Recently, he and his colleagues examined samples of a mud core extracted from between 860 metres and 1626 metres beneath the sea floor off the coast of Newfoundland. They found simple organisms known as prokaryotes in every sample. Prokaryotes are organisms that often have just one cell. Their peculiarity is that, unlike any other form of life, their DNA is not neatly packed into a nucleus.
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Where cells living so far beneath the sea floor could have come from remains a mystery. They may have been gradually buried in sediment as millions of years passed by, and adapted to the increasing temperatures and pressure, he says.

Another possibility is that they were sucked deep into the mud from the sea water above. Hydrothermal vents pulse hot water out of the seabed and into the ocean. This creates a vacuum in the sediment, which draws fresh sea water into the marine aquifer.

It is important to understand the way the cells got down there, because that has implications for their age. The cells are not very active and according to Parkes they have very few predators. “We find very few viruses, for example, down there,” he says. “At the surface, if you don’t divide you get eaten. But if there are no predators, the pressure to reproduce decreases and you can spend more energy on repairing your damaged molecules.”
Ancient life

This means it is conceivable – but unproven – that some of the cells are as old as the sediment. At 1.6 km beneath the sea, that’s 111 million years old. But in an underworld where cells divide excruciatingly slowly, if at all, age tends to lose its relevance, says Parkes.