Sazuna/UAT_keywords huggingface dataset:
Benzoic Acid as the Preferred Precursor for the Chlorobenzene Detected on Mars: Insights from the Unique Cumberland Analog Investigation. The Cumberland drill sample from the Sheepbed mudstone in Gale Crater, Mars, revealed the first evidence of an indigenous Martian organic molecule, chlorobenzene, with the Sample Analysis at Mars (SAM) instrument on Curiosity. We created in the laboratory a mineralogical analog of the Cumberland sample (CBA) to aid in the understanding of the precursor organic molecule(s) that led to the detection of chlorobenzene. The CBA was analyzed by visible/near-infrared spectrometry, and the results are in accordance with Mastcam multispectral and the Chemical Camera passive analyses of Cumberland on Mars, demonstrating that the CBA is a relevant analog. CBA aliquots were spiked with 0.5 wt. % of benzoic acid and 1-2 wt. % of magnesium perchlorate and were run in SAM Testbed (TB). The TB evolved gas analysis (EGA) showed similarities with the Cumberland EGA on Mars in terms of the major volatiles H2O, CO2, and O2. The TB gas chromatography mass spectrometry displayed the presence of chlorobenzene at 23-28 pmol and dichlorobenzene. CBA aliquots were also analyzed in the laboratory with SAM-like EGA and the results on the laboratory setup confirmed the generation of chlorobenzene by a reaction between the benzoic acid and the magnesium perchlorates. The case for benzoic acid as a potential precursor for the chlorobenzene detected in the Martian regolith is strengthened with this new supporting laboratory data from the CBA. The quantification of chlorobenzene in the TB led to prediction of organic precursor abundance on Mars of hundreds, if not thousands, of parts per millions by weight.

Keywords: Mars, Astrobiology, Planetary science, Pre-biotic astrochemistry
Could the Migration of Jupiter Have Accelerated the Atmospheric Evolution of Venus?. In the study of planetary habitability and terrestrial atmospheric evolution, the divergence of surface conditions for Venus and Earth remains an area of active research. Among the intrinsic and external influences on the Venusian climate history are orbital changes due to giant planet migration that have both variable incident flux and tidal heating consequences. Here, we present the results of a study that explores the effect of Jupiter's location on the orbital parameters of Venus and subsequent potential water-loss scenarios. Our dynamical simulations show that various scenarios of Jovian migration could have resulted in orbital eccentricities for Venus as high as 0.31. We quantify the implications of the increased eccentricity, including tidal energy, surface energy flux, and the variable insolation flux expected from the faint young Sun. The tidal circularization timescale calculations demonstrate that a relatively high tidal dissipation factor is required to reduce the eccentricity of Venus to the present value, which implies a high initial water inventory. We further estimate the consequences of high orbital eccentricity on water loss, and estimate that the water-loss rate may have increased by at least ∼5% compared with the circular orbit case as a result of orbital forcing. We argue that these eccentricity variations for the young Venus may have accelerated the atmospheric evolution of Venus toward the inevitable collapse of the atmosphere into a runaway greenhouse state. The presence of giant planets in exoplanetary systems may likewise increase the expected rate of Venus analogs in those systems.

Keywords: Habitable planets, Venus, Exoplanet systems, Orbital evolution
Changes in a Dusty Ringlet in the Cassini Division after 2010. A dusty ringlet designated R/2006 S3, also known as the "Charming Ringlet," is located around 119,940 km from the center of Saturn within the Laplace Gap in the Cassini Division. Prior to 2010, the ringlet had a simple radial profile and a predictable eccentric shape with two components, one forced by solar radiation pressure and the other freely precessing around the planet. However, observations made by the Cassini spacecraft since late 2012 revealed a shelf of material extending inwards from the ringlet that was not present in the earlier observations. Closer inspection of images obtained after 2012 shows that sometime between 2010 and 2012, the freely precessing component of the ringlet's eccentricity increased by over 50%, and that for at least 3 yr after 2012, the ringlet had longitudinal brightness variations that rotated around the planet at a range of rates corresponding to ∼60 km in orbital semimajor axis. Some event therefore disturbed this ringlet between 2010 and late 2012.

