It's been a long time coming, but the US Postal Service has released its designs for its 2016 stamps and one set rightfully features the biggest space story of 2015* - NASA's New Horizons mission to Pluto.
Top 10 Space Stories of 2015: Readers' Choice
In 2006, when the spacecraft was being prepped for its near-decade long odyssey to the outer solar system, principal investigator Alan Stern made sure a 1991-minted Pluto stamp was attached to the body of the spacecraft. That stamp, which included the type "Pluto - Not yet explored", had become a planetary exploration "call to arms", according to an Astronomy Magazine interview.
Indeed, Pluto was the final "classical" planet of the solar system to be explored, but on July 14, 2015, that changed dramatically when New Horizons blasted through the Pluto system, revealing the dwarf planet in all it's astonishing glory. Suddenly, the "planetary debate" was forgotten and Pluto and it's incredible system of moons wowed the world. Pluto has become the most fascinating, mysterious and awe-inspiring world, proving that the frozen outermost reaches of the solar system is a surprisingly dynamic place.