, Automated telescopes, Broad band photometry, Comets, Comet volatiles , Oort cloud objects
High Heat Flux near Miranda's Inverness Corona Consistent with a Geologically Recent Heating Event. Uranus's moon Miranda has a complex surface reflecting multiple episodes of activity. We estimated the heat flux near Inverness Corona, the youngest terrain on Miranda ( ${100}_{-100}^{+400}$ Ma), to gain insight into recent endogenic resurfacing. We modeled flexure associated with Argier Rupes, which separates Inverness from the Cratered Terrain. Our results indicate an elastic thickness of 2.2-3.1 km and a heat flux of 35-140 mW m-2 in this region, assuming Miranda's lithosphere is composed of pure H2O ice without porosity. Because the formation of the bounding flexure that we analyzed followed the formation of Argier Rupes, our results indicate that Miranda experienced high heat flux in the past ${100}_{-100}^{+400}$ Ma. These results are also consistent with heating from a past resonance, possibly an Ariel-Umbriel 5:3 mean motion resonance, estimated to have generated heat fluxes &gt;100 mW m-2 on Miranda. However, if Miranda instead has a porous lithosphere, our heat flux estimates are lower: 34-135 mW m-2 for 5% porosity, 29-114 mW m-2 for 15% porosity, and 20-81 mW m-2 for 25% porosity. Alternatively, if Miranda's lithosphere includes NH3-hydrates, then our are estimates are even lower, 7-56 mW m-2 without porosity. These estimates decrease further when assuming NH3-hydrates and porosity: 7-54 mW m-2 for 5% porosity, 6-46 mW m-2 for 15% porosity, and 4-32 mW m-2 for 25% porosity. Better constraints on Miranda's heat fluxes require more information on its ice shell properties.

Keywords: Uranian satellites, Natural satellite surfaces, Natural satellites (Solar system), Planetary science, Tectonics
Photometric Observations of the Binary Near-Earth Asteroid (65803) Didymos in 2015-2021 Prior to DART Impact. We performed photometric observations of the binary near-Earth asteroid (65803) Didymos in support of the Double Asteroid Redirection Test (DART) mission that will test the Kinetic Impactor technology for diverting dangerous asteroids. It will hit the Didymos secondary, called Dimorphos, on 2022 September 26. We observed Didymos with 11 telescopes with diameters from 3.5 to 10.4 m during four apparitions in 2015-2021, obtaining data with rms residuals from 0.006 to 0.030 mag. We analyzed the light-curve data and decomposed them into the primary rotational and secondary orbital light curves. We detected 37 mutual eclipse/occultation events between the binary system components. The data presented here, in combination with 18 mutual events detected in 2003, provide the basis for modeling the Dimorphos orbit around the Didymos primary. The orbit modeling is discussed in detail by Scheirich &amp; Pravec and Naidu et al. The primary light curves were complex, showing multiple extrema on some epochs. They suggest a presence of complex topography on the primary's surface that is apparent in specific viewing/illumination geometries; the primary shape model by Naidu et al. (Icarus 348, 113777, 2020) needs to be refined. The secondary rotational light-curve data were limited and did not provide a clear solution for the rotation period and equatorial elongation of Dimorphos. We define the requirements for observations of the secondary light curve to provide the needed information on Dimorphos's rotation and elongation when Didymos is bright in 2022 July-September before the DART impact.

