New Horizons (Pluto Flyby)

Launched in 2006 — before Pluto was even demoted from planet status — New Horizons traveled 5 billion km to reach the dwarf planet in July 2015. The first close-up images revealed a geologically active world with nitrogen glaciers, a heart-shaped plain (Tombaugh Regio), and mountains of water ice as tall as the Rockies. Nobody expected Pluto to be interesting. New Horizons proved it was one of the most dynamic bodies in the solar system. It then flew past Arrokoth in 2019, the most distant object ever visited.