Washington - Scientists on Friday called Nasa's Opportunity rover gimpy and arthritic but hailed its new discoveries about early water on Mars made 10 years after it was launched toward the Red Planet.
The unmanned solar-powered vehicle has just analysed what may be its oldest rock ever, known as Esperance 6. It contains evidence that potentially life-supporting water once flowed in abundance, leaving clay minerals behind.
"This is powerful evidence that water interacted with this rock and changed its chemistry, changed its mineralogy in a dramatic way," said principal investigator Steve Squyres of Cornell University.
He described the research as "some of the most important" of the decade-long mission because it showcases a very different chemistry than most of the previous discoveries about water on Mars, which is now quite dry.
Scientists believe that a lot of water once flowed through these rocks through some sort of fracture, leaving an unusually high concentration of clay.
The analysis reveals traces of a likely drinkable type of water that dates to the first billion years of Martian history, when clay rocks were forming under a more neutral pH, before conditions became more harsh and water more acidic, Squyres said.
The rover's rock abrasion tool, alpha particle X-ray spectrometer and microscopic imager provided the details to Earth-based scientists, who can learn about the Red Planet's history without bringing its rocks to Earth.
Opportunity and its twin rover Spirit launched in 2003 and landed in January 2004 for what was initially meant to be a three-month exploration. Both discovered evidence of wet environments on ancient Mars.