NASA's Messenger probe began its seven-year journey to Mercury early Tuesday, blasting off from Cape Canaveral, Fla., at 1:16 a.m. CDT after a day's delay caused by Tropical Storm Alex.
Although Mercury is about 50 million miles from Earth -- a distance that would take less than three months on a direct route -- Messenger will follow a convoluted path designed by Chen-Wan Yen of the Jet Propulsion Laboratory in Pasadena, Calif. Its journey will total nearly 5 billion miles as the craft sweeps repeatedly by the inner planets to slow it enough to orbit Mercury.
It will be the first visit to the innermost planet, where temperatures range as high as 850 degrees, since Mariner 10 swung by three times in 1974 and 1975. That mission mapped about 45 percent of Mercury's surface, revealing a heavily cratered planet with a surface that has not been altered by the volcanism, erosion and earthquakes that have transformed Venus, Earth and Mars.
Planetologists hope that, with the exception of the cratering, Mercury's surface will turn out to be as it was when it was created along with the other planets 4.5 billion years ago.