An asteroid big enough to wipe out a city will zip harmlessly between Earth and the moon's orbit this weekend. Saturday’s close encounter will offer astronomers the chance to study a space rock from just over 100,000 miles away. That’s less than half the distance from here to the moon. While asteroid flybys are common, NASA says a big one like this comes this close only once a decade. Scientists estimate its size somewhere between 130 feet and 300 feet. It won't be back this way again until 2026.
