DPS 35th Meeting, 1-6 September 2003
Session 2. Io I
Oral, Chair: R. W. Carlson and R. Lopes, Tuesday, September 2, 2003, 10:30am-12:00noon, DeAnza III

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[2.03] Regional Geologic Mapping of Io using Galileo Spacecraft Data

D.A. Williams, R. Greeley (ASU), L.P. Keszthelyi (USGS), E.P. Turtle, J. Radebaugh, W.L. Jaeger, M.P. Milazzo, A.S. McEwen (U. Arizona), J.M. Moore (NASA Ames), P.M. Schenk (LPI), R.M.C. Lopes (JPL)

NASA’s Galileo spacecraft successfully completed 5 flybys of the volcanic moon Io during its recently concluded Mission to Jupiter. These flybys generated a wide range of images of various resolutions, mostly of the antijovian hemisphere which was poorly imaged during the 1979 Voyager flybys. These images provide an excellent resource for planetary geologic mapping, which we are performing for specific regions of Io. Our goals for this mapping include: 1) defining the volcanic histories of these regions; 2) identifying the styles and diversity of explosive and effusive materials; and 3) developing guidelines for future global-scale mapping.

Our approach focuses on mapping from regional (150-300 m/pixel) mosaics that cover a variety of surface features. Our basemaps are Galileo Solid-State Imaging grayscale mosaics, including versions that have been merged with lower-resolution global color data. Because active eruptions can introduce surface changes between observations, we restrict our use of the merged mosaics to color interpretations of features that appear unchanged. We also use Galileo Near-Infrared Mapping Spectrometer data where possible to note the locations of active hotspots, any changes in activity, and estimates of SO2 abundance. We have completed (July 2003) maps of the Chaac-Camaxtli region (Williams et al., 2002, 2003) and the Culann-Tohil region (Williams et al., Icarus, in revision).

We have defined five primary types of material units: plains, patera floors, flows, mountains, and diffuse deposits. The plains have various degrees of layering and texturing, resulting from a complex history of deposition and erosion. Patera floors have a wide range of colors, albedos, and textures that depend upon the composition and eruption styles of the materials that cover them. Lava flows also have a range of colors and albedos; dark flows are thought to be mafic to ultramafic lavas and bright flows are thought to be sulfur and/or sulfur dioxide (SO2) flows. Mountains resulted from uplift of crustal blocks and erosion by mass movement. Diffuse deposits (white, black, yellow, red, and green) are produced when material of various compositions ejected in explosive plume eruptions settles on the surface.

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Bulletin of the American Astronomical Society, 35 #4
© 2003. The American Astronomical Soceity.