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J. Radebaugh, A. S. McEwen (University of Arizona)
During the early Galileo mission (1996-1998), the SSI visible to near-IR camera obtained global eclipse images of Jupiter’s moon Io, in which hotspot emissions from active volcanoes appeared as sub-pixel source smear ellipsoids [1,2]. We reprojected these images onto high-resolution global Voyager and Galileo basemaps of Io to determine the locations of all hotspots with respect to surface features. We used known volcanic centers as tiepoints; e.g., Pele's hotspot position is known because thermal emission was detected in illuminated images.
Correlating global Galileo eclipse images with underlying geography has enabled us to more precisely determine the locations of the hottest areas within flow fields (e.g., Gish Bar, Loki, Amirani, Isum). Many active hotspots (e.g., Zal, Marduk) are accompanied by diffuse red deposits related to ephemeral short-chain sulfur, typical of volcanically active regions on Io [1].
Some hotspots maintained consistently bright emissions from observation to observation, separated by months (e.g., Pele, Janus, Kanehekili), also seen later by groundbased [3,4]. Others were active during some observations and relatively inactive (no SSI signal) during others (e.g., Gish Bar, Pillan, Camaxtli). This indicates some volcanic centers have long-lived, steady eruptions, perhaps typical of insulated lava flows or lava lakes, while others erupt in bursts of energy and then fade [2,5,6].
A cluster of hotspots near the sub-Jovian point is likely related to concentration of tidal heating. Most of these hotspots are confined to small paterae (volcano-tectonic depressions); this corroborates the work of [7,8] that 79% of all hotspot eruptions occur within paterae.
The authors acknowledge support of NASA’s Planetary Geology and Geophysics program.
References: [1] McEwen e.a. Icarus 1998; [2] Keszthelyi e.a. JGR 2001; [3] dePater e.a. Icarus 2004; [4] Marchis e.a. Icarus 2005; [5] Davies e.a. JGR 2001; [6] Lopes e.a. Icarus 2004; [7] Radebaugh e.a. LPSC 2004; [8] Lopes e.a. LPSC 2004.
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Bulletin of the American Astronomical Society, 37 #3
© 2004. The American Astronomical Soceity.