Sazuna/UAT_keywords huggingface dataset:
Lower Bounds on the Thickness and Dust Content of Layers within the North Polar Layered Deposits of Mars from Radar Forward Modeling. The Mars Reconnaissance Orbiter's Shallow Radar (SHARAD) emits radar signals and records their reflections from layer boundaries within the Martian north polar ice cap. Previous studies have suggested that the ice cap is composed of thin dust-rich layers between thicker layers of nearly pure water ice. The prevailing hypotheses suggest that each dust-rich layer represents either a period of ice sublimation at the poles or a period of reduced ice deposition relative to dust deposition. To test whether thin dust beds are a plausible hypothesis for the observed SHARAD reflectors, we use RadSPy (radar sounding simulator in Python, https://github.com/scourvil/RadSPy.git), an open-source N-layer radar sounder forward-modeling software that we have developed and describe herein. We forward model radar data from thin dust-rich beds interspersing pure ice, and compare them to observed radar reflection data over Gemina Lingula in the north polar layered deposits (NPLD). We consider two end-member cases: (1) thin beds composed entirely of dust, but with thickness varying from 0.05 m to 0.4 m; and (2) dust beds all with the same thickness, but with varying dust content. We find that the observed reflections can be explained by either scenario, i.e., varying thickness or varying dust content, and we conclude that a combination of both is likely. More importantly, our results provide lower bounds on the layer thickness and dust fraction for the flat-lying reflectors of Gemina Lingula in the NPLD. Our findings support the thin dust layer hypothesis, providing new constraints on layer composition and geometry for Mars climate researchers.

Keywords: Planetary science
Identification of Possible Heat Sources for the Thermal Output of Enceladus. We have calculated the amount of radioactive heat production (RHP) that could possibly prevent the postulated underground ocean of Enceladus from freezing. An internal heat source is necessary to justify the observed heat output from Enceladus and to allow the tidal dissipation heating models to work. Also based on the terrestrial evidence, we have assumed that the most common radiogenic element that can produce such internal heat is 238U. Our results show that a minimum amount in the range 38.10-76.59 ppm of 238U, averaged over the whole mass of Enceladus, is necessary to obtain the required RHP. The range of values increases to 63.60-127.70 ppm if we consider only the mass of the rocky portion and 2890-5775 ppm if we consider the mass of the rock + ice portion of Enceladus just below the southern polar area. Even in the latter case, the concentration of uranium is still well below the amount found in high-grade ore on Earth.

Keywords: Tidal interaction, Planetary interior, Saturnian satellites
Polarimetric Decomposition of Near-Earth Asteroids Using Arecibo Radar Observations. The polarization state of radar echoes from planetary bodies contains information about the scattering mechanisms present on the surface and thus the near-surface physical properties. Polarimetric radar scatter from complex surfaces, such as those observed for spacecraft-visited near-Earth asteroids (NEAs), is not well understood in terms of relating observed polarimetry to surface properties. Here we present an improved methodology for polarimetric analyses of ground-based radar observations of NEAs, extending techniques derived for larger bodies. We calculate the Stokes vector for delay-Doppler images of NEAs and use this to perform the m-chi decomposition and derive polarimetric products such as the degree of polarization, circular polarization ratio, and degree of linear polarization. We apply this methodology to radar observations of NEAs (53319) 1999 JM8, (101955) Bennu, and (33342) 1998 WT24 obtained by the Arecibo Observatory. We also perform numerical simulations of the m-chi decomposition for irregular boulders to augment the interpretation of the results for NEAs. Our analyses show that significant components of radar echoes are depolarized (random polarization) and linearly polarized. The numerical simulations confirm that depolarization is increased by single scattering from nonspherical wavelength-scale particles. Our analysis suggests that 1999 JM8 is possibly covered in regolith and that surface scatterers dominate the scattering properties of Bennu. The NEA 1998 WT24 displays diverse polarimetric properties, which we reconcile with optical and thermal observations by assuming a fine-grained regolith mantling a rugged, dense interior. In this work, we demonstrate the usefulness of radar polarimetry in characterizing the physical properties of planetary surfaces.