Keywords: Saturn, Orbits, Solar system, Planetary rings, Celestial mechanics, Interplanetary dust
Detection of a Satellite of the Trojan Asteroid (3548) Eurybates—A Lucy Mission Target. We describe the discovery of a satellite of the Trojan asteroid (3548) Eurybates in images obtained with the Hubble Space Telescope. The satellite was detected on three separate epochs, two in 2018 September and one in 2020 January. The satellite has a brightness in all three epochs consistent with an effective diameter of d2 = 1.2 ± 0.4 km. The projected separation from Eurybates was s ∼ 1700-2300 km and varied in position, consistent with a large range of possible orbits. Eurybates is a target of the Lucy Discovery mission and the early detection of a satellite provides an opportunity for a significant expansion of the scientific return from this encounter.

Keywords: Trojan asteroids, Natural satellites (Solar system)
Colliding in the Shadows of Giants: Planetesimal Collisions during the Growth and Migration of Gas Giants. Giant planet migration is an important phenomenon in the evolution of planetary systems. Recent works have shown that giant planet growth and migration can shape the asteroid belt, but these works have not considered interactions between planetesimals. We have calculated the evolution of planetesimal disks, including planetesimal-planetesimal collisions, during gas giant growth and migration. The numbers, locations, and impact velocities of these collisions depend on the specific growth and migration path. We find that giant planet growth alone has little effect on impact velocities, and most of the planetesimals scattered by growing giants do not undergo collisions. In contrast, we find that giant planet migration induces large numbers of high-velocity collisions between planetesimals. These impacts have sufficient velocities to cause shock-induced vaporization for both water ice and silicate components of planetesimals and to cause disruption of the bodies. New bodies may form from impact debris. Collisional evolution reduces the efficiency of planetesimal implantation into the asteroid belt. A small fraction of the largest planetesimals implanted into the asteroid belt would have been processed via collisions. We identify important consequences of planetesimal collisions that have not been considered in planet accretion models. The prevalence of high-velocity collisions during giant planet migration, and their potential links to the properties of meteorites and the formation of chondrules, makes impact vaporization a critically important phenomenon. The consequences of vaporizing planetesimal constituents require further detailed study. New collision outcome models for impacts within the nebula, and models for new planetesimal formation are needed.

Keywords: Impact phenomena, Solar system formation, Chondrites, Small Solar System bodies, Solar system planets, Chondrules, Protoplanetary disks, Planetary science, Planetesimals, Meteorites, Asteroid belt, Planet formation
Detection Limits for Chiral Amino Acids Using a Polarization Camera. The detection of biosignatures on a planetary surface is of high scientific interest, and enantiomeric excesses of organic molecules are one such signature. Enantiomeric excesses can be detected by their polarizing effects on transmitted light. As part of instrument development work for a microscopic imager, the Cold Lightweight Imager for Europa (C-LIFE), we assess the potential of polarization measurements to quantify enantiomeric excesses. We investigated the optical rotation of the amino acids serine and phenylalanine for a range of enantiomeric abundances. Measurements were made with mixtures of serine and phenylalanine as well as Europa-relevant salts to determine how well these combinations can be detected. We also conducted a small number of measurements on samples of bacteria taken from glacial environments. We found that concentrations greater than 10-3 M are needed to detect serine and concentrations greater than 10-4 M are needed to detect phenylalanine, with larger concentrations needed for smaller enantiomeric excesses. Salts do not have a significant effect on the optical rotation. Optical rotation of bacterial samples were detected at concentrations &gt;106 cells ml-1. Systematic errors in our polarization detector limited our sensitivity to optical activity changes of ∼0.008°, leading to an inability to distinguish enantiomeric abundances separated by 5%, but tests show that improvements to our laboratory technique can yield a factor of 20 improvement in sensitivity.

