Pluto Explored

Explanation: In 2006, NASA placed a 29–cent 1991 'Pluto: Not Yet Explored' stamp in the New Horizons spacecraft. In 2015 the spacecraft carried the stamp on its history-making mission to Pluto and beyond. With this stamp, the Postal Service recognizes the first reconnaissance of Pluto in 2015 by NASA's New Horizon mission. The souvenir sheet of four stamps contains two new stamps appearing twice. The first stamp shows an artists' rendering of the New Horizons spacecraft and the second shows the spacecraft's enhanced color image of Pluto taken near closest approach.

Pluto

Image credit: USPS/Antonio Alcalá © 2016 USPS