Amazing dunes reveal climate change on Mars

Spectacular detailed images of Mars have revealed how climate change shaped the Red Planet over millions of years.

More than 1,000 observations taken by the high resolution camera on NASA's Mars Reconnaissance Orbiter have revealed details on the surface as small as a desk.

A number of dramatic icy dunes are thought to reflect how the Martian climate changed over time.

One picture shows layered deposits in the north polar region, which have formed a layered stack of dusty ice up to two miles thick. The layer exposed on the cliff face shows not just dusty ice but sand as well, suggesting each layer was a dune field that was only later covered by ice as the temperature cooled.

The colours seen in the images are not the natural colours seen with normal human vision, but are important to distinguish ice, frost, dust and rock on the Martian surface.

The 1,005 Mars observations made between April 26 and July 21st are the latest to be released by scientists working on the High Resolution Imaging Science Experiment. The camera has revealed the highest resolution images of a planet's surface ever seen from an orbiter.

'Scientists all over the world are already using these images to understand many previously-unexplained phenomena on the Red Planet. We might also discover brand new types of features never seen before,' a spokesman said.

The data forms part of NASA's mission archive, called the Planetary Data System.

The orbiter is being used to identify minerals and individual rock outcrops - information needed to choose future Mars landing sites.

Alfred McEwen, HiRISE principal investigator, is involved in selecting the best possible landing site for NASA's Mars Science Laboratory that is slated to launch in 2009.

He said recent evidence from both U.S. and European Mars orbiters shows clays that contain iron, magnesium and aluminium are widespread throughout ancient Mars bedrock.

'That's a shocking discovery,' he said.

'The actual environments and processes that deposited and altered these clay minerals is poorly understood. But these places have very quickly become where we have to go with future rovers and sample-return missions.'

Scientists hope studies of Mars will reveal more about how the Earth was formed. They believe life in our solar system formed during or even before the Late Heavy Bombardment of 3.9 billion years ago, when large impact craters were formed on the Moon and the surrounding planets.

'We know that Mars underwent heavy bombardment and that it was water-ice rich,' McEwen said.

'The rock record from this time is much better preserved on Mars than it is on Earth.'

HiRISE images show that part of Mars' hardened, ancient crust is exposed on the planet's surface as 'megabreccia,' a collection of large, chaotic rock fragments that formed from energetic events, mostly large impacts on ancient Mars.Three potential sites for the new Mars Science Laboratory are within rover reach of the deposits.