More evidence of flowing water on Mars

Small gullies can be seen on the slopes of some of the peaks to the upper left of the picture

New images taken from space show further evidence of gullies on the surface of Mars that may have been carved by water.

The pictures reveal channels in the peaks of sand dunes within one of the planet's southern craters.

Wide angle view of the area depicted in close-up

The pictures come from Nasa's Mars Global Surveyor (MGS) spacecraft, which is currently in orbit around the Red Planet.

Earlier this year, scientists at the US space agency and Malin Space Science Systems, who operate MGS, presented photographic evidence pointing towards the presence of recent, running water on Mars. "Recent" in this sense means within the last two million years.

The announcement, which ran counter to prevailing theories about the presence of water on the Red Planet, caused a sensation. The "discovery" gave fresh impetus to Nasa exploration plans that were under threat at the time because of the loss of two probes.

Hale crater

What is happening on Mars?

Compared with the rest of the Martian surface, the pictured channels appear to be extremely young

Some of the channels are free of dust, suggesting they were only recently washed clean

Scientists suggest that sudden floods have cut the grooves

Atmospheric pressure is so low on Mars that liquid water will rapidly boil away

Any evaporating seepage would be likely to freeze the ground and dam waters building up behind

These waters might burst out, flooding down the side of cliffs and cutting gullies

Each flood could contain as much as 2,500 cubic metres of water - enough water to fill seven community-sized swimming pools

Volcanic heating could be driving the whole process

The new pictures are of the 136-kilometre- (85-mile-) wide Hale crater in the planet's southern hemisphere.

The Mars Global Surveyor made the observations on 10 November. The top of the picture shows peaks up to 630 metres (2,070 feet) above the crater floor.

Small gullies can be seen on the slopes of some of the largest peaks. Nasa scientists believe these channels may have been carved by running water.

The new pictures add to a growing body of evidence gleaned by the MGS which suggests that water could exist in a porous layer of rock buried just below the Martian surface.

If liquid water does still flow on Mars, and some experts remain sceptical, the planet's southern hemisphere would be a good place to look. More than 90% of the gullies are located there, in the cooler areas away from sunlight.

Martian autumn

Winter in the Martian southern hemisphere begins in mid-December. Over the next few months, Nasa scientists will examine closely new pictures of the planet in an attempt to bolster their evidence.

Liquid water is the key ingredient for supporting life. If the discovery were confirmed, it would have profound implications for the chance of finding existing, microbial extra-terrestrial life.

But some experts are cautious about the findings. It had been thought that water on Mars was in the form of ice below the surface and unlikely to run free on the surface.

Mars enthusiasts will be awaiting eagerly the opportunity, in the next few years, to place a lander on the surface of the planet in an attempt to resolve the question one way or the other.