Sazuna/UAT_keywords huggingface dataset:
Dust Outburst Dynamics and Hazard Assessment for Close Spacecraft-Comet Encounters. Using the gas drag by sublimating cometary surface ices for the acceleration of dust particles and deceleration by the gravity field of the nucleus combined with basic laws of mechanics, the sizes, velocities, and number densities of escaping particles are calculated and evaluated with respect to the hazard assessment of comet-spacecraft flybys and encounters. We find good agreement between our analytical method and the more elaborate and precise DSMC calculations, but, being simpler, our method can more easily be used to explore a wide range of cometary conditions and can be more easily scaled to specific comets with different nucleus sizes, masses, and gravity potentials and various gas and dust production rates. Our analytical method is applied to outbursts expanding into a cone of ~60°, where the gas density falls off with height from the surface rather than radial distance from the center of a uniformly outgassing nucleus. In this scenario, larger dust particles can be ejected and attain ballistic trajectories, go into orbit, or escape from the nucleus, thus being potentially more hazardous to a spacecraft. Sample calculations are carried out for potential dust outbursts for the highly active Centaur/Comet 29P/Schwassmann-Wachmann 1 for various assumed active areas and dust particle size distributions. Particle velocity ranges for ballistic trajectories, orbiting particles, and particles escaping into the coma are presented. These calculations are used to estimate the coma particle number densities during outbursts to get an assessment of the hazards and required mitigation for a flyby or orbiting space mission.

Keywords: Space probes, Comae
No Activity among 13 Centaurs Discovered in the Pan-STARRS1 Detection Database. Centaurs are small bodies orbiting in the giant planet region that were scattered inward from their source populations beyond Neptune. Some members of the population display comet-like activity during their transition through the solar system, the source of which is not well understood. The range of heliocentric distances where the active Centaurs have been observed and their median lifetime in the region suggest that this activity is driven neither by water-ice sublimation nor entirely by supervolatiles. Here we present an observational and thermodynamical study of 13 Centaurs discovered in the Pan-STARRS1 detection database aimed at identifying and characterizing active objects beyond the orbit of Jupiter. We find no evidence of activity associated with any of our targets at the time of their observations with the Gemini North telescope in 2017 and 2018, or in archival data from 2013 to 2019. Upper limits on the possible volatile and dust production rates from our targets are 1-2 orders of magnitude lower than production rates in some known comets and are in agreement with values measured for other inactive Centaurs. Our numerical integrations show that the orbits of six of our targets evolved interior to r ~ 15 au over the past 100,000 yr, where several possible processes could trigger sublimation and outgassing, but their apparent inactivity indicates that either their dust production is below our detection limit or the objects are dormant. Only one Centaur in our sample-2014 PQ70-experienced a sudden decrease in semimajor axis and perihelion distance attributed to the onset of activity for some previously known inactive Centaurs, and therefore it is the most likely candidate for any future outburst. This object should be a target of high interest for any further observational monitoring.

Keywords: Comets, Centaur group, Trans-Neptunian objects
A Case for a Small to Negligible Influence of Dust Charging on the Ionization Balance in the Coma of Comet 67P. A recent work aided by Rosetta in situ measurements set constraints on the dust-to-gas mass emission ratio and the size distribution of dust escaping the nucleus of comet 67P/Churyumov-Gerasimenko near perihelion. Here we use this information along with other observables/parameters as input into an analytical model aimed at estimating the number density of electrons attached to dust particles near the position of Rosetta. These theoretical estimates are compared to in situ measurements of the degree of ionization. The comparison proposes that Rosetta, while near perihelion, was typically not in electron-depleted regions of the inner coma of 67P. Our work suggests a typical level of electron depletion probably below 10% and possibly below 1%. In line with previous studies, we find, again with certain assumptions and other observables/parameters as input, that the observed negative spacecraft charging to a few tens of volts does not significantly impact the detection of charged dust grains, with a possible exception for grains with radii less than ~10 nm.

