81P/Wild

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**81P/Wild**
Comet (List of comets)
Enhanced image from the Stardust spacecraft
Discovery
Discoverer	Paul Wild
Discovery date	1978
Alternate designations	1978 XI; 1984 XIV; 1990 XXVIII
Orbital elements ^A
Epoch March 6, 2006
Eccentricity (e)	0.5384
Semi-major axis (a)	3.45 AU
Perihelion (q)	1.592 AU
Aphelion (Q)	5.308 AU
Orbital period (P)	6.408 a
Inclination (i)	3.2394°
Last perihelion date	September 25, 2003
Next est. perihelion date	2010

Comet 81P/Wild, also known as Wild 2, is a comet named after Swiss astronomer Paul Wild (pronounced Vilt), who discovered it in 1978.

It is believed that for most of its 4.5 billion-year lifetime, Wild 2 had a more distant and circular orbit. In 1974, it passed within only about one million kilometers of the planet Jupiter, whose strong gravitational pull altered the comet's orbit and brought it into the inner solar system. Its orbital period changed from 40 years to about 6 years, and its perihelion is now about 1.59 AU (astronomical unit).

NASA's Stardust Mission launched a spacecraft, named Stardust, on February 7, 1999. It flew by Wild 2 on January 2, 2004 and collected particle samples from the comet's coma, which were returned to Earth along with interstellar dust it collected during the journey. 72 close-up shots were taken of Wild 2 by Stardust. They revealed a surface riddled with flat-bottomed depressions, with sheer walls and other features that range from very small to up to 2 kilometres across. These features are believed to be caused by impact craters or gas vents. During Stardust's flyby, at least 10 gas vents were active. The comet itself has a diameter of 5 kilometres.

Stardust's "sample return canister," was reported to be in excellent condition when it landed in Utah, on January 15, 2006. A NASA team Analyzed the particle capture cells and removed individual grains of comet and interstellar dust, then sent them to about 150 scientists around the globe [1]. NASA is collaborating with The Planetary Society who will run a project called "Stardust@Home," using volunteers to help locate particles on the Stardust Interstellar Dust Collector (SIDC).

So far[2], the composition of the dust has contained a surprising amount of anorthite and diopside, materials only formed under high heat. This is a surprise, because the conventional wisdom among a majority of scientists has been that comets form only in the coldest, deepest reaches of a planetary system, and should have no hot-formed materials.