Keywords: Asteroid satellites, CCD photometry, Near-Earth objects
Low-speed Impacts into Ice-Dust Granular Mixtures. We present the results of a series of laboratory low-speed impacts (&lt; 4 m s-1) of centimeter-sized spherical projectiles into simulated dry and icy regolith samples. The target material was comprised of JSC-1 (Johnson Space Center) lunar simulant grains in the size range 100-250 μm, mixed with similar-sized water ice grains. Impacts were performed under vacuum, either at room temperature for JSC-1 samples or at cryogenic temperatures (&lt;150 K) for icy mixtures. We measured the ejecta masses from a collection plate and impact crater dimensions from post-impact crater photographs. We find that both the ejecta masses and crater diameters followed trends predicted by established scaling laws, albeit with different fitting parameters, and we were able to fit a strength regime π scaling to our measured crater diameters. The water ice in our target material took two forms: grains mixed with the regolith grains and frost from air condensation coating regolith grains. In both cases, the presence of water ice in the sample led to lower ejected masses and smaller crater sizes. In addition, our measured crater sizes were several orders of magnitude larger than expected for impacts into solid rock or water ice. Using our measured scaling parameters, we applied our findings to a planetary context for the study of secondary craters on icy moons, as well as eroding collisions occurring in Saturn's rings. We found that the deviation of our measurements from solid targets and from commonly used scaling parameters allowed us to reconcile our measurements with the models in both cases.

Keywords: Impact phenomena, Planetary surfaces, Small Solar System bodies, Planetary rings, Surface ices
Ejecta Formation, Early Collisional Processes, and Dynamical Evolution after the DART Impact on Dimorphos. NASA's DART spacecraft is planned to reach and impact asteroid Dimorphos, the small moon of binary asteroid (65803) Didymos, at a velocity of 6 km s-1 in late 2022 September. DART will be the first mission to test the "kinetic impactor" technique, aimed at deflecting the orbital path of a potentially hazardous asteroid. The success and effectiveness of this technique resides in the efficiency of momentum exchange between the spacecraft and the impacted target. This depends on many factors, including the cratering process, the formation of ejecta, and their fate, as they remain in the system or escape from it, carrying momentum away. Here we provide an overview of the cratering process, including ejecta formation and their subsequent dynamical evolution. We use different methodologies to model the physics of the problem, including smoothed particle hydrodynamics to model the cratering and ejecta formation process after the hypervelocity impact, N-body granular simulations to model early collisional processes between ejecta fragments right after cratering, and high-fidelity planetary propagation to model the dynamical evolution of ejecta during their purely ballistic phase. We highlight the key features of each phase and their role in defining the dynamical fate of ejecta. We investigate the effect of surface cohesion in the impacted target and identify the qualitative behavior of ejecta particles as a function of the key parameters of the problem. We provide quantitative estimates for the specific case study related to the DART-Dimorphos scenario and a selected range of target properties.

Keywords: Impact phenomena, Astrodynamics, Ejecta, Asteroid dynamics, N-body problem, Three-body problem, Planetary science
Lightcurves and Rotations of Trans-Neptunian Objects in the 2:1 Mean Motion Resonance with Neptune. We report the rotational lightcurves of 21 trans-Neptunian objects (TNOs) in Neptune's 2:1 mean motion resonance obtained with the 6.5 m Magellan-Baade telescope and the 4.3 m Lowell Discovery Telescope. The main survey's goal is to find objects displaying a large lightcurve amplitude that is indicative of contact binaries or highly elongated objects. In our sample, two 2:1 resonant TNOs showed a significant short-term lightcurve amplitude: 2002 VD130 and (531074) 2012 DX98. The full lightcurve of 2012 DX98 infers a periodicity of 20.80 ± 0.06 hr and amplitude of 0.56 ± 0.03 mag, whereas 2002 VD130 rotates in 9.85 ± 0.07 hr with a 0.31 ± 0.04 mag lightcurve amplitude. Based on lightcurve morphology, we classify (531074) 2012 DX98 as a likely contact binary but 2002 VD130 as a likely single elongated object. Based on our sample and the lightcurves reported in the literature, we estimate the lower percentage of nearly equal-sized contact binaries at only 7%-14% in the 2:1 resonance, which is comparable to the low fraction reported for the dynamically cold classical TNOs. This low contact binary fraction in the 2:1 Neptune resonance is consistent with the lower estimate of the recent numerical modeling. We report the Sloan g', r', and i' surface colors of 2002 VD130, which is an ultra-red TNO whereas 2012 DX98 is a very red object based on published surface colors.

