While hunting for volcanic plumes on Io, the Hubble telescope captured these images of the volatile moon sweeping across the giant face of Jupiter. Only a few weeks before these dramatic pictures were taken, the orbiting telescope snapped a portrait of one of Io's volcanoes spewing sulfur dioxide "snow."
These stunning images of the planetary duo are being released to commemorate the ninth anniversary of the Hubble telescope's launch on April 24, 1990. The three overlapping snapshots show in crisp detail Io passing above Jupiter's turbulent clouds. The close-up picture of Io [bottom right] reveal a 120-mile-high (200-kilometer) plume of sulfur dioxide "snow" emanating from Pillan, one of the moon's active volcanoes.