Last August, Jupiter’s moon Io experienced three massive volcanic eruptions within just two weeks. Once thought to be rare outbursts, astronomers now think they’re far more common on Io and could help us understand early Earth processes.
Io is the innermost of Jupiter’s four Galilean moons. Like Earth, this satellite has volcanoes that erupt hot lava, and with its low gravity, large volcanic eruptions can produce debris rising hundreds of kilometers into space. In fact, Io is more volcanically active than any other other moon or planet in our solar system.
“We typically expect one huge outburst every one or two years, and they’re usually not this bright,” says Imke de Pater from the University of California, Berkeley, in an university release. “Here we had three extremely bright outbursts, which suggest that if we looked more frequently we might see many more of them on Io.”
De Pater and colleagues discovered the first two eruptions on August 15, 2013 using the near-infrared camera coupled to the Keck II telescope in Hawaii. The brighter of the two occurred at a caldera named Rarog Patera, and it produced a 130-square-kilometer, 9-meter thick lava flow. The other happened near a caldera named Heno Patera and produced flows covering 310 square kilometers. Both were located in Io’s southern hemisphere and didn’t appear in images taken five days later.
The third and brightest eruption -- one of Io’s brightest ever -- occurred on August 29, 2013 and was observed using the Gemini North telescope on Mauna Kea as well as NASA’s Infrared Telescope Facility (IRTF) nearby. The thermal source had an area up to 83 square kilometers at the time of the eruption, and according to models, the event was dominated by lava fountains gushing out of fissures, forming flows that quickly spread over the moon’s surface. The team tracked the heat of this outburst for two weeks.
These images show the eruptions taken from different infrared wavelengths with Keck II on August 15 (a-c) and Gemini North on August 29 (d). Loki Patera is a lava lake that was active at around the same time.
The high eruption temperature of that third outburst indicates a composition of magma that, on Earth, only occurred in our planet’s formative years. Io resembles an early Earth, when heat from the decay of radioactive elements created high-temperature lava. Io remains volcanically active for a different reason: Jupiter and its moons Europa and Ganymede are constantly tugging on it. But these new eruptions are similar to those that shaped the surfaces of inner solar system planets like Earth and Venus when they were young.
"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," says Ashley Davies of NASA’s Jet Propulsion Laboratory in a news release.
Images: NSF/NASA/JPL-Caltech/UC Berkeley/Gemini Observatory/Katherine de Kleer (top), NSF/NASA/JPL-Caltech//UC Berkeley/Gemini Observatory/W. M. Keck Observatory/Imke de Pater and Katherine de Kleer (middle)