Munich

Past evidence: Reull Vallis, a channel once formed by flowing water, as seen from Mars Express. Credit: ESA/DLR/FU BERLIN/G. NEUKUM

Spectacular pictures from the European Space Agency's Mars Express mission are being beamed back to Earth each day now. Their beauty and clarity are thrilling geologists — and laying the foundations for the richest database ever gathered of any planet, even our own.

The pictures are the product of the High Resolution Stereo Camera (HRSC). The €70-million (US$87-million) instrument was originally developed by scientists at the German Space Agency for Russia's failed Mars '96 mission and has been updated for Mars Express.

Digital processing helps to create the stunning three-dimensional views, but instrument builders say that the pictures are ‘real’. Like a normal camera, the HRSC takes photographs through a single lens, which is pointed at the planet's surface each time Mars Express's elliptical orbit reaches its lowest altitude, about 250 kilometres.

Behind the lens, however, is a complex system of parallel sensors, which are sensitive to red, green, blue and near-infrared light. By shooting points on the planet's surface from three different perspectives — forwards, downwards and backwards — the camera collects information that is then processed back on Earth to create a digital model of the terrain with a spatial resolution of 10 metres per pixel or less.

As of 23 January, after 10 days of observation, 2 million square kilometres — or about 2% of the Mars surface — had been surveyed. After some 5,000 flyovers, which would take a maximum of four Earth years to complete, the topography of Mars would have been surveyed more comprehensively than that of Earth, where military considerations prevent complete topographical surveys from reaching public databases.

“We can clearly make out slopes and valleys that were almost certainly eroded by running water,” says Gerhard Neukum, a planetary scientist at the Free University in Berlin, and principal investigator on the HRSC project. “Moreover, we have found moraines, which proves there must have been glaciers on Mars.”

The camera might also be able to spot the large white parachutes of the Beagle 2 lander, which went missing on 25 December last year. But so far the search has been in vain. “There is dust and lack of contrast where we assume it must be,” says Neukum.