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Serious stomach upsets could be one of the biggest obstacles to distant space travel.

Scientists at NASA have found that radiation exposure sustained on a trip to Mars or further into space could result in major damage to astronauts' stomachs and intestines, resulting in long term problems.

Astronauts could suffer problems which could lead to their death, such as an inability to absorb nutrients or even develop cancer.

They discovered the issue by exposing mice to doses of charged iron particles, or ions, known to be one of the most harmful forms of galactic cosmic radiation.

The aim was to simulate what astronauts would experience in deep space.

The mice exposed to the heavy ions failed to absorb nutrients properly, formed cancerous polyps, and exhibited signs of an increasing number of cells that stopped dividing.

Only a low dose was given to the mice, but the damage appeared to be permanent.

The researchers also found that exposure to heavy ions on space trips could cause impairment to brain tissue and accelerated ageing.

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Dr Kamal Datta, the lead scientist at NASA's specialised centre of research at Georgetown university, said it was difficult to protect astronauts from harmful effects of radiation with the current technology.

"While short trips, like the times astronauts travelled to the moon, may not expose them to this level of damage, the real concern is lasting injury from a long trip such as a Mars or other deep space missions which would be much longer," he said.

It may be possible to use medicines to counter the effects of space radiation - but the technology has not been developed yet.

"It is important to understand these effects in advance so we can do everything we can to protect our future space travellers," Dr Datta said.

Humans and animals on Earth are protected from the destructive power of the ions by the atmosphere.