Boffins have found evidence that suggests an ancient glacier was once at the bottom of a huge chasm known as the Grand Canyon of Mars.

It has long been speculated that glacial action formed the massive Valles Marineris canyon, which stretches for about 4,000km (2,500 miles) along the surface of the Red Planet. But this theory has proven controversial and unproven.

A team from the Bryn Mawr College in Pennsylvania and the Freie Universitat in Berlin claimed they had found a deposit of a "new type" of jarosite, a sulphate mineral often found on Earth, within the canyon.

On Earth, jarosite is formed when atmospheric sulphur is trapped within ice and then warmed by the Sun, leaving behind a sulphate of potassium and iron. The boffins claimed they spotted jarosite halfway up a 4.8km (3-mile) high cliff at the western end of the chasm.

The process the boffins hypothesised has been observed here on Earth within the glaciers on Svalbard, a Norwegian archipelago in the Arctic Ocean.

If the scientists are right, it could mean that much of the surface of Mars was carved by the slow movement of glaciers.

A paper on the research was published in the journal Geology. ®