Methuselamoeba

Hundreds of meters below the ocean floor, scientists have found enormous bacterial colonies, some of them as much as 16 million years old.

"It might be that life was developing in the sub-surface long before [3.8 billion years] where it was protected from meteorite impacts," he said. "And as soon as the surface of the Earth became more hospitable, the bacteria were able to move up and colonize it."

[...] Evidence of life in ancient rock sediments was found some time ago but, until now, it was assumed that most of it was long dead. In the past scientists have stained bacterial cells so they stood out against the sediment background, but that method cannot differentiate between living and dead cells. Dr Parkes and his team used a new technique that could identify living cells - and they were surprised to find about 30% of the cells in deep sediment samples are in fact living. [...] Some of the cells are imbedded in sediments that are many millions of years old, which means they must be too.

"These bacteria are growing very slowly in the subsurface," said Dr Parkes. "They could effectively be immortal."

Pretty heady stuff, and leading some to suggest that as much as 60-70% of our bacteria live deep below the Earth's surface. Pair this story with the announcement that the Mars Express Orbiter has located what appears to be a giant ice sea just below the surface that would have formed relatively recently in Mars' history and everything gets very intriguing, doesn't it?