Sazuna/UAT_keywords huggingface dataset:
On the Fate of Interstellar Objects Captured by Our Solar System. With the recent discoveries of interstellar objects Oumuamua and Borisov traversing the solar system, understanding the dynamics of interstellar objects is more pressing than ever. These detections have highlighted the possibility that captured interstellar material could be trapped in our solar system. The first step in rigorously investigating this question is to calculate a capture cross section for interstellar objects as a function of hyperbolic excess velocity, which can be convolved with any velocity dispersion to compute a capture rate. Although the cross section provides the first step toward calculating the mass of alien rocks residing in our solar system, we also need to know the lifetime of the captured objects. We use an ensemble of N-body simulations to characterize a dynamical lifetime for captured interstellar objects and determine the fraction of surviving objects as a function of time (since capture). We also illuminate the primary effects driving their secular evolution. Finally, we use the resulting dynamical lifetime function to estimate the current inventory of captured interstellar material in the solar system. We find that capture from the field yields a steady-state mass of only ~10-13 M⊕, whereas the mass remaining from capture events in the birth cluster is roughly 10-9 M⊕.

Keywords: Kuiper belt, Small Solar System bodies, Oort cloud, Solar system, Interstellar objects, Dynamical evolution
Thermophysical and Compositional Analyses of Dunes at Hargraves Crater, Mars. We analyze thermal emission spectra using the 2001 Mars Odyssey Thermal Emission Imaging System and the Mars Global Surveyor Thermal Emission Spectrometer to characterize grain size and mineralogical composition of dunes at Hargraves crater, Mars. Thermal inertia and bulk composition of the dunes were compared to inferred provenances from the thermal infrared response of surface constituent materials. We use a Markov Chain Monte Carlo technique to estimate the bulk amount of mineralogy contributed by each inferred provenance to the dune field composition. An average thermal inertia value of 238 ± 17 Jm-2 K-1 s-0.5 was found for the dunes, corresponding to a surface composed of an average effective grain size of ~391 ± 172 μm. This effective particle size suggests the presence of mostly medium sand-sized materials mixed with fine and coarse grain sands. The dunes are likely composed of a weakly indurated surface mixed with unconsolidated materials. Compositional analysis specifies that the dunes are composed of a mixture of feldspar, olivine, pyroxene, and relatively low bulk-silica content. Dune materials were likely derived from physical weathering, especially aeolian erosion, predominantly from the crater ejecta unit at the crater, mixed with a small amount from the crater floor and crater rim and wall lithologies-indicating that the dune materials were likely sourced locally.

Keywords: Mars, Solar system planets, Solar system, Solar system astronomy
Mass and Shape Determination of (101955) Bennu Using Differenced Data from Multiple OSIRIS-REx Mission Phases. The Origins, Spectral Interpretation, Resource Identification, and Security-Regolith Explorer (OSIRIS-REx) mission collected a sample from the rubble-pile asteroid (101955) Bennu for return to Earth. For the successful Touch And Go sample acquisition maneuver, the shape and mass of the asteroid needed to be known precisely. Here we use a combination of radiometric, image landmark, and laser altimetry data to determine Bennu's mass, shape, and orientation simultaneously and to verify existing models thereof. Our shape determination consists of estimating a scale factor and three frame rotation angles that apply to both the global digital terrain model (GDTM) and the landmark coordinates. We use a data type called image constraints, where we take the difference of the observation of the same landmark in images taken at two different times. We analyze data from two phases of the OSIRIS-REx mission, Orbital B and Recon B, and show that interphase image constraints greatly reduce interdependencies between estimated parameters for mass, GDTM scale, and biases on the altimetry data. This results in an improved solution for the mass and shape relative to considering a single mission phase. We find Bennu's gravitational parameter GM to be 4.89256 ± 0.00035 m3 s-2, and we find a scale factor of 1.000896 ± 0.00036 for the altimetry-based GDTM. Using the scaled volume, this results in a bulk density of 1191.57 ± 1.74 kg m-3 , which is within the uncertainties of previous analyses but more precise.

