Hot springs microbes hold key to dating sedimentary rocks, resea...(drew water from a hot springs vent and c...)

Angel Terrace at Mammoth Hot Springs in Yellowstone National Park is an ideal, natural laboratory because of the high precipitation rates and the abundance of microbes, Fouke said. Calcium carbonate grows so fast millimeters per day we can examine the interaction between microorganisms and the calcium-carbonate precipitation process.

The researchers found that the rate of precipitation drops drastically sometimes by more than half when microbes are not present.

So one of the fingerprints of calcium carbonate deposition that will tell us for sure if there were microbes present at the time it formed is the rate at which it formed, Fouke said. And, within the environmental and ecological context of the rock being studied, we can now use chemistry to fingerprint the precipitation rate.

In a second paper, to appear in the Journal of Sedimentary Research, Fouke and colleagues show how the calcium carbonate record in a springs primary flow path can be used to reconstruct the pH, temperature and flux of ancient hot springs environments. The researchers also show how patterns in calcium carbonate crystallization can be used to differentiate signatures of life from those caused by environmental change.

This means we can go into the rock record, on Earth or other planets, and determine if calcium carbonate deposits were associated with microbial life, Fouke said.

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