IRTF Data Archive Program Information

# # Program information file # PROGRAM_ID 2021B083 PROGRAM_TITLE Non-water ice components on Jupiter's icy moons PROGRAM_INV1 Tom Nordheim PROGRAM_INV2 Thomas Greathouse PROGRAM_INV3 James Sinclair PROGRAM_INV4 Richard Cartwright PROGRAM_INV5 Kevin Hand PROGRAM_SCICAT solar system PROGRAM_ABSTRACT_BEG The Galilean satellites Europa, Ganymede, and Callisto host vast sub-surface oceans beneath their surfaces and are therefore prime targets for astrobiology. However, the exact chemical composition of these oceans isnot currently known. At least one unknown non-water ice species is present on the surfaces of Europa and Ganymede, and may represent material that has been upwelled from the interior. Several different chemicalspecies have been invoked to explain the near-infrared spectral signatures of the non-water ice material.However, this identification is inconclusive because the candidate species do not exhibit strong distinguishable spectral features in the near-infrared. These species do, however, exhibit distinctive spectral features at mid-infrared wavelengths. We propose to observe Europa and Ganymede in the mid-infrared using the TEXES [Texas Echelon Cross Echelle Spectrograph] instrument to search for known spectral features of candidate non-water ice materials. We will also use TEXES to observe Callisto, as its ancient, inactive, and less irradiated surface represents an end-member by which we can compare our Europa and Ganymede observations. Observations are requested in the September-November 2021 timeframe , when TEXES will likely be mounted on IRTF. In this time period, Jupiter [and its moons] are visible at airmasses less than 2 for approximately 6 hours. The observations will be executed when each moon is visible and not in eclipse or transit by Jupiter. TEXES will be used to measure the spectrum of Europa, Callisto and Ganymede in three settings: 8.9-9.15, 9.15-9.4 and 10 -- 10.25 um. We will record spectra using TEXES' 75 l/mm grating mode [without echelon], which results in a spectral resolving power of R ~ 4000 over a ~0.25-um spectral range. PROGRAM_ABSTRACT_END