One thing you don’t expect when planning a nine-year mission to the most distant planet in our solar system is the eventuality that Pluto might not be a planet once you got there.
Yet that’s exactly what went down in 2006. That January, NASA launched its unmanned New Horizons probe, a baby grand piano-sized, 1,054-pound spacecraft, on the first-ever route to Pluto. Then, in August 2006, the International Astronomical Union demoted Pluto to the diminutive status of “dwarf planet.”