Mars was covered with seas and rivers a billion years later than previously thought, NASA revealed today. The announcement follows the discovery by an orbiting space probe of a new type of mineral spread widely across the planet.

It shows that liquid water remained on the surface as recently as two billion years ago. It could make a huge difference in whether Mars ever hosted life.

The mineral deposits are known as hydrated silica, commonly known as opal, and are tell-tale signs of where and when water was present in the ancient past.

They were detected over large regions of the planet by an instrument called an imaging spectrometer on the Mars Reconnaissance Orbiter. Scientists are still looking for traces of the water left on Mars today.

Before now, only two major groups of hydrated minerals – called phyllosilicates and hydrated sulphates – had been observed. Those were formed much earlier, between three and 3.5 billion years ago.

“This is an exciting discovery because it extends the time range for liquid water on Mars, and the places where it might have supported life,” said NASA scientist Scott Murchie.

Chief investigator Ralph Milliken said: “What’s important is that the longer liquid water existed on Mars, the longer the window during which Mars may have supported life.”

One region where the new mineral has been found is a giant rift on Mars called Valles Marineris that dwarfs the Grand Canyon on Earth.

Picture: The cream-coloured deposits in the photo are the newly discovered mineral. (NASA/JPL-Caltech/Univ. of Arizona).

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