Keywords: Gravitational fields, Small Solar System bodies
The Determination of the Rotational State and Interior Structure of Venus with VERITAS. Understanding the processes that led Venus to its current state and will drive its future evolution is a major objective of the next generation of orbiters. In this work we analyze the retrieval of the spin vector, the tidal response, and the moment of inertia of Venus with VERITAS, a NASA Discovery-class mission. By simulating a systematic joint analysis of Doppler tracking data and tie points provided by the onboard synthetic aperture radar, we show that VERITAS will provide accuracies (3σ) in the estimates of the tidal Love number k2 to 4.6 × 10-4, its tidal phase lag to 0°05, and the moment of inertia factor to 9.8 × 10-4 (0.3% of the expected value). Applying these results to recent models of the Venus interior, we show that VERITAS will provide much-improved constraints on the interior structure of the planet.

Keywords: Venus, Solar system terrestrial planets, Remote sensing, Planetary science, Planetary interior, Orbit determination, Planetary structure
Do Oceanic Convection and Clathrate Dissociation Drive Europa's Geysers?. Water vapor geysers on Europa have been inferred from observations made by the Galileo spacecraft, the Hubble Space Telescope, and the Keck Observatory. Unlike the water-rich geysers observed on Enceladus, Europa's geysers appear to be an intermittent phenomenon, and the dynamical mechanism permitting water to sporadically erupt through a kilometers-thick ice sheet is not well understood. Here we outline and explore the hypothesis that the Europan geysers are driven by CO2 gas released by dissociation and depressurization of CO2 clathrate hydrates initially sourced from the subsurface ocean. We show that CO2 hydrates can become buoyant to the upper ice-water interface under plausible oceanic conditions, namely, if the temperature or salinity conditions of a density-stratified two-layer water column evolve to permit the onset of convection that generates a single mixed layer. To quantitatively describe the eruptions once the CO2 has been released from the hydrate state, we extend a one-dimensional hydrodynamical model that draws from the literature on volcanic magma explosions on Earth. Our results indicate that for a sufficiently high concentration of exsolved CO2, these eruptions develop vertical velocities of ~700 m s-1. These high velocities permit the ejecta to reach heights of ~200 km above the Europan surface, thereby explaining the intermittent presence of water vapor at these high altitudes. Molecules ejected via this process will persist in the Europan atmosphere for a duration of about 10 minutes, limiting the timescale over which geyser activity above the Europan surface may be observable. Our proposed mechanism requires Europa's ice shell thickness to be d ≲ 10 km.

Keywords: Volcanism, Ocean planets, Europa
Thermal and Tidal Evolution of Uranus with a Growing Frozen Core. The origin of the very low luminosity of Uranus is unknown, as is the source of the internal tidal dissipation required by the orbits of the Uranian moons. Models of the interior of Uranus often assume that it is inviscid throughout, but recent experiments show that this assumption may not be justified; most of the interior of Uranus lies below the freezing temperature of H2O. We find that the stable solid phase of H2O, which is superionic, has a large viscosity controlled by the crystalline oxygen sublattice. We examine the consequences of finite viscosity by combining ab initio determinations of the thermal conductivity and other material properties of superionic H2O with a thermal evolution model that accounts for heat trapped in the growing frozen core. The high viscosity provides a means of trapping heat in the deep interior while also providing a source of tidal dissipation. The frozen core grows with time because its outer boundary is governed by the freezing transition rather than compositional layering. We find that the presence of a growing frozen core explains the anomalously low heat flow of Uranus. Our thermal evolution model also predicts time-varying tidal dissipation that matches the requirements of the orbits of Miranda, Ariel, and Umbriel. We make predictions that are testable by future space missions, including the tidal Love number of Uranus and the current recessional rates of its moons.

