Space

Late last month, NASA announced the winners of 12 awards for studying the biological effects of radiation. Topping the list is a $1.75 million project to irradiate up to 18 squirrel monkeys in an effort to find out what space radiation does to the central nervous system.

If it goes ahead, the experiment will be the first NASA-funded primate project to begin in more than 30 years. What will the experiment do and what does NASA hope to learn? New Scientist investigates.

What will this new experiment entail?

A group at Harvard Medical School's McLean Hospital in Belmont, Massachusetts, will expose the monkeys to a single dose of radiation that will be equivalent to the total amount of radiation astronauts will absorb during a three-year-long Mars mission. The monkeys' performance before and after exposure will be tested by measuring how they respond to visual cues on a computer touch screen.

The experiment is designed to investigate the effects of solar flares and galactic cosmic rays: both will bombard astronauts with charged particles in greater numbers once they leave the protection of Earth's magnetosphere.

Why does NASA want to do this experiment?

Since 2004, the US has been following a plan to return astronauts to the moon, with the eventual aim of going to Mars. There are hints that space radiation affects the brain, but it is still unclear how much of a risk it poses to deep-space explorers. NASA says it wants to find out what is needed to protect them.

How is this different from the radiation research NASA has done before?

The agency's last research project on primates began in the early 1970s, when NASA and the US air force studied the effect of radiation on cataract formation in rhesus monkeys.

But NASA has been examining the neurological effects of radiation for some time. In 2007, a helmet covered with particle counters and an electroencephalograph were sent to the International Space Station to assess how astronaut brain activity changes in real time in response to radiation. To date, the only animal research on the neurological effects of space radiation has been done in rodents.

What has the animal research shown so far?

Experiments on mice and rats have shown that irradiation can affect learning and memory. Rats, for example, have a difficult time navigating mazes and seem less interested in novel objects if they have been exposed to radiation. They also have a harder time learning to press a lever for more food and experience more anxiety in stressful situations.

In many experiments, the effects are similar to those seen in older rats. The cause of the damage is still poorly understood, but radiation is known to create highly reactive oxygen-containing molecules in the body. Such molecules are also suspected to contribute to the effects of ageing.

Why extend the study to primates?

"The data we have now, I think, is a basis for concern," says Bernard Rabin of the University of Maryland, Baltimore County, who has received support from NASA to study radiation effects on rodents. "There is a potential for cognitive deficits for astronauts within the dose range that NASA expects they would experience on a Mars mission."

But rat behaviour is too distant from human behaviour to allow straightforward predictions of how radiation will affect astronaut performance and brain function. To make a solid comparison with humans, a primate model is essential.

When will the experiment begin?

It's not yet clear. The research proposal is still awaiting approval by the Brookhaven National Laboratory in Upton, New York, where the irradiation would take place.

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