Keywords: Comets
A Recipe for the Geophysical Exploration of Enceladus. Orbital geophysical investigations of Enceladus are critical to understanding its energy budget. In this paper, we identified key science questions for the geophysical exploration of Enceladus, answering which would support future assessment of Enceladus' astrobiological potential. Using a Bayesian framework, we explored how science requirements map to measurement requirements. We performed mission simulations to study the sensitivity of single-spacecraft and dual-spacecraft configurations to static gravity and tidal Love numbers of Enceladus. We find that mapping Enceladus' gravity field, improving the accuracy of the physical libration amplitude, and measuring Enceladus' tidal response would provide critical constraints on the internal structure and establish a framework for assessing Enceladus' long-term habitability. This kind of investigation could be carried out as part of a life search mission at little additional resource requirements.

Keywords: Astrodynamics, Gravitational fields, Space observatories, Planetary interior, Saturnian satellites
Evidence for a Recent Collision in Saturn's Irregular Moon Population. Using CFHT imaging data, we searched a 1.1 deg2 field on each side of Saturn down to magnitude mw ≃ 26.3, corresponding to diameters of D ≃ 3 km. We detected 120 objects, which were comoving with Saturn and are nearly certainly irregular moons. For example, all but one of our detections brighter than magnitude 25.5 link to known Saturnian irregulars, with 40 linkages that thus extend the orbital arc of previous discoveries. Extrapolating our sample's characterized detections (those for which we can debias the search) to the entire Saturnian irregular population, we estimate that there are 150 ± 30 moons down to D = 2.8 km, which is approximately three times as many irregular moons as Jupiter down to the same size. At the smallest sizes, from D = 3.8 down to 2.8 km, we find that the Saturnian irregular population exhibits a steep size distribution of the differential power-law index $q={4.9}_{-0.6}^{+0.7}$ . We believe this steep size distribution is the signature of a relatively recent (few hundred Myr ago) collisional event in Saturn's retrograde irregular population.

Keywords: Irregular satellites, Saturn, Saturnian satellites, Natural satellites (Solar system)
Characterizing the Discovery of a New Trans-Neptunian Object Binary in a Trailed Point-spread Function Search. The Latitude Density Search utilized the Hyper Suprime-Cam on the Subaru Telescope to discover 60 moving objects in the outer solar system, 54 of which have semimajor axes beyond 30 au. The images were acquired in exceptional seeing (0"4) and reached a detection limit of mr ≃ 25.2. The two night arcs were used to calculate orbits that are poorly constrained; however, the distance and inclination are the parameters best constrained by short arcs, and a reasonable determination can be made of which objects are cold classical trans-Neptunian objects (TNOs) and which are dynamically excited. We identify 10 objects as likely cold classical objects. We searched all of the detections for binary sources using a trailed point-spread function (PSF) subtraction method and identified one binary object with a separation of 0"34 and a secondary with 17% the brightness of the primary (2.0 magnitudes fainter). This is the brightest TNO in the sample, the previously known object (471165) 2010 HE79, which has a dynamically excited orbit. Because of the excellent seeing, this search was sensitive to secondaries with 0"34 separation and a brightness of ≥50% the primary brightness for seven objects, including one cold classical. This gives an intrinsic binary fraction of ${17}_{-10}^{+19}$ % (one of six) for the dynamically excited objects within our detection limits. The trailed PSF subtraction method used in the Latitude Density Search to identify binaries, fit the two components, and determine the sensitivity limits is a useful tool that could be more broadly applied to identify binary TNOs and track known binary TNO orbits.

Keywords: Kuiper belt, Classical Kuiper belt objects, Trans-Neptunian objects
Titan's "Average" Ionospheric Structures from Cassini. The decadal observations of Titan's neutral atmosphere and ionosphere by the Ion and Neutral Mass Spectrometer mass spectrometer and other instruments on board the Cassini spacecraft at the Saturnian system provide a precious data set concerning the large-scale structure of Titan's upper ionosphere. An attempt is made in this study to generate average 3D ion density distributions for different ion species by using a simple approximation of the solar zenith angle dependence. Both altitude dependence and neutral gas number density dependence of the ion density distributions will be presented. This empirical approach allows a comprehensive visualization of the global properties of Titan's ionosphere that could be useful as engineering models for future missions to Titan.

