volcanic eruptions on Io
August 5, 2014

Astronomers Document An Explosive Two Weeks Of Volcanic Activity On Jupiter’s Moon Io

April Flowers for redOrbit.com - Your Universe Online

In August of last year, Jupiter's moon Io surprised astronomers with three massive volcanic eruptions within a two-week period. Two studies, accepted for publication in the journal Icarus, suggest that these volcanic "outbursts" might occur more commonly than previously 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. "Here we had three extremely bright outbursts, which suggest that if we looked more frequently we might see many more of them on Io."

Jupiter's four largest moons are known as the "Galilean" moons because they were discovered by Italian astronomer Galileo Galilei in 1610, according to NASA. Io is the largest of these moons, and the only other known location in our solar system with volcanoes that spew extremely hot lava. Io's low gravity, and the heat generated by the tidal push and pull of Jupiter's gravitational influence, cause the debris from these explosions to rise high into space.

Ashley Davies, volcanologist from NASA's Jet Propulsion Laboratory (JPL), said the new eruptions are comparable to past events that spewed tens of cubic miles of lava over hundreds of square miles in a short time period.

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

The team suggests that all three events were likely characterized by "curtains of fire" as the lava exploded from fissures that could have been several miles long each. The largest and strongest of the three explosions occurred on August 29, 2013.

David R. Ciardi of the NASA Exoplanet Science Institute/California Institute of Technology took infrared images for de Pater while researching at the W.M. Keck Observatory in Hawaii. “I saw this as a nice opportunity to more closely connect one end of solar system formation/evolution to another,” he said. “Understanding our solar system will help understand all the other systems we are finding and vice versa.”

The first two eruptions were discovered by de Pater on August 15, 2013. They occurred in Io's southern hemisphere and were imaged using the near-infrared camera (NIRC2) coupled to the adaptive optics system on the Keck II telescope. The eruption seen at the caldera Rarog Patera was the brighter of the two. The team calculated that this eruption produced a 50-square-mile, 30-foot-thick lava flow. At the caldera named Heno Patera, lava flows covered 120 square miles.

The largest and brightest eruption happened on August 29, 2013. This was one of the brightest eruptions that have been recorded on Io. Two different facilities caught the eruption: the Near-Infrared Imager with adaptive optics on the Gemini North telescope on Mauna Kea, and the SpeX near-infrared spectrometer on NASA's nearby Infrared Telescope Facility (IRTF). Katherine de Kleer, a UC Berkeley graduate student, used the simultaneously captured images to show that the eruption temperature is likely much higher than eruptions temperatures on Earth, "indicative of a composition of the magma that on Earth only occurred in our planet's formative years," she said.

According to de Kleer, the Gemini observations, “… represent the best day-by-day coverage of such an eruption – thanks to Gemini’s rapid and flexible scheduling capabilities.” The team was able to monitor the volcanic activity over nearly the first two weeks of eruption, thanks to the Gemini data, giving them a critical new perspective on the events.

De Kleer and her colleague, UC Berkeley research astronomer Máté Ádámkovics, conclude that "the energy emitted by the August 29 eruption was approximately 20 Terrawatts and expelled many cubic kilometers of lava. At the time we observed the event, an area of newly-exposed lava on the order of tens of square kilometers was visible” says de Kleer. “We believe that it erupted in fountains from long fissures on Io’s surface, which were over ten-thousand-times more powerful than the lava fountains during the 2010 eruption of Eyjafjallajokull, Iceland, for example.”

The researchers have a third paper, also accepted by Icarus, which examines a decade of Io observations using the Keck and Gemini facilities. They map Io's surface, noting more than two dozen hot spots whose spatial distribution changed significantly between 2001 and 2010.