Comet Wild 2
The comet whose dust Stardust brought back to Earth, and which turned out to contain grains made close to the young Sun.
Key facts
- Designation
- 81P/Wild
- Type
- Jupiter-family comet
- Orbital period
- about 6.4 years
- Closest to the Sun
- about 1.6 AU (about 240 million km)
- Farthest from the Sun
- about 5.3 AU
- Tilt of orbit
- about 3°
- Nucleus
- about 5.5 × 4.0 × 3.3 km
- Discovered
- by Paul Wild at Zimmerwald near Bern on 6 January 1978
- Returns
- at perihelion in 2022; next in 2029
Orbit
Until 1974 Wild 2 orbited between Jupiter and Uranus. On 10 September 1974 it passed within about 1 million km of Jupiter, which threw it inward onto its present path, between Mars and Jupiter. It had therefore made few passes close to the Sun, and its surface was thought to be fresh.
Size and nature
Stardust's images showed a rounded body about 5 km across covered with deep, flat-floored pits and pinnacles, with jets rising from more than 20 places.
History
The Swiss astronomer Paul Wild found it in January 1978, four years after its Jupiter encounter.
Missions
Stardust flew through the comet's coma on 2 January 2004, passing about 237 km from the nucleus. A collector filled with aerogel, a glassy foam so light it is mostly air, caught thousands of dust grains travelling at about 6 km/s. The capsule landed in Utah on 15 January 2006. The grains surprised everyone. Many were not icy interstellar dust but minerals formed at very high temperatures, including olivine, pyroxene and a grain like the calcium-aluminium-rich inclusions found in chondrite meteorites. Some chondrule-like fragments were found too. They show that material made close to the young Sun was carried out to where comets formed, mixing the Solar System from inside to out. Scientists also identified the amino acid glycine in the samples.
Space missions
- Stardust The first sample from a comet, and the surprise that it contained rock formed close to the Sun.
Key dates
| Date | What happened |
|---|---|
| 10 September 1974 | Comet Wild 2 passed close to Jupiter, which threw it into the inner Solar System. |
| 6 January 1978 | Paul Wild discovered Comet Wild 2. |
| 2 January 2004 | Stardust flew through the coma of Comet Wild 2 and collected its dust. |
| 15 January 2006 | The Stardust capsule landed in Utah with dust from Comet Wild 2. |
Did you know?
Its name is pronounced 'Vilt', after its Swiss discoverer.
Volunteers at home helped search Stardust's aerogel for tiny interstellar grains.
A white grain from Wild 2, nicknamed Inti, closely resembles the oldest solids in meteorites.