Electron microscope image of a part of a meteorite from Mars: ALH 84001 (Wikipedia

Two NASA astronomers shocked the world with an announcement in 1996: Alien life discovered in a meteorite from Mars. Though NASA eventually retracted the paper on the face of new evidence that suggested some of the carbonate globules were formed at rather high temperatures that would likely preclude life, the announcement still served to tantalize the public about the prospects of life traveling about in space. We see that even today with major news about a controversy over another potential discovery of life from a meteorite. Unfortunately, the life that was discovered may be due to contamination from the Earth.

Wikipedia: ALH 84001