Magma ocean found inside Jupiter moon

An ocean of magma sloshes beneath the crust of Jupiter's moon Io, and that is why active volcanoes erupt all over its surface, a new study suggests.

The ocean is located 30 to 50 kilometres below Io's surface and its temperature is likely higher than 1,200 C, reported the study led by University of California at Los Angeles planetary physicist Krishan Khurana and published online Thursday in Science Express.

According to NASA, volcanoes on Io produce 100 times more lava each year than all the volcanoes on Earth. Io, the fourth largest of Jupiter's 50 named moons, is the only object in the solar system besides Earth with any active volcanoes.

Khurana and his team reached their conclusion by reanalyzing data from NASA's Galileo spacecraft, which flew by Io in 1999 and 2000.

The data collected by Galileo contained unusual signatures produced by the interaction between Jupiter's magnetic field and Io's magnetic field.

But at that time, scientific understanding of magnetic field interactions was "not yet sophisticated enough for us to understand what was going on in Io's interior," Xianzhe Jia, a University of Michigan space scientist and co-author of the study, said in a statement.

In the past 20 years, mineral physicists have shown that a certain type of volcanic material called "ultramafic" rocks can carry substantial electric current when they are melted.

Khurana and his team reanalyzed Galileo's magnetometer data and found that the signatures were consistent with a magma layer of ultramafic material at least 50 kilometres thick that was at least 20 per cent liquid melt by volume.

While Io has volcanoes all over its surface, Earth's volcanoes are restricted to specific hotspots.

"Scientists are excited we finally understand where Io's magma is coming from," Khurana said in a statement.

According to NASA, scientists believe Earth and its moon may have had similar magma oceans when they first formed billions of years ago, but those oceans have since cooled.