![]() The image is centered at 0.3 degrees north latitude and 137.5 degrees west longitude. However, some topographic shading can be seen here due to the combination of relatively high resolution (1.3 kilometers or 0.8 miles per picture element) and the rugged topography over parts of Io. This illumination geometry is good for imaging color variations, but poor for imaging topographic shading. North is to the top of the picture and the sun illuminates the surface from almost directly behind the spacecraft. Most of the high-resolution targets for these flybys are seen on the hemisphere shown here. Galileo will make two close passes of Io beginning in October of this year. In this region bright, white material can also be seen to emanate from linear rifts and cliffs. ![]() Some volcanic centers have bright and colorful flows, perhaps due to flows of sulfur rather than silicate lava (Cutout D of false color image). However, they are now seen to exist as both diffuse deposits and sharp linear features like fissures (Cutout C of false color image). Bright red areas were seen previously only as diffuse deposits. Some of the bright (whitish), high-latitude (near the top and bottom) deposits have an ethereal quality like a transparent covering of frost (Cutout B of false color image). The improved resolution reveals small-scale color units which had not been recognized previously and which suggest that the lavas and sulfurous deposits are composed of complex mixtures (Cutout A of false color image). A false color version of the mosaic has been created to enhance the contrast of the color variations. Most of Io's surface has pastel colors, punctuated by black, brown, green, orange, and red units near the active volcanic centers. This color mosaic uses the near-infrared, green and violet filters (slightly more than the visible range) of the spacecraft's camera and approximates what the human eye would see. NASA's Galileo spacecraft acquired its highest resolution images of Jupiter's moon Io on 3 July 1999 during its closest pass to Io since orbit insertion in late 1995.
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