Prometheus (volcano)

Prometheus is an active volcano on Jupiter's moon Io. It is located on Io's hemisphere facing away from Jupiter at 1°31′S 153°56′W / 1.52°S 153.94°W / -1.52; -153.94.^[2]

Prometheus consists of a 28-kilometer-wide (17 mi) volcanic pit named Prometheus Patera and a 100-kilometer-long (62 mi) compound lava flow, all surrounded by reddish sulfur and circular, bright sulfur dioxide (SO
₂) volcanic plume deposits.^[3] The volcano was first observed in images acquired by the Voyager 1 spacecraft in March 1979.^[4] 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 6,700-square-kilometer (2,600 sq mi) flow field was emplaced.^[5] Later Galileo observations of this flow field revealed numerous small breakouts, particularly on the western end of the flow field.^[6]

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 75-to-100-kilometer-tall (47 to 62 mi), SO
₂-rich dust plume erupting from the active flow front at the other end.^[3] 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 SO
₂-rich plume is generated as lava at the western end of the flow field covers sulfur dioxide frost, heating and vaporizing it.^[7] This is accomplished at multiple breakouts, generating gas and dust for the visible dust plume.^[8] Prometheus' plume has been observed by both Voyager spacecraft, Galileo, and New Horizons, at every appropriate imaging opportunity.

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