Keywords: Near-Earth objects, Polarimetry, Radar telescopes
Surfaces of (Nearly) Dormant Comets and the Recent History of the Quadrantid Meteor Shower. The parent of the Quadrantid meteor shower is the inactive solar system small body (196256) 2003 EH1. EH1 has likely only gone dormant in the past few hundred years, and may be related to the bright comet C/1490 Y1. Compared with the other best-studied inactive meteor shower parent (3200) Phaethon, EH1 has received comparatively minimal characterization of its surface properties. We present the first reflectance spectrum and additional photometry of EH1, as well as new spectra of the nuclei of three nearly dormant comets P/2006 HR30 (Siding Spring), 364P/Pan-STARRS, and 249P/LINEAR for comparison. We also present new short-term high-resolution orbital integrations of these bodies for context. EH1s spectrum is red in color below 0.8 μm in between C and D types, consistent with previous photometric measurements, but is blue beyond 0.8 μm until at least 1.02 μm. 249P and 364P have both red slopes consistent with C taxonomic types and HR30 has a classic comet nucleus D-type slope. If the downturn in EH1's spectrum is due to an absorption feature, magnetite and olivine are plausible candidates, but more data are needed. 249P and 364P have similar recent and historical dynamical evolutions in addition to their similar surface properties. We discuss the interrelation between the dynamical histories and modern surfaces of these four objects and suggest avenues for further study to better constrain how the Quadrantids and Geminids were created.

Keywords: Comet nuclei, Orbital evolution, Comet surfaces, Meteor showers, Meteor streams, Spectroscopy, Spectrophotometry
Uncertainties on Asteroid Albedos Determined by Thermal Modeling. We present an analysis of the accuracy of geometric albedos determined for asteroids through the modeling of observed thermal infrared radiation. We show that albedo uncertainty is dominated by the uncertainty on the measured HV absolute magnitude, and that any analysis using albedos in a statistical application will also be dominated by this source of uncertainty. For all but the small fraction of asteroids with a large amount of characterization data, improved knowledge of the HV magnitude will be fundamentally limited by incomplete phase-curve coverage, incomplete light-curve knowledge, and the necessary conversion from the observed band to the V band. Switching the absolute magnitude standard to a different band such a $r^{\prime} $ would mitigate the uncertainty due to band conversion for many surveys, but this only represents a small component of the total uncertainty. Therefore, techniques making use of these albedos must ensure that their uncertainties are properly accounted for.

Keywords: Asteroids, Photometry
Characterizing the Manx Candidate A/2018 V3. Manx objects approach the inner solar system on long-period comet (LPC) orbits with the consequent high inbound velocities, but unlike comets, Manxes display very little to no activity even near perihelion. This suggests that they may have formed in circumstances different from typical LPCs; moreover, this lack of significant activity also renders them difficult to detect at large distances. Thus, analyzing their physical properties can help constrain models of solar system formation as well as sharpen detection methods for those classified as NEOs. Here, we focus on the Manx candidate A/2018 V3 as part of a larger effort to characterize Manxes as a whole. This particular object was observed to be inactive even at its perihelion at q = 1.34 au in 2019 September. Its spectral reflectivity is consistent with typical organic-rich comet surfaces with colors of $g^{\prime} -r^{\prime} =0.67\pm 0.02$ , $r^{\prime} -i^{\prime} =0.26\pm 0.02$ , and $r^{\prime} -z^{\prime} =0.45\pm 0.02$ , corresponding to a spectral reflectivity slope of 10.6 ± 0.9%/100 nm. A least-squares fit of our constructed light curve to the observational data yields an average nucleus radius of ≍2 km assuming an albedo of 0.04. This is consistent with the value measured from NEOWISE. A surface brightness analysis for data taken 2020 July 13 indicated possible low activity (≲0.68 g s-1), but not enough to lift optically significant amounts of dust. Finally, we discuss Manxes as a constraint on solar system dynamical models as well as their implications for planetary defense.

