A NASA scientist working on the current mission to Mars says the Curiosity rover has discovered something "for the history books".
The rover mission's principal investigator John Grotzinger told NPR radio in the US the Curiosity recently analysed a soil sample taken from the red planet, and the results could be momentous.
"This data is gonna be one for the history books," Grotzinger said. "It's looking really good."
The Curiosity rover, which landed on Mars on August 5, is equipped with the Sample Analysis at Mars instrument, an on-board lab known as SAM.
The purpose of SAM is to determine what minerals and chemicals are in the sand, rocks and atmosphere of Mars by collecting and processing samples.
A previous air sample analysed by SAM initially showed the presence of methane, a gas that is produced by living organisms.
However the NASA team held off announcing the finding while they checked the air being tested was from Mars and not brought along from the rover's launchpad at Cape Canaveral.
"We knew from the very beginning that we had this risk of having brought air from Florida. And we needed to diminish it and then make the measurement again," Grotzinger said.
When scientists tested the sample again, the signs of methane had disappeared.
Scientists at NASA's Jet Propulsion Laboratory in Pasadena are keeping mum on exactly what they've found from the most recent sample while they run additional tests over the next "several weeks", but SPACE.com reports an announcement will be made in early December.