“It’s like finding Moby Dick in Lake Ontario,” says 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.

No place for a worm

Onstott says no one thought multicellular organisms would be found living in this so-called fracture water. He points out that microbiologists are still trying to prove and understand how even single-celled organisms can exist at these depths. “The lack of oxygen, temperature and food is a big dissuader,” he says.

“We’ve had this preconception that there can only be certain types of organisms in certain environments,” says Scharf. “But it’s not true at all. There are more complex organisms in these bizarre environments.”

Animals on Mars

If complex life forms are able to survive inside cracks deep inside Earth, it raises the possibility that they might have survived undetected in similar environments on Mars.

, director of NASA’s Astrobiology Institute in Moffett Field, California, points out that Onstott has previously discovered a bacterium living 2.8 kilometres underground, completely isolated from all other ecosystems on Earth (Science, DOI: ). The bug gets its energy from the radioactive decay of elements in the surrounding rocks. “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.

Until now, it was thought such an ecosystem could be made of bacteria only. But Onstott’s new findings have completely changed that. “It has extended the [earlier] work to an animal,” says Pilcher.

“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 [small enough to fit in tiny cracks] could coexist with microbial ecosystems all powered by radioactivity.”

Journal reference:

Update 21 March 2011: that, in the run-up to the Japanese earthquake, the Tokyo Electric Power Company failed to carry out several scheduled inspections at the stricken Fukushima Daiichi plant. Thirty-three pieces of equipment were not inspected, including a backup power generator for reactor 1. Japan’s nuclear watchdog, NISA, .

With the Fukushima-Daiichi nuclear plant still crippled in the aftermath of last week’s devastating earthquake and tsunami, questions are being raised about the preparedness of its operator, the (TEPCO). Why, for instance, were the diesel motors supposed to power the cooling system in an emergency so vulnerable to flooding?

As this timeline shows, the readiness of Japan’s reactors to survive major seismic events has been a growing concern. What’s more, the nation’s entire industry – not just TEPCO – has an undistinguished history of nuclear accidents and a poor record for transparency when things go wrong.

December 1995

Eight tonnes of sodium coolant leak from a pipe at the experimental fast-breeder reactor, run by the now-defunct Power Reactor and Nuclear Fuel Development Corporation (Donen). Monju’s managers tell the Japan Science and Technology Agency that the leak was discovered 8 hours later than was actually the case, and supply a doctored video excluding the worst of the spill. The attempted cover-up causes public outrage.

March 1997

An explosion rocks the Tokaimura waste reprocessing facility, triggered by a fires in a building where waste is mixed with asphalt for storage in drums. Donen officials initially report radiation levels 20 per cent above normal outside the building, but later admit that the true level of contamination was at least 10 times higher. Seven maintenance staff are later found to have been out playing golf.

May 1998

The Japanese parliament passes a bill to reconstitute the discredited Donen as the Japan Nuclear Fuel Cycle Development Institute, monitored by an independent panel of experts. This in turn became part of the in 2005.

July 1999

Twenty tonnes of radioactive water leaks from a cracked pipe at the , run by the . Although the leak was contained within the plant, elevated radiation levels mean that clean-up workers can only spend only 3 hours a day in the area.

September 1999

In what is billed as the worst nuclear accident since Chernobyl, three reprocessing workers at Tokaimura inadvertently create a critical mass of uranium, severely irradiating themselves and triggering chain reactions that continue for several hours.

International safety experts are flabbergasted to learn that the workers were pouring a solution of uranium oxide in nitric acid into a sedimentation tank by hand, using buckets. JCO, the company that now runs the facility, and the Japanese government are criticised both for allowing such a dangerous procedure and for a sluggish response to the incident.

December 1999

Hisashi Ouchi, one of the workers irradiated in the Tokaimura criticality accident, dies after three months in intensive care; his colleague Masato Shinohara perishes four months later.

October 2000

Six managers from JCO are arrested and charged with professional negligence for failing to prevent the dangerous procedures that triggered the chain reaction at Tokaimura.

September 2002

Freshly revealed reports from the International Atomic Energy Agency (IAEA), dating from the 1990s, describe safety precautions at Japanese nuclear reactors as dangerously weak. IAEA inspectors visited four reactors in 1992 and 1995, finding 90 deficiencies in safety procedures.

The revelation follows the confession by four companies – TEPCO, , Japan Atomic Power and – that they concealed flaws in their reactors from government regulators.

August 2004

In the deadliest workplace incident for Japan’s nuclear industry, a steam leak from a power turbine at the Mihama plant kills four people and injures seven. There is no radiation leak, but the Kansai Electric Power Company is criticised for failing to inspect the failed pipe.

March 2006

A diplomatic cable from the US embassy in Tokyo, , discusses a case in which a court orders the to shut down a reactor at its Shika nuclear plant because of concerns over its ability to withstand powerful earthquakes. Both the company and the Japanese government oppose the ruling. The cable states: “Though not legally obligated to cease operations in this case since this is a civil suit, [the company] will face an uphill battle to regain the support of local citizens for operating a nuclear facility in their backyards.”

A court did indeed order the plant to be shut down, but a higher court reversed the decision, and the plant resumed operation in 2009.

July 2007

Three reactors at the world’s largest nuclear plant, , shut down after a 6.8-magnitude earthquake. A fire briefly breaks out in one of the units. TEPCO initially says that the quake caused no radiation leaks, but days later admits that 1200 litres of radioactive water had washed into the sea and several drums containing nuclear waste lost their lids after falling over.

In the wake of the incident, experts debate whether Japan’s nuclear plants are engineered to standards high enough to cope with major quakes – the country’s stipulates that all new plants must be built to withstand only a magnitude-6.5 event. Worldwide, there are .

December 2008

According to from the US embassy in Tokyo, an IAEA representative has said that guides for seismic safety have been revised only three times in the past 35 years, and that the IAEA is now re-examining them. The cable continues: “Also, the presenter noted recent earthquakes in some cases have exceeded the design basis for some nuclear plants, and that this a serious problem that is now driving seismic safety work.”