Keywords: Long period comets, Comets, Oort cloud objects
NEOWISE Observed CO and CO<SUB>2</SUB> Production Rates of 46P/Wirtanen During the 2018-2019 Apparition. We present measurements of comet 46P/Wirtanen obtained by the NEOWISE spacecraft in 2017 through 2019. We detected signal in excess of the dust in the 4.6 μm channel attributable to the presence of CO, or more likely, CO2 emission. The excess, when the comet was outbound at a heliocentric distance of 1.9 au, was consistent with a CO2 production rate of 1.3(±0.07) × 1026 molecules per second, which is equivalent to an active area on the order of a percent of the comet nucleus' total surface. * Released on 2020 September 30th.

Keywords: Comets, Short period comets, Comet volatiles , Infrared photometry
Constraints on Sub-Neptune Planet Candidate KOI-972.01 via Joint Variability/Gravity-darkening Analysis. We analyze Kepler photometry of transiting planet candidate KOI-972.01, accounting for both stellar variability and gravity darkening. KOI-972.01 stands out because of its small radius, less than that of Neptune, and because of its intermediate orbit period at 13.12 days, long enough to avoid significant tidal evolution, and thus it represents an underexplored exoplanet class. The parent star of KOI-972.01 is a rapidly rotating δ-Scuti variable, complicating transit lightcurve interpretation but also offering a potential independent source of stellar parameters. We measure the stellar rotation period (16.2 hr) by identifying the stellar rotation frequency and subsequently place a constraint on the stellar obliquity of no greater than 10°, but have difficulty isolating individual oscillation modes in the periodogram owing to time variation of the δ-Scuti oscillations. After subtracting the stellar oscillations, lightcurve fits place the transiting object radius at 3.07 ± 0.09 R⊕, but the shallow transit prevents useful constraints on the system's spin-orbit alignment.

Keywords: Planetary alignment, Exoplanet systems, Exoplanet astronomy, Exoplanet evolution, Mini Neptunes, Exoplanet formation, Gravity darkening
Standing on Apollo's Shoulders: A Microseismometer for the Moon. Seismometers deployed on the Moon by the Apollo astronauts from 1969 to 1972 detected moonquakes and impacts, and added to our understanding of the lunar interior. Several lunar missions are currently being planned, including the Commercial Lunar Payload Services (CLPS), the Lunar Geophysical Network, and the astronaut program Artemis. We propose a microseismometer for the Moon: the Silicon Seismic Package (SSP). The SSP's sensors are etched in silicon, and are predicted to have a noise floor below $2\times {10}^{-10}\,({\rm{m}}\,{{\rm{s}}}^{-2})/\sqrt{\mathrm{Hz}}$ between 0.3 and 3 Hz (similar to the Apollo instruments between 0.3 and 0.5 Hz, and better than Apollo above 0.5 Hz). The SSP will measure horizontal and vertical motion with the three sensors in a triaxial configuration. The instrument is robust to high shock and vibration and has an operational range from -80°C to +60°C, allowing deployment under harsh conditions. The first-generation version of this sensor, the SEIS-SP, was deployed on Mars in 2018 as part of the InSight mission's seismic package. We will reconfigure the seismometer for the lower gravity of the Moon. We estimate that a single SSP instrument operating for one year would detect around 74 events above a signal-to-noise ratio of 2.5, as well as an additional 500+ above the noise floor. A mission lasting from lunar dawn until dusk, carried on a CLPS lander, could test the instrument in situ, and provide invaluable information for an extensive future network.

Keywords: Lunar interior, Lunar seismology
Experimental Simulation of the Volatile Hydrocarbons Generated by the Long-UV Photoprocessing of (C<SUB>6</SUB>H<SUB>6</SUB>) Ices with Relevance to Titan's Southern Stratospheric Ice Clouds. Ice clouds containing benzene (C6H6) have recently been detected in the stratosphere at the south pole of Titan. Their subsequent aging process induced by long-UV solar photons could lead to a photoreactivity that may release some volatile organic compounds in the gas phase. The characterization of this volatile organic fraction coming from the photoprocessing (λ &gt; 230 nm) of such icy C6H6 has been characterized by a gas chromatograph coupled to a mass spectrometer. Complex molecular diversity is observed through the identification of C3 to C8 photoproducts, which belong to the alkane, alkene, and alkyne families and aromatic derivatives. Thereafter, these hydrocarbons will potentially be transported down to the surface, as condensed ices. Because the energy of solar UV photons decrease with altitude, most of these solid-state hydrocarbons will not be photochemically degraded and may contribute at the end to the organic layer that covers Titan's surface. As these materials would be probed by DraMS, the mass spectrometer on board the future Dragonfly mission, these analyses could serve as benchmarks for future molecule detection on Titan's surface.

