By Steve Gorman (Reuters) – NASA’s DART spacecraft successfully slammed into a distant asteroid at hypersonic speed on Monday in the world’s first test of a planetary defense system, designed to prevent a potential doomsday meteorite collision with Earth. Humanity’s first attempt to alter the motion of an asteroid or any celestial body played out in a NASA webcast from the mission operations center outside Washington, D.C., 10 months after DART was launched. The livestream showed images taken by DART’s camera as the cube-shaped “impactor” vehicle, no bigger than a vending machine with two rect…