Io's volcanic plains are shown in this Voyager 1 image mosaic. Also visible are numerous volcanic calderas and lava flows. Ra Patera with its multihued lava flows is below and right of the mosaic's center. This scene is about 1300 miles (2100 km) long. The composition of Io's volcanic plains and lava flows has not been determined, but they could consist dominantly of sulfur or of silicates (such as basalt) coated with sulfur condensates. The bright whitish patches probably consist of freshly deposited SO2 frost.