Sazuna/UAT_keywords huggingface dataset:
Exo-Daisy World: Revisiting Gaia Theory through an Informational Architecture Perspective. The Daisy World model has long served as a foundational framework for understanding the self-regulation of planetary biospheres, providing insights into the feedback mechanisms that may govern inhabited exoplanets. In this study, we extend the classic Daisy World model through the lens of semantic information theory (SIT), aiming to characterize the information flow between the biosphere and planetary environment—what we term the information architecture of Daisy World systems. Our objective is to develop novel methodologies for analyzing the evolution of coupled planetary systems, including biospheres and geospheres, with implications for astrobiological observations and the identification of agnostic biosignatures. To operationalize SIT in this context, we introduce a version of the Daisy World model tailored to reflect potential conditions on M dwarf exoplanets, formulating a system of stochastic differential equations that describe the coevolution of the daisies and their planetary environment. Analysis of this exo-Daisy World model reveals how correlations between the biosphere and environment intensify with rising stellar luminosity and how these correlations correspond to distinct phases of information exchange between the coupled systems. This rein control provides a quantitative description of the informational feedback between the biosphere and its host planet. Finally, we discuss the broader implications of our approach for developing detailed ExoGaia models of inhabited exoplanetary systems, proposing new avenues for interpreting astrobiological data and exploring biosignature candidates.

Keywords: M dwarf stars, Solar-planetary interactions, Exoplanet surface variability, Exoplanet evolution, Exoplanet surface characteristics, Planetary science, Star-planet interactions, Astronomical simulations
Lucy Mission Search Plans for Activity around Its Jovian Trojan Flyby Targets. Activity in small bodies, defined here as the episodic or continuous release of material, was long thought to be exclusively a behavior of comets, but it has since been discovered in some centaurs, main-belt asteroids, and near-Earth asteroids. To date, however, no activity has been discovered on Jovian trojan asteroids, the target of NASA's Lucy Discovery Program mission. Although Lucy was originally conceived without studies of or searches for trojan activity, it was realized in 2016–2017 that the spacecraft and scientific payload aboard Lucy could provide unique and meaningful constraints or detections on activity in these trojans. Here we describe how the Lucy mission will search for such activity using (i) its terminal tracking navigation camera to search for wide-field coma scattered light, (ii) its Lucy Long Range Reconnaissance Imager narrow-angle camera to also search for scattered light from any coma or jets, and (iii) its Multispectral Visible Imaging Camera imager to search for CN emission (a common activity tracer species in comets). Sensitivity estimates for each of those measurements are discussed below.

Keywords: Small Solar System bodies, Neutral coma gases, Jupiter trojans, Coma dust
Europa's Sodium and Potassium Exosphere during Juno's Flyby. Jupiter's icy moon Europa is enveloped in gaseous sodium and potassium that resonantly scatter sunlight as optical emission lines. The High Resolution Echelle Spectrograph on the Keck I telescope has spatially mapped these alkalis contemporaneously with Juno's PJ45 flyby. Beyond 3 Europa radii, where emission becomes separable from bright surface reflectance, their extended radial profiles indicate atmospheric escape. This suggests that alkalis are ejected from the ice by a high-energy process—likely ion sputtering—into an exosphere where initial energies are not appreciably dampened through collisions with the cold O2 atmosphere and icy surface. The neutral sodium cloud exhibits remarkable symmetry east–west and north–south, a sign that incident plasma has access to the majority of Europa's surface, and the effects of centrifugal latitude may be negligible at the time of observations. However, sodium is more extended east–west, suggesting an oval-shaped cloud. The Na column density is a few × 1010 atoms cm‑2, and the Na/K ratio is 28 ± 8 at 10 Europa radii, consistent with prior estimates. However, this ratio decreases with distance despite sodium's lower mass and lifetime against ionization. Doppler broadening in the resolved Na line profiles grows with tangent altitude from a few thousand kelvins to &gt;15,000 K by 25 Europa radii. Considering the more than twofold increase in Io's Na loss at this time, brightness levels in good agreement with past data reinforce an interpretation that Europa is a net source of alkali atoms that ultimately derive from its subsurface brines or saline ocean.

