Thursday, November 12, 2009

Early Life In Cool Oceans

Oxygen and hydrogen isotope evidence for a temperate climate 3.42 billion years ago. 2009. M. T. Hren, et al. Nature 462: 205-208.
Early life on Earth may have developed more quickly than previously thought.
The Earth's climate was far cooler – perhaps more than 50 degrees – billions of years ago. That means that conditions for life were much easier, and that life that did exist at the time was not under as much stress as previously believed.

The team examined rocks from the Buck Reef Chert in South Africa that are known to be about 3.4 billion years old, among the oldest ever discovered. They found features in them that are consistent with formation at water temperatures significantly lower than previous studies had suggested.

"Our research shows that the water temperature 3.4 billion years ago was at most 105 degrees, and while that's potentially very warm, it's far below the temperatures of 155 degrees or more that previous research has implied," Tice explains.

SubHuman © M. Ryan & M. Schultz
The situation could be compared to the geysers currently found in Yellowstone National Park. The hundreds of hot spring pools in the park vary considerably in temperature but the water in the pools that is farthest from the center is cooler.

When water temperatures fall to below 163 degrees or so, close to the high temperatures previously hypothesized for the early ocean, communities of green photosynthetic bacteria begin to grow on the pool floor. These communities become thicker as water temperature continues to drop off away from the pool centers.

"There is life even in the hottest water, and microbes there have evolved to grow in those harsh conditions. But there is even more life present in the cooler waters," he notes. "We think this is similar to what conditions might have been like billions of years ago." link