Missions · Space Codex
New Horizons
The first spacecraft to Pluto, and the only one to explore a Kuiper belt object up close.
Pluto and the Kuiper belt
At a glance
Key points
Now past 60 AU, it studies the outer heliosphere.
- Pluto flyby 14 July 2015
- Arrokoth flyby 1 January 2019
- Past 60 AU since October 2024
A world nobody expected
Instead of a frozen relic, New Horizons found glaciers of nitrogen ice, water-ice mountains and a hazy blue atmosphere on Pluto.
Arrokoth, a pristine relic
On 1 January 2019 the spacecraft flew past Arrokoth, a reddish body about 35 km long made of two flattened lobes joined at a narrow neck. It is the most distant object ever explored up close. Its smooth, gently fused shape suggests the two lobes formed together and touched at walking pace, a strong hint that planetesimals in the outer solar system grew by gentle collapse rather than violent collisions.
Liquid on Pluto?
In August 2026 the team reported a new reading of 2015 images: dark streaks at the northern edge of Sputnik Planitia may have been wetted from time to time by liquid nitrogen seeping up through cracks, perhaps from melting at the base of the glacier. It is not rain, which Pluto's conditions rule out. If confirmed, it would be the first evidence of liquid flowing on Pluto in the recent past.
Sleeping through the Kuiper belt
To save fuel and staff time, New Horizons now spends long stretches in hibernation, waking to send data. Its latest sleep, 321 days, ended on 23 June 2026 with every status beacon green. Its ultraviolet spectrograph, particle detectors and student-built dust counter keep sampling the outer heliosphere, while astronomers search for another Kuiper belt object within reach. None is known yet.
What we still don't know
Whether Pluto hides a liquid ocean beneath Sputnik Planitia.
Missions
- 2006–
New Horizons
NASAActivePluto flyby 14 Jul 2015; Arrokoth 1 Jan 2019; now studying the outer heliosphere.
Related entries
- PlutoDwarf planet · heart of the Kuiper belt
- CharonPluto's half-sized partner
- 486958 ArrokothThe most distant world explored up close
Sources
- NASA Science: New Horizons finds evidence of recent liquid on Pluto's surface (opens in a new tab)
- NASA Science: New Horizons (opens in a new tab)
- NASA Science: New Horizons wakes from hibernation (opens in a new tab)
- NASA: New Horizons to continue exploring the outer solar system (opens in a new tab)
Last reviewed against these sources. Built from public NASA, ESA and JPL data; not affiliated with or endorsed by any agency.