Just days after revealing clear evidence that liquid water was once present at one rover鈥檚 landing site on Mars, NASA scientists have reported the same at the other, halfway round the planet.
The signs found in a rock examined by Spirit point to a much smaller amount of water than the 鈥渟oaking鈥� amounts indicated by Opportunity, said deputy mission scientist Ray Arvidson, of Washington University in St Louis, Missouri.
But it is significant that the twin rover mission, sent specifically to search for signs of past water, has achieved a double success just halfway through its planned 90 days of surface operations. And project engineers say it is likely that the mission could keep going for twice that long or more.
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Spirit landed inside a possible ancient lakebed, called Gusev crater. The new evidence for water comes from microscopic analysis of a rock dubbed Humphrey, whose surface was ground clean by the rover鈥檚 Rock Abrasion Tool.
Cavities and fissures
The rock itself is clearly a volcanic basalt, but the images show that some other mineral has formed inside tiny cavities and fissures in the rock. 鈥淥n Earth, we鈥檇 say it鈥檚 a volcanic rock that鈥檚 had a little bit of fluid move through it,鈥� Arvidson told a news conference at NASA鈥檚 Jet Propulsion Laboratory on Friday. 鈥淣ot gobs of water 鈥� but some.鈥�
A new image showing the polished part of the rock Humphrey is so stunningly clear and shows such interesting evidence of different geological processes, Arvidson said, that it is likely to appear 鈥渋n every geology textbook in the next 10 years鈥�.
While Humphrey is volcanic, the evidence for the action of water at Opportunity鈥檚 landing site, Meridiani Planum, was found in clearly sedimentary rocks. 鈥淭his means that Mars is a diverse place,鈥� he said, adding to the excitement of further exploration.
Spirit is now less than 90 metres away from a deep crater called Bonneville, and is expected to reach its rim within the next week.
