Detection of Molecular H<sub>2</sub>O on Nominally Anhydrous Asteroids
Anicia Arredondo, Margaret McAdam, C. I. Honniball, Tracy M. Becker, Joshua P. Emery, A. S. Rivkin, D. Takir, Cristina A. Thomas
Abstract
Abstract We used the FORCAST instrument on SOFIA to obtain mid-infrared spectra (4.9–13.7 μ m) of four S-type asteroids: (7) Iris, (11) Parthenope, (18) Melpomene, and (20) Massalia. Three of these four silicate-rich asteroids (Iris, Melpomene, and Massalia) were observed to have 3 μ m features indicative of hydration by McAdam et al. We report a detection of a 6 μ m feature that is unambiguously attributed to molecular water on two asteroids, Iris and Massalia, with peak heights of 4.532% ± 0.011% and 4.476% ± 0.012%, respectively. We estimate the abundance of molecular water based on these peak heights to be 454 ± 202 μ g g −1 and 448 ± 209 μ g g −1 , consistent with values found on the sunlit Moon by SOFIA+FORCAST.