How cryogenic sleep could soon bring astronauts to Mars

In the future, astronauts could be able to sleep on the International Space Station and still be fully functional when they wake up. The trick will be getting that to work on a regular basis.

If all goes to plan, scientists from the European Space Agency (ESA) and University of Bern in Switzerland plan to perform what they call "cryogenic deep-sleep" on ISS astronauts in the next year or two. Their aim is to bring them to the "bottom of space," where they will still be fully functional when they wake up.

The researchers say that if they succeed, they can extend the ISS' lifespan and also open up possibilities for longer trips to Mars. And there's no harm in the ESA testing out what may be the first step towards a potential Martian vacation – so we might as well get started.

The plan is to take the ISS crew into a lower-than-normal orbit. This will require astronauts to go through a process known as hypoxia, where the body starts to deprive itself of oxygen through a lack of atmospheric pressure. This low-oxygen state is the result of the crew breathing nitrogen gas rather than air – much like when you suffer from altitude sickness. As pressure is reduced, water in the blood begins to pool in the body's extremities. The heart rate and brain activity also drops.

Sleeping in such an environment will put the crew into a state of near-complete hibernation, where they will technically still be alive. But they'll have no pulse, breathing, or blood circulation.

"Hypoxia was expected to result in serious impairment of the crew's cognitive performance for several days, but in fact we observed that there was a significant residual cognitive reserve in the longer term," says the study's lead author Gerald Clarke, a professor of medicine at University of Bern, in a statement.

These findings were published this week in the Journal of Physiology. The experiments were done with six astronauts in total, after some of them had already spent a year in microgravity aboard the ISS. Clarke says the difference is the amount of time in which the astronauts went through hypoxia, because it allows them to get a better sense of the effects.

The ESA is planning a flight of its Transient-Hypoxic-Exposure Therapy, or TRIGHT, to be launched in 2020. This will include five astronauts being put into a cryogenic chamber, where they will remain for up to five days.

The experiments to test the hypothesis are far from complete, but if successful, the ESA could open up possibilities for extended human exploration of space – including trips to Mars, Clarke says.

"That we have achieved the first studies that systematically show the neural mechanisms that return a mind to a restful state after prolonged hypoxia opens up a number of potential applications," he says. "Most importantly, it means we are now able to investigate how to accomplish this more effectively."

The key is to "freeze the brain in these conditions and then bring it out of the hypoxic state in a way that the neurons can communicate with each other," Clarke says. This may involve delivering a specific chemical to the brain or injecting it with a serum to restore neurotransmitter levels and oxygen levels in the brain.

"The next step would be to extend this deep-sleep procedure with astronauts who are to take part in human missions to Mars,"