French researchers explain how

Oct 3, 2009 08:02 GMT  ·  By

In a study that could change the way planetary scientists look at rocks forever, French researchers recently reported, in the September issue of the journal Geobiology, that they discovered how microorganisms become fossils in laboratory conditions. This may provide geologists with leads into understanding how microbes or bacteria may have been stored inside Martian rocks, for example. However, at this point, there is still no way to extract the remains of these organisms, if they exist at all, from the rocks, unless larger, fossilized colonies are discovered. The study could have implications for the rocks on our planet as well, Space reports.

“Environmental conditions were similar on the young terrestrial planets and traces of early Martian life may have been similarly preserved as silicified microfossils,” the authors write in their journal entry. The study focused on examining the fossilization process of Pyrococcus abyssi (PA) and Methanocaldococcus jannaschii (MJ), which are two types of extremophiles able to flourish in very hot temperatures, and much reduced oxygen concentrations. There are those in the scientific community who believe that such an environment may have been the place where life first appeared on Earth, and maybe even on Mars.

Normally, organisms such as the ones studied only fossilize when they come in contact with silica flows and other minerals near hydrothermal sources. But the French scientists wanted to see if normal, laboratory conditions were sufficient for the process to take place. “They do fossilize a little bit, but do not survive the test of time,” explains the team supervisor, Frances Westall. He is a paleobiologist at the Center National de la Recherche Scientifique, in Orleans, France. He reveals that MJ cells all died within a week and that they only left behind a subtle organic signature, after being inoculated with silica solutions.

On the other hand, PA cells persisted for up to four months, exhibiting a large number of their original, key traits. Still, they too degraded after that time, and failed to fossilize properly. But the study also hints that other types of microorganisms, studied under different conditions, may indeed fossilize. Johnson Space Center expert Dorothy Oehler, who was not involved in the new research, says that this is evidenced by the microbe fossils that were discovered in silica layers near hydrothermal vents.

But discovering the organisms' traces in rocks is a long-shot, for two simple reasons. One is the planet's “recycling program,” which draws rocks under the crust and heats them up, melts them, and then forms then again and spews them out in eruptions. Naturally, it's highly unlikely that traces of living things would survive. The second reason is the fact that, even if the geological processes don't get them, the rocks are then subjected to constant rain, wind and temperature variations, which eventually grind them into sand.