Astronomers have discovered three asteroids that have been hidden by the glare of the sun. The space rocks are circulating in an area between the orbits of Earth and Venus, and two of them are so massive they're described as "planet killers." Astronomers at NASA's Center for Near Earth Object Studies say one of them has an orbit path that could one day force it to come into contact with Earth. "Come into contact" is an understatement, according to astronomers who say it would "cause planetwide destruction." But planetary scientists say something like that happening in the foreseeable future has "extremely low probability."