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Arxiv: Estimate of water and hydroxyl abundance on asteroid (16) Psyche from JWST data Published: 7/16/2024 11:40:06 PM Updated: 7/16/2024 11:40:06 PM

Paper abstract: Our understanding of Solar System evolution is closely tied tointerpretations of asteroid composition, particularly the M-class asteroids.These asteroids were initially thought to be the exposed cores ofdifferentiated planetesimals, a hypothesis based on their spectral similarityto iron meteorites. However, recent astronomical observations have revealedhydration on their surface through the detection of 3-\mum absorptionfeatures associated with OH and potentially H2O. We present evidence ofhydration due mainly to OH on asteroid (16) Psyche, the largest M-classasteroid, using data from the James Webb Space Telescope (JWST) spanning 1.1 -6.63 \mum. Our observations include two detections of the full 3-\mumfeature associated with OH and H2O resembling those found in CY-, CH-, andCB-type carbonaceous chondrites, and no 6-\mum feature uniquely associatedwith H2O across two observations. We observe 3-\mum depths of between 4.3 and6% across two observations, values consistent with hydrogen abundance estimateson other airless bodies of 250 - 400 ppm. We place an upper limit of 39 ppm onthe water abundance from the standard deviation around the 6-\mum featureregion. The presence of hydrated minerals suggests a complex history forPsyche. Exogenous sources of OH-bearing minerals could come from hydratedimpactors. Endogenous OH-bearing minerals would indicate a composition moresimilar to E-or P-class asteroids. If the hydration is endogenous, it supportsthe theory that Psyche originated beyond the snow line and later migrated tothe outer main belt.