Eruptions on Io. Galileo spacecraft image of two volcanic eruptions on Io, a moon of Jupiter. A 120 kilometre-high (km) plume from the Pillan Patera volcano appears as a grey patch at Io's lower left edge. The second, from the Prometheus volcano, is visible as a plume (grey) & its shadow (black) at centre. Prometheus may have been erupting cont- inuously for at least 18 years, whilst this is the first Pillan Patera eruption ever seen. Io's vol- canoes are powered by the strong internal tidal forces created because the moon orbits so close to Jupiter. Image taken by Galileo's solid state ima- ging camera at a range of 600,000km on 28 June 1997. The smallest visible objects are 2km across.