Keywords: Planetary atmospheres
Small Penetrator Instrument Concept for the Advancement of Lunar Surface Science. Fundamental scientific objectives concerning the surface and subsurface material and dynamics of the Moon are the drivers for the use and advancement of penetrators, which emplace a suite of scientific instruments by impact into a planetary surface, typically at velocities of dozens to hundreds of meters per second. Small lunar penetrators are poised to become a valuable new tool for lunar science and exploration during the next decade. These low-cost ballistic probes can be deployed in large numbers from orbit, or from descending robotic or crewed vehicles, in order to explore and characterize the diversity of extreme lunar shallow subsurface environments. In this paper, we describe the general overview of penetrator objectives, potential instrumentation, and how these would benefit the advancement of lunar science at various extreme environments.

Keywords: Lunar composition, Lunar probes, The Moon, Lunar science, Lunar surface
Constraining the Positive Ion Composition in Saturn's Lower Ionosphere with the Effective Recombination Coefficient. The present study combines Radio and Plasma Wave Science/Langmuir Probe and Ion and Neutral Mass Spectrometer data from Cassini's last four orbits into Saturn's lower ionosphere to constrain the effective recombination coefficient α300 from measured number densities and electron temperatures at a reference electron temperature of 300 K. Previous studies have shown an influx of ring material causes a state of electron depletion due to grain charging, which will subsequently affect the ionospheric chemistry. The requirement to take grain charging into account limits the derivation of α300 to upper limits. Assuming photochemical equilibrium and using an established method to calculate the electron production rate, we derive upper limits for α300 of ≲ 3 × 10-7 cm3 s-1 for altitudes below 2000 km. This suggests that Saturn's ionospheric positive ions are dominated by species with low recombination rate coefficients like HCO+. An ionosphere dominated by water group ions or complex hydrocarbons, as previously suggested, is incompatible with this result, as these species have recombination rate coefficients &gt; 5 × 10-7 cm3 s-1 at an electron temperature of 300 K.

Keywords: Space plasmas, Saturn, Recombination, Planetary science
Zwicky Transient Facility Observations of Trojan Asteroids: A Thousand Colors, Rotation Amplitudes, and Phase Functions. We introduce a new method for analyzing sparse photometric data of asteroids and apply it to Zwicky Transient Facility observations of the Jupiter Trojan asteroids. This method relies on the creation of a likelihood model that includes the probability distribution of rotational brightness variations at an unknown rotation phase. The likelihood model is analyzed via a Markov Chain Monte Carlo to quantify the uncertainty in our parameter estimates. Using this method, we provide color, phase parameter, absolute magnitude, and amplitude of rotation measurements for 1049 Jupiter Trojans. We find that phase parameter is correlated with color and the distribution of Trojan asteroid rotational amplitudes is indistinguishable from that of main-belt asteroids.

Keywords: Sky surveys, Light curves, Multi-color photometry, Jupiter trojans
Primordial Porous Structure of Chondrite Parent Bodies Due to Self-gravity. The porosity of an asteroid is important when studying the evolution of our solar system through small bodies and for planning mitigation strategies to avoid disasters due to asteroid impacts. Our knowledge of asteroid porosity largely relies on meteorites sampled on Earth. However, chondrites sampled on Earth are suggested to be sorted by strength. In this study, we obtained an estimate of the most porous structure of primordial "granular" chondrite parent bodies based on measurements of the compaction behavior of chondrite component analogs. We measured compaction curves of dust and dust-bead mixture samples. The dust sample consisted of various spherical and irregular particles with diameters on the order of 100-101 μm. The mixture sample consisted of dust and beads with different dust volume fractions (∼0.2-1). We used 1.5 and 4.8 μm particles as dust as a first step, although the typical size of materials in matrix may be much smaller. We approximated the compaction curve of each sample with a power-law form and calculated the porosity structure of the primordial chondrite parent bodies using the experimental results. Our results show that the primordial parent bodies are likely to have higher porosity than the chondrites. Moreover, the relatively higher volume fraction of the matrix may be one of the reasons why most meteorites with high porosity are carbonaceous chondrites.

