Posted on Jul 30, 2016
In February 2001 an eruption from the Surt volcano on the Jupiter-facing hemisphere of Io, the volcanic epi-center of our solar system, occurred with an estimated output of 78,000 Gigawatts. By comparison, the 1992 eruption of Mt Etna, Sicily, was estimated at 12 Gigawatts. During its peak, observed by the WM Keck II Telescope on Hawaii, its output almost matched the eruptive power of all of Io’s active volcanoes combined.
“It is clear that this eruption is the most energetic ever seen, both on Io and on Earth,” Franck Marchis and Imke de Pater, professor of astronomy and of earth and planetary science at UC Berkeley. “The Surt eruption appears to cover an area of 1,900 square kilometers, which is larger than the city of Los Angeles and even larger than the entire city of London. The total amount of energy being released by the eruption is amazingly high, with the thermal output from this one eruption almost matching the total amount of energy emitted by all of the rest of Io, other volcanoes included.”
“This eruption is truly massive,” said Ashley Davies, PhD, a scientist at NASA’s Jet Propulsion Laboratory who aided in modeling the eruption. “The observed energy indicates the presence of a vigorous, high-temperature volcanic eruption. The kind of eruption to produce this thermal signature has incandescent fire fountains of molten lava which are kilometers high, propelled at great speed out of the ground by expanding gases, accompanied by extensive lava flows on the surface.”
Io’s volcanism has been monitored for the last eight years by the Galileo spacecraft and now, with the advent of adaptive optics systems, by Earth-bound astronomers such as those at the Keck 11 Observatory on Maui, Hawaii and the Gemini North Observatory.
Thanks to an orbital resonance with two of its neighboring moons, Europa and Ganymede, Io is continuously squeezed. The resulting friction heats Io’s interior enough to create a mushy magma ocean only 50 kilometers (30 miles) beneath its surface. It is likely that this partially molten asthenosphere provides the source for basaltic silicate lava that erupts at hundreds of volcanoes across Io’s surface (though future missions to Io will be needed to confirm the existence of this magma ocean). Recent ground-based observations shed new light on the most powerful of Io’s volcanic eruptions.
This volcanic activity has been monitored over the last 35 years by ground-based observatories, the Hubble Space Telescope, and several spacecraft that have visited Jupiter over the years. Unfortunately, the most recent spacecraft to visit the Jupiter system was New Horizons seven years ago and the next spacecraft to visit the system, the European Space Agency’s Jupiter Icy Moon Explorer (JUICE), will not arrive until 2030. In the meantime, ground-based observations can make a significant contribution toward filling the gap, regularly monitoring Io’s volcanic activity.
Many of Io’s volcanoes are persistent, meaning they maintain relatively consistent levels and styles of activity for years or even decades. Examples include Pele, a lava lake whose thin crust is regularly broken up by churning from below, and Prometheus, a lava flow field that heats up the sulfur dioxide frost below it to produce an umbrella-shaped plume of gas and dust 100 kilometers (62 miles) tall.
Many of Io’s lava lakes and lava flow fields (some reaching 300 kilometers or 186 miles in length) are persistent, but can show significant fluctuations in activity. However, some volcanoes are much less regular in their volcanic activity, remaining quiescent for years before experiencing “outburst” eruptions. These outbursts can begin suddenly, starting at fissures in Io’s crust, and generate fire fountains that can jet lava up to a kilometer (0.62 miles) into space before falling back to the ground to produce extensive lava flows. Over the course of hours and days, outburst eruptions quiet down as the fire fountaining subsides and lava flows through insulated channels along the surface.
Recent observations by astronomers Imke de Pater, Katherine de Kleer, and Ashley Davies at the Infrared Telescope Facility (IRTF), Gemini-North and Keck II Observatories atop Mauna Kea in Hawaii revealed an astonishing three outburst eruptions over the course of two weeks in August 2013 at Rarog Patera, Heno Patera, and an unnamed volcano 350 kilometers (217 miles) west of Isum Patera (201308C).
All three eruptions are among the 10 most powerful eruptions ever observed on Io (the most powerful was the eruption at Surt, which was three times more powerful than the 201308C eruption, which is the second or third most).
The Daily Galaxy via planetary.org and berkeley.edu