Io - Voyager 1

Jupiter's satellite, Io, from 377,000 km

Io
Image of Jupiter's innermost Galilean satellite, Io, taken by Voyager 1. Io is about 3,600 km in diameter. The smallest features visible in this image are about 10 km (6 miles) across. Most of the colorful areas are probably recent volcanic deposits. Many of the dark round features may be volcanoes or volcanic vents (Voyager 1, P-21227c) 

Io;
Galilean Satellites;
Volcanism in the Solar System;
Voyager Missions