Widespread Occurrence of Lava Lakes on Io Observed From Juno

Abstract

We report recent observations of lava lakes within patera on Io made by the JIRAM (Jovian InfraRed Auroral Mapper) imager on board the Juno spacecraft, taken during close observations that occurred during the extended mission. At least 40 lava lakes have been identified from JIRAM observations. The majority (>50%) of paterae have elevated thermal signatures when imaged at sufficiently high spatial resolution (a few km/pixel), implying that lava lakes are ubiquitous on Io. The annular width of the spattering region around the margins, a characteristic of lava lakes, is of the order of few meters to tens of meters, while the diameter of the observed lava lakes ranges from 10 to 100 km. The thickness of the crust in the center of some lava lakes is of the order of 5–10 m; we estimate that this crust is a few years old. Also, the bulk of the thermal emission comes from the much larger crust and not from the smaller exposed lava, so the total power output cannot be calculated from the 5-μm radiance alone. Eight of the proposed lava lakes have never been reported previously as active hotspots.