Keywords: Twotinos, Resonant Kuiper belt objects, Trans-Neptunian objects
The Dynamical Viability of an Extended Jupiter Ring System. Planetary rings are often speculated as being a relatively common attribute of giant planets, partly based on their prevalence within the solar system. However, their formation and sustainability remain a topic of open discussion, and the most massive planet within our planetary system harbors a very modest ring system. Here, we present the results of an N-body simulation that explores dynamical constraints on the presence of substantial ring material for Jupiter. Our simulations extend from within the rigid satellite Roche limit to 10% of the Jupiter Hill radius, and include outcomes from 106 and 107 yr integrations. The results show possible regions of a sustained dense ring material presence around Jupiter that may comprise the foundation for moon formation. The results largely demonstrate the truncation of stable orbits imposed by the Galilean satellites, and dynamical desiccation of dense ring material within the range ~3-29 Jupiter radii. We discuss the implications of these results for exoplanets, and the complex relationship between the simultaneous presence of rings and massive moon systems.

Keywords: Exoplanets, Planetary rings, Orbital evolution, Jupiter, Jovian satellites
Modeling Thermal Emission under Lunar Surface Environmental Conditions. Thermal emission spectra can provide key insights into the composition and thermophysical properties of the regolith on the Moon and other airless bodies. However, under lunar surface environmental conditions, the uppermost millimeters of the regolith (from which thermal emission originates) cannot be characterized by a single temperature, leading to changes in spectral characteristics that should be accounted for in interpreting thermal emission measurements. Here, we develop and apply a Monte Carlo radiative transfer method to model thermal emission from particulate media with varying, nonisothermal subsurface temperature profiles. We model emission spectra for three major lunar mineral phases (pyroxene, olivine, and plagioclase), and investigate the effects of particle size and packing density. Modeled spectra are compared to lab measurements acquired under both ambient and simulated lunar conditions. We find that in some cases, the model provides useful constraints on the magnitude of the temperature profile established in a lab sample under lunar-like conditions, whereas in other cases, lab spectra are not well represented by the linear temperature profiles considered in this work. The model is generally successful at predicting changes in spectral contrast under lunar-like conditions, but less successful in accurately predicting shifts in the position of the Christiansen feature emissivity maximum; we illustrate and discuss the validity of the modeling approach for a range of different cases. Model results can also be used to quantify the depth within which observed thermal emission originates; this depth depends on composition and grain size, and ranges from ~100 to 1000 μm for representative packing densities.

Keywords: The Moon, Radiative transfer, Spectroscopy
T-matrix and Hapke Modeling of the Thermal Infrared Spectra of Trojan Asteroids and (944) Hidalgo: Implications for Their Regolith Particle Size and Porosity. Trojan asteroids (911) Agamemnon, (1172) Aneas, and (624) Hektor and primitive asteroid (944) Hidalgo share a common thermal infrared spectral feature: a prominent 10 μm plateau that is also present in cometary comae spectra. To fit these asteroid spectra, we modeled individual minerals using the light-scattering multiple sphere T-matrix (MSTM) and Hapke reflectance models. Modeled mineral spectra were then combined using a weighted least-squares (WLS) model that included a spectral library of varied particle sizes and porosities. We later refined our method by using the mineral abundances, particle sizes, and porosities computed by WLS as an input to rerun the MSTM and Hapke models. We were able to model the asteroid spectral features using a mixture of olivine components, fine particles, and lunar-like porosities. The Trojan asteroids and (944) Hidalgo are comparable in mineral composition and particle size to spectrally similar bodies such as comet Hale-Bopp and CO3 and CY chondrite meteorites. While the required porosities for modeling are like those present on the lunar surface, they are lower than those in the meteorites and higher than those in comets.

