Mars crater big enough to bury Everest

A LASER-GUIDED relief map of Mars has found that it is a planet of extremes: shaped like a pear, with both the highest mountain and the deepest crater in the Solar System - the latter wide and deep enough to swallow Mount Everest.

The new three-dimensional map of the planet shows that the range between its highest and lowest points is 20 miles (32 km) - about 50 per cent greater than on Earth.

Part of that range stems from the crater named Hellas, which was probably created when an asteroid blasted into the surface billions of years ago. According to David Smith of the US space agency Nasa, the crater is deeper than any other in the Solar System, stretching 1,500 miles (2,400 km) across and six miles (10km) down.

The impact threw material thousands of miles across Mars's surface, and probably created the strange effect which means that the planet slopes from the north to the south pole.

By contrast Mars is also home to a volcanic mountain, called Olympus Mons, that soars almost 17 miles (27 kilometers) above "sea level" - the planet's average elevation - making it the highest volcano in the solar system.

The map of Earth's next-door planetary neighbour was created by the orbiting Mars Global Surveyor spacecraft, which beamed pulses of laser light at 27 million points around the planet.

Measuring the time taken for those pulses to return produced a three- dimensional map accurate to at least 42 feet (13m), with those in the flatter southern hemisphere precise to 6 feet (2m).

"This means that we now know the topography of Mars better than many continental regions on Earth," said Dr Carl Pilcher at Nasa. "It should inspire a variety of new insights about the planet's geologic history and the ways that water has flowed across its surface during the past four billion years."

The work is reported in the latest edition of Science magazine. The new data has helped scientists estimate the amount of frozen water at the Martian poles.

The upper limit is now thought to be between 800,000 and 1.2 million cubic miles, or about 1.5 times the amount of ice covering Greenland.