Four billion years ago, Mars was a hotter place with the water flowing across the surface so fresh it could have supported life.

Researchers have found what may once have been the most liveable mud on the red planet after analysing some of the oldest minerals ever studied by NASA’s Mars Opportunity Rover program.

The findings are in a special edition of the journal Science released to coincide with the 10th anniversary of the Mars Opportunity Rover and its twin, Spirit, landing on the planet.

CSIRO’s Paulo de Souza said a major focus on NASA’s decade of research on Mars was whether the planet may ever have been habitable.

The latest findings show the geochemistry of the four-billion-year-old rocks at the rim of a vast meteor crater indicates extensive deposits of past water that’s among the freshest, most life-sustaining found so far on Mars.

“If there was ever life on Mars, then this would have been the mud for it to live in,” Dr de Souza said.

Dr de Souza said he is very proud of the Opportunity Rover, a golf buggy-sized all-terrain vehicle known as Oppy, whose tenth birthday is on Friday.

Oppy travelled 38 kilometres in 10 years instead of the few hundred metres originally planned that were expected to take a few months.

It collected information about Mars’ surface with a high-tech tool kit of rock scrapers, chemical sensors, and spectral analysers.

Oppy beamed a decade’s worth of data back to space receiving stations on Earth, including the Canberra Deep Space Communication Centre outside Canberra at Tidbinbilla managed by CSIRO.

Dr de Souza said their next plan is to see how extensive are the mineral deposits they have just been analysing.

It would take Oppy another ten years go cross the 22-kilometre crater formed by a meteor strike so they are going around the rim.

They are doing it to increase knowledge about the universe, how life is formed and also whether the Earth could be like Mars in the future if it loses its protection from solar storms.