The Little Bacterium That Could

Candidatus Desulforudis audaxviator doesn't need sunlight, doesn't even need photosynthesis. Therefore it is not so surprising it was discovered 3 kilometres below the Earth's surface in a South African goldmine.

Report from New Scientist:

Such a self-sufficient organism is virtually unheard of. It means the ecosystem's only species must extract everything it needs from an otherwise dead environment.

...Chivian's analysis shows that the new bacterium gets its energy from the radioactive decay of uranium in the surrounding rocks. It also has genes to extract carbon and nitrogen from its environment - both essential for making proteins.

"It's philosophically exciting to know that everything necessary for life can be packed into a single genome," says Chivian. NASA's Chris McKay says this is just the kind or organism that could survive on Mars.

They fall short of suggesting it may have come from Mars, or elsewhere.