New Horizons Pluto Flyby
NASA's New Horizons spacecraft made the first close flyby of Pluto
July 14, 2015
The Last Unexplored World
On July 14, 2015, NASA's New Horizons spacecraft swept past Pluto at 14 kilometers per second, completing humanity's first close-up survey of every classical planet in the solar system. Pluto had been a blurry dot in even the best telescopes — a mysterious object at the edge of the solar system discovered in 1930. New Horizons changed that in an instant. The first clear images revealed a world with mountains of water ice as tall as the Rockies and a vast, heart-shaped nitrogen plain now called Tombaugh Regio.
A 9.5-Year Journey
New Horizons launched in January 2006 — the same year the International Astronomical Union reclassified Pluto as a dwarf planet. The spacecraft traveled more than 4.8 billion kilometers to reach its target. Because radio signals take about 4.5 hours to travel from Pluto to Earth, mission controllers had to upload commands far in advance and trust the probe to execute them on its own. The closest approach lasted only a few minutes, but the probe collected enough data to keep scientists busy for years.
What It Revealed
Scientists expected a dead, geologically inert world. Instead they found evidence of recent geological activity — possible ice volcanoes, flowing nitrogen glaciers, and a hazy atmosphere with multiple layers. Pluto's largest moon, Charon, showed a deep canyon system and a reddish polar cap stained by organic compounds. New Horizons continued past Pluto and in 2019 flew by a small Kuiper Belt object called Arrokoth, the most distant object ever visited by a spacecraft. Use the date calculator to find how many days have passed since the flyby.