A New View of the Most Explosive Moon in the Solar System

Every year that Dr. Morgenthaler has monitored volcanic activity via IoIO, he has noticed some type of increase in the concentration or brightness of the gases in the plasma torus. These changes are correlated with volcanic explosions, the intensities of which can be measured by the levels of sodium emitted by the moon. But, from September to December 2022, after a large volcanic outburst, he noted that the torus contained much less sulfur dioxide than the size of the eruption would suggest. The bull was not as bright as it should have been.

This could mean that the eruption had a different chemical composition than the others, or that different types of minerals had been disturbed. It would be like Mount St. Helens, a steep-sided stratovolcano that can erupt explosively, sending dirt, rock, and sodium into the atmosphere, erupting on Earth, instead of Mauna Loa, a gently sloping shield volcano that it erupts with liquid lava flows. Or it could mean that the bull spread rapidly in response to the intense eruption.

More than anything, Dr. Morgenthaler said, it’s a call for more research.

“I’m just raising the flag and saying, ‘This has happened,’” Dr. Morgenthaler said after announcing the observation this month.

Studying the anomaly could extract, in greater detail, the different types of volcanoes on Io, as well as the interactions between the plasma torus and other massive moons around Jupiter. However, much more data will need to be collected to put all the pieces together, including from other powerful telescopes on Earth, such as the James Webb Space Telescope, as well as the Juno space probe.

At the moment, to study Io’s gases, Dr. Morgenthaler said his method, which is cheap and could be adapted by small research organizations and even some home astronomers, is often underused. But his work may open the door to similar, widespread research that could provide data to help understand the Jovian system.

Dr Davies said this kind of piecemeal research is critical to understanding Io. “You can think of it like looking at different parts of an elephant,” he said.

The fact that Dr. Morgenthaler’s most recent observation was made with widely available instruments opens the possibility of further studies, similar and different, of the same type. “The more monitoring we can get, the better it will be,” Dr. Davies said.