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Interpretations of Potential Hydration Features on Psyche’s Surface from JWST Observations

Presentation #107.08 in the session Asteroids: Future Mission Targets (Oral Presentation)

Published onOct 23, 2023
Interpretations of Potential Hydration Features on Psyche’s Surface from JWST Observations

We used the James Webb Space Telescope (JWST) to observe Psyche, the prototypical M-type asteroid and target of the soon-to-launch NASA Discovery mission ‘Psyche’. The observations were designed to assess the presence of hydration on Psyche’s surface and to distinguish between any indications of hydration resulting from either hydroxyl or water molecules. Our program obtained high SNR (~200), high spectral resolution (~0.003 µm), near to mid-IR spectra (0.97 – 6.73 µm) of Psyche to detect the entire 3-µm and 6-µm absorption and emission bands attributed to hydroxyl and/or water. JWST’s unique capability to measure the entire 3 and 6-µm bands enables us to constrain Psyche’s surface composition and impact history, providing critical context for the upcoming ‘Psyche’ mission and interpretations of hydration features observed on asteroids. We observed Psyche with a total of two visits using the NIRSpec Integral Field Unit and MIRI Medium Resolution Spectroscopy instruments. The NIRSpec observations were separated by ~1/2 of Psyche’s rotation period, and the MIRI observations were separated by 5 days with a ~70% offset in rotation period. Psyche was nearly pole-on during these observations, and therefore the two visits associated with each instrument are not anticipated to reveal significantly different portions of the asteroid’s surface. However, we were able to resolve Psyche across ~10 pixels in diameter, enabling identification of compositional variability across a single hemisphere within each observation. We will present on the current state of our ongoing analysis of potential 3 and 6-µm features observed along with their variation across Psyche’s surface, and speculate on the implications for Psyche’s composition, origin and evolution, and the broader context of these findings as they relate to M-type asteroids and the evolution of the solar system.

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