Laurel (United States) (AFP) – NASA’s DART mission to test deflecting an asteroid using “kinetic impact” with a spaceship is just one way to defend planet Earth from an approaching object — and for now, the only method possible with current technology. The operation is like playing billiards in space, using Newton’s laws of motion to guide us. If an asteroid threat to Earth were real, a mission might need to be launched a year or two in advance to take on a small asteroid, or decades ahead of projected impact for larger objects hundreds of kilometers in diameter that could prove catastrophi…