New Horizons
The first visit to Pluto, and to Arrokoth, a pristine building block of the planets.
Key facts
- Agency
- NASA (United States)
- Type of mission
- Flybys of Pluto and a Kuiper belt object
- Target
- Pluto and its moons; 486958 Arrokoth
- Launched
- 19 January 2006
- Status
- Operating in the Kuiper belt
New Horizons is the fastest spacecraft ever launched directly from Earth. After a gravity assist from Jupiter in 2007, it flew past Pluto on 14 July 2015, revealing a world of nitrogen-ice plains, water-ice mountains and a thin blue haze, far more active than expected.
Arrokoth
On 1 January 2019 it flew past a much smaller object, about 36 kilometres long, more than 6.5 billion kilometres from the Sun. Arrokoth turned out to be two flattened lobes gently joined at a narrow neck. It is red, covered with organic material, and has very few craters.
The shape matters. The two lobes must have come together slowly, at walking pace or less, which means they formed side by side in a calm cloud of pebbles that collapsed under its own gravity. Arrokoth is a planetesimal: a surviving example of the bodies that grew into planets, almost unchanged for 4.5 billion years.
A dust counter
New Horizons carries an instrument built by students, the Venetia Burney Student Dust Counter, named after the eleven-year-old girl from Oxford who suggested the name Pluto in 1930. It counts dust grains striking the spacecraft. Far beyond Neptune it has found more dust than expected, perhaps because the Kuiper belt extends further than thought.
Why it matters to meteorites
The way Arrokoth formed supports the same pebble-collapse idea used to explain how chondrite parent bodies grew in the inner Solar System. Kuiper belt dust also drifts inwards, and some micrometeorites collected on Earth may come from there.
Key dates
| Date | What happened |
|---|---|
| 19 January 2006 | New Horizons launched on an Atlas V rocket. |
| 28 February 2007 | Flew past Jupiter for a gravity assist. |
| 14 July 2015 | Flew past Pluto. |
| 1 January 2019 | Flew past Arrokoth, the most distant object ever visited. |
See where this mission fits among all the others in the mission timeline.
Did you know?
New Horizons carries some of the ashes of Clyde Tombaugh, who discovered Pluto in 1930.
Its signals from Arrokoth took more than six hours to reach Earth.