Long space visits 'quicken ageing'

15 April 2008 12:00am

Astronauts who spend too long in space may end up prematurely old and prone to cancer, new research suggests.

The findings from US scientists could have major implications for plans to build moon bases and send explorers to Mars.

Researchers at Georgetown University Medical Centre in Washington DC found that exposure to space radiation could be more damaging than previously realised.

Tests showed that the high energy particles which flood through space triggered a harmful oxidative stress response in mice.

Their cells generated large numbers of free radicals - destructive molecules which can damage DNA, leading to cancer. The effect was most pronounced in the gut, where the stress response continued for as long as two months after exposure to the radiation.

In a report the scientists, funded by the American space agency Nasa, said the kind of damage they observed is likely to increase the risk of colon cancer. They also found that mice subjected to radiation aged rapidly, turning their fur prematurely grey.

Dr Kamal Datta, who led the study at Georgetown's Lombardi Comprehensive Cancer Centre, said: "Radiation exposure, either intentional or accidental, is inevitable during our lifetimes. But with plans for a mission to Mars, we need to understand more about the nature of radiation in space. There is currently no conclusive information for estimating the risk that astronauts may experience."

The kind of radiation found in space is known as high linear energy transfer (LET) radiation.

It consists mainly of high energy sub-atomic particles and causes concentrated damage to living tissue. Low LET radiation, such as gamma and X-rays which are used for medical imaging and treating cancer, tend to cause more diffuse damage. Dr Datta's team found that low LET radiation did not generate free radicals in the same way as high LET radiation.

Solar flares pour out large quantities of high LET radiation which could present a real hazard to space farers. People on Earth are shielded by the planet's atmosphere, but in space there is nothing to stop astronauts being blasted by the particles.

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