Sazuna/UAT_keywords huggingface dataset:
OSSOS. XXVII. Population Estimates for Theoretically Stable Centaurs between Uranus and Neptune. We calculate the upper bounds of the population of theoretically stable Centaur orbits between Uranus and Neptune. These small bodies are on low-eccentricity, low-inclination orbits in two specific bands of semimajor axis, centered at ~24.6 and ~25.6 au. They exhibit unusually long Gyr-stable lifetimes in previously published numerical integrations, orders of magnitude longer than that of a typical Centaur. Despite the increased breadth and depth of recent Solar System surveys, no such objects have been found. Using the Outer Solar System Origins Survey simulator to calculate the detection efficiency for these objects in an ensemble of fully characterized surveys, we determine that a population of 72 stable Centaurs with absolute magnitude H  r  ≤ 10 (95% confidence upper limit) could remain undetected. The upcoming Legacy Survey of Space and Time will be able to detect this entire intrinsic population, due to its complete coverage of the ecliptic plane. If detected, these objects will be interesting dynamically accessible mission targets-especially as comparison of the stable Centaur orbital phase space to the outcomes of several modern planetary migration simulations suggests that these objects could be close to primordial in nature.

Keywords: Centaur group, Small Solar System bodies, Surveys, Orbits, Astrostatistics, Trans-Neptunian objects, Planetary migration
Giant Planet Lightning in Nonideal Gases. Lightning has been directly observed or inferred on all giant planets, generally accepted to be occurring in their water clouds. However, much as Earth has both cloud-cloud and cloud-ground lightning, this does not mean all flashes occur in a narrow altitude range: on Jupiter, the Galileo spacecraft detected lightning flashes apparently below the cloud base, explicable as lightning due to precipitation, and the Juno SRU detected small flashes far above it, at pressures of only 1-2 bars. We use a computationally light 1D entraining plume model, incorporating particle growth and noninductive charging, which predicts this wide range of Jovian lightning provides freezing point depressions caused by ammonia, and modify it to use a van der Waals equation of state instead of an ideal gas, as well as integrating the evaporation of rain; this allows modeling of planets colder than Jupiter, where clouds and lightning occur at greater pressures. For Saturn, the uppermost lightning is predicted at 3-4 bars; unlike on Jupiter, ammonia is not required to match the Cassini observations. For Uranus and Neptune, depending on their convective structures, very high rates of lightning are possible in the deep water clouds; while deeper than on Jupiter or Saturn, lightning is predicted likely to peak above the water cloud base, at pressures around 100 bars. Voyager 2's radio observations of Uranian and Neptunian sferics may thus be either due to attenuation of deep water lightning of this type, or due to lightning in the shallow ammonia clouds; future observations are required to resolve this dichotomy.

Keywords: Uranus, Saturn, Water vapor, Neptune, Atmospheric clouds, Planetary atmospheres, Solar system gas giant planets, Planetary science, Solar system astronomy, Lightning
Observation of a Lunar Eclipse at 89, 150, and 183 GHz. We describe the measurement of the brightness temperature of the Moon from space during a total lunar eclipse by using a microwave sounder aboard a weather satellite. Previous observations of lunar eclipses were inconsistent and did not cover the frequency range between 100 and 200 GHz. In this work, we seek to establish a reliable relationship between frequency and drop in brightness temperature during a total eclipse for millimeter wavelengths. For this purpose, we chose the eclipse on 2004 October 28, because it coincided with appearances of the Moon in the deep space view of the Advanced Microwave Sounding Unit-B on NOAA-15. It was therefore possible to measure its disk-integrated radiance at 89, 150, and 183 GHz at 100 minutes intervals. Our observations are, to the best of our knowledge, the only ones between 100 and 200 GHz, and demonstrate the nearly linear dependency on frequency of the maximum relative drop in effective temperature during an eclipse. The slope of this function is m = 0.00114 ± 0.00017 GHz-1 in the range 88-300 GHz. The good agreement between the variations of the effective lunar temperature and a new radiative-transfer model suggests that the Moon is suitable as a flux standard for microwave observations with beam sizes larger than 0.5°.

