These are the bacteria-like shapes found in the sample ALH84001.
In August '96, NASA announced that they do not have actual proof, but that they have found an "unique pattern of organic molecules, carbon compounds that are the basis of life. We also found several mineral phases that are known by-products of primitive microscopic organisms of Earth. Structures that could be microfossils seem to support all of this. The relationship of all these things on terms of location - within a few hundredths of an inch of one another - is the most compelling evidence." (Dr. David McKay NASA)