TRAPPED inside ice crystals under 3 kilometres of snow, microbes can survive for more than 100,000 years.
Physicist Buford Price and his graduate student Robert Rohde, both at the University of California, Berkeley, calculated that virtually any microbe can remain alive in ice, resisting temperatures down to -55 掳C and pressures of 300 atmospheres. The secret is the thin film of liquid water that forms spontaneously around a cell lodged within an ice crystal. Oxygen, hydrogen, methane and other gases would then diffuse into this layer from bubbles nearby.
Many bacteria obtain energy from such molecules, and while this wouldn鈥檛 be enough for them to grow and reproduce, they could still repair any molecular damage and so remain viable for more than 1000 centuries. 鈥淚t is not life as we generally think about it,鈥� says Rohde. 鈥淸They] are just sitting there surviving, hoping that the ice will melt.鈥�
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To test their hypothesis, the researchers examined samples taken at various depths in the Antarctic and Greenland ice sheets. They detected isolated microbes, which must be trapped inside ice crystals as they suggest, rather than in veins of liquid water in between (Proceedings of the National Academy of Sciences, ).
The study helps to explain why living bacteria have been found in ice samples from more than 3000 metres down. While smaller microbes can live on dust particles and inside thin veins of water, larger ones will be encased in solid ice, waiting to revive.
