Galileo at Io: Results from high-resolution imaging

During late 1999/early 2000, the solid state imaging experiment on the Gali leo spacecraft returned more than 100 high-resolution (5 to 500 meters per pixel) images of volcanically active lo. We observed an active Lava lake, a n active curtain of lava, active Lava flows, calderas, mountains, plateaus, and plains. Several of the sulfur dioxide-rich plumes are erupting from di stal flows, rather than from the source of silicate Lava (caldera or fissur e, often with red pyroclastic deposits). Most of the active flows in equato rial regions are being emplaced slowly beneath insulated crust, but rapidly emplaced channelized flows are also found at all latitudes. There is no ev idence for high-viscosity Lava, but some bright flows may consist of sulfur rather than mafic silicates. The mountains, plateaus, and calderas are str ongly influenced by tectonics and gravitational collapse. Sapping channels and scarps suggest that many portions of the upper similar to 1 kilometer a re rich in volatiles.