Keywords: Planetary ionospheres, Titan
Thermophysical Investigation of Asteroid Surfaces. I. Characterization of Thermal Inertia. The thermal inertia of an asteroid is an indicator of the thermophysical properties of the regolith and is determined by the size of grains on the surface. Previous thermophysical modeling studies of asteroids have identified or suggested that object size, rotation period, and heliocentric distance (a proxy for temperature) are important factors that separately influence thermal inertia. In this work we present new thermal inertia values for 239 asteroids and model all three factors in a multivariate model of thermal inertia. Using multiepoch infrared data of this large set of objects observed by WISE, we derive the size, albedo, thermal inertia, surface roughness, and sense of spin using a thermophysical modeling approach that does not require a priori knowledge of an object's shape or spin axis direction. Our thermal inertia results are consistent with previous values from the literature for similarly sized asteroids, and we identify an excess of retrograde rotators among main-belt asteroids &lt;8 km. We then combine our results with thermal inertias of 220 objects from the literature to construct a multivariate model and quantify the dependency on asteroid diameter, rotation period, and surface temperature. This multivariate model, which accounts for codependencies between the three independent variables, identifies asteroid diameter and surface temperature as strong controls on thermal inertia.

Keywords: Infrared astronomy, Asteroids, Infrared photometry, Asteroid surfaces
Asteroid Diameters and Albedos from NEOWISE Reactivation Mission Years Six and Seven. We present diameters and albedos computed for the near-Earth and main belt asteroids (MBAs) observed by the Near-Earth Object Wide-field Infrared Survey Explorer (NEOWISE) spacecraft during the sixth and seventh years of its Reactivation mission. These diameters and albedos are calculated from fitting thermal models to NEOWISE observations of 199 near-Earth objects (NEOs) and 5851 MBAs detected during the sixth year of the survey and 175 NEOs and 5861 MBAs from the seventh year. Comparisons of the NEO diameters derived from Reactivation data with those derived from the WISE cryogenic mission data show a ~30% relative uncertainty. This larger uncertainty compared to data from the cryogenic mission is due to the need to assume a beaming parameter for the fits to the shorter-wavelength data that the Reactivation mission is limited to. We also present an analysis of the orbital parameters of the MBAs that have been discovered by NEOWISE during Reactivation, finding that these objects tend to be on orbits that result in their perihelia being far from the ecliptic, and thus missed by other surveys. To date, the NEOWISE Reactivation survey has provided thermal fits of 1415 unique NEOs. Including the mission phases before spacecraft hibernation increases the count of unique NEOs characterized to 1845 from WISE's launch to the present.

Keywords: Infrared astronomy, Near-Earth objects, Asteroids
On the Feasibility of Informative Biosignature Measurements Using an Enceladus Plume Organic Analyzer. The icy moons of Saturn and Jupiter are high priority locations in which to search for biomarkers of life elsewhere in our solar system. In particular, the ice plumes that jet out through the ice surface at Enceladus provide an enticing opportunity to sample the organic components of its subsurface ocean for possible biosignatures while ameliorating challenges of planetary protection. Extensive high- and hypervelocity light gas gun experiments, the first to model the Enceladus ice plume encounter accurately, have demonstrated that organic-rich ice particles can be efficiently captured using plume transits at and below 3 km s-1 without significant organic destruction. Realistic scenarios for the amount of ice captured and for the ability of organic chemical analysis instruments, especially microfluidic capillary electrophoresis with laser-induced fluorescence, to produce meaningful detection levels for biosignatures are then presented and compared with results from terrestrial models. This analysis indicates that an Enceladus plume fly-by mission carrying microfluidic instrumentation is capable of biosignature measurements with a sensitivity and analytical capability that is highly informative about the extent of extraterrestrial biological processes.

