Discovery of Volcanoes on Io

Date: March 8, 1979 • Location: Rome, Italy

Images taken by Voyager 1 proved the existence of volcanoes on Io (pictured), a moon of Jupiter.

Voyager 1 is a space probe launched by NASA on September 5, 1977, as part of the Voyager program, to study the outer Solar System and the interstellar space beyond the Sun's heliosphere. It was launched 16 days after its twin, Voyager 2. It communicates through the NASA Deep Space Network (DSN) to receive routine commands and to transmit data to Earth. Real-time distance and velocity data are provided by NASA and JPL. At a distance of 172.52 AU as of October 2026, it is the most distant human-made object from Earth. Voyager 1 is projected to reach a distance of one light day from Earth on November 18, 2026.