Three massive volcanic eruptions light up Jupiter’s moon Io

Images from August 15 at three different wavelengths, and one image from August 29 showing the third eruption.

Imke de Pater and Katherine de Kleer, UC Berkeley

Jupiter’s moon Io is the most volcanically active body in our solar system, so it’s not a shock that astronomers captured several eruptions while their telescopes were trained on the satellite. However, the three eruptions were uncommonly massive (among the 10 largest seen there) and occurred within the span of a couple of weeks—eruptions of this class are only thought to occur every other year, on average. Researchers may be able to glean enough from these images to help us get to the bottom of a couple of Ionian mysteries.

Io’s prodigious volcanic output is the result of tidal heating—gravitational squeezing as a result of its slightly oblong orbit around Jupiter, along with some tugs by fellow Jovian moons. Though Io is roughly the same size as Earth’s own Moon, the flow of heat from its core toward its surface is roughly 30 times greater than that of Earth. As a result, there’s usually at least one active volcano whenever astronomers observe Io. In fact, a huge lava lake some 200 kilometers across, called Loki Patera, is usually visible to infrared telescopes. On thirteen occasions between 1978 and 2006, unusually large eruptions called outbursts were observed. Three more have now been added to that number.

Jupiter’s magnetic field holds a curious torus (or ring donut if you’re hungry) of plasma believed to originate from Io’s volcanism. A new Japanese space telescope, launched in September, had been scheduled to spend some time studying that plasma torus, and so several ground-based telescopes had begun monitoring Io’s volcanic activity in August. On August 15, a telescope at the Keck Observatory in Hawaii recorded two bright infrared spots in the far south of Io, which hasn’t been known for this kind of activity.