Keywords: Impact phenomena, Biosignatures, Saturnian satellites
On Charon's Far-ultraviolet Surface Reflectance. We present the first measurements of Charon's far-ultraviolet (FUV) surface reflectance, obtained by the Alice spectrograph on New Horizons. We find no measurable flux shortward of 1650 Å, and Charon's geometric albedo is &lt;0.019 (3σ) at 1600 Å. From 1650 to 1725 Å, Charon's geometric albedo increases to 0.166 ± 0.068 and remains nearly constant until 1850 Å. As this spectral shape is characteristic of H2O ice absorption, Charon is the first Kuiper Belt object with a H2O ice surface to be detected in the FUV. Charon's geometric albedo is ~3.7 times lower than Enceladus's at these wavelengths but has a very similar spectral shape. We attribute this to similarities in their surface compositions and the difference in absolute reflectivity to a high concentration or more-absorbing contaminants on Charon's surface. Finally, we find that Charon has different solar phase behavior in the FUV than Enceladus, Mimas, Tethys, and Dione, with a stronger opposition surge than Enceladus and a shallower decline at intermediate solar phase angles than any of these Saturnian satellites.

Keywords: Ultraviolet photometry, Plutonian satellites
Volatility of Sodium in Carbonaceous Chondrites at Temperatures Consistent with Low-perihelion Asteroids. Solar system bodies with surface and subsurface volatiles will show observational evidence of activity when they reach a temperature where those volatiles change from solid to gas and are released. This is most frequently seen in comets, where activity is driven by the sublimation of water, carbon dioxide, or carbon monoxide ices. However, some bodies (notably the asteroid (3200) Phaethon) show initiation of activity at very small heliocentric distances, long after they have reached the sublimation temperatures of these ices. We investigate whether the sodium present in the mineral matrix could act as the volatile element responsible for this activity. We conduct theoretical modeling which indicates that sodium has the potential to sublimate in the conditions that Phaethon experiences, depending on the mineral phase it is held in. To test this, we then exposed samples of the carbonaceous chondrite Allende to varying heating events, similar to what would be experienced by low-perihelion asteroids. We measured the change in sodium present in each sample and find that the highest temperature samples show a significant loss of sodium from specific mineral phases over a single heating event, comparable to a day on the surface of Phaethon. Under specific thermal histories possible for Phaethon, this outgassing could be sufficient to explain this object's observed activity. This effect would also be expected to be observed for other low-perihelion asteroids as well and may act as a critical step in the process of disrupting small low-albedo asteroids.

Keywords: Near-Earth objects, Comet volatiles , Asteroids
<SUP>13</SUP>C Isotopic Ratios of HC<SUB>3</SUB>N on Titan Measured with ALMA. We present the first determination of the abundance ratios of 13C substitutions of cyanoacetylene (HC3N), [H13CCCN]:[HC13CCN]:[HCC13CN], in Titan's atmosphere measured using millimeter-wave spectra obtained by the Atacama Large Millimeter/submillimeter Array. To compare the line intensities precisely, data sets that include multiple molecular lines were extracted to suppress effects of Titan's environmental conditions and observation settings. The [HC13CCN]:[HCC13CN] and [H13CCCN]:[HCC13CN] ratios were obtained from 12 and 1 selected data sets, respectively. As a result, nearly the uniform [H13CCCN]:[HC13CCN]:[HCC13CN] abundance ratios of 1.17 ( ±0.20) : 1.09 ( ±0.25) : 1 (1σ) were derived, whereas previously reported ratios for the interstellar medium (ISM) have shown large anomalies that may be caused by 13C concentrations in precursors. The result obtained here suggests that 13C concentration processes suggested in the ISM studies do not work effectively on precursors of HC3N and HC3N themselves owing to Titan's high atmospheric temperature and/or depletion of both 13C and 13C+.

