DIX Planetary Science Seminar
The snowline in protoplanetary disks is often invoked as a location for rapid dust accumulation and ensuing planetesimal formation. While dust is recognized as the primary source of disk opacity, the question of how its accumulation drives snowline evolution remains largely unaddressed. Here, we simulate the disk temperature response to evolving radial distributions of rocky and icy dust, as well as water vapor. Across typical ranges of disk parameters, the snowline naturally evolves into an extended region few AU wide, held at its defined temperature, within thousands of years. This region, termed the ``snowband," facilitates rapid planetesimal formation and pebble accretion owing to the enhanced ``stickiness" and size of near-sublimation pebbles. We incorporate the snowband into a revised model for the origin of non-carbonaceous (NC) and carbonaceous (CC) Solar System planetesimals, showing that it accommodates the diverse oxidation states of NC bodies, and the segregation of NC and CC materials via an early formed Jupiter. Applying the snowband framework to extrasolar systems, we show that it naturally explains the correlation between stellar metallicity and giant planet occurrence. In particular, giant planets form more readily around high-metallicity stars as greater dust abundance translates to wider snowbands wherein pebble accretion is favored.
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JWST NIRSpec observations of Europa's leading hemisphere have revealed a strong spatial correlation between CO₂ abundance and geologically disrupted terrain, and resolved the ν₃ absorption feature into a distinct doublet at 4.25 and 4.27 μm. Since Europa's surface is airless and thermally unstable for solid CO₂, these observations imply an active source and a mechanism for trapping CO₂, neither of which is currently known. Radiolysis of carbonate salts has been proposed as a potential pathway, though it has not previously been demonstrated experimentally. We present the first laboratory investigation of carbonate radiolysis under simulated Europan conditions. Using diffuse reflectance FTIR spectroscopy, we monitor the spectral behavior of carbonates subjected to 10 keV electron irradiation at cryogenic temperatures in vacuum. We complement these measurements with temperature-programmed desorption studies to probe the thermal stability and release behavior of the generated CO₂. Our results provide the first experimental evidence that radiolysis of carbonate salts can both generate and retain CO₂ at conditions relevant to icy Jovian satellites. We also report preliminary results for mixed salt systems which may be more representative of the Europan surface and discuss potential implications for Europa. Our findings support the hypothesis that carbonate-bearing materials may act as endogenous CO₂ reservoirs on irradiated icy bodies in the outer solar system.