Geochemistry

Preserved in Salt

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Science  29 Apr 2005:
Vol. 308, Issue 5722, pp. 603
DOI: 10.1126/science.308.5722.603c

The most ancient living organism is claimed to be a bacterium that has been extracted and cultured from a small bubble of fluid trapped in a Permian-aged (∼250 million years ago) salt crystal, similar to the way that, for example, insects are trapped in amber. The idea is that this bacterium became entombed in a fluid inclusion in the salt crystal and remained dormant until it was resuscitated. One criticism has been that the inclusion in the salt crystal, and hence the bacterium, might be a contaminant of an uncertain and possibly younger age; the retention of younger fluids flowing through or adjacent to older rock is not uncommon.

Satterfield et al. have now determined the chemistry of the fluid inclusions in these salt crystals. Earth's ocean chemistry has changed over time, and the Late Permian oceans were depleted in Mg and sulfate as compared with today's oceans, which provides a signature that is diagnostic for this time period. The chemistry of the inclusions fits with that of Permian seawater, suggesting that the bacterium is indeed old. — BH

Geology 33, 265 (2005).

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