Thursday, October 22, 1998 Published at 09:03 GMT 10:03 UK
New hope of finding life on Mars
The Red Planet: Water may lie under polar ice caps
New research has boosted hopes of finding life on Mars.
Data from a Nasa probe has revealed that enough heat from inside the Red Planet might be trapped at the poles to melt underground water ice.
The Global Surveyor probe has also detected what may be a clathrate - a layer of water surrounding carbon dioxide molecules under the surface.
This would help retain heat and nurture life.
When the Voyager spacecraft passed Jupiter in the 1970s they discovered that Europa - only slightly smaller than our own moon - was covered in a layer of ice.
But because Europa may have a warm interior it was suggested that between the ice crust and the warm rocks may be an ocean of warm water.
Since the Galileo spacecraft arrived at Jupiter in December 1995 it has taken many photographs of Europa and all of them have tantalised astronomers with the possibility of a sub-surface ocean.
Search for life
Despite lacking a magnetic field, Europa seems to disturb Jupiter's strong field, a fact that scientists say is best explained by water beneath its icy surface.
Many scientists now regard Europa - not Mars - as the most promising place to look for life off the Earth. There are plans to send a probe to orbit the moon.
The proposal is to land on its surface and use hot water to melt a way through the ice crust and emerge into the dark ocean below - to begin a search for life.