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Massive eruptions observed on Jupiter's moon Io

Jenny Winder, News Writer
Aug 6, 2014, 14:11 UTC

Sen—Three massive volcanic eruptions have occurred on Jupiter's moon Io within just two weeks, suggesting that these presumed rare "outbursts" might be much more common than previously thought.

The observations were made using the W. M. Keck Observatory and Gemini Observatory, both near the summit of Mauna Kea, Hawaii.   

"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 2300 miles (3700 km) across and 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. Such outbursts can send material hundreds of miles above the surface.

The recent eruptions resemble past events that spewed tens of cubic miles of lava over hundreds of square miles in a short period of time. All three events, including the largest, most powerful eruption of the trio on 29 August, 2013, were likely characterized by “curtains of fire," as lava blasted out of fissures perhaps several miles long.

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The 29 August, 2013, outburst on Io was among the largest ever observed on the most volcanically active body in the solar system. Infrared image taken by Gemini North telescope. Image credit: Katherine de Kleer, UC Berkeley.

The brightest eruption at a caldera named Rarog Patera, was calculated to have produced a 50 square-mile, 30ft thick lava flow, while another close to a caldera called Heno Patera, produced flows covering 120 square miles. Both were located in Io's southern hemisphere, near its limb, and were nearly gone when imaged five days later.

Coauthor Ashley Davies, a volcanologist with NASA's Jet Propulsion Laboratory at the California Institute of Technology who has developed models to predict the volume of magma erupted based on spectroscopic observations said, "This will help us understand the processes that helped shape the surfaces of all the terrestrial planets, including Earth, and the Moon."

The team tracked the heat of the third outburst for almost two weeks after its discovery to investigate how volcanoes influence Io’s atmosphere and how these eruptions feed a doughnut of ionized gas—the Io plasma torus—that surrounds Jupiter near Io’s orbit.

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Images of Io obtained at different infrared wavelengths (in microns, μm, or millionths of a metre) with the 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.  Image credit: Imke de Pater and Katherine de Kleer, UC Berkeley.

Large eruptions, creating vast lava flows in some cases thousands of square miles in area, were thought to be rare. Only 13 were observed between 1978 and 2006.

"We are using Io as a volcanic laboratory, where we can look back into the past of the terrestrial planets to get a better understanding of how these large eruptions took place, and how fast and how long they lasted," Davies said.

The team's map of the surface of Io pinpointed more than two dozen hot spots whose distribution changed significantly between 2001 and 2010.

The team hopes that monitoring Io's surface annually will reveal the style of volcanic eruptions on the moon, constrain the composition of the magma, and accurately map the spatial distribution of the heat flow and potential variations over time.