Io Volcanism Seen by New Horizons: A Major Eruption of the Tvashtar Volcano

Jupiter's moon lo is known to host active volcanoes. In February and March 2007, the New Horizons spacecraft obtained a global snapshot of lo's volcanism. A 350-kilometer-high volcanic plume was seen to emanate from the Tvashtar volcano (62°N, 122°W), and its motion was observed. The plume's morphology and dynamics support nonballistic models of large lo plumes and also suggest that most visible plume particles condensed within the plume rather than being ejected from the source. In images taken in Jupiter eclipse, nonthermal visible-wavelength emission was seen from individual volcanoes near lo's sub-Jupiter and anti-Jupiter points. Near-infrared emission from the brightest volcanoes indicates minimum magma temperatures in the 1150- to 1335-kelvin range, consistent with basaltic composition.