Keywords: Lunar eclipses, The Moon, Total eclipses, Millimeter astronomy
Mechanical Modification of Chondrule Fine-grained Rims by Dusty Nebular Shocks. The mechanical processes that convert an initially fluffy chondrule fine-grained rim (FGR) into a more compact structure remain poorly characterized. Given the presence of shocks in protoplanetary disks, we use numerical simulations to test the hypothesis that dust-laden shocks in the solar nebula contributed to FGR modification. We use the iSALE2D shock physics code to model the collision of dusty nebular shock fronts (which we term "dust clouds") into chondrule surfaces that host a porous FGR. In our simulations, dust particles are modeled as dunite disks. The dust radii follow the Mathis-Rumpl-Nordsieck distribution of interstellar grains. Chondrules are modeled as rectangular dunite slabs. We vary the impact speed v imp, the fractional abundance f cloud of dust grains in the impacting shock, and the fractional abundance f FGR of dust grains in the pre-existing FGR. We thus compute dust temperatures and pressures resulting from the collisions, as well as the net mass accretion of dust by the FGRs. Dust temperatures increase upon impact, depending on the kinetic energy of the dust cloud and on f FGR. Dust rims with a higher f FGR heat up more than those with a lower f FGR, with possibly important implications for the composition and structure of FGRs. Maximum impact pressures increase with f cloud. Fine-grained rims can experience mass gain from the impacting cloud, but in some instances, mass is lost from the rim. We find qualitative similarities in the topography of the FGR-chondrule interface between our simulations and petrographic analyses of the Paris CM chondrite by other authors.

Keywords: Meteorites, Shocks, Chondrules, Chondrites
Spitzer IRS Observations of Titan as a Precursor to JWST MIRI Observations. In this work, we present for the first time infrared spectra of Titan from the Spitzer Space Telescope (2004-2009). The data are from both the short wavelength-low resolution (SL; 5.13-14.29 μm, R ~ 60-127) and short wavelength-high resolution (SH; 9.89-19.51 μm, R ~ 600) channels showing the emissions of CH4, C2H2, C2H4, C2H6, C3H4, C3H6, C3H8, C4H2, HCN, HC3N, and CO2. We compare the results obtained for Titan from Spitzer to those of the Cassini Composite Infrared Spectrometer (CIRS) for the same time period, focusing on the 16.35-19.35 μm wavelength range observed by the SH channel but impacted by higher noise levels in the CIRS observations. We use the SH data to provide estimated haze extinction cross sections for the 16.67-17.54 μm range that are missing in previous studies. We conclude by identifying spectral features in the 16.35-19.35 μm wavelength range that could be analyzed further through upcoming James Webb Space Telescope Cycle 1 observations with the Mid-Infrared Instrument (5.0-28.3 μm, R ~ 1500-3500). We also highlight gaps in the current spectroscopic knowledge of molecular bands, including candidate trace species such as C60 and detected trace species such as C3H6, that could be addressed by theoretical and laboratory study.

Keywords: Titan, Transmission spectroscopy, Infrared astronomy, Natural satellite atmospheres, Radiative transfer, Atmospheric composition, Saturnian satellites
Synchronous Rotation in the (136199) Eris-Dysnomia System. We combine photometry of Eris from a 6 month campaign on the Palomar 60 inch telescope in 2015, a 1 month Hubble Space Telescope WFC3 campaign in 2018, and Dark Energy Survey data spanning 2013-2018 to determine a light curve of definitive period 15.771 ± 0.008 days (1σ formal uncertainties), with nearly sinusoidal shape and peak-to-peak flux variation of 3%. This is consistent at part-per-thousand precision with the P = 15.785 90 ± 0.00005 day sidereal period of Dysnomia's orbit around Eris, strengthening the recent detection of synchronous rotation of Eris by Szakáts et al. with independent data. Photometry from Gaia are consistent with the same light curve. We detect a slope of 0.05 ± 0.01 mag per degree of Eris's brightness with respect to illumination phase averaged across g, V, and r bands, intermediate between Pluto's and Charon's values. Variations of 0.3 mag are detected in Dysnomia's brightness, plausibly consistent with a double-peaked light curve at the synchronous period. The synchronous rotation of Eris is consistent with simple tidal models initiated with a giant-impact origin of the binary, but is difficult to reconcile with gravitational capture of Dysnomia by Eris. The high albedo contrast between Eris and Dysnomia remains unexplained in the giant-impact scenario.

