Prometheus is an active volcano on Jupiter's moon Io. It is located on Io's hemisphere facing away from Jupiter at .[1]
Prometheus consists of a 28km (17miles) volcanic pit named Prometheus Patera and a 100km (100miles) compound lava flow, all surrounded by reddish sulfur and circular, bright sulfur dioxide volcanic plume deposits.[2] The volcano was first observed in images acquired by the Voyager 1 spacecraft in March 1979.[3] Later that year, the International Astronomical Union named this feature after a Greek fire god, Prometheus.
Prometheus is the site of a volcanic eruption that has been ongoing since at least the Voyager 1 encounter in 1979. Between the Voyager encounters and the first observations by Galileo, a 6700km2 flow field was emplaced.[4] Later Galileo observations of this flow field revealed numerous small breakouts, particularly on the western end of the flow field.[5]
Prometheus is the site of two volcanic eruption plumes: a small, sulfur-rich plume erupting from the magma-source vent at the eastern end of the flow field and a 75to, -rich dust plume erupting from the active flow front at the other end.[2] The former forms a diffuse, red deposit to the east of the Prometheus flow field. The latter forms a bright, circular deposit surrounding the entire volcano and lava flow. The -rich plume is generated as lava at the western end of the flow field covers sulfur dioxide frost, heating and vaporizing it.[6] This is accomplished at multiple breakouts, generating gas and dust for the visible dust plume.[7] Prometheus' plume has been observed by both Voyager spacecraft, Galileo, and New Horizons, at every appropriate imaging opportunity.