Next Exit: Pluto!

Explanation: After more than nine years in space, on a voyage taking it farther to its primary destination than any mission before it, NASA's New Horizons spacecraft is within one astronomical unit of Pluto - meaning it's closer to Pluto than the Earth is to the Sun. Speeding along at nearly 33,000 miles per hour, New Horizons sailed past its last symbolic deep space mile marker at about 5:20 p.m. EDT on March 10.


Image credit: Johns Hopkins University Applied Physics Laboratory.