Workers from NASA, in a study of the martian meteorite ALH 84001, observed elliptical, rope-like, and tubular structures in fractures in the carbonate mineral globules; they interpreted the structures as possible fossil bacteria. These structures are so small, each only 20 to 100 billionths of a meter across (or nanometer), that they could only be seen with an electron microscope. This is the image that was obtained. These were for some time thought to be a form of fossilized life, although this conclusion has not been sustained. This image was provided by NASA.