FatLittleMonkey writes "Researchers from Princeton University have discovered nematodes at depth of up to 3.6km in three gold mines in South Africa, likely feeding on the radiation-consuming bacteria also discovered by the same team. Carbon dating their environment confirms that the 500 micrometres long critters have been there for at least 3000 years and are not a recent contaminant. The finding means that unexpectedly complex ecosystems occur deep underground, increasing the chance that complex life may have survived on Mars according to Carl Pilcher, director of NASA's Astrobiology Institute, "The significance was that you could imagine an ecosystem existing in the subsurface of a planet that didn't have a photosynthetic biosphere, like Mars," he says.
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Until now, it was thought such an ecosystem could be made of bacteria only. But Onstott's new findings have completely changed that. "These nematodes are grazing on microbes. So now you could imagine that if animal life had ever developed on a planet, and the surface of that planet became lifeless," Pilcher explains, "you could imagine that animals could coexist with microbial ecosystems all powered by radioactivity."