Space radiation would be likely to kill or severely weaken astronauts long before they reached Mars, a study by Nasa suggests.

New research has found that the assault on space travellers’ intestines would form at least as big an obstacle to reaching the red planet as the technological challenge.

The exposure on a trip to Mars or beyond would be likely to result in long-term functional impairments, such as ineffective nutrient absorption, or cancer.

Scientists made the discovery after exposing mice to low doses of electrically charged iron particles, one of the most harmful forms of galactic cosmic radiation (GCR).

Atoms and molecules that carry an electric charge are known as ions.

Heavy ions such as iron and silicon act like tiny, fast-moving bullets and are more destructive than X-rays and gamma rays, which are mass-less high frequency forms of light.

Life on Earth is protected from energetic heavy ions by the planet's magnetic field, which deflects them away.