The red plains of Mars were once covered by a vast ocean... and lush planet could have supported extra-terrestrial life



A vast ocean once covered a third of the surface of Mars, scientists revealed last night.

Far from being a dusty red desert, our neighbouring planet was once wet and rainy - raising the prospect that it was home to extra-terrestrial life.

The ocean stretched across 36 per cent of the red planet around 3.5 billion years ago and contained 30million cubic miles of water.

Life-sustaining: The ocean and shoreline of Mars as it might have looked 3.5billion years ago

The discovery is based on a detailed study of the dried-up river deltas and thousands of river valleys that scatter the Martian surface.

Scientists from the University of Colorado at Boulder are unsure why the water vanished, but many suspect traces of the ocean remain in ice buried deep beneath the surface.

Dr Brian Hynek, who took part in the study published in the journal Nature Geoscience, said Mars probably once had a water cycle like the Earth's - with rain falling into rivers and oceans, evaporating into the atmosphere and forming clouds.

The Martian sea - which has not been named - contained around a tenth of all the water found in Earth's oceans, he said. Mars is slightly more than half the size of Earth.

Long lived oceans may have teemed with microbes at a time when the life is thought to have also been starting on Earth.

Vast: Mars's northern hemisphere ocean held 10 times more water than all the Earth's, research suggests

Using detailed maps of Maps created by orbiting Nasa and European Space Agency spacecraft, the researchers looked at the remains of 52 river deltas, each fed by numerous river valleys.

More than half were at the same altitude and appeared to mark the boundaries of a massive ocean. The amount of water in the ocean would have formed the equivalent of a 1,800 foot layer spread out over the entire planet.

Barren: Dry and dusty, how Mars looks today

Co-author Dr Gaetano Di Achille said: ‘On Earth, deltas and lakes are excellent collectors and preservers of signs of past life. If life ever arose on Mars, deltas may be the key to unlocking Mars' biological past.’

A second study also detected around 40,000 river valleys - four times more than have previously been spotted.

The valleys were the source of sediment that was carried downstream and dumped into the deltas.

Dr Hynek said: 'The abundance of these river valleys required a significant amount of precipitation.'

The idea of a large ancient ocean on Mars has been debated for two decades. However, the new study provides compelling evidence that the sea existed - and raises tantalising questions about the planet's history.

'One of the main questions we would like to answer is where all of the water on Mars went,’ said Dr Di Achille.