"It's like finding Moby Dick in Lake Ontario," says Tullis Onstott of the nematode worms his Princeton University team discovered living far beneath the Earth's surface in South Africa.
The tiny worms – just 500 micrometres long – were found at depths ranging from 900 metres to 3.6 kilometres, in three gold mines in the Witwatersrand basin near Johannesburg. That's an astonishing find given that multicellular organisms are typically only found near the surface of the Earth's crust – Onstott's best guess is in the top 10 metres.
The creatures seem to live in water squeezed between the mines' rocks, can tolerate temperatures reaching 43 °C and feed off bacteria. Carbon dating of compounds dissolved in the water suggests that the worms have been living at these depths for between 3000 and 12,000 years.
"To have complex life sustain itself for such a long period completely sealed away from everything else – from sunlight, from surface chemistry – is pretty amazing," says Caleb Scharf of the Columbia Astrobiology Center in New York City.
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