Keywords: Planetary interior, Uranian satellites, Uranus
Taurid Stream #628: A Reservoir of Large Cometary Impactors. The Desert Fireball Network observed a significant outburst of fireballs belonging to the Southern Taurid Complex of meteor showers between 2015 October 27 and November 17. At the same time, the Cameras for Allsky Meteor Surveillance project detected a distinct population of smaller meteors belonging to the irregular IAU shower #628, the s-Taurids. While this returning outburst was predicted and observed in previous work, the reason for this stream is not yet understood. 2015 was the first year that the stream was precisely observed, providing an opportunity to better understand its nature. We analyze the orbital elements of stream members and establish a size-frequency distribution from millimeter to meter size range. The stream is highly stratified with a large change of entry speed along Earth's orbit. We confirm that the meteoroids have orbital periods near the 7:2 mean motion resonance with Jupiter. The mass distribution of this population is dominated by larger meteoroids, unlike that for the regular Southern Taurid shower. The distribution index is consistent with a gentle collisional fragmentation of weak material. A population of meter-sized objects is identified from satellite observations at a rate consistent with a continuation of the size-frequency distribution established at centimeter size. The observed change of longitude of perihelion among the s-Taurids points to recent (a few centuries ago) activity from fragmentation involving surviving asteroid 2015 TX24. This supports a model for the Taurid Complex showers that involves an ongoing fragmentation cascade of comet 2P/Encke siblings following a breakup some 20,000 yr ago.

Keywords: Fireballs, Meteor streams, Short period comets
Variable X-Ray Emission of Comet 46P/Wirtanen. In this paper, we present an analysis of X-ray and optical/ultraviolet (UV) data from the favorable (Δ ~ 0.077 au) 2018 apparition of comet 46P/Wirtanen. The comet was observed during three different epochs (before, during, and after perihelion) over a 1.5 month period using the X-Ray Telescope (XRT) and Ultraviolet and Optical Telescope (UVOT) instruments on board the Neil Gehrels Swift Observatory and the Advanced CCD Imaging Spectrometer (ACIS) on board the Chandra X-ray Observatory. We clearly detected the comet's charge exchange-induced emission during the first two epochs (Fx = (11.2 ± 0.8) and (6.9 ± 0.5) × 10-13 erg cm-2 s-1, respectively), while only an upper limit on the flux could be placed for the third epoch (Fx &lt; 1.38 × 10-13 erg cm-2 s-1). As such, 46P/Wirtanen is one of the least luminous comets to be detected in X-rays. X-ray emission from the charge exchange between solar wind ions and the neutrals in the coma were analyzed against the water-production rate (Swift/UVOT) and space weather measurements. Further analyses of the emission features show that the solar wind properties inferred from the observed X-ray spectrum are in good agreement with those measured by the Advanced Composition Explorer (ACE) and Solar and Heliospheric Observatory (SOHO) spacecraft, proving the approach is reliable for solar wind diagnostics. It is also found that, despite the variability of the comet's properties (e.g., the water-production rate used as a neutrals density proxy), cometary X-ray emission is primarily modulated by the solar wind.

Keywords: Comets, Solar wind, Charge exchange recombination
Volatile Composition and Outgassing in C/2018 Y1 (Iwamoto): Extending Limits for High-resolution Infrared Cometary Spectroscopy between 2.8 and 5.0 μm. We used the powerful high spectral resolution cross-dispersed facility spectrograph, iSHELL, at the NASA Infrared Telescope Facility (IRTF) to observe C/2018 Y1 (Iwamoto), a long-period comet from the Oort cloud. We report production rates for water and eight other parent molecules (native ices), C2H6, CO, CH4, H2CO, CH3OH, HCN, NH3, and C2H2, on three preperihelion UT dates, 2019 January 13 and (near perihelion) February 4-5. We present abundance ratios relative to both C2H6 (a nonpolar molecule) and H2O (a polar molecule), thereby providing a more complete picture of the parent volatile composition of C/2018 Y1 and potential associations of ices in its nucleus. Overall, the measured spatial distributions for polar molecules (in particular, H2O and CH3OH) were broader, exhibiting more complex structure compared with nonpolar or weakly polar species (CH4, C2H6, and CO). Our January 13 results permitted quantitatively assessing the significant improvement in sensitivity delivered by iSHELL compared with previous capabilities at the IRTF. The efficient spectral coverage of iSHELL plus the favorable geocentric Doppler shift of C/2018 Y1 allowed for measuring &gt;50% of CH4 ν3-band emission intensity on both January 13 and February 5. Compositionally, compared to their respective mean abundances among comets from the Oort cloud, C2H6 and CH3OH were enriched, CH4 and HCN were near normal, and all other species were depleted. The abundance ratio CH3OH/C2H6 was higher by 45% ± 8% on January 13 versus February 5, whereas CH4/C2H6 was unchanged within the uncertainty, suggesting nonhomogeneous composition among regions of the nucleus dominating activity on these dates.

