Giant Crater Explains Strange Shape of Mars

A giant crater made by an asteroid or comet explains why Mars is so lopsided, with a basin on one hemisphere and high terrain on the other, three separate teams of scientists said today.
As reported in the journal Nature, the impact gouged out a hole 5,200 miles across and 6,500 miles long -- the size of the combined areas of Asia, Europe and Australia.
It would be the largest impact yet found in the solar system.

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