Wild 2

81P/Wild

Comet Wild 2 (81P/Wild) nucleus in 2004
Discovery
Discovered by	Paul Wild
Discovery date	1978
Alternative designations	1978 XI; 1984 XIV; 1990 XXVIII
Orbital characteristics A
Epoch	March 6, 2006
Aphelion	5.308 AU
Perihelion	1.592 AU
Semi-major axis	3.45 AU
Eccentricity	0.5384
Orbital period	6.408 a
Inclination	3.2394°
Jupiter MOID	0.012 AU (1,800,000 km)
Last perihelion	July 20, 2016 February 22, 2010
Next perihelion	December 15, 2022

Comet 81P/Wild, also known as Wild 2 (pronounced "vilt two") (/ˈvɪlt/ VILT), is a comet named after Swiss astronomer Paul Wild, who discovered it on January 6, 1978, using a 40-cm Schmidt telescope at Zimmerwald, Switzerland.

For most of its 4.5 billion-year lifetime, Wild 2 probably had a more distant and circular orbit. In September 1974, it passed within one million kilometers of the planet Jupiter, the strong gravitational pull of which perturbed the comet's orbit and brought it into the inner Solar System. Its orbital period changed from 43 years to about 6 years, and its perihelion is now about 1.59 astronomical unit (AU).

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.