Keywords: Small Solar System bodies, Comae, Solar system, Comets, Comet volatiles
SOFIA Observations of Variability in Jupiter's Para-H<SUB>2</SUB> Distribution and Subsurface Emission Characteristics of the Galilean Satellites. We observed Jupiter's thermal emission with SOFIA/FORCAST in 2018 August and 2019 July. Both broad-band images (8-37 μm) and spectra (17-37 μm) were obtained. We used the shape of the Jovian spectra to determine the latitudinal distribution of temperatures and para-H2 in the upper troposphere, and compared this to similar data obtained in Fletcher et al. (2017). The two data sets were taken approximately half a Jovian year apart, the first (2014) during northern summer (Ls = 158°) and the second (2019) during southern summer (Ls = 304°). During both epochs the high northern latitudes are cooler than the south. Para-H2 is observed in sub-equilibrium at the equator and in super-equilibrium near the poles during all epochs. The largest difference between the two epochs is the detection of high-para-H2 content at high southern latitudes in 2019, in contrast to the earlier (2014) observations. This implies that the high-latitude para-H2 appears to vary over multi-year timescales. In addition to aiding in the calibration of and providing context to the Jovian spectra, the images were used to determine spectra of the four Galilean satellites. Over the 8-35 μm wavelength range the brightness temperatures of all four satellites drop with increasing wavelength. Although this is expected as longer wavelengths probe the satellites' deeper, cooler layers, our data quantify the brightness temperature gradient with wavelength.

Keywords: Jupiter
Resolving Io's Volcanoes from a Mutual Event Observation at the Large Binocular Telescope. Unraveling the geological processes ongoing at Io's numerous sites of active volcanism requires high spatial resolution to, for example, measure the areal coverage of lava flows or identify the presence of multiple emitting regions within a single volcanic center. In de Kleer et al. (2017) we described observations with the Large Binocular Telescope during an occultation of Io by Europa at ~6:17 UT on 2015 March 8 and presented a map of the temperature distribution within Loki Patera derived from these data. Here we present emission maps of three other volcanic centers derived from the same observation: Pillan Patera, Kurdalagon Patera, and the vicinity of Ulgen Patera/PV59/N Lerna Regio. The emission is localized by the light curves and resolved into multiple distinct emitting regions in two of the cases. Both Pillan and Kurdalagon Paterae had undergone eruptions in the months prior to our observations, and the location and intensity of the emission are interpreted in the context of the temporal evolution of these eruptions observed from other facilities. The emission from Kurdalagon Patera is resolved into two distinct emitting regions separated by only a few degrees in latitude that were unresolved by Keck observations from the same month.

