# # Program information file # PROGRAM_ID 2021A002 PROGRAM_TITLE Investigating the origin and evolution of ammonia on the Saturnian moons Enceladus and Iapetus PROGRAM_INV1 Richard Cartwright PROGRAM_INV2 Tom Nordheim PROGRAM_INV3 PROGRAM_INV4 PROGRAM_INV5 PROGRAM_SCICAT solar system PROGRAM_ABSTRACT_BEG We propose to use SpeX on selected nights to observe the Saturnian moons Enceladus and Iapetus to characterize absorption bands centered near 2.21 and 2.97 microns, which have been previously attributed to ammonia-bearing species. We collected SpeX spectra of these two moons in 2020A, confirming the presence of these two features. However, the origin and evolution of the possible NH3-bearing constituents contributing to these bands remains uncertain. Therefore, to further investigate the nitrogen systems operating on these moons, we require new SpeX observations to constrain the longitudinal distribution and spectral signatures of these bands, as well as other possible N-bearing features we detected in 2020A. The SXD mode of SpeX [R ~750, 0.8'' slit] is ideal for characterizing the 2.21-micron band, which is ~0.013 microns wide, requiring R ~500 to place at least 3 points along this band. The LXD_short mode of SpeX [R ~937, 0.8' slit] is ideal for characterizing the 2.97-micron band, which is ~0.02 microns wide, requiring R ~450 to place at least 3 points along this band. Using the SpeX observation calculator, and accounting for overheads, we estimate that 29 to 48 min of total time are required to achieve our signal-to-noise goals for our SXD observations. Additionally, we estimate that 115 to 192 min of total time are required to achieve our signal-to-noise goals for our LXD_short observations. We will guide with MORIS [0.7 micron dichroic]. PROGRAM_ABSTRACT_END