flows, volcanoes, and volcanic craters (Figure 11.6). However,
pictures from Voyager 1 (and later from Galileo) did not
show a single impact crater, making Io unique among all the
solid planetary bodies seen so far in planetary exploration.
With a surface so young, Io must currently be volcanically
active, with lava flows and volcanic ash burying impact
craters as quickly as they form. Postencounter images from
Voyager looking back toward this moon showed explosive
volcanic eruptions sending debris hundreds of kilometers
above Io’s surface.