Io - Mirror to Young Earth

Jupiter's moon, Io, holds mirror to young Earth

Washington: New images of monster volcanoes and lava lakes on Jupiter's moon, Io, could help scientists look back in time to Earth's younger, more volcanic days, according to astronomers.

There are uncanny similarities between the new pictures of Io sent by NASA's Galileo space probe, and photographs of the active Kilauea volcano on the island of Hawaii. Of course, the volcanic features on Io are as much as 100 times bigger.

Io, which is about the same size as Earth's moon, is the most volcanic body in the solar system. "This might be a glimpse at Earth's past," Alfred McEwen of the University of Arizona said, at a briefing at NASA headquarters on Friday (19Nov99). He was referring to a picture of the Ionian volcano Pele - for the Hawaiian Goddess of volcanoes.

The last time Earth had volcanoes as big as Io's, was about 15 million years ago, long before humans were able to record anything about them. The last time volcanoes were as hot as Io's - some 1500 Celcius - was 2 billion years ago. Galileo's pictures of Io give humans a chance to see what Earth might have been like in those early days.

The Galileo images focussed on Pele and two other active volcanoes, named Loki and Prometheus.

Like Kilauea, Pele has a red-hot centre of lava when viewed from overhead. But unlike its earthly cousin, Pele's hot spot is remarkably stable, and does not erupt in spurts and spread in large lava flows. A thin red line about 10km long on Pele actually glows in the dark, and led McEwen and other scientists to believe that there is a huge roiling lava lake on Pele covered by a thin cooling crust. The thin red line could be the exposed hot lava at the "shore" of the lava lake.

Pele also has a reddish ring around it that would stretch across continental US. Io's Loki, which exudes more heat than all of the Earth's active volcanoes combined, has a massive bowl-like crater called a caldera which according to the latest pictures, keeps refilling with lava.

The images of Prometheus gave the astronomers a puzzle to solve: How did a lava plume move 100km in 20 years? The last time the NASA scientists took a close look at it, in 1979, using the Voyager probe, the lava was in a different place.

The Galileo images were made in October at the end of the space probe's productive life, and more pictures are expected following another pass by Io next week.

Click here for the Galileo pictures.

-Reuters