Mars soil tests start

The Spirit rover has used its entire tool kit for the first time to analyse the composition of the Martian soil.

Nasa scientists said yesterday that the examination revealed as many questions as answers.

"We have now a number of hypotheses about what's going on in the Martian soil," said Steve Squyres, principal investigator from Cornell University.

The six-wheeled robot turned its attention yesterday to the large, sharply angled rock scientists have dubbed Adirondack.

One instrument told scientists the soil contained a mixture of materials that included a mineral called olivine.

Scientists were surprised to find olivine, which is usually associated with volcanic eruptions, said Squyres. Mission members now believed the soil could be a layer of finely ground lava, he said.