DPS 2001 meeting, November 2001
Session 9. Cassini and Galileo at Jupiter Posters
Displayed, 9:00am Tuesday - 3:00pm Saturday, Highlighted, Tuesday, November 27, 2001, 5:00-7:00pm, French Market Exhibit Hall

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[9.03] Distribution of SO2 and other compounds on Io surface from regional and local NIMS observations (I24, I25, I27 and I31 orbits): links with volcanoes and eruption styles

S. Doute' (LPG, CNRS), R. Lopes (JPL, NASA), B. Schmitt (LPG, CNRS), R. Carlson, L. W. Kamp (JPL, NASA), Galileo NIMS Team

Another successful fly-by of Io by the resistant Galileo spacecraft occurred on August 6 2001 (orbit I31). This opportunity allowed the Near Infrared Mapping Spectrometer to acquire new data which enrich the important collection of local and regional IR spectral images of the satellite inherited from the previous fly-bys (I24, I25 and I27). The images target active volcanoes (e.g. Prometheus, Amirani and Tvashtar) and the surrounding regions with a spatial resolution ranging from 3 to 30 km. They map thermal emission from hot-spots and the distribution of SO2 and other compounds in the 1.0-4.7 microns spectral range at 12 wavelengths. We focus here on the spectral analysis of the data.

Spectral end-members were extracted from 3 regional observations from I24, I25 and I31 by carefully selecting small geographic areas of interest and averaging their individual spectra. These end-members, characterized by unique spectral morphologies, define 3 broad classes in which most of the spectra of the observations can be classified. The resulting image classification was compared with SSI images in the visible and related to the history and eruption style of the observed volcanoes. The first type of spectra corresponds to isolated spots of very abundant and pure SO2 on the flanks of Emakong and inside Balder Patera (near Chaac Patera). Prometheus ring and the adjacent large Bosphorus Regio also belong to this type. The second type is linked with abundant but slightly contaminated SO2 deposits occurring around the Amirani lava flow and close to Zal caldera. The third type of spectra displays shallow SO2 bands and very distinctive non-SO2 absorptions. It covers large areas, depleted in SO2 and coated with dark pyroclastics emitted by formerly or presently active explosive volcanoes of pillanian type (e.g. Tvashtar, I31A, Camaxli, Tupan, Gish Bar). This contrasts with the extended fields of quite pure SO2 generated by the quiescent and long-lived volcanic activity prevailing, for example, at Prometheus and Amirani. Spectra of cold dark lava flows and of associated pyroclastics were also extracted from local observations of Tvashtar Catena, Gish Bar and Chaac Caldera. Identification of the responsible compounds (minerals or sulfur allotropes) is ongoing.

The author(s) of this abstract have provided an email address for comments about the abstract: sylvain.doute@obs.ujf-grenoble.fr

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