Nasa scientists say their Opportunity rover has made new discoveries about early water on Mars which may have been drinkable.
The unmanned solar-powered vehicle, described as “arthritic” as it nears 10 years since its launch, 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 the rocks through some sort of fracture, leaving an unusually high concentration of clay.
The analysis reveals traces of a what may have been a drinkable type of water that dates to the first billion years of Martian history.
The clay rocks were forming under a more neutral pH, before conditions became more harsh and water more acidic, Dr Squyres said.
The rover’s rock abrasion tool, alpha particle X-ray spectrometer and microscopic imager provided the details to scientists, who can learn about the 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.
“What Opportunity has mostly discovered evidence for was sulphuric acid,” Dr Squyres told reporters, outlining the major difference detected in the Esperance rock’s formation. “This is water you could drink,” he said.