The Opportunity rover has made new discoveries about early water on Mars which may have been drinkable, reveal NASA scientists.
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, Sky News reported.
Principal investigator Steve Squyres of Cornell University said that this is powerful evidence that water interacted with this rock and changed its chemistry, changed its mineralogy in a dramatic way.
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.