From NASA's Planetary Photojournal
NASA's Galileo spacecraft acquired its highest resolution [1.3 kilometers (0.8 miles) per picture element] images of Jupiter's moon Io on 3 July 1999 during its closest pass to Io. North is to the top of the picture and the sun illuminates the surface from almost directly behind the spacecraft. This illumination geometry is good for imaging color variations, but poor for imaging topographic shading 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. Most of Io's surface has pastel colors, punctuated by black, brown, green, orange, and red units near the active volcanic centers. Comparison of this image to previous Galileo images reveals many changes due to the ongoing volcanic activity.
The improved resolution reveals small-scale color units which had not been recognized previously. The lavas and sulfurous deposits are probably composed of complex mixtures. Some of the bright (whitish), high-latitude (near the top and bottom) deposits have an ethereal quality like a transparent covering of frost. Bright red areas were seen previously only as diffuse deposits. However, they exist as both diffuse deposits and sharp linear features like fissures. Some volcanic centers have bright and colorful flows, perhaps due to flows of sulfur rather than silicate lava. In this region bright, white material can also be seen to emanate from linear rifts and cliffs.
Image Title: Global image of Io (true color)
Catalog #: PIA02308
Target Name: Io, a satellite of Jupiter
Mission: Galileo
Spacecraft: Galileo Orbiter Instrument: Solid State Imaging
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Last Modified On: Monday, December 18, 2000