Keywords: Biosignatures, Astrobiology, Polarimetry, Jovian satellites
A Deep Search for Stable Venus Co-orbital Asteroids: Limits on the Population. A stable population of objects co-orbiting with Venus was recently hypothesized in order to explain the existence of Venus's co-orbital dust ring. We conducted a five days twilight survey for these objects with the Cerro-Tololo Inter-American Observatory 4 m telescope covering about 35 unique square degrees to 21 mag in the r band. Our survey provides the most stringent limit so far on the number of Venus co-orbital asteroids; it was capable of detecting 5% of the entire population of those asteroids brighter than 21 mag. We estimate an upper limit on the number of co-orbital asteroids brighter than 21 mag (approximately 400-900 m in diameter depending on the asteroid albedo) to be $N={18}_{-14}^{+30}$ . Previous studies estimated the mass of the observed dust ring co-orbiting with Venus to be equivalent to an asteroid with a 2 km diameter ground to dust. Our survey estimates &lt;6 asteroids larger than 2 km. This implies the following possibilities: that Venus co-orbitals are nonreflective at the observed phase angles, have a very low albedo (&lt;1%), or that the Venus co-orbital dust ring has a source other than asteroids co-orbiting Venus. We discuss this result, and as an aid to future searches, we provide predictions for the spatial, visual magnitude, and number density distributions of stable Venus co-orbitals based on the dynamics of the region and magnitude estimates for various asteroid types.

Keywords: Amor group, Near-Earth objects, CCD observation, Small Solar System bodies, Asteroids, Atira group, Venus, Orbital resonances, Ground-based astronomy
Stellar Occultation by the Resonant Trans-Neptunian Object (523764) 2014 WC510 Reveals a Close Binary TNO. We report on the stellar occultation by (523764) 2014 WC510 observed on 2018 December 1 UT. This occultation campaign was part of the Research and Education Collaborative Occultation Network (RECON), a network of small telescopes spread over 2000 km in western USA and Canada. Light curves from six stations revealed three groups of two or more consecutive flux drops correlated in time between adjacent stations. A Bayesian model comparison reveals that a model with a double object occulting a double star is favored over alternative models considered. For the statistically favored model, we determined that the primary component of the object has a diameter dp = 181 ± 16 km and the secondary ds = 138 ± 32 km, assuming identical geometric albedo between the two components. The two components have a projected separation of 349 ± 26 km. Adopting an absolute magnitude for the system of HV = 7.2 from the Minor Planet Center, we derive a geometric albedo of pV = 5.1% ± 1.7%. This is the smallest resonant object with an occultation size measurement and with a detected secondary from a ground-based stellar occultation, filling a region of the size versus separation parameter space of binary objects that is largely unexplored. The results show the capabilities of the unique design of the RECON experiment sensitive to small objects and close binaries. 2014 WC510 is presently at a low galactic latitude where the high surface density of stars will provide good occultation opportunities in the upcoming years.

Keywords: Stellar occultation, Resonant Kuiper belt objects, Bayesian statistics, Trans-Neptunian objects
Evaporation from the Lunar Magma Ocean Was Not the Mechanism for Fractionation of the Moon's Moderately Volatile Elements. The cause of chemical depletion and isotopic fractionation of moderately volatile elements (MVEs) in the Moon is a long-standing problem. Here we examine MVE isotopic fractionation during Moon formation using potassium as a primary example. We show that the degree of isotopic fractionation due to evaporation of the lunar magma ocean (LMO) depended critically on the vapor pressure above the LMO. Based on our analysis of evaporation and escape of the resulting rock-vapor atmosphere, LMO evaporation alone could not have caused the observed MVE isotopic compositions. The combination of exposure of the liquid of the LMO to the surface for on the order of 102-103 yr, near-equilibrium evaporation at the melt surface, and hydrodynamic escape facilitated by proximity of the Earth leads to no resolvable isotope or elemental fractionation. This study provides a basis for the simplifying assumption that rock vapor immediately above a magma ocean will be in thermodynamic equilibrium with the melt at the surface of the planetary body even where hydrodynamic escape is operative.

