# # Program information file # PROGRAM_ID 2023B004 PROGRAM_TITLE Determining the spectral signature and longitudinal distribution of possible organic residues on the icy Galilean moons using SpeX PROGRAM_INV1 Richard Cartwright PROGRAM_INV2 Tom Nordheim PROGRAM_INV3 Chloe Beddingfield PROGRAM_INV4 Katherine de Kleer PROGRAM_INV5 Carl Schmidt PROGRAM_SCICAT major planets / satellites PROGRAM_ABSTRACT_BEG We propose to use SpeX on IRTF to measure the distribution and spectral signature of a 4.57-micron absorption feature on the icy Galilean moons Europa, Ganymede, and Callisto. The 4.57-um band was originally attributed to CN-bearing species that are possibly native to these moons. However, because of the low resolving power of NIMS [R ~200] and generally low S/N of NIMS spectra at wavelengths > 4.3 microns, the 4.57-micron band has been difficult to assess using NIMS data. The spatial distribution of this feature is not well constrained, and it is still uncertain whether it is stronger on Callisto's leading or trailing hemisphere, and it is uncertain whether this band is present at all on Europa and Ganymede. These proposed observations will provide key data for unraveling the surface chemistry of the Galilean moons and will help inform the spectroscopic objectives of the upcoming NASA Europa Clipper and ESA JUICE missions to the Jovian system. SpeX in LXD_long mode [~2.0 - 5.3 microns, 0.3'' slit] is ideal for detecting and characterizing the 4.57-micron band, with sufficient resolving power [R ~2500] to characterize the shape of this feature. Using the online SpeX Observation Calculator, we estimate that we can achieve sufficient signal-to-noise to achieve our project goals in 3000 s for Europa [Vmag ~5.3], 2800 s for Ganymede [Vmag ~5.0], and 3600 s for Callisto [Vmag ~6.0]. We will primarily guide using MORIS and will occasionally use Guidedog for guiding under twilight conditions. PROGRAM_ABSTRACT_END