NASA’s Stardust mission returned rocky material from the coma of comet 81P/Wild 2 (pronounced ‘Vilt 2’) to Earth on January 15, 2006. Comet Wild 2 contains volatile ices and likely accreted beyond the orbit of Neptune. It was expected that the Wild 2 samples would contain abundant primordial molecular cloud material — interstellar and circumstellar grains. Instead, the interstellar component of Wild 2 was found to be very minor, and nearly all of the returned particles formed in broad and diverse regions of the Solar Nebula. While some characteristics of the Wild 2 material are similar to primitive chondrite meteorites, its compositional diversity testifies to a very different origin and evolution history than asteroids. Collisional debris from asteroids is mostly absent in Wild 2, and it likely accreted dust from the outer and inner Solar System before dispersal of the Solar Nebula.
Wild 2 is a small comet with the shape of a flattened sphere and measures about 1.65 x 2 x 2.75 km (1.03 x 1.24 x 1.71 miles).
Discovered by Paul Wild on January 6, 1978, the comet has an orbital period of 6.2 years.
Wild 2 is known as a fresh periodic comet. It orbits the Sun between Mars and Jupiter, but it did not always travel the course of its orbit here.
Originally, this comet’s orbit lay between that of Uranus and Jupiter. On September 9, 1974, gravitational interactions between Wild 2 and Jupiter changed its orbital period from 43 years to 6.2 years.
“Eighteen years after NASA’s Stardust mission returned to Earth with the first samples from a known comet, the true nature of that icy object is coming into focus,” said Washington University in St. Louis researcher Ryan Ogliore, author of the new study.
“When Stardust launched in 1999, many scientists expected the comet’s rocky material would be dominated by the primordial dust that built the Solar System — the ‘stardust’ that gave the mission its name.”
“But the actual samples told a different…
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