On July 14, at 7:50 a.m. ET, NASA's New Horizons spacecraft will make history by being the first to reach Pluto and its moons. History will also be made by a little postage stamp affixed to the craft that will be present at the very event that will make the slogan it contains no longer accurate.
The stamp was issued by the US Postal service in 1991 and says, "PLUTO: Not Yet Explored." It was part of a series of stamps (see gallery below) that depicted the nine planets in our solar system -- Pluto didn't lose its planetary status until 2006 -- along with the spacecraft that had been sent to explore them. In 1991, no one had yet launched a vessel to Pluto. But on Tuesday as New Horizons gets its closest look at the dwarf planet and begins sending data back to us here on Earth, Pluto's status will switch to "explored."
"It was my idea to send it," New Horizons Principal Investigator Alan Stern told Astronomy magazine. "For many years, people had waved that stamp around as sort of a call to arms -- as a motivating graphic. That stamp had been in so many presentations by that point, I knew it would please people to have it go along."
The stamp has been affixed to the body of the New Horizons craft, and in addition to having the distinction of being present at the event that will effectively invalidate it, it also will hold the record for being the postage stamp that's traveled the farthest.
Now, if it comes back marked "Return to Sender," we'll have some questions.