London - The theory that there could once have been life on Mars was dealt a blow yesterday after a scientist claimed the red planet's giant canyons were formed by vast dry floods rather than water.
The icy equivalent of the rivers of ash which erupt from volcanoes may have eroded the surface of Mars, according to the controversial new theory, published in the journal New Scientist.
Australian geologist Nick Hoffman said that "density flows", which can travel at high speed and cover vast areas, may have formed the canyons on the planet.
Just as the city of Pompeii was destroyed by the gas, ash and rubble which erupted over it in 79 A.D., Mars may have been covered in a river of supercooled dry ice 3.5 billion years ago.