Io acts as an electrical generator as it moves through Jupiter's magnetic field, developing 400,000 volts across its diameter and generating an electric current of 3 million amperes that flows along the magnetic field to the planet's ionosphere . Views of Io See also Galileo Images of Io . The brown, orange areas are probably covered by sulphur or a mixture containing sulphur. Almost all the features visible here have volcanic origins, including several calderas and eruption plumes that were active at the time of the Voyager 1 encounter. Io's volcanic plains are shown in this Voyager 1 image mosaic which covers the area roughly from latitude 60 degrees N. to latitude 60 degrees S. and longitude 100-345.
North is up.
Numerous volcanic calderas, lava flows, and volcanic eruption plumes are visible here. The bright whitish patches probably consist of freshly deposited sulfur dioxide frost. This image of Jupiter and its satellite Io were taken on March 5, 1994. Io is too small for ground-based telescopes to see the surface details. Several of the volcanoes periodically are active because Io is heated by tides raised by Jupiter's powerful gravity.