IO ~ Moon of Jupiter

IO Taken by Galileo Spacecraft - Courtesy of NASA

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Io Global Image Mosaic and Geologic Map

Image mosaics were produced by USGS.  Geologic map was authored by Dr. David Williams (Arizona State University) and was published by the USGS as scientific investigations map (SIM) 3168. The geologic map was published in 2012. The global mosaic base was created in 2006 from spacecraft images (Voyager, 1979 and Galileo, 1996-2001) Credit: U.S. Geological Survey

Geologic Map of Io

By David A. Williams, Laszlo P. Keszthelyi, David A. Crown, Jessica A. Yff, Windy L. Jaeger, Paul M. Schenk, Paul E. Geissler, and Tammy L. Becker


Io, discovered by Galileo Galilei on January 7–13, 1610, is the innermost of the four Galilean satellites of the planet Jupiter (Galilei, 1610). It is the most volcanically active object in the Solar System, as recognized by observations from six National Aeronautics and Space Administration (NASA) spacecraft: Voyager 1 (March 1979), Voyager 2 (July 1979), Hubble Space Telescope (1990–present), Galileo (1996–2001), Cassini (December 2000), and New Horizons (February 2007). The lack of impact craters on Io in any spacecraft images at any resolution attests to the high resurfacing rate (1 cm/yr) and the dominant role of active volcanism in shaping its surface. High-temperature hot spots detected by the Galileo Solid-State Imager (SSI), Near-Infrared Mapping Spectrometer (NIMS), and Photopolarimeter-Radiometer (PPR) usually correlate with darkest materials on the surface, suggesting active volcanism. The Voyager flybys obtained complete coverage of Io's subjovian hemisphere at 500 m/pixel to 2 km/pixel, and most of the rest of the satellite at 5–20 km/pixel. Repeated Galileo flybys obtained complementary coverage of Io's antijovian hemisphere at 5 m/pixel to 1.4 km/pixel. Thus, the Voyager and Galileo data sets were merged to enable the characterization of the whole surface of the satellite at a consistent resolution. The United States Geological Survey (USGS) produced a set of four global mosaics of Io in visible wavelengths at a spatial resolution of 1 km/pixel, released in February 2006, which we have used as base maps for this new global geologic map. Much has been learned about Io's volcanism, tectonics, degradation, and interior since the Voyager flybys, primarily during and following the Galileo Mission at Jupiter (December 1995–September 2003), and the results have been summarized in books published after the end of the Galileo Mission. Our mapping incorporates this new understanding to assist in map unit definition and to provide a global synthesis of Io's geology.

Credits: Williams, D.A., Keszthelyi, L.P., Crown, D.A., Yff, J.A., Jaeger, W.L., Schenk, P.M., Geissler, P.E., and Becker, T.L., 2011, Geologic map of Io: U.S. Geological Survey Scientific Investigations Map 3168, scale 1:15,000,000, 25 p., available at U.S. Geological Survey


This global color mosaic of Io contains Voyager and Galileo data. I combined five individual mosaics to produce this detailed global (2048x4096) map. About 40% of this image (mainly in the projovian hemisphere) comes from Laika's cylindrical color map . The color balance was modified slightly to make it look more "realistic" based on Galileo's colors. Intensities were also adjusted slightly over broad regions so it would blend better with the other images.
For the second image a near-hemispheric Galileo mosaic was used for about 40% of the map. This was reprojected from a vertical perspective projection (spacecraft view - similar to orthographic) onto the cylindrical lat/lon grid. For the third image a portion of this Galileo mosaic was reprojected to cover about 10% of the map. The color balance was adjusted and saturation was subdued to undo the "enhanced" color in the posted Galileo image. The fourth image comes from a portion of this Galileo mosaic, reprojected to cover the remaining 10% of the map. This fourth color image was augmented by higher resolution intensity information from a black and white USGS map.

Seams were blended gradually between the various images to reduce their prominence. Some further color adjustments are being made to compensate for the extended wavelength range of the Galileo filters.
~ Steve Albers NOAA

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IO ~ Moon of Jupiter