Keywords: Astronomy data modeling, Jupiter trojans, Spectroscopy
The Spectral Properties of Pitted Impact Deposits on Vesta as Seen by the Dawn VIR Instrument. Pitted impact deposits (PIDs) on Vesta have been shown to exhibit distinct spectral characteristics with respect to their surrounding host deposits and other typical Vestan areas regarding the first major pyroxene absorption near 0.9 μm. The PIDs, especially those in the ejecta blanket of the large crater Marcia, show higher reflectance and pyroxene band strength with respect to their impact deposit surroundings. This study complements the spectral characterization of the PIDs on Vesta with Visible and Infrared Spectrometer observations obtained by NASA's Dawn mission. In particular, we focus on the second major pyroxene absorption near 1.9 μm. We analyze nine PIDs in the ejecta blanket of the crater Marcia, as well as PIDs within the crater-fill deposits of the craters Marcia, Cornelia, and Licinia. We find that the second pyroxene absorption behaves in similar ways as the first major pyroxene absorption. The PIDs in Marcia's ejecta blanket show higher reflectance and pyroxene band strength with respect to their immediate impact deposit surroundings. The PIDs present in the crater-fill deposits of Marcia, Cornelia, and Licinia, however, do not show such spectral characteristics. This is also consistent with previous observations of the first pyroxene absorption band. Based on the experimental results of other studies, we speculate that the observed spectral distinctness arises from an oxidation process in the interior of impact deposits, where Fe cations migrate within their host pyroxene grains. Thus, the surfaces of (melt-bearing) impact deposits might be different from their interiors, apart from space-weathering effects.

Keywords: Vesta, Spectroscopy, Asteroid surfaces
Spectral Rotational Characterization of the Didymos System prior to the DART Impact. The smallest member of the Didymos binary near-Earth object system (Dimorphos) is the target of the DART/LICIACube mission, the first attempt to change the orbit of another celestial body via a kinetic impactor. It is important to characterize the unperturbed system prior to the DART impact. In this work we obtained, for the first time, spectral characterization of the system at several rotational phases from TNG+DOLORES in the visible range (0.34-0.81 μm). This is crucial in order to disentangle the primary and secondary bodies and highlight eventual dishomogeneities on their surfaces. We confirm that a subtle but persistent spectral variability appears, even when compared with data obtained from previous 2003 and 2019 apparitions. While the reason for such variability is still under investigation, our analysis hints that different compositions could play a role. Future observations during the brighter 2022 apparition in synergy with data obtained from LUKE on board LICIACube will definitely tackle this conundrum. *Based on observations made with the Italian Telescopio Nazionale Galileo (TNG) operated on the island of La Palma by the Fundación Galileo Galilei of the Istituto Nazionale di Astrofisica (INAF) at the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofisica de Canarias (Program AOT42-TAC8).

Keywords: Near-Earth objects, Spectrometers, Ground telescopes
Heliocentric Effects of the DART Mission on the (65803) Didymos Binary Asteroid System. The Double Asteroid Redirect Test (DART) is NASA's first kinetic impact-based asteroid deflection mission. The DART spacecraft will act as a projectile during a hypervelocity impact on Dimorphos, the secondary asteroid in the (65803) Didymos binary system, and alter its mutual orbital period. The initial momentum transfer between the DART spacecraft and Dimorphos is enhanced by the ejecta flung off the surface of Dimorphos. This exchange is characterized within the system by the momentum enhancement parameter, β, and on a heliocentric level by its counterpart, β ⊙. The relationship between β and the physical characteristics of Dimorphos is discussed here. A nominal set of Dimorphos physical parameters from the design reference asteroid and impact circumstances from the design reference mission are used to initialize the ejecta particles for dynamical propagation. The results of this propagation are translated into a gradual momentum transfer onto the Didymos system barycenter. A high-quality solar system propagator is then used to produce precise estimates of the post-DART encounters between Didymos and Earth by generating updated close approach maps. Results show that even for an unexpectedly high β ⊙, a collision between the Didymos system and Earth is practically excluded in the foreseeable future. A small but significant difference is found in modeling the overall momentum transfer when individual ejecta particles escape the Didymos system, as opposed to imparting the ejecta momentum as a single impulse at impact. This difference has implications for future asteroid deflection campaigns, especially when it is necessary to steer asteroids away from gravitational keyholes.

Keywords: Near-Earth objects, Close encounters, Asteroid dynamics