Keywords: Tidal friction, Small Solar System bodies, Dwarf planets, Asteroid rotation, Trans-Neptunian objects
Astrobiology eXploration at Enceladus (AXE): A New Frontiers Mission Concept Study. The Saturnian moon Enceladus presents a unique opportunity to sample the contents of a subsurface liquid water ocean in situ via the continuous plume formed over its south polar terrain using a multi-flyby mission architecture. Previous analyses of the plume's composition by Cassini revealed an energy-rich system laden with salts and organic compounds, representing an environment containing most of the ingredients for life as we know it. Following in the footsteps of the Cassini-Huygens mission, we present Astrobiology eXploration at Enceladus (AXE), a New Frontiers class Enceladus mission concept study carried out during the 2021 NASA Planetary Science Summer School program at the Jet Propulsion Laboratory, California Institute of Technology. We demonstrate that a scientifically compelling geophysical and life-detection mission to Enceladus can be carried out within the constraints of a New Frontiers-5 cost cap using a modest instrument suite, requiring only a narrow angle, high-resolution telescopic imager, a mass spectrometer, and a high-gain antenna for radio communications and gravity science measurements. Using a multi-flyby mission architecture, AXE would evaluate the habitability and potential for life at Enceladus through a synergistic combination of in situ chemical analysis measurements aimed at directly detecting the presence of molecular biosignatures, along with geophysical and geomorphological investigations to contextualize chemical biosignatures and further evaluate the habitability of Enceladus over geologic time.

Keywords: Mass spectrometry, Enceladus, Geological processes, Astrobiology, Planetary geology, Biosignatures, Saturnian satellites, Flyby missions
Energetic Constraints on Ocean Circulations of Icy Ocean Worlds. Globally ice-covered oceans have been found on multiple moons in the solar system and may also have been a feature of Earth's past. However, relatively little is understood about the dynamics of these ice-covered oceans, which affect not only the physical environment but also any potential life and its detectability. A number of studies have simulated the circulation of icy-world oceans, but have come to seemingly widely different conclusions. To better understand and narrow down these diverging results, we discuss the energetic constraints for the circulation on ice-covered oceans, focusing in particular on Snowball Earth, Europa, and Enceladus. The energy input that can drive ocean circulation on ice-covered bodies can be associated with heat and salt fluxes at the boundaries as well as ocean tides and librations. We show that heating from the solid core balanced by heat loss through the ice sheet can drive an ocean circulation, but the resulting flows would be relatively weak and strongly affected by rotation. Salt fluxes associated with freezing and melting at the ice sheet boundary are unlikely to energetically drive a circulation, although they can shape the large-scale circulation when combined with turbulent mixing. Ocean tides and librations may provide an energy source for such turbulence, but the magnitude of this energy source remains highly uncertain for the icy moons, which poses a major obstacle to predicting the ocean dynamics of icy worlds and remains an important topic for future research.

Keywords: Ocean planets, Hydrosphere, Europa, Planetary science, Saturnian satellites
Titan's North-South Haze Asymmetry Ratio and Boundary at Visible Wavelengths over the Cassini Mission. We document the evolution of the north-south asymmetry (NSA) of Titan's haze albedo during the Cassini mission between 2004 and 2017. We analyze coadded cube images taken at 96 distinct wavelengths between 0.35 and 1.05 μm by the Cassini Visual and Infrared Mapping Spectrometer (VIMS-V) instrument from 14 Titan flybys. Over half of a Titan year, we observe a near-complete transition in the NSA boundary latitude across the geographic equator from the southern to the northern hemisphere, including a 3 yr fading of the boundary for several years after the equinox. The fading transition of the NSA matches previous observations of a reversal of the NSA in Hubble Space Telescope images of Titan before the winter solstice between 1997 and 2000. A comparison of NSA images taken at similar times but different phase angles shows the NSA boundary is detectable, albeit with less contrast, at moderately high phase angles (~90°). Analysis of the NSA boundary in T61 and T67 VIMS images further supports a small tilt between the superrotating atmosphere and the solid body of Titan, as suggested in a previous analysis of 0.890 μm images from the Cassini Imaging Science Subsystem.

