Bennu
Key facts
- What it is
- Near-Earth asteroid (Apollo group)
- Size
- About 490 m across
- Discovered
- 1999
- Spacecraft
- OSIRIS-REx (2018–2021); samples returned 2023
- Orbit group
- Apollo
- Average distance from the Sun
- 1.13 au (about 170 million km)
- Time to go round the Sun
- 437 days
- Closest and farthest from the Sun
- 0.9 to 1.36 au
- Tilt of its orbit
- 6°
- Closest its orbit comes to Earth's
- 480,000 km (1.3 times the Moon's distance)
- Spins once every
- 4.3 hours
An au (astronomical unit) is Earth's average distance from the Sun, about 150 million km. Orbit figures are from open tracking data, figures last updated 1 Nov 2026.
Bennu is a small, dark asteroid about 490 metres across that has been studied more closely than almost any other. NASA's OSIRIS-REx spacecraft arrived in December 2018, mapped it in great detail and on 20 October 2020 reached down to collect a sample. The capsule landed in the Utah desert on 24 September 2023 carrying about 120 grams of rock and dust, the largest sample ever returned from an asteroid.
The visit was full of surprises. Bennu's surface was covered in boulders instead of the expected fine gravel, and the asteroid was seen flinging small pebbles into space. When the sampling arm touched down, it sank into the surface as if into a ball pit, showing that the outer layer is a loose heap held together by Bennu's very weak gravity.
Bennu's samples are carbon-rich and water-altered, like the most primitive carbonaceous chondrites. They contain amino acids, including many of those used by life on Earth, all five of the bases found in DNA and RNA, and salts that formed as salty water evaporated inside its parent body long ago. They show that many of the ingredients for life were present on small bodies in the early Solar System.
Bennu's orbit has been measured with exceptional precision. Scientists calculate a small chance, about 1 in 2,700, that it could strike Earth in the late 2100s. Put the other way round, that is a 99.96 per cent chance that it will miss. Tracking will continue, and Bennu is one of the best-understood asteroids there is.
Coming close to Earth
Its next passes within about 30 million km of Earth, worked out from its orbit. Each one is a safe miss.
| Date | Distance | In Moon distances |
|---|---|---|
| 11 Feb 2037 | 15,000,000 km | 38 |
| 9 Feb 2043 | 14,000,000 km | 38 |
| 14 Nov 2048 | 18,000,000 km | 47 |
| 7 Mar 2049 | 27,000,000 km | 71 |
| 30 Sept 2054 | 5,900,000 km | 15 |
| 23 Sept 2060 | 750,000 km | 1.9 |