Keywords: Chondrites, Asteroids, Planet formation, Planetesimals
Near-infrared Reflectance of Rocks at High Temperature: Preliminary Results and Implications for Near-infrared Emissivity of Venus's Surface. Light emitted from Venus's surface can be viewed through spectral "windows" in its atmosphere, in the near-infrared (NIR) around 1000 nanometer (nm) wavelengths. The NIR emissivity of Venus's surface can constrain rock types and their weathering state; emissivities can be measured directly or calculated from reflectances. We measured the reflectances of igneous and sedimentary rocks at Venus's surface temperature, 400 °C-500 °C at 850 and 950 nm; samples were heated in a box furnace in air, illuminated by light-emitting diodes (LEDs), and imaged with a modified charge-coupled device (CCD) camera. Reflectances were also measured at 25 °C from 350 to 1400 nm. Rock reflectances at 850 and 950 nm and 400 °C-500 °C are nearly identical to those at 25 °C, except for the effects of nanophase hematite forming on some surfaces. Fresh basalts have reflectances (high and low temperatures) near 7.5%; a leucogranite similarly has reflectances near 50%. Pigmentary hematite has nearly identical reflectances at high- and low-temperature at these wavelengths. Pigmentary hematite appears dark brown 400 °C-500 °C because its absorption edge has shifted to beyond the limit of human vision. These rock reflectances imply that basalts should have emissivities near 0.9, and granite (and similar felsic rocks) should have lower emissivities ∼0.5. Thus, basalt and felsic rock should be easily distinguished in NIR emissivity measurements of Venus's surface, such as are baselined in recent Venus mission proposals. Other sedimentary rocks should have even lower emissivities: quartz sand at around ∼0.3, and anhydrite as low as 0.1.

Keywords: Extrasolar rocky planets, Venus, Infrared photometry
Low Radio Frequency Observations from the Moon Enabled by NASA Landed Payload Missions. A new era of exploration of the low radio frequency universe from the Moon will soon be underway with landed payload missions facilitated by NASA's Commercial Lunar Payload Services (CLPS) program. CLPS landers are scheduled to deliver two radio science experiments, Radio wave Observations at the Lunar Surface of the photoElectron Sheath (ROLSES) to the nearside and Lunar Surface Electromagnetics Experiment (LuSEE) to the farside, beginning in 2021. These instruments will be pathfinders for a 10 km diameter interferometric array, Farside Array for Radio Science Investigations of the Dark ages and Exoplanets (FARSIDE), composed of 128 pairs of dipole antennas proposed to be delivered to the lunar surface later in the decade. ROLSES and LuSEE, operating at frequencies from ≈100 kHz to a few tens of megahertz, will investigate the plasma environment above the lunar surface and measure the fidelity of radio spectra on the surface. Both use electrically short, spiral-tube deployable antennas and radio spectrometers based upon previous flight models. ROLSES will measure the photoelectron sheath density to better understand the charging of the lunar surface via photoionization and impacts from the solar wind, charged dust, and current anthropogenic radio frequency interference. LuSEE will measure the local magnetic field and exo-ionospheric density, interplanetary radio bursts, Jovian and terrestrial natural radio emission, and the galactic synchrotron spectrum. FARSIDE, and its precursor risk-reduction six antenna-node array PRIME, would be the first radio interferometers on the Moon. FARSIDE would break new ground by imaging radio emission from coronal mass ejections (CME) beyond 2R⊙, monitor auroral radiation from the B-fields of Uranus and Neptune (not observed since Voyager), and detect radio emission from stellar CMEs and the magnetic fields of nearby potentially habitable exoplanets.

Keywords: Magnetospheric radio emissions, Solar system planets, The Moon, Lunar science, Solar radio emission, Radio telescopes, Lunar atmosphere, Space telescopes, Radio astronomy, Habitable planets