10 years of Opportunity and Spirit on Mars have given us some interesting insights, like that the oldest minerals show that around four billion years ago Mars had liquid water so fresh it could have supported life.

NASA loves to invoke 'may have implications for life on other planets', it gets the public excited - no bucks, no Buck Rogers so selling some sizzle is important - and thus a focus for NASA's decade of research on Mars surface was whether the planet may ever have been able to be habitable. 

"While Mars is too cold now to have the liquid water needed for life, we've had evidence for past water activity on the planet from satellite images of valleys and analysis of rocks by the Rovers," said co-author Dr. Paulo de Souza of CSIRO. "But the water that once shaped those landscapes and minerals was as acidic as vinegar. "Our latest research has found not only the earliest episode of water activity documented yet by the Opportunity Rover, but that the geochemistry of the 4 billion year old rocks indicates extensive deposits of past water that's among the freshest, most life-sustaining found so far anywhere on Mars.

"If there was ever life on Mars, then this would have been the mud for it to live in."

de Souza has worked with NASA since the Mars Exploration Rover Program began, having collaborated with NASA's research teams for many years. "Opportunity's Mars mission was expected to last just months but she's still going strong 10 years on with no signs of stopping. She's traveled 38km instead of the few hundred meters planned.

"Along the way, Oppy's collected invaluable information about Mars' surface with her high tech toolkit of rock scrapers, chemical sensors, and spectral analyzers." 

Published in Science.