PIA00351: Ganymede at 2.6 million miles
 Target Name:  Ganymede
 Is a satellite of:  Jupiter
 Mission:  Voyager
 Spacecraft:  Voyager 1
 Instrument:  VG ISS - Narrow Angle
 Product Size:  300 x 300 pixels (w x h)
 Produced By:  JPL
 Producer ID:  P21180
 Addition Date:  1996-07-17
 Primary Data Set:  Voyager EDRs
 Full-Res TIFF:  PIA00351.tif (33.81 kB)
 Full-Res JPEG:  PIA00351.jpg (4.17 kB)

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Original Caption Released with Image:

This photo of Ganymede, largest of Jupiter's Galilean satellites and the third from the planet, was taken shortly after midnight March 1, from a distance of 2.6 million miles (4.2 million kilometers). Ganymede is slightly larger than the planet Mercury, but is much less dense; it has = roughly twice the density of water. Ganymede's surface brightness is = four times that of Earth's Moon. This photo shows dark features = reminiscent of the dark, mare regions on the Moon. On Ganymede, however, = these features have twice the brightness of lunar mare. Scientists = believe they are unlikely to be composed of rock or lava as the Moon's = mare regions are. Ganymede's north polar region appears to be covered = with brighter material, and scientists say it could be water frost. = Later photos of Ganymede will be taken from closer range and will = therefore have higher resolution if those photos of the polar region show = underlying terrain blanketed by frost, it could indicate movement of water= across Ganymede's surface, possibly in a very thin atmosphere. Brighter = spots are also scattered across this hemisphere of Ganymede. They may be = related to impact craters, or may represent source regions of fresh ice. = JPL manages and controls the Voyager project for NASA's Office of Space = Science.

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