Jovian System Data Analysis Program

Cover Page/Proposal Summary

ROSS-99    NRA 99-OSS-01

Date Due: 5/5/99

We propose a multi-spectral investigation of the Galilean satellites, Io, Europa, Ganymede and Callisto, by analyzing data from the Galileo Ultraviolet Spectrometer (UVS) in combination with data from the Galileo Near Infrared Mapping Spectrometer (NIMS). By investigating and correlating the trends of the ultraviolet and infrared spectra of each satellite, we expect to increase our understanding of the environments, surface processes and histories of these bodies, and of the Jovian system as a whole. During GalileoÕs primary mission, the UVS and NIMS performed many simultaneous observations of JupiterÕs four largest satellites. These observations were performed at a variety of spatial resolutions, over varying latitudes and longitudes, and covered many different terrain types. The UVS covers the 200-323 nm wavelength range, while the NIMS observes in the 0.7-5.2 micron range. These two wavelength ranges each provide unique information about the surfaces of these bodies. In the ultraviolet, evidence is seen of SO2 (in several forms), O3, hydrogen peroxide, and other materials. The infrared wavelength range reveals information about water ice coverage, particle size and temperature, as well as non-ice materials such as SO2, CO2 and tholins. To further understand IoÕs SO2 atmosphere, and its spatial and temporal variations in coverage and density, we will use NIMS and UVS data to model IoÕs SO2 frost and gas coverage. For Europa, we will investigate the possible correlation between the NIMS-measured asymmetric water ice bands and the UVS-measured 280 nm absorption feature, and their relation with the endogenic dark terrain on EuropaÕs trailing hemisphere. On Ganymede and Callisto, we will research the potential correlations between NIMS-measured non-ice materials and water ice concentration and grain size variations with UVS-measured ozone, hydrogen peroxide, and SO2.