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Monitoring Io’s Insane Volcanic Activity from the Comfort of Earth


Watching active volcanic eruptions should definitely be done from a distance, but a group of California researchers has figured out how to do it from the comfort of home. Using an ingenious combination of Earth-based telescopic surveys and archival data, they have gathered nearly 40 distinct snapshots of effusive volcanic eruptions and high temperature outbursts on Jupiter’s tiny moon, Io, showing details as small as 100 km (60 miles) on the moon’s surface.

Since 2003, using their own observing programs and archival data, the team led by Franck Marchis, a researcher at the Carl Sagan Center of the SETI Institute, has gathered approximately 40 epochs of observations of Io in the near-infrared. These images show details as small as 100 km (60 miles) on the surface of the satellite.

Their observations have revealed young and energetic eruptions called outbursts. These are easily detectable from their immense thermal emission at shorter wavelengths, implying a high eruption temperature. The team observed the awakening of the volcano Tvashtar simultaneously with the New Horizons spacecraft, which flew past Jupiter on its way to Pluto. From a combined survey based on three large telescopes, they report that the eruption was detectable from April 2006 to September 2007. Older observations from the Galileo spacecraft and the W.M. Keck observatory show that this volcano previously displayed a similar fire fountain eruptive style which started in November 1999 and lasted for 15 months. Similarly, Pillan, an energetic eruption detected with the Galileo spacecraft from 1996 to 1999, had sporadic activity again in August 2007 which was reported by the team using the W.M. Keck telescope.

“The episodicity of these volcanoes points to a regular recharge of magma storage chambers” said Ashley Davies a volcanologist at the Jet Propulsion Laboratory, California Institute of Technology, and a member of the study. “This will allow us to model the eruption process and understand the how heat is removed from Io’s deep interior by this particular style of volcanic activity”.

Four additional young eruptions were detected during this survey including an extremely active volcano located at a region which had never showed activity in the past (planetocentric coordinates 17S, 5W) in May 2004. This new and sporadic outburst had a total output of 10% the average Io thermal output, so it was more energetic than Tvashtar in 2001, implying a fire fountain style eruption. Interestingly, the team did not observe any “mega-outburst” during this survey, with an energetic output similar to the eruption on Surt in 2001, the most energetic eruption ever witnessed in the solar system. They conclude that those outbursts should be extremely rare or very sporadic, lasting for a few days.

TMT and Adaptive Optics

The next generation of AO systems will provide a better image quality and open the visible wavelength range to planetary astronomers. These systems are currently under development and will have their first light in the coming years. Colorful surface changes due to volcanic activity, such as plume deposits or lava flow fields, will be detectable from the ground.

“The next giant leap in the field of planetary astronomy is the arrival of Giant Segmented Mirror Telescopes, such as the Thirty Meter Telescope expected to be available in 2021. It will provide a spatial resolution of 35 km in the near-infrared, equivalent to the spatial resolution of global observations taken by the Galileo spacecraft. When pointed at Io, these telescopes will offer the equivalent of a spacecraft flyby of the satellite”, said Marchis. Marchis presented results from ground-based telescopic monitoring of volcanic activity on Io over the past decade at the 2012 DPS Meeting in Reno, Nevada.

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