Keywords: The Moon, Lunar science, Isotope shifts, Lunar evolution, Earth-moon system
Spatial Variations of Low-mass Negative Ions in Titan's Upper Atmosphere. Observations with Cassini's Electron Spectrometer discovered negative ions in Titan's ionosphere, at altitudes between 1400 and 950 km. Within the broad mass distribution extending up to several thousand amu, two distinct peaks were identified at 25.8-26.0 and 49.0-50.1 amu/q, corresponding to the carbon chain anions CN- and/or ${{\rm{C}}}_{2}{{\rm{H}}}^{-}$ for the first peak and C3N- and/or C4H- for the second peak. In this study we present the spatial distribution of these low-mass negative ions from 28 Titan flybys with favorable observations between 2004 October 26 and 2012 May 22. We report a trend of lower densities on the night side and increased densities up to twice as high on the day side at small solar zenith angles. To further understand this trend, we compare the negative ion densities to the total electron density measured by Cassini's Langmuir Probe. We find the low-mass negative ion density and the electron density to be proportional to each other on the day side but independent of each other on the night side. This indicates photochemical processes and is in agreement with the primary production route for the low-mass negative ions being initiated by dissociative reactions with suprathermal electron populations produced by photoionisation. We also find the ratio of ${\mathrm{CN}}^{-}/{{\rm{C}}}_{2}{{\rm{H}}}^{-}$ to ${{\rm{C}}}_{3}{{\rm{N}}}^{-}/{{\rm{C}}}_{4}{{\rm{H}}}^{-}$ to be highly constrained on the day side, in agreement with this production channel, but notably displaying large variations on the night side.

Keywords: Saturnian satellites, Earth ionosphere
Haze Formation in Warm H<SUB>2</SUB>-rich Exoplanet Atmospheres. New observing capabilities coming online over the next few years will provide opportunities for characterization of exoplanet atmospheres. However, clouds/hazes could be present in the atmospheres of many exoplanets, muting the amplitude of spectral features. We use laboratory simulations to explore photochemical haze formation in H2-rich exoplanet atmospheres at 800 K with metallicity either 100 or 1000 times solar. We find that haze particles are produced in both simulated atmospheres with small particle size (20-140 nm) and relatively low production rate (2.4 × 10-5 to 9.7 × 10-5 mg cm-3 hr-1), but the particle size and production rate is dependent on the initial gas mixtures and the energy sources used in the simulation experiments. The gas phase mass spectra show that complex chemical processes happen in these atmospheres and generate new gas products that can further react to form larger molecules and solid haze particles. Two H2-rich atmospheres with similar C/O ratios (∼0.5) yield different haze particle size, haze production rate, and gas products, suggesting that both the elemental abundances and their bonding environments in an atmosphere can significantly affect the photochemistry. There is no methane (CH4) in our initial gas mixtures, although CH4 is often believed to be required to generate organic hazes. However, haze production rates from our experiments with different initial gas mixtures indicate that CH4 is neither required to generate organic hazes nor necessary to promote the organic haze formation. The variety and relative yield of the gas products indicate that CO and N2 enrich chemical reactions in H2-rich atmospheres.

Keywords: Laboratory astrophysics, Planetary atmospheres, Exoplanet atmospheres
The Population of Kilometer-scale Retrograde Jovian Irregular Moons. We have searched a 2010 archival data set from the Canada-France-Hawaii Telescope for very small (km-scale) irregular moons of Jupiter in order to constrain the size distribution of these moons down to radii of ∼400 m, discovering 52 objects that are moving with Jupiter-like on-sky rates and are nearly certainly irregular moons. The four brightest detections, and seven in total, were all then linked to known Jovian moons. Extrapolating our characterized detections (those down to magnitude mr = 25.7) to the entire retrograde circum-Jovian population, we estimate the population of radius &gt;0.4 km moons to be 600 (within a factor of 2). At the faintest magnitudes, we find a relatively shallow luminosity function of exponential index α = 0.29 ± 0.15, corresponding to a differential diameter power law of index q ≃ 2.5.

