On February 15, 2013, the people of Chelyabinsk, Russia, witnessed something terrifying. A six-story-tall asteroid weighing nearly 10,000 metric tons tore through the atmosphere at more than 64,000 km ...

Because their orbits are unstable, a possibility exists that the asteroids could break off from their current trajectory and one day head on a collision course for Earth. The Venusian space rocks are ...