Evidence for life on Mars. Coloured scanning electron micrograph of tube-like structures (coloured yellow) on a meteorite which originated from Mars. Structures such as these have been interpreted as possibly being microfossils of primitive, bacteria-like organisms which may have lived on Mars more than 3.6 billion years ago. The structures are less than 1/100th the diameter of a human hair. The meteorite, called ALH84001, was discovered in Antarctica in 1984, and has since been studied at NASA's Johnson Space Center and at Stanford University.