W. M. Keck Observatory: Extreme Volcanic activity on Jupiter's moon Io

These are images of Io obtained at different infrared wavelengths (in microns, μm, or millionths of a meter) with the W. M. Keck Observatory's 10-meter Keck II telescope on Aug. 15, 2013 (a-c) and the Gemini North telescope on Aug. 29, 2013 (d). 

The bar on the right of each image indicates the intensity of the infrared emission. 

Note that emissions from the large volcanic outbursts on Aug. 15 at Rarog and Heno Paterae have substantially faded by Aug. 29. 

A second bright spot is visible to the north of the Rarog and Heno eruptions in c and to the west of the outburst in d. 

This hot spot was identified as Loki Patera, a lava lake that appeared to be particularly active at the same time. 

Credit: Imke de Pater and Katherine de Kleer, UC Berkeley.

Three massive volcanic eruptions occurred on Jupiter's moon Io within a two-week period last August, leading astronomers to speculate that these presumed rare "outbursts," which can send material hundreds of miles above the surface, might be much more common than astronomers thought.

"We typically expect one huge outburst every one or two years, and they're usually not this bright," said Imke de Pater, professor and chair of astronomy at the University of California, Berkeley, and lead author of one of two papers describing the eruptions.

"Here we had three extremely bright outbursts, which suggest that if we looked more frequently we might see many more of them on Io."

Io, the innermost of Jupiter's four large "Galilean" moons, is about 2,300 miles across, about the size of Earth's moon.

Aside from Earth, is the only known place in the solar system with volcanoes erupting extremely hot lava like that seen on Earth.

Because of Io's low gravity, large volcanic eruptions produce an umbrella of debris that rises high into space.

Images of Io were taken in the near-infrared with adaptive optics at the Gemini North telescope tracking the evolution of the eruption as it decreased in intensity over 12 days. 

Due to Io's rapid rotation, a different area of the surface is viewed on each night; the outburst is visible with diminishing brightness on Aug. 29 & 30 and Sept. 1, 3, & 10. 

Credit: Katherine de Kleer/UC Berkeley/Gemini Observatory/AURA

De Pater's long-time colleague and coauthor Ashley Davies, a volcanologist with NASA's Jet Propulsion Laboratory at the California Institute of Technology in Pasadena, Calif., said that the recent eruptions match past events that spewed tens of cubic miles of lava over hundreds of square miles in a short period of time.

"These new events are in a relatively rare class of eruptions on Io because of their size and astonishingly high thermal emission," he said.

"The amount of energy being emitted by these eruptions implies lava fountains gushing out of fissures at a very large volume per second, forming lava flows that quickly spread over the surface of Io."

All three events, including the largest, most powerful eruption of the trio on 29 Aug. 2013, were likely characterised by "curtains of fire", as lava blasted out of fissures perhaps several miles long.

The papers, one with lead author Katherine de Kleer, a UC Berkeley graduate student, and coauthored by UC Berkeley research astronomer Máté Ádámkovics, and the other coauthored by Ádámkovics and David R. Ciardi of Caltech's NASA Exoplanet Science Institute, have been accepted for publication in the journal Icarus.

More Information: Near-infrared monitoring of Io and detection of a violent outburst on 29 August 2013 - Authors: Katherine de Kleera, Imke de Patera, Ashley Gerard Daviesd, Máté Ádámkovicsa: DOI: 10.1016/j.icarus.2014.06.006