LYCOS RETRIEVER 
Io: Usgs Voyager
built 659 days ago
Voyager 2 took this picture of Io on the evening of July 9, 1979, from a range of 1.2 million kilometers (745,700 miles). On the limb of Io are two blue volcanic eruption plumes about 100 kilometers (62 miles) high. These two plumes were first seen by Voyager 1 in March 1979 and are designated Plume 5 (upper) and Plume 6 (lower). They apparently had been erupting for a period of at least four months and probably longer. A total of six plumes were seen by Voyager 2, all of which were first seen by Voyager 1. Plume 1, the largest volcano viewed by Voyager 1, was no longer erupting when Voyager 2 arrived.
Source:
Since the first volcanic plume was discovered by Voyager in 1979, Io has remained under intense scrutiny. Astronomers using ground-based telescopes can monitor large volcanic eruptions from Earth by recording outbursts of infrared emission. Such measurements combined with Voyager and Galileo data show that some volcanoes on Io have been active for at least 20 years.
Source:
This color image of Io was created by combining the color channels of the low resolution USGS Voyager controlled color mosaic with Tayfun Oner's high resolution Galileo mosaic. The brown, orange areas are probably covered by sulphur or a mixture containing sulphur. The light areas may be sulphur dioxide snow and the pock-marks are mostly volcanic calderas up to 200 kilometers (124 miles) across. Mountainous regions exist near both poles, with some features rising 8 kilometers (5 miles) or more above their surroundings. (Courtesy A.Tayfun Oner)
Source:
The Voyager probes obtained images of about 35% of Io at a resolution of 5 km. In some areas resolution was as good as 0.5 km. These images allowed geologic maps of Io to be constructed. Geologists could recognize mountains, plains, and volcanic vents, and the relative ages of these features. Nine eruption plumes were discovered during the Voyager 1 mission. Voyager 2 arrived four months later. Voyager 1 image taken on the morning of March 5, 1979 at a range of 377,000 kilometers (226,200 miles).
Source:
One theory proposed after the NASA Voyager spacecraft flybys in the late 1970s is that dust particles emitted from Io's volcanoes could become electrically charged and then swept away by Jupiter's rotating magnetic field. Recent modifications to this theory suggest that the dust is subsequently accelerated in the magnetosphere and flung outward from Jupiter at high
Source:
MORE ABOUT
Usgs Voyager