Keywords: Atmospheric evolution, Astronomy data modeling, Computational astronomy, Titan, Albedo, Atmospheric dynamics, Astronomy image processing
A Past Episode of Rapid Tidal Evolution of Enceladus?. Saturn possesses a dynamically rich system containing numerous moons and impressive rings. Whether the rings of Saturn are much younger than the planet itself has been a long-standing open question; more recently a young age has been proposed for some moons. The recent detection of the fast orbital evolution of Rhea and Titan strongly suggests a highly frequency-dependent tidal response of Saturn, possibly through the excitation of inertial waves within the planet's convective envelope. Here we show that resonance locking to inertial waves cannot explain the dynamical structure of the Saturnian system or the current tidal heating of Enceladus. On the other hand, both the observations and our modeling results indicate that the system is not consistent with evolution under equilibrium tides. We propose that the system's architecture can best be explained by a relatively high "background" tidal response coupled with discrete resonant modes. In this view, only Titan may be in a true long-term resonance lock with a tidal mode of Saturn. Rhea is most likely currently experiencing a transient period of fast tidal evolution as it passes through a mode, rather than being locked into it. Assuming that Enceladus went through a temporary period of fast tidal evolution, we can reproduce its present resonance with Dione and satisfy other dynamical constraints. Additionally, we conclude that the long-term tidal response of Saturn to Tethys must be weaker than expected from frequency-independent tides, as already found by observations.

Keywords: Saturnian satellites
Orbits and Masses of the Small Satellites of Pluto. We present a new orbit and mass solution for the four small satellites of Pluto: Styx, Nix, Kerberos, and Hydra. We have reanalyzed all available observations of the Pluto system obtained by the Hubble Space Telescope from 2005 to 2019 with the ACS, WFPC2, and WFC3 instruments, as well as the New Horizons LORRI images taken on approach to Pluto in 2015. We have used this high-precision astrometry to produce updated orbits and mass estimates with uncertainties for all four of the small satellites. We find that the masses of Nix and Hydra are smaller than previously published estimates, with a dynamical mass of (1.8 ± 0.4) × 10-3 km3 s-2 ((2.7 ± 0.6) × 1016 kg) for Nix and (2.0 ± 0.2) × 10-3 km3 s-2 ((3.0 ± 0.3) × 1016 kg) for Hydra. These masses are 60% and 63% of the mean estimates by Brozovic et al., respectively, although still consistent with their 1σ uncertainties, and correspond to densities of 1.0 ± 0.2 g cm-3 for Nix and 1.2 ± 0.2 g cm-3 for Hydra given the moon volume estimates from Porter et al. Although these densities are consistent with a range of ice-rock compositions, depending on the unknown bulk porosity in the moon interiors, the moons' high albedos and predominantly icy surfaces are most easily explained if their interiors are ice-rich. The tiny masses of Kerberos and Sytx remain very poorly constrained; we find 1σ upper limits for dynamical mass of 3 × 10-5 km3 s-2 (5 × 1014 kg) for Styx and 5 ×10-5 km3 s-2 (8 × 1014 kg) for Kerberos, consistent with densities of &lt;2.1 g cm-3 for both bodies.

Keywords: Natural satellite dynamics, Plutonian satellites, Pluto
First Optical Constants of Laboratory-generated Organic Refractory Materials (Tholins) Produced in the NASA Ames COSmIC Facility from the Visible to the Near Infrared (0.4-1.6 μm): Application to Titan's Aerosols. We have measured the complex refractive indices, from 0.4 to 1.6 μm, of five laboratory-generated organic refractory materials (tholins) produced at low temperature (150 K) using plasma chemistry in the stream of a supersonic expansion in NASA Ames' COsmic SImulation Chamber (COSmIC) facility. Three samples were produced from N2:CH4 gas precursors (with different voltages inducing different degrees of ionization in the plasma), one sample was produced from N2:CH4:C2H2, and one sample was produced from Ar:CH4 in order to produce a purely carbonaceous sample. The optical constants, n and k, of the samples were determined using spectral reflectance measurements. We observe that both n and k appear to be correlated with the nitrogen content in the solid sample, with samples containing more nitrogen having higher n and k. Comparisons to previous laboratory studies and Titan aerosol optical constants derived from observations show that the COSmIC tholins with a higher nitrogen content (higher n and k) are closer analogs of Titan aerosols. We also present a new analysis of Cassini Visible Infrared Mapping Spectrometer observations of Titan's atmosphere in the visible to near infrared using the COSmIC tholin optical constants in a radiative transfer model. The COSmIC tholin sample produced from N2:CH4 with the lowest energy level has a spectral behavior that appears well suited to reproduce the observed Titan aerosol properties. This study has therefore demonstrated that this COSmIC tholin sample has valuable and promising optical properties for the analysis of Cassini's Titan atmospheric observations.