Keywords: Jupiter, Europa, Atomic spectroscopy, Collisional broadening, Spectroscopy, Io, Galilean satellites, Jovian satellites
Asteroids Fail to Retain Cometary Impact Signatures. A bombardment of comets is thought to have occurred in the inner solar system as a result of a dynamical instability among the giant planets after gas disk dispersal. Vesta, the second largest asteroid in the main asteroid belt, likely differentiated before gas disk dispersal, implying its crust witnessed the cometary bombardment. The composition of howardite, eucrite, and diogenite (HED) meteorites, which represent fragments of Vesta's crust, could therefore have been altered by cometary impacts. Here we combine noble gas mass spectrometry measurements, N-body simulations, collision rate calculations, and impact simulations to estimate the cometary contribution to Vesta. While our dynamical simulations indicate that Vesta likely underwent a significant number of collisions with large comets, we find no xenon cometary signature in HED meteorites. This apparent contradiction arises due to the fact that cometary impacts were at high speeds and Vesta's weak gravitational attraction made it incapable of retaining cometary material. Smaller asteroids are even less likely to retain such material. Therefore, if a cometary xenon signature is ever detected in an asteroid belt object, it must have been acquired during formation, within the same source region as comet 67P/Churyumov-Gerasimenko, and have been implanted later into the asteroid belt.

Keywords: Isotopic abundances, Asteroids, Small Solar System bodies, Comet dynamics, Solar system, Solar system evolution
A JWST Study of CO<SUB>2</SUB> on the Satellites of Saturn. Solid state CO2 has been detected throughout the outer solar system, even at temperatures where crystalline CO2 is unstable, requiring that the CO2 be trapped in a separate host material. The Saturnian satellites provide an ideal laboratory for the study of this trapped CO2, allowing us to examine objects with identical insolation, but with a range of environments, ice exposure, organic abundance, and formation locations. Here, we present JWST spectra of eight mid-sized satellites of Saturn, including Mimas, Enceladus, Tethys, Dione, and Rhea interior to Titan, and Hyperion, Iapetus, and Phoebe exterior. The ∼4.26 μm CO2ν3 band is detected on each satellite, and the ∼2.7 μm ν1 + ν3 band is detected on all but Phoebe and the leading hemisphere of Iapetus. Based on the wavelength shifts of these bands, we find four separate types of trapped CO2 on the satellites. On the inner satellites, CO2 appears trapped in amorphous ice sourced from Saturn's E ring, and a second component of CO2 is associated with the dark material most prominent on the trailing hemispheres of Dione and Rhea. On the outer satellites, CO2 appears to be produced by irradiation of organics on Phoebe, which are then transported to the dark leading hemisphere of Iapetus and onto the dark regions of Hyperion. CO2 is also trapped by water ice on the trailing hemisphere of Iapetus and on Hyperion. These observations point to the continued need for laboratory studies to better understand the sources and trapping mechanisms of CO2 throughout the outer solar system.

Keywords: Saturnian satellites, Carbon dioxide
Detection of New Auroral Emissions at Io and Implications for Its Interaction with the Plasma Torus. We observed Io's optical aurora in eclipse on six nights between 2022 and 2024 using Keck I/HIRES. Spectra revealed 13 new auroral emissions not identified previously, tripling the total number of optical emissions lines detected at Io. These included the O I lines at 777.4 and 844.6 nm, the Na I lines at 818.3 and 819.5 nm, the [S I] lines at 458.9 and 772.5 nm, the S I triplet at 922.3 nm, the [O II] lines at 732.0 and 733.0 nm, and the [S II] lines at 406.9, 407.6, 671.6, and 673.1 nm. We leveraged these new detections by comparing with imaging data from the 2001 Cassini flyby to better understand the distribution of atmospheric species and their contribution to the observed auroral brightnesses. Our auroral emission model showed that the observed 557.7, 777.4, and 844.6 nm oxygen emission-line brightnesses could be explained by excitation by electron impact of canonical 5 eV torus electrons on an atmosphere composed of O, SO2, and an isoelectronic proxy for SO. The SO2 emission did not decrease immediately after eclipse ingress, suggesting that the emitting column may be restricted to higher altitudes. The derived O/SO2 mixing ratio was typically about 10%, but it also exhibited order-of-magnitude variance during some observations. Io's 630.0 nm [O I] brightness did not strongly vary with plasma sheet distance, suggesting that electron flux at Io varies substantially beyond model predictions.