Keywords: Occultation, Interferometry, Io, Galilean satellites, Volcanism
Atomic Iron and Nickel in the Coma of C/1996 B2 (Hyakutake): Production Rates, Emission Mechanisms, and Possible Parents. Two papers recently reported the detection of gaseous nickel and iron in the comae of over 20 comets from observations collected over two decades, including interstellar comet 2I/Borisov. To evaluate the state of the laboratory data in support of these identifications, we reanalyzed archived spectra of comet C/1996 B2 (Hyakutake), one of the nearest and brightest comets of the past century, using a combined experimental and computational approach. We developed a new, many-level fluorescence model that indicates that the fluorescence emissions of Fe I and Ni I vary greatly with heliocentric velocity. Combining this model with laboratory spectra of an Fe-Ni plasma, we identified 22 lines of Fe I and 14 lines of Ni I in the spectrum of Hyakutake. Using Haser models, we estimate the nickel and iron production rates as QNi = (2.6-4.1) × 1022 s-1 and QFe = (0.4-2.8) × 1023 s-1. From derived column densities, the Ni/Fe abundance ratio log10[Ni/Fe] = -0.15 ± 0.07 deviates significantly from solar abundance ratios, and it is consistent with the ratios observed in solar system comets. Possible production and emission mechanisms are analyzed in the context of existing laboratory measurements. Based on the observed spatial distributions, excellent fluorescence model agreement, and Ni/Fe ratio, our findings support an origin consisting of a short-lived unknown parent followed by fluorescence emission. Our models suggest that the strong heliocentric velocity dependence of the fluorescence efficiencies can provide a meaningful test of the physical process responsible for the Fe I and Ni I emission.

Keywords: Atomic spectroscopy, Comets, Laboratory astrophysics, Spectral line identification
Analysis of Cohesion in Fast-spinning Small Bodies. In this paper, the structural stability of a fast-spinning small body is investigated. In particular, a nonlinear yield condition in tensile stress is applied to estimate the required cohesion in a fast-spinning small body. The least upper bound of required cohesion is investigated for both ellipsoid and irregular shape models. The stress state of a fast-spinning ellipsoid is discussed analytically, and the effects of spin rates and size ratios are analyzed. For an irregularly shaped body, an element average stress method is developed to estimate the range of stress of any element in the body, where only self-gravity and centrifugal force are considered. The maximum tensile stress in the whole body is used to solve the required cohesion. Finally, the proposed methods are applied to different asteroid shape models. The result shows that the least upper bound of cohesion is mainly determined by the spin rate and length of the major axis, but an irregular shape will change the stress distribution and cause a stressed surface. The required cohesion of a fast-spinning small body varies between tens to 1000 Pa. The methods developed in this paper can rapidly provide a conservative lower bound on the cohesion in a fast-spinning body and qualitatively show the distribution of stress, which provides an effective way to study the structural stability of fast-spinning bodies of those bodies.

Keywords: Small Solar System bodies, Near-Earth objects, Asteroids, Planetary structure
Evolution of Mercury's Earliest Atmosphere. MESSENGER observations suggest a magma ocean formed on proto-Mercury, during which evaporation of metals and outgassing of C- and H-bearing volatiles produced an early atmosphere. Atmospheric escape subsequently occurred by plasma heating, photoevaporation, Jeans escape, and photoionization. To quantify atmospheric loss, we combine constraints on the lifetime of surficial melt, melt composition, and atmospheric composition. Consideration of two initial Mercury sizes and four magma ocean compositions determines the atmospheric speciation at a given surface temperature. A coupled interior-atmosphere model determines the cooling rate and therefore the lifetime of surficial melt. Combining the melt lifetime and escape flux calculations provides estimates for the total mass loss from early Mercury. Loss rates by Jeans escape are negligible. Plasma heating and photoionization are limited by homopause diffusion rates of ~106 kg s-1. Loss by photoevaporation depends on the timing of Mercury formation and assumed heating efficiency and ranges from ~106.6 to ~109.6 kg s-1. The material for photoevaporation is sourced from below the homopause and is therefore energy limited rather than diffusion limited. The timescale for efficient interior-atmosphere chemical exchange is less than 10,000 yr. Therefore, escape processes only account for an equivalent loss of less than 2.3 km of crust (0.3% of Mercury's mass). Accordingly, ≤0.02% of the total mass of H2O and Na is lost. Therefore, cumulative loss cannot significantly modify Mercury's bulk mantle composition during the magma ocean stage. Mercury's high core:mantle ratio and volatile-rich surface may instead reflect chemical variations in its building blocks resulting from its solar-proximal accretion environment.

Keywords: Upper atmosphere, Planetary atmospheres, Solar system terrestrial planets, Planetary science, Mercury (planet), Atmospheric composition