Jupiter moon may have ocean

Fractured crust: What is driving these surface features?

Scientists say they have found evidence that Jupiter's largest moon, Ganymede, may have an ocean of water, a key ingredient of life.

The researchers said magnetic readings taken by the Galileo space probe suggested the presence of a vast body of water in liquid form beneath the moon's frozen surface.

On Earth, wherever there is water, there is usually life. The same is certainly not true in space, but this discovery will heighten expectations that one day extraterrestrial life may be found.

The University of California scientists stressed they could not be certain they had discovered water on Ganymede, which is larger than Mercury or Pluto.

Persuasive results

Margaret Kivelson of the University of California-Los Angeles said that readings taken in May this year were "highly suggestive" that a salty, liquid ocean existed there.

Ganymede: Larger than Mercury or Pluto

"It would need to be something more electrically conductive than solid ice," she said, explaining that a melted layer of water several kilometres thick about 200 km beneath the surface would fit the data if it were about as salty as Earth's oceans.

Other scientists have identified what appear to be salty minerals on the moon's crust, indicating that salt water was once found on the surface.

"They are similar to the hydrated salt minerals we see on Europa, possibly the result of brine making its way to the surface by eruptions or through cracks," said Thomas McCord, a geophysicist at the University of Hawaii, Honolulu.

The hypothesis of water on Ganymede has been bolstered by new, high-resolution images of Ganymede sent back by Galileo.

The images hint that water or slushy ice may have surfaced through the fractured crust to create smooth areas in between separated areas of crust.