Researchers are sure they hold a lot of clues

Mar 2, 2010 07:36 GMT  ·  By
Fossilized stromatolite in Glacier National Park. The cross-sectioning of the layers can be seen because of erosion
   Fossilized stromatolite in Glacier National Park. The cross-sectioning of the layers can be seen because of erosion

Stromatolites are stony structures that were produced billions of years ago by microbes. In fact, they are so old that most of them were produced about 1.1 billion years ago. Researchers don't yet know how these cabbage leaf-layered stromatolites were formed, but they are aware that microbial colonies most likely played a very important part in this. As such, they are currently focusing their attention on areas of the world where similar structures are now being produced. And one such place is the Yellowstone National Park, LiveScience reports.

One of the things that scientists do know for sure about these multiple rock layers is that they most likely formed in shallow, inter-tidal and sub-tidal environments. They may have been produced as mats of microbes, living generation after generation, lived on top of each other, producing the layer-like appearance. Some stromatolites are 3.5 billion years old, and experts are very curious to learn how the microbes that produced them may have looked like. They are therefore currently turning their attention to the next best thing, microbes inside hot springs at Yellowstone. The microorganisms also produce stromatolites, and scientists hope that comparative studies will give them a clue of the ancient world.

The new study is being conducted with funding secured through the NASA Exobiology and Evolutionary Biology program. It is being performed by scientists at the Montana State University, who are led by expert David Ward. “We are studying the present as a key to the past,” the team leader says. He also explains that the fossil record of stromatolites is very small, on account of the fact that many animals capable of eating the microbial mats appeared some 530 million years ago, after the Cambrian explosion. Ward explains that minerals accumulate in between the microbial layers over them, and that at some point they crystallize to form rocks.

As this happens, a number of chemicals from the colonies are also trapped in the minerals. At this point, chemists can isolate and analyze these molecules, and tell the story of their origins. As a direct adaptation to the fact that animals could eat them, microbial mats now moved into areas where their predators can't reach them. “They've gone to extreme environments where the animals that eat them can't live,” Ward adds. The Shark Bay saline lagoon, on the western coast of Australia, and the hot springs at Yellowstone are good examples of such environments.

“Ideally, geologic and biological research will inform each other. Studies of ancient stromatolites produce a set of observations in need of explanation by lab and field research of modern systems.  Biologists, in turn, can help geologists to view ancient rocks with new eyes,” says Harvard University expert Andy Knoll, who is not involved in the new research effort.