Waves of lava seen in Io’s largest volcanic crater

Taking advantage of a rare orbital alignment between two of Jupiter’s moons, Io and Europa, we have obtained an exceptionally detailed map of the largest lava lake on Io, the most volcanically active body in the solar system. On March 8, 2015, Europa passed in front of Io, gradually blocking out light from the volcanic moon (see animation on the left). Because Europa’s surface is coated in water ice, it reflects very little sunlight at infrared wavelengths, allowing us to accurately isolate the heat emanating from volcanoes on Io’s surface. The infrared data showed that the surface temperature of Io’s massive molten lake steadily increased from one end to the other, suggesting that the lava had overturned in two waves that each swept from west to east at about a kilometer (3,300 feet) per day.