NASA is believed to have found strong evidence that there was once life on Mars.
Scientists working on a meteorite discovered in 1984 told the Spaceflight Now website that mineral microstructures in the rock were the remains of magnetic bacteria.
Back in 1996, NASA reported that it had found what looked like tiny fossils in the Allen Hills (ALH) 84001 meteorite, which crashed in Antarctica around 13,000 years ago. But critics argued that the shapes were formed by non-biological processes or that the rock was contaminated.
The team has been using high resolution electron microscopy to focus on magnetite crystals found in the rock. These crystals are found in certain bacteria on Earth, where they have very unusual shapes - shapes which parallel those found in the meteorite, says NASA.
In addition, certain chemical signatures in the rock indicate a bilogical rather than geological origin, and a possible interaction with water.
The findings are expected to be released by NASA in the next few days, and published in Geochimica et Cosmochimica Acta.