Water reserves found on Mars

Pits and smooth terrain may be made of dust and ice

By BBC News Online science editor Dr David Whitehouse

There could still be vast quantities of water on the planet Mars.

A new analysis of images returned by the Mars Global Surveyor (MGS) spacecraft provides "observational evidence for near-surface water-ice," say scientists.

At mid-latitudes in both the northern and southern hemispheres "unique, young terrain" has been seen that appears to be made of layers of dust cemented together with water-ice.

The total amount of water-ice may be about 40,000 cubic km (almost 10,000 cubic miles), or enough to cover the entire planet to a depth of about 25 centimetres (10 inches).

If confirmed, this finding, along with other evidence of recently flowing water on Mars, will make life on the Red Planet more likely and provide an invaluable resource for future colonists.

Young terrain

A survey of over 8,000 MGS images undertaken by scientists at Brown University in the US has revealed examples of smooth terrain at mid-latitudes on the planet.

The terrain has few impact craters, suggesting it is very young, perhaps only 100,000 years old.

Water may have flowed on Mars recently

"We infer the terrain to be made of dust held together in some way," write the researchers in the journal Nature.

Grooves in the landscape and the occasional pit allow them to determine how strong and deep it is.

They believe that the dust layer is porous and between one and 10 metres (3-32 feet) deep. It is in the pores that the scientists believe ice has formed that cements the dust particles together.

Calculations suggest that the winds on Mars are not strong enough to disrupt the surface. Only the occasional more energetic dust devils that wind over the Martian surface have enough energy to scatter the dust.

Climatic cycles

According the one theory of climatic cycles on Mars - that changes in its orbit produce wetter and warmer conditions every 100,000 years or so - there was much more water-ice in Martian soils in the past.

Only dust devils can disturb the surface

Even though it is in slow decline, the sheer quantity and proximity to the surface of the water-ice has profound implications for life on Mars, in the past as well as the future.

Sifting the ice-crusted dust to look for signs of fossilised or dormant micro-organisms may become the top priority for unmanned probes searching for evidence of life on the planet.

Also, the readily available water would be a vital asset for future colonists, who could use it to drink as well as to manufacture oxygen and hydrogen-based rocket fuel for their return journey to Earth.