Io, the most volcanically active body of the Solar system
Animation of Europa sweeping across Loki Patera and obscuring different portions of its floor. The lower panels show the infrared intensity of the lava lake as a function of time as it is covered (ingress) and uncovered (egress) by Europa. The red curve is the best-fit map to the observations. (Katherine de Kleer video).
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 innermost moon of Jupiter and the most volcanically active body in the solar system (see de Kleer et al., Nature 545, 2017). Io, which is slightly larger than Earth’s own moon, is considered the most geologically active body in the entire solar system. At least 300 volcanic structures dot its surface. The largest of these features is a volcanic pit named after Loki, the Norse trickster god. The depression is filled with a sulfur-encrusted lake measuring around 125 miles (200 kilometers) across. The Voyager 1 spacecraft first discovered Io’s volcanism back on March 5, 1979, when it barnstormed the Jovian moon and snapped dramatic imagesof a giant, nearly 200-mile-tall plume (300 kilometers) rising into space, later revealed to be emanating from Loki. On March 8, 2015, Europa passed in front of Io, gradually blocking out light from the volcanic moon. 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. Two years earlier, we have been able to capture detailed images of the heat rising from the volcano using the twin 8.4-meter mirrors of the Large Binocular telescope observatory in Arizona (see Conrad et al., AJ 149, 2015).