# # Program information file # PROGRAM_ID 2024B053 PROGRAM_TITLE Confirming an Unidentified 4-micrometer Absorption on Hygiea [and Ceres?] PROGRAM_INV1 Andrew Rivkin PROGRAM_INV2 Richard Cartwright PROGRAM_INV3 Cristina Thomas PROGRAM_INV4 PROGRAM_INV5 PROGRAM_SCICAT main-belt / Trojan asteroids PROGRAM_ABSTRACT_BEG Publicly-available JWST NIRSpec spectra of Hygiea show evidence of a ~0.8-um wide, ~2-3% deep absorption from 3.8--4.6 um. Because of a chip gap in NIRSpec at high spectral resolution and saturation at low spectral resolution, there is no coverage and no prospect of coverage from 4.0--4.2 um from JWST. We wish to 1] confirm the presence of this feature on Hygiea; 2] Close the coverage gap as much as possible [recognizing the CO2 atmospheric feature will be the limiting factor]; 3] Determine if Ceres also has this feature. There is no obvious compositional identification for this feature yet, but confirming and better characterizing it will help us understand the largest low-albedo asteroids/dwarf planets. Ceres and Hygiea are bright targets, but we need SNR > 100 for these measurements. We will use LXD long in order to cover the long-wavelength end of the possible band. The absorption is broad enough that it will bracket the atmospheric CO2 band. PROGRAM_ABSTRACT_END