DART
The first test of moving an asteroid: a spacecraft deliberately crashed into a small moon.
Key facts
- Agency
- NASA (United States), with the Italian Space Agency
- Type of mission
- Kinetic impactor test
- Target
- Dimorphos, the moonlet of asteroid 65803 Didymos
- Launched
- 24 November 2021
- Status
- Completed 2022
DART, the Double Asteroid Redirection Test, asked a simple question: if an asteroid were ever found on course for Earth, could we push it aside by hitting it? The target posed no danger. Didymos is an asteroid about 780 metres across, and its small moon, Dimorphos, about 150 metres across, circles it every 11 hours and 55 minutes. A change in that short orbit could be measured from Earth with telescopes.
The impact
On 26 September 2022, after ten months in space, the spacecraft steered itself into Dimorphos at about 6.1 kilometres per second. Its camera sent back pictures until the last second, showing a rubble-strewn surface of boulders. A small Italian cubesat, LICIACube, released two weeks earlier, flew past and photographed the bright plume of debris that followed.
The result
Telescopes measured that the moon's orbit had shortened by about 33 minutes, far more than the minimum of 73 seconds that counted as success. The debris thrown out gave an extra push, roughly as large again as the spacecraft's own blow, because recoil from the plume acted like a rocket. Dimorphos was even reshaped. Material from the impact formed a long tail, and some of it may one day reach Earth and Mars as meteors.
Why it matters to meteorites
Didymos is an S-type asteroid whose light matches the ordinary chondrites, the most common meteorites, so DART tested the sort of body that delivers most meteorites. The European Hera mission is going back to measure the crater and the moon's mass.
Key dates
| Date | What happened |
|---|---|
| 24 November 2021 | DART launched on a Falcon 9 rocket. |
| 11 September 2022 | Released the Italian cubesat LICIACube. |
| 26 September 2022 | Struck Dimorphos at about 6.1 km/s. |
| 11 October 2022 | NASA announced that the moon's orbit had been shortened by about half an hour. |
See where this mission fits among all the others in the mission timeline.
Did you know?
DART was about the size of a small car and weighed roughly 570 kg when it struck.
It was the first time humans had changed the motion of a natural body in space.