Number 432 (Story #3), June 7, 1999 by Phillip F. Schewe and Ben Stein THE SURFACE OF MARS has been mapped to 13-meter precision, better than for some places on Earth. Laser light sent from and returning to the orbiting Mars Global Surveyor spacecraft reveals that the southern hemisphere is one big highland (6 km higher) compared to the northern hemisphere. Surface water, if there was any, would have collected in the North, although there is not yet definitive proof of any boreal ocean. One thing that is known about the northern lowland: it is the flattest place in the solar system. The South's elevation is due at least in part to an immense amount of material raised during an ancient impact which fashioned a huge crater known as the Hellas basin. (Science, 28 May 1999.)