Keywords: Optical astronomy, Natural satellite atmospheres, Io, Aurorae
Plume Activity on Europa: Current Knowledge and Search Strategy for Europa Clipper. The presence of cryovolcanic activity in the form of geyser-like plumes at Jupiter's moon Europa is a much-debated topic. As an active plume could allow direct sampling by a passing spacecraft of a potentially habitable interior environment, the detection and analysis of ongoing plume activity would be of the highest scientific value. In the past decade, several studies have interpreted different remote and in situ observations as providing evidence for large gaseous plumes at different locations on Europa. However, definitive proof is elusive, and visible imaging data taken during spacecraft flybys do not reveal clear indications of ongoing activity. After arrival at Jupiter in 2030, the NASA Europa Clipper spacecraft will systematically search for and constrain plume activity at Europa utilizing a variety of investigations and methods during, before, and after close flybys. Given the lack of a confirmed plume detection to date, the Europa Clipper science team has adopted a global plume search strategy, not focusing on any specific geographical area or any specific type of observation. This global search strategy assigns enhanced value to data obtained early in the mission, which allows time for further observations and characterization of any observed plume at later times. Here we describe the current state of knowledge on plume activity, the Europa Clipper search strategy, and the role of various instruments on the Europa Clipper payload in this search.

Keywords: Natural satellite surfaces, Natural satellites (Solar system), Geological processes, Natural satellite atmospheres, Volcanism
A Multifrequency Global View of Callisto's Thermal Properties from ALMA. We present thermal observations of Callisto's leading and trailing hemispheres obtained using the Atacama Large Millimeter/submillimeter Array (ALMA) at 0.87 mm (343 GHz), 1.3 mm (233 GHz), and 3 mm (97 GHz). The angular resolution achieved for these observations ranged from  0.″09to0.″24 , corresponding to ∼420─1100 km at Callisto. Global surface properties were derived from the observations using a thermophysical model constrained by spacecraft data. We find that Callisto's millimeter emissivities are high, with representative values of 0.85─0.97, compared to 0.75─0.85 for Europa and Ganymede at these wavelengths. It is clear that models parameterized by a single thermal inertia are not sufficient to model Callisto's thermal emission, and clearly deviate from the temperature distributions in the data in systematic ways. Rather, more complex models that adopt either two thermal inertia components or that treat electrical skin depth as a free parameter fit the data more accurately than single thermal inertia models. Residuals from the global best-fit models reveal thermal anomalies; in particular, brightness temperatures that are locally 3─5 K colder than surrounding terrain are associated with impact craters. We identify the Valhalla impact basin and a suite of large craters, including Lofn, as key cold anomalies (∼3─5 K) and geologic features of interest in these data. These data provide context for Callisto JWST results as well as the other ALMA Galilean moon observations, and may be useful ground-based context for upcoming Galilean satellite missions (JUICE and Europa Clipper).

Keywords: Planetary surfaces, Callisto, Surface processes, Galilean satellites, Radio interferometry, Jovian satellites
Modeling Ice and Dust in Comet C/2017 K2 (Pan-STARRS)'s Coma. C/2017 K2 (Pan-STARRS) is a long-period comet that has been active since 24 au inbound and likely as far out as 35 au, far beyond where the sublimation of water ice can power cometary activity. Near-infrared spectroscopic observations were obtained with SpeX on the NASA Infrared Telescope Facility at a heliocentric distance of RH = 6.50 au, which show clear signs of water ice in K2's coma. Subsequently, more near-infrared spectra of K2 were collected with the Near-Infrared High-Throughput Spectrograph instrument on the Lowell Discovery Telescope and FLAMINGOS-2 on the Gemini South Telescope in order to further characterize the initially detected water ice. The SpeX data show strong water ice absorption features with an overall red slope while the later observations show decreasing ice fractions. We ran several different spectral models utilizing a Markov chain Monte Carlo approach to characterize the dust and ice in the coma, resulting in a range of ice fractions from 5% to 12% in the SpeX data depending on the mixing method, ice crystallinity, and assumed scattering regime(s). Modeling the SpeX data showed two classes of solutions, one with redder dust and more ice and one with less red dust and less ice, with significant differences in the derived properties of interest like the typical size of the ice grains. We utilize the later dust-dominated observations to recontextualize our observations of K2's icier coma further out and to facilitate a discussion of how its coma evolved as a function of heliocentric distance. We also discuss best practices in modeling reflected light from cometary comae.

