A year in the life of a Marsonaut

Today six men from four countries are celebrating a bizarre anniversary that could become more normal in the future. These "Marsonauts" have spent exactly one full year simulating the journey to the Red Planet and back, mostly sitting inside a mock spaceship,.

That still leaves another 165 days before they complete the 520-day Mars-500 isolation experiment, which is being run by the Russian Academy of Science's Institute for Biomedical Problems in Moscow. But what have these wannabe interplanetary travellers achieved so far?

For one, a Mars landing. In February, three crew members detached from the mother ship and made a beeline for the surface - in reality a room with a high, domed ceiling and a floor covered in reddish sand and rocks - in their simulated lander. In pairs, the three took turns exploring the Martian surface: planting Russian, Chinese and European Space Agency flags, taking soil and rock samples using tools developed for the cancelled Soviet lunar programme, and dealing with a simulated "abnormal" situation - what to do when a Marsonaut falls down (answer: partner to the rescue).

They've also managed to trick at least one individual: the landing looked so real when shown on local television, says Mark Belakovsky, chief manager of the Mars-500 project, that his 90-year-old father called him and said: "Listen... did the Americans land on Mars? Or is this you with your experiment?"

At the end of February, the landing party - one Russian, one European and one Chinese - ditched their lander and rejoined the two Russians and one European who stayed behind in the "orbiting modules". Now they're all headed home, scheduled to "land" back on Earth in November.

Just like the real thing, life on a mock spaceship doesn't always run smoothly, however. The crew has successfully dealt with two simulated emergency situations: a day without electricity in December, where they sat in near-darkness and played games like chess and cards by the glow of a few flashlights, and a week of radio silence from the experiment's ground control centre last month.

They've also survived the excruciating monotony of isolation that might drive an ordinary Earthling crazy. Indeed, even participants in the 105-day precursor experiment got a bit tired of seeing the same five faces every day. That crew's commander, cosmonaut Sergei Ryzansky, says: "I found that I really missed being in traffic jams, in Moscow, sitting in my car and looking at other people sitting in other cars."

But the most challenging part of the journey for the 520-day crew is still to come, says Aleksandr Suvorov, the project's lead doctor: "We've passed all the stages of the experiment that they waited for and trained for, with the flight, walking on the [Mars] surface, the experiments."

Now, he says, there's nothing new for the crew - no new food, no new procedures, nothing. "Now comes the very hardest psychological period, where they have to be patient, find ways to keep themselves busy," particularly in their free time, Suvorov says.

In the meantime, the Mars-500 crew will be greeted with messages from project directors and loved ones, congratulating them on the anniversary and, no doubt, nudging them to hang in there. Here you can read their answers to a list of questions posed to them to mark the important day.

Gold-mine worm shows animals could be living on Mars

"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.

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.

Carl Pilcher, 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: 10.1126/science.1127376). 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."