New Mars Rocks

Thirteen months and still going. The Mars rover Spirit is still making new discoveries months after it was supposed to dead.

(Image: NASA/JPL/Cornell)

The Mars rover Spirit has found the most interesting and significant exposure of bedrock so far in its 13 months of Red Planet exploration. The outcrop - dubbed Peace - is in the Columbia Hills which rise above the ancient lakebed of Gusev Crater.

The exciting feature of Peace for scientists is that it contains higher levels of sulphur than anything yet examined by Spirit. Other rocks encountered to date had sulphur minerals forming a surface crust, but little in the interior.

In contrast, Peace contains high levels of sulphur deep inside, says Ralf Gellert of the Max Planck Institute in Mainz, Germany. Because it is highly correlated with magnesium in the rock, it suggests the presence of magnesium sulphate, he says.

"This is probably the most interesting and important rock Spirit has examined," says chief rover scientists, Steven Squyres at Cornell University, New York, US. "It gives us even more compelling evidence for water playing a major role in altering the rocks here."

More evidence of water on Mars in the past.

The science team concluded that the rock seems to consist of sand-sized grains of typical Martian volcanic rock - olivine, pyroxene and magnetite - cemented together in a matrix of magnesium-sulphate salt.

That suggests two possible formation mechanisms, says Squyres, with both mechanisms involving the action of water.

The first is that liquid water, laden with dissolved magnesium sulphate, percolated through the rock and then evaporated away leaving the salt behind. The second is that the rock was weathered over a long period by dilute sulphuric acid in the air, reacting with magnesium-rich minerals already in the rock. The team hopes to pin down which way the layered bedrock formed by studying more areas in the coming weeks.

The Spirit's partner, Opportunity....

...has also shattered all previous Mars travel records, covering 157 metres (514 feet) in one day - 30 January 2005. This speed is far faster that the average rate of about 6.4 metres (21.1 feet) per day that it achieved during its first year of operation.

Tax dollars well spent.