Viking: Viking 1 on the surface of Mars in 1976. Two of the Viking biology experiments gave strong signals of life in the Martian soil.
Mars_magnetite: The best evidence for life in meteorites from Mars comes from chains of crystals of magnetite (magnetic iron oxide) which are identical to such chains made by bacteria on Earth. Top: A chain of magnetite crystals inside a modern bacterium, as seen in an electron microscope. Bottom: A chain of magnetite crystals in the Mars meteorite ALH84001 (shown by arrows). The diameter of a single crystal is about one-millionth of an inch.
Mars methane: Hot spots of methane on Mars. This map shows where methane emission is strongest in the northern hemisphere summer on the Red Planet. Plumes have been seen rising up from regions known as Arabia Terra, Nili Fossae, and south-east Syrtis Major.
Phoenix UMOs: First glimpse of Martians? A time-lapse sequence of images taken by the microscope aboard the Mars Phoenix Lander in 2009. They show three small objects, labeled A, B, and C, which have clearly moved, while all other features in the images have stayed in the same place. The size of these objects is consistent with them being single-celled organisms.