Keywords: Ice spectroscopy, Long period comets, Markov chain Monte Carlo, Comets, Coma dust
A Large Outburst, Coma Asymmetries, and the Color of Comet 243P/NEAT. Water ice is a fundamental building material of comets and other bodies in the outer solar system. Yet the properties of cometary water ice are challenging to study, due to its volatility and the typical distances at which comets are observed. Cometary outbursts, impulsive mass-loss events that can liberate large amounts of material, offer opportunities to directly observe and characterize cometary water ice. We present a study of comet 243P/NEAT, instigated by a ‑3 mag outburst that occurred in 2018 December. Optical images and a 251-day light curve were examined to characterize the outburst and the comet's quiescent activity. Variations in the quiescent light curve appear to be dominated by coma asymmetries, rather than changing activity levels as the comet approached and receded from the Sun. Furthermore, the light curve shows evidence for one to two additional small outbursts (–0.3 mag) occurring in 2018 September. The large 2018 December outburst likely ejected water-ice grains, yet no signatures of ice were found in color photometry, a color map, or a near-infrared spectrum. We discuss possible dynamical and thermal reasons for this nondetection. In this context, we examined the comae of comets 103P/Hartley 2 and C/2013 US10 (Catalina), and we show that a one-to-one mapping between continuum color and the presence of water ice cannot be supported. We also discuss possible causes for the large outburst, and we find that there is an apparent grouping in the kinetic energy per mass estimates for the outbursts of five comets.

Keywords: Multi-color photometry, Infrared spectroscopy, Comet dynamics, Comet dust tails, Coma dust
The NASA Exoplanet Archive and Exoplanet Follow-up Observing Program: Data, Tools, and Usage. The NASA Exoplanet Archive (NEA) and the Exoplanet Follow-up Observing Program service are two widely used resources for the exoplanet community. The NEA provides a complete and accurate accounting of exoplanetary systems published by NASA missions and by the community in the refereed literature. In anticipation of continued exponential growth in the number of exoplanetary systems and the increasing complexity in our characterization of these systems, the NEA has restructured its primary tables and interfaces, as well as extending and standardizing their modes of access. The Exoplanet Follow-up Observing Program service provides the exoplanet community with a venue for coordinating and sharing follow-up and precursor data for exoplanets, their host stars, and stars that might eventually be targets for future planet searches and recently reached 1 million files uploaded by the community. In this paper, we describe the updates to our data holdings, functionality, accessibility, and tools, as well as future priorities for these two services.

Keywords: Exoplanet detection methods, Exoplanet catalogs, Exoplanet atmospheres, Exoplanets
Leveraging Ceres to Gain Insights into the Candidate Ocean Worlds of Umbriel and Oberon That Orbit Uranus. Ceres, located in the asteroid belt, exhibits intriguing parallels with two of the large Uranian satellites: Umbriel and Oberon. These similarities include size, bulk compositions, and dominantly radiogenic internal heat sources. We identify morphologically similar features on Ceres, Umbriel, and Oberon and introduce new formation hypotheses, to consider alongside those that already exist, for the following two morphological features: (1) Brines from an impact-induced melt reservoir, potentially replenished by a subsurface ocean, may have formed the bright deposit in Wunda crater, on Umbriel, which we present as a new hypothesis alongside the previously proposed cold-trapped CO2 ice deposit and cryovolcanism hypotheses. (2) A slurry of brine and solids, also potentially sourced from a subsurface ocean, may have formed the unnamed mountain on Oberon as a cryovolcanic dome, which we present as an additional possibility alongside the previously proposed impact crater central peak, tectonic feature, and remnant equatorial ridge hypotheses. We identify the data that could be collected by a future mission to test these hypotheses, in particular panchromatic images of at least 1 km pixel‑1 and spatially resolved spectra in the infrared of at least 8 km pixel‑1. Future observations such as these would contribute to the overall understanding of the evolution of these candidate ocean worlds and their potential habitability.

