New Horizons

New Horizons left Earth on January 19, 2006, at 36,400 mph — the fastest launch velocity ever achieved — and still needed nine and a half years to reach Pluto. On July 14, 2015, it swept past the dwarf planet and transformed a blurry dot into a world: nitrogen glaciers flowing across a heart-shaped plain, mountains of water ice, and hazes tinting the sky blue.

Pluto turned out to be geologically alive, defying every expectation for a small frozen body. New Horizons flew on to Arrokoth in 2019, the most distant object ever explored, whose gentle two-lobed shape preserved a pristine record of how planetesimals first formed. The spacecraft continues outward through the Kuiper Belt today.