The status of Pluto is about to change again. A century ago it went from an unknown entity to a new discovery, hailed as the ninth planet. A few years ago it traded that title for a designation as the first dwarf planet. Now, thanks to the New Horizons spacecraft currently en route to Pluto, the small world's distinction as "unexplored" is about to fall away.
Stamp enthusiasts may recall a block of postage stamps, issued in 1991, celebrating the planets paired with their spacecraft visitors, such as Viking with Mars and Pioneer 11 with Jupiter. One stamp in the series called attention to the aloneness and unknown-ness of Pluto. Its message, "Pluto not yet explored," struck some astronomers as a call to action.
Several mission designs and more than a decade later, New Horizons lifted off from Cape Canaveral in January 2006. Pluto was still a planet then. But in August of that year, the International Astronomical Union approved a resolution that defined the word planet in terms that excluded Pluto.
Triumphant Pluto-deniers and disgruntled Plutophiles still debate the Pluto decision, but both camps anticipate the findings that New Horizons will report upon its 2015 arrival. Already, the possibility of a new postage stamp is in the offing, drawn by space artist Dan Durda.
If you like the idea of a philatelic return to Pluto, please help the New Horizons team win over the U.S. Postal Service by signing their petition before March 13. Even if you communicate solely by e-mail and social networks, I hope you'll agree that "New Horizons First Spacecraft to Explore Pluto" deserves to find its place on the corners of envelopes "Forever."