Ryugu
Key facts
- What it is
- Near-Earth asteroid (Apollo group)
- Size
- About 900 m across
- Discovered
- 1999
- Spacecraft
- Hayabusa2 (2018–2019); samples returned 2020
- Orbit group
- Apollo
- Average distance from the Sun
- 1.19 au (about 180 million km)
- Time to go round the Sun
- 475 days
- Closest and farthest from the Sun
- 0.96 to 1.42 au
- Tilt of its orbit
- 5.9°
- Closest its orbit comes to Earth's
- 81,000 km (0.2 times the Moon's distance)
- Spins once every
- 7.6 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.
Ryugu is a dark, carbon-rich asteroid about 900 metres across, shaped like a spinning top with a ridge around its equator. Japan's Hayabusa2 spacecraft studied it from June 2018 to November 2019 and brought back about 5.4 grams of its material in December 2020.
The mission was ambitious. Hayabusa2 dropped small hopping rovers onto the surface, and in April 2019 it fired a copper projectile into Ryugu to dig an artificial crater, so that it could reach material from below the surface, protected from space weathering. It made two touchdowns to collect samples, the second near the new crater, and sealed them in a capsule that landed in the Australian outback.
Ryugu turned out to be a rubble pile covered with boulders, much rougher than expected, which made choosing a safe touchdown site difficult.
The samples are among the most primitive material ever studied. They closely match the rare CI chondrites, the meteorites whose chemistry is closest to the Sun's own. Unlike meteorites, they have never been exposed to Earth's air and water, so their delicate minerals and carbon compounds are untouched. They contain clay minerals and carbonates formed when water flowed through Ryugu's parent body, and a rich mix of organic molecules, including amino acids and uracil, one of the bases used in RNA.
Ryugu was discovered in 1999 by a survey telescope in New Mexico. Its name comes from a Japanese folk tale, in which a fisherman visits Ryugu, a palace under the sea, and returns with a mysterious box.
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 |
|---|---|---|
| 21 Dec 2033 | 7,100,000 km | 18 |
| 16 Feb 2047 | 21,000,000 km | 56 |
| 16 Nov 2063 | 21,000,000 km | 55 |
| 6 Dec 2076 | 1,600,000 km | 4.1 |
| 29 Dec 2101 | 8,800,000 km | 23 |
| 12 Nov 2105 | 29,000,000 km | 76 |