31. Ancient Life: Apex Chert Microfossils
This slide shows pictures of some of the oldest known fossils from Earth, bacteria fossils from the Apex Chert in Western Australia. Approximately 3.5 billion years ago, this rock was sediment on the floor of an ancient lake or ocean. Bacteria or algae lived on (and in) the sediment and were trapped and preserved in it. These bacteria fossils are only 10–20 micrometers long, so they can only be seen through a microscope. This slide shows 3 of the 11 different kinds of bacteria fossils in the Apex Chert. Most are chains of single cells, forming filaments, very much like bacteria and blue-green algae do today on the floors of modern lakes. These filaments of cells have the same shapes as some structures in ALH 84001 (slide #28), which suggests that the structures in the meteorite might also be fossils of bacteria.