Keywords: Geological processes, Planetary geology
Contrast Reversal and Emergent Features on Pluto. Features that change in appearance between different NASA New Horizons images of Pluto are analyzed. Contrast reversal features (CRs) appear to transition from darker to brighter than their surroundings, more likely due to changes of imaging geometry, specifically increasing solar phase angle, than temporal change. Contrast emergent features (CEs) are not apparent in low- and intermediate-solar-phase-angle images but brighter than their surroundings in high-solar-phase-angle image(s), also more likely due to the increase of solar phase angle than temporal change. Hypotheses for Pluto's CRs and CEs include plumes, clouds, wind streaks, snow, frost, precipitated haze, lags, pits, glints, slopes, and particle size, compaction, and geometric effects. The CRs and CEs could be on and/or above Pluto's surface and/or within its shallow subsurface. These hypotheses are investigated via mapping, color, morphology, photometry, and comparison with Triton's fans. Pluto's CRs and CEs are likely different manifestations of the same or similar phenomena. They are likely not diffuse deposits of Pluto's dark red equatorial material(s) on or above or within volatile-ice-rich regions, sunglints, or geometric effects from spatially resolved slopes. They are consistent with less backward-scattering and more forward-scattering surfaces and shallow subsurfaces than their surroundings, as well as optically thin, preferentially forward scattering between the surface and global haze, including atmospheric (e.g., cloud) and surface-coating (e.g., condensation deposit) features. Surface and/or shallow subsurface features, possibly atmospheric derived, are favored over atmospheric features.

Keywords: Albedo, Photometry, Pluto
Exploring Organic-mineral Evolution in Planetary Analogs: Insights from Hydrothermal Alteration of Aromatic Molecules and Mafic Minerals. Organic-mineral interactions are crucial drivers of diversity in abiotic systems on planetary surfaces. Despite their significance, the evolution of these systems, particularly the role of organic molecules in newly formed minerals, remains underexplored. In this study, we proposed new experiments on analogs to explore the interactions between organic molecules likely present in planetary environments and primary minerals. We examine interactions between aromatic benzyl-group compounds and igneous minerals (olivine, feldspar) under mid-temperature aqueous conditions, analogous to hydrothermal systems hypothesized to exist on early Martian and terrestrial environments. Using multiscale techniques—gas chromatography, infrared spectroscopy, mass spectrometry, X-ray diffraction, microscopy, and adsorption studies—we analyzed the analogs after 45 days at 100°C. The results reveal that the presence of minerals influences the distribution of newly formed organic compounds, for example, by promoting the formation of organic chelates. Minerals altered in the presence of organics formed secondary phases, such as phyllosilicates and amorphous materials resembling serpentines or smectites. Organic compounds impacted dissolution rates, secondary mineral parageneses, and porosity, enriching the diversity of hydrated mineral phases compared to mineral alteration without organic matter. Significant carbon and nitrogen were found filling mineral porosity (up to 7 wt% C), modifying physical properties compared to systems without organics. These findings highlight the pivotal role of organics in shaping mineralogy on planetary surfaces and underscore the need for broader studies of organic-mineral analogs to improve interpretations of in situ and remote organic detections in extraterrestrial samples.

Keywords: Cosmochemistry, Planetary mineralogy, Complex organic molecules, Astrochemistry
Placing the Near-Earth Object Impact Probability in Context. Near-Earth objects (NEOs) have the potential to cause extensive damage and loss of life on Earth. Advancements in NEO discovery, trajectory prediction, and deflection technology indicate that an impact could be prevented, with sufficient warning time. We derive an impact frequency of NEOs 140 m and larger, using the NEOMOD2 NEO population model and JPL Horizons. We then place that frequency in context with other preventable causes of death, allowing for comparison between a planet-wide event and individual events that cause fatalities such as car crashes and carbon monoxide poisoning. We find that the chance of a &gt;140 m asteroid hitting the Earth is more likely than the chance of an individual being struck by lightning.

Keywords: Near-Earth objects, Asteroids, Asteroid dynamics