Astronomers Monitor Volcanic Activity On Jupiter’s Moon Io From Earth

Lawrence LeBlond for redOrbit.com – Your Universe Online

Watching active volcanic eruptions should be done so from a safe distance. Observing active eruptions here on Earth can be easily accomplished from the comfort of your home with proper equipment. But observing an Earthen volcanic eruption from home is nothing when compared to what a group of California researchers have been privy to.

Using an ingenious combination of ground-based telescopic surveys and archival data, the Golden State researchers were able to gather 40 distinct snapshots of effusive volcanic eruptions and high temperature outbursts just a wee bit farther away–on Io, Jupiter’s tiny moon.

Io, the innermost moon of the Jovian giant, has proven to be an insanely active volcanic wonderland. Although the Galileo Jupiter orbiter mission (ended in 2003) has taken far more detailed images of the volcanic activity on the tiny moon, the new work by the researchers, led by Franck Marchis of the SETI Institute, means volcano studies of Io can continue. And since there is no planned mission to make it back to Jupiter until at least 2030, Marchis and colleagues will likely be tasked with following Io’s activity for years to come.

Marchis will present the results gleaned from his research over the past decade at the upcoming 2012 DPS Meeting in Reno, Nevada.

Classic ground-based telescopes, while able to view the moon itself, cannot view the volcanic goings-on on Io, which is a relatively small natural satellite about 2,300 miles in diameter (about the size of our moon) and is more than 390 million miles away.

To overcome this limitation, engineers developed spacecraft to venture out into the cosmos to visit such bodies around the Jovian system. Voyager I was the first of such spacecraft, which revealed Io’s dynamic volcanic activity for the first time in 1979, taking close-up pictures of its surface, capturing the bizarre volcanic terrains, active plumes and hot spots. Galileo became the next probe to visit the gas giant, arriving in 1995 and studying the planet and its moons for 8 years. Galileo observed more than 160 active volcanoes and a broad range of eruptions during its tenure. And the New Horizons orbiter just recently caught a glimpse of Io’s volcanic activity on its pass-by toward Pluto.

After Galileo’s commanded descent into Jupiter in 2003, several questions remained. And astronomers were left with a limited understanding of the evolution of Io’s volcanic history.

However, a new design was in the works to break the visual barrier of ground-based telescopes, drastically improving on their qualitative assessments. In the early days of the 21st century, researchers were able to correct the blurring that occurs naturally due to the constant motion of the Earth’s atmosphere with adaptive optics. This provided a much clearer resolution and, as such, all large 8-10cm telescopes have been equipped with this technology.

“Since our first observation of Io in 2001 using the W. M. Keck II 10m telescope from the top of Mauna Kea in Hawaii and its AO system, our group became very excited about the technology. We also began using AOs at the Very Large Telescope in Chile, and at the Gemini North telescope in Hawaii. The technology has improved over the years, and the image quality and usefulness of those complex instruments has made them part of the essential instrument suite for large telescopes”, Marchis said in a press release.

Since 2003, Marchis and colleagues have 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.

Over the past decade, Marchis and his colleagues observed numerous eruptions, including the awakening of the volcano Tvashtar, with which New Horizons simultaneously observed on its flyby. Marchis reported that the Tvashtar eruption was detectable from April 2006 to September 2007. Older observations from Galileo and the Keck observatory show that this volcano last had a spectacular eruptions in November 1999 that lasted nearly 15 months. Galileo also observed similar eruptions from Pillan from 1996 to 1999, with sporadic eruptions witnessed by Marchis and colleagues in August 2007.

“The episodicity of these volcanoes points to a regular recharge of magma storage chambers” said Ashley Davies a volcanologist at the Jet Propulsion Laboratory, CALTECH, 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”.

Marchis’ team and other groups are continuing to monitor Io’s volcanic activity, and have noticed since about September 2010, Io has entered a quiescent phase, although a dozen or so permanent, low-temperature eruptions, are still constantly detectable across the surface.

“Spacecraft have only been able to capture fleeting glimpses of Io’s volcanoes, Voyager for a few months, Galileo a few years, and New Horizons a few days. Ground-based observations, on the other hand, can continue to monitor Io’s volcanoes over long time-scales. The more telescopes looking at Io, the better time coverage we can obtain.” Said Julie Rathbun from Redlands University, a planetary scientist not directly involved in this study. “AO observations from 8-10m class telescopes are a dramatic improvement in spatial resolution over previous ground-based observations. Soon they will not only be our only way to monitor Io’s volcanoes, but the best way. We should be making these observations more often.”

The next generation of AO systems will provide a better image quality and open the visible wavelength range to planetary astronomers. These systems are now in development and should be ready for primetime in the near future. These systems should allow for observations of color 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,” Marchis concluded in the release.

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