Establishing whether life has ever existed on Mars has been an area of huge interest
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Researchers say they have "a powerful new case" that life has existed on Mars.
Nasa scientists working on a meteorite discovered in 1984 have found "strong evidence of Martian life," sources told the Spaceflight Now website.
It is believed that a comet or asteroid hit Mars and diverted the rock off the planet's surface, before it crashed in Antarctica 13,000 years ago.
In 1996 Nasa found what looked like tiny fossils in the meteorite and said they were traces of Martian organisms.
President Bill Clinton said at the time: "It speaks of the possibility of life... Its implications are as far-reaching and awe-inspiring as can be imagined."
But many had doubts.
Some scientists argued the rock was contaminated, while others claimed the 'fossil' shapes could have been formed when the rock was first blasted into space.
Now the Nasa team has claimed that new evidence strengthens the case for life, reports say.
The researchers have been using new techniques focusing on so-called "magnetic bacteria", which leave behind distinctive shapes just like those in the meteorite.
Dr Dennis Bazylinski reviewed the findings for the journal of the Geochemical Society and the Meteoritic Society.
He told Spaceflight Now: "One indication there was life on ancient Mars are these particular magnetite crystals in the meteorite that look like they came out of magnetic bacteria."
Emily Baldwin, deputy editor of the UK's Astronomy Now magazine, told Sky News Online: "If the features in the meteorite do turn out to have an extra-terrestrial biological origin then that's pretty exciting stuff in terms of understanding how life is distributed across the solar system."
The findings are expected to be officially released by Nasa in the next few days.