Keywords: Irregular satellites, Natural satellites (Solar system), Jupiter, Jovian satellites
HST UV Observations of Asteroid (16) Psyche. The Main Belt Asteroid (16) Psyche is the target object of the NASA Discovery Mission Psyche. We observed the asteroid at ultraviolet (UV) wavelengths (170-310 nm) using the Space Telescope Imaging Spectrograph on the Hubble Space Telescope during two separate observations. We report that the spectrum is very red in the UV, with a blue upturn shortward of ∼200 nm. We find an absorption feature at 250 nm and a weaker absorption feature at 275 nm that may be attributed to a metal-oxide charge transfer band. We find that the red-sloped, relatively featureless spectrum of (16) Psyche is best matched with the reflectance spectrum of pure iron; however, our intimate mixture models show that small grains of iron may dominate the reflectance spectrum even if iron only comprises up to 10% of the material on the surface. We also stress that there is a limited database of reflectances for planetary surface analogs at UV wavelengths for comparison with the spectrum of (16) Psyche. The mid- and far-UV spectra (&lt;240 nm) are markedly different for each of the four asteroids observed at these wavelengths so far, including ones in the same spectral class, indicating that UV observations of asteroids could be used to better understand differences in the composition and processing of the surfaces of these small bodies.

Keywords: Ultraviolet astronomy, Hubble Space Telescope, Main belt asteroids
Mapping of Ice Storage Processes on the Moon with Time-dependent Temperatures. Lunar cold traps are defined by extremely low time-integrated sublimation loss, so that water ice is expected to accumulate in them. Due to the strong dependence of the sublimation rate on temperature, they have heretofore been delineated by the peak rather than the time-averaged sublimation rate. Here, time-averaged sublimation rates are calculated for the south polar region of the Moon based on 11 yr of Diviner surface temperature measurements. Data for each spatial pixel are binned according to subsolar (diurnal) and ecliptic (seasonal) longitude. Frequency-domain filtering of temperature time series is applied to interpolate and smooth the data set. The cold trap area is 17,000 km2 from 80°S to the south pole, about 24% larger than defined by peak temperature. In addition, subsurface ice stability is mapped based on solutions of the heat equation with Diviner surface temperatures as the upper boundary condition. Even a thin layer of dust reduces the sublimation loss dramatically. A third potential mechanism for ice storage, vapor pumping by temperature cycles, is also mapped, based on a model for the time-variable population of adsorbed water molecules on the lunar surface. The area of significant pumping is estimated to be 96,000 km2 poleward of 80°S. In summary, a new processing technique has been developed that exploits information about the time variability of lunar surface temperatures measured by Diviner, and it results in new maps for the geographic distribution of potential water-ice deposits in the south polar region of the Moon.

Keywords: Lunar surface, The Moon, Surface ices
Unprecedented Molecular Diversity Revealed in Meteoritic Insoluble Organic Matter: The Paris Meteorite's Case. The insoluble organic matter (IOM) contained in carbonaceous chondrites has witnessed a diverse suite of processes possibly starting from the evolution of the parent molecular cloud down to the protosolar nebula and finally to asteroidal processes that occurred on the chondrites' parent bodies. Laser desorption coupled with ultra-high-resolution mass spectrometry reveals that the IOM of the Paris meteorite releases a large diversity of molecules. Various molecular families ranging from hydrogenated amorphous carbon to CHNOS aromatic molecules were detected with heteroatoms (nitrogen, oxygen, and sulfur) mainly incorporated within aromatic structures. Molecules bearing nitrogen atoms present a significant variation in aromaticity. These unprecedented results allow the proposal that small molecules bearing heteroatoms could be trapped in the large macromolecular network of the IOM by hydrophobic interactions. This molecular diversity could originate from different sources, such as the soluble organic matter, the hydrothermal alteration inside the Paris's parent body, or even generated during the IOM extraction procedure. It has to be noted that some of the molecular diversity may reflect fragmentation and rearrangement of the IOM constituents during the laser desorption ionization, although care was taken to minimize such damage.

Keywords: Meteorites, Mass spectrometry, Carbonaceous chondrites, Meteorite composition