Keywords: Submillimeter astronomy, Radio astronomy, Planetary atmospheres
Detailed Morphologic Mapping and Traverse Planning for a Rover-based Lunar Sample Return Mission to Schrödinger Basin. Schrödinger basin, a 312 km diameter complex impact structure located near the lunar south pole, has been widely cited as a prime target for future lunar exploration. In 2020 NASA identified Schrödinger as a high-priority landing site for a 2024 mission supported by the Payloads and Research Investigations on the Surface of the Moon solicitation and the Commercial Lunar Payload Services program. Schrödinger basin hosts an uplifted peak ring that would provide a surface mission with access to materials that originated deep within the lunar crust, as well as material ejected from the larger South Pole-Aitken basin. Schrödinger basin also hosts well-preserved mare and pyroclastic deposits that could provide valuable insight into volcanic processes on the Moon. This study used high-resolution Wide Angle Camera and Narrow Angle Camera images from the Lunar Reconnaissance Orbiter, elevation data from the Lunar Orbiter Laser Altimeter, and spectral data from the Clementine mission to produce a high-resolution morphologic map of the basin center consisting of 10 distinct morphologic units. This new map was used to plan traverse paths for a rover mission to the region. The design requirements for this traverse were based on those originally developed for the multiagency Human-Enhanced Robotic Architecture and Capability for Lunar Exploration and Science (HERACLES) mission and the Canadian Space Agency Precursor to Humans And Science Rover concept. The proposed traverse path includes up to 20 sample collection stops with the goal of better understanding lunar chronology, lunar volcanism, and the impact cratering process.

Keywords: Lunar craters, Lunar composition, Lunar science, Lunar impacts, Lunar surface, Rovers
Siderite Dissolution in Mars-analog Brines: Kinetics and Reaction Products. This study examines siderite (FeCO3) reactivity in MgCl2 and MgSO4 brines with varying salt concentrations (0.01M, 1M, and 3M) at both acidic (pH ~ 2 and pH ≤ 2) and near-neutral (pH ~ 7) conditions. We measured aqueous Fe concentrations through time to determine dissolution rates and characterized the solid reaction products with scanning electron microscopy, electron dispersive X-ray spectroscopy, and Raman spectroscopy. Iron-based siderite dissolution rates at pH 2 were equivalent in the 0.01M and 1M MgSO4 brines and slower in 3M MgSO4; rates in the MgCl2 brines slow systematically with increasing brine concentration for equivalent initial pH values. Fe-based dissolution rates could not be determined in the neutral pH experiments due to precipitation of iron (hydr)oxide phases. After 1 day in acidic brines, abundant etch pits were observed; however, in the neutral experiments, siderite was identified with Raman spectroscopy even after 1 yr of dissolution along with a range of iron (hydr)oxide phases. Scanning electron microscopy imaging of the neutral experiment products found Mg-sulfate brines produced a chaotic surface texture. Therefore, micron-scale textural observations could be used to discriminate between alteration in chloride and sulfate brines. Initial iron release rates were similar in dilute brines, but decreased by less than an order of magnitude in the two highest-concentration pH 2 brine experiments; therefore, siderite-bearing assemblages exposed to acidic fluids, regardless of salinity, would likely dissolve completely over geologically short periods of time, thus erasing siderite and likely other carbonate minerals from the geologic record.

Keywords: Mars
The Orbit and Density of the Jupiter Trojan Satellite System Eurybates-Queta. We report observations of the Jupiter Trojan asteroid (3548) Eurybates and its satellite Queta with the Hubble Space Telescope and use these observations to perform an orbital fit to the system. Queta orbits Eurybates with a semimajor axis of 2350 ± 11 km at a period of 82.46 ± 0.06 days and an eccentricity of 0.125 ± 0.009. From this orbit we derive a mass of Eurybates of 1.51 ± 0.03 × 1017 kg, corresponding to an estimated density of 1.1 ± 0.3 g cm-3, broadly consistent with densities measured for other Trojans, C-type asteroids in the outer main asteroid belt, and small icy objects from the Kuiper Belt. Eurybates is the parent body of the only major collisional family among the Jupiter Trojans; its low density suggests that it is a typical member of the Trojan population. Detailed study of this system in 2027 with the Lucy spacecraft flyby should allow significant insight into collisional processes among what appear to be the icy bodies of the Trojan belt.

Keywords: Asteroid satellites, Jupiter trojans