Keywords: Optical observation, Experimental data, Laboratory astrophysics, Titan, Near infrared astronomy, Optical constants (Dust)
Jupiter's Early Luminosity May Have Driven off Io's Initial Water Inventory. After its formation, Jupiter was substantially more luminous than it is at the present day (104 times). Right after formation, the inner satellites Io and Europa would have received an order-of-magnitude larger incoming flux from Jupiter, than solar insolation. However, little work has been done to examine the impact this would have had on the Galilean satellites. In this work we explore the possibility that Jupiter's early luminosity could have caused the loss of any initial water inventory on Io and Europa. We find that, depending on Jupiter's luminosity after the proto-Jovian disk dissipates, heating from Jupiter could drive rapid water loss via hydrodynamic escape. If early tidal heating dehydrated Io's accreted silicates, this may provide a mechanism to lose Io's initial water inventory.

Keywords: Natural satellite formation, Jupiter, Europa, Io, Atmospheric dynamics, Jovian satellites
V-type Asteroids as the Origin of Mesosiderites. We present the results of a campaign of hypervelocity impact experiments on natural mesosiderite targets, using representative main asteroid belt impact speeds. The objective is to document further the surface evolution of iron-rich asteroids. In contrast with iron meteorites, we demonstrate the fragile behavior of mesosiderite at impact since experiments result in both cratering and catastrophic disruption. The behavior of metal-rich asteroids at impact is thus highly influenced by the original ratio of metal/silicate. A visible to near-infrared spectral analysis shows that the pyroxene silicate signature of impacted mesosiderites, or their ejecta, is fully preserved. Our results thus rule out a mesosiderite hypothesis for the very nature of M/X-type asteroids including (16) Psyche, despite a small fraction of its surface possibly being covered by mesosiderite-like materials. Finally, we address the question of whether mesosiderites and howardite-eucrite-diogenite (HED) meteorites are genetically linked to (4) Vesta or other differentiated asteroids in the main belt based on their spectral similarity.

Keywords: Asteroids
Interstellar Comets from Post-main-sequence Systems as Tracers of Extrasolar Oort Clouds. Interstellar small bodies are unique probes into the histories of exoplanetary systems. One hypothesized class of interlopers are "Jurads," exocomets released into the Milky Way during the post-main-sequence as the thermally pulsing asymptotic giant branch (AGB) host stars lose mass. In this study, we assess the prospects for the Legacy Survey of Space and Time (LSST) to detect a Jurad and examine whether such an interloper would be observationally distinguishable from exocomets ejected during the (pre-)main-sequence. Using analytic and numerical methods, we estimate the fraction of exo-Oort Cloud objects that are released from 1-8 M ⊙ stars during post-main-sequence evolution. We quantify the extent to which small bodies are altered by the increased luminosity and stellar outflows during the AGB, finding that some Jurads may lack hypervolatiles and that stellar winds could deposit dust that covers the entire exocomet surface. Next, we construct models of the interstellar small body reservoir for various size-frequency distributions and examine the LSST's ability to detect members of those hypothesized populations. Combining these analyses, we highlight the joint constraints that the LSST will place on power-law size-frequency distribution slopes, characteristic sizes, and the total mass sequestered in the minor planets of exo-Oort Clouds. Even with the LSST's increased search volume compared to contemporary surveys, we find that detecting a Jurad is unlikely but not infeasible given the current understanding of (exo)planet formation.

Keywords: Sky surveys, White dwarf stars, Asymptotic giant branch stars, Interstellar objects, Comets, Exocomets