Scientists have made a discovery that could lead to a revolutionary drug that actually reverses ageing.

The drug could help damaged DNA to miraculously repair and even protect Nasa astronauts on Mars by protecting them from solar radiation.

A team of researchers developed the drug after discovering a key signalling process in DNA repair and cell aging.

During trials on mice, the team found that the drug directly repaired DNA damage caused by radiation exposure or old age.

'The cells of the old mice were indistinguishable from the young mice after just one week of treatment,' said lead author Professor David Sinclair.

Human trials of the pill will begin within six months.