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| Comet 81P/Wild | |
|---|---|
| Name | 81P/Wild |
| Designation | 81P |
| Discoverer | Paul Wild |
| Discovery date | 1978-01-06 |
| Semimajor axis | 3.45 AU |
| Eccentricity | 0.537 |
| Period | 6.4 yr |
| Inclination | 3.24° |
Comet 81P/Wild is a periodic Jupiter-family comet discovered by Swiss astronomer Paul Wild in 1978. The comet gained prominence after an extensive study and an active encounter by the NASA mission Stardust in 2004, which returned the first samples of cometary dust to Earth, influencing research at institutions such as the Smithsonian Institution and the Jet Propulsion Laboratory. Its orbit, physical properties, and returned samples have been referenced by projects at the European Space Agency, the Max Planck Society, and the California Institute of Technology.
Comet 81P/Wild was discovered by Paul Wild at the Zimmerwald Observatory near Bern on 6 January 1978, a discovery that placed it among other late 20th-century finds like Comet Halley rediscoveries and surveys by observatories including Kitt Peak National Observatory and Mount Palomar Observatory. The comet received the periodic comet designation under conventions administered by the Minor Planet Center and was subsequently studied by teams at the International Astronomical Union. Its naming follows tradition established by earlier discoverers such as Giuseppe Piazzi and William Herschel.
81P/Wild is a Jupiter-family comet with an orbital period of about 6.4 years and a semimajor axis near 3.45 AU, placing it among other short-period objects cataloged with comets like 2P/Encke and 9P/Tempel 1. Its eccentricity (~0.537) and low inclination (~3.24°) result in perihelion passages inside the orbit of Mars and aphelion near the orbit of Jupiter, making it susceptible to perturbations by Jupiter, interactions similar to those affecting Comet Shoemaker–Levy 9 and members of the Jupiter-family comets. Long-term integrations by researchers at NASA and the European Space Agency model its orbital evolution alongside minor bodies tracked by the Minor Planet Center and the International Astronomical Union.
Wild 2's nucleus is an irregular, roughly kilometre-scale body with a surface showing low albedo and a heterogeneous composition, compared by laboratory analyses to samples from Antarctic meteorites and materials studied at the Max Planck Institute for Chemistry. The Stardust sample return and follow-up measurements at facilities such as the Johnson Space Center and the Carnegie Institution for Science revealed a mix of refractory minerals, silicates, organics, and possible presolar grains, invoking comparisons with findings from Rosetta at 67P/Churyumov–Gerasimenko and laboratory work by scientists affiliated with Caltech and the University of Arizona. Isotopic studies performed with instruments in laboratories at MIT and Harvard University provided constraints used in models developed at the University of California, Berkeley and Brown University.
The primary spacecraft encounter was by NASA's Stardust mission, which flew through Wild 2's coma on 2 January 2004, collecting dust with an aerogel collector and imaging the nucleus using the spacecraft's navigation camera, analogous to imaging campaigns by Voyager 2, Galileo, and Deep Impact. The returned samples were curated and studied at the NASA Johnson Space Center and by international teams from institutions including Caltech, the Smithsonian Institution, University of Washington, and the Max Planck Society. Ground-based campaigns using facilities at Mauna Kea Observatories, Arecibo Observatory, and the European Southern Observatory complemented the encounter, as did observations from the Hubble Space Telescope and radio observations coordinated with the National Radio Astronomy Observatory.
Wild 2 exhibits episodic jet activity and localized outgassing, producing a coma and a dust environment sampled by Stardust and characterized in subsequent photometric and spectroscopic campaigns by teams at the Lowell Observatory, Institut d'Astrophysique de Paris, and the University of Hawaii. Observations in infrared by the Spitzer Space Telescope and in millimetre wavelengths by the Atacama Large Millimeter/submillimeter Array have probed volatile species and dust grain properties