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Mapping Io's Surface Composition With Juno/JIRAM
Author(s) -
Tosi F.,
Mura A.,
Lopes R. M. C.,
Filacchione G.,
Ciarniello M.,
Zambon F.,
Adriani A.,
Bolton S. J.,
Brooks S. M.,
Noschese R.,
Sordini R.,
Turrini D.,
Altieri F.,
Cicchetti A.,
Grassi D.,
Hansen C. J.,
Migliorini A.,
Moriconi M. L.,
Piccioni G.,
Plainaki C.,
Sindoni G.
Publication year - 2020
Publication title -
journal of geophysical research: planets
Language(s) - English
Resource type - Journals
eISSN - 2169-9100
pISSN - 2169-9097
DOI - 10.1029/2020je006522
Subject(s) - frost (temperature) , jovian , latitude , infrared , geology , range (aeronautics) , absorption (acoustics) , absorption band , chemical composition , composition (language) , physics , remote sensing , astrophysics , materials science , geodesy , optics , meteorology , linguistics , philosophy , planet , saturn , composite material , thermodynamics
The surface composition of Io is dominated by SO 2 frost, plus other chemical species identified or proposed over the past decades by combining Earth‐based and space‐based observations with laboratory data. Here we discuss spectroscopic data sets of Io obtained by the Jovian InfraRed Auroral Mapper (JIRAM) spectro‐imager onboard Juno in nine orbits, spanning a 3‐year period. We display average spectral profiles of Io in the 2–5 μm range, and we use band depths derived from those profiles to map the geographic distribution of SO 2 frost and other spectral features. This data set allows for an ~22% surface coverage at 58 to 162 km/px and in a broad range of latitudes. Our results confirm the broadly regional SO 2 ‐frost trends already highlighted by Galileo/NIMS. Io's average spectral profiles as well as the mapping of the 4.47‐μm band also confirm that SO 2 exists in the 32 S 16 O 18 O isotopic form. Surprisingly, the mapping performed by JIRAM shows that the absorption band at 2.1 μm is unrelated to SO 2 frost, while we map for the first time the depth of the 2.65‐μm band, highlighting regions enriched in this absorber, possibly H 2 S. JIRAM data confirm that the 3.92‐μm band, likely due to Cl 2 SO 2 , is largely related to the SO 2 distribution. The correlation between Cl 2 SO 2 and ClSO 2 , possibly revealed at 4.62 μm, is not equally clear. The simultaneous presence of two very weak spectral features at 4.55 and 4.62 μm suggests that nitrile compounds or tholins may also be present on the surface.