The biggest crater in the solar system has been discovered on Mars. Scientists believe it was blasted out of the Red Planet by another world around 1,200 miles wide – bigger than Pluto.

They say the discovery explains why Mars has strikingly different terrain in its northern and southern hemispheres. There are smooth lowlands in the north but a rough, heavily cratered landscape up to five miles higher in the south.

A relief map of Mars, using false colour, shows the dramatic
difference in height between north and south (NASA/JPL)

New research suggests that a giant area in the north, covering about 40 per cent of Mars’ surface, was caused by a massive impact at least 3.9 billion years ago.

Called the Borealis basin, it is 5,300 miles across and about four times wider than the next-biggest such feature on the planet, the Hellas basin.

The cause of the impact site was decided following intensive study of information from two spacecraft, Mars Reconnaissance Orbiter and Mars Global Surveyor.

Jeffrey Andrews-Hanna and co-authors Maria Zuber, of the Massachusetts Institute of Technology, and Bruce Banerdt of NASA’s Jet Propulsion Laboratory, California, report the new findings in the journal Nature this week.

The true nature of the impact basin was hidden by a line of giant volcanoes that formed along part of the crater’s rim, creating a huge region of high, rough terrain that obscured its outlines.

Astronomers believe that the Moon was formed when a similar impact by a body the size of Mars blasted material out of the Earth in the early days of the solar system. For more Mars news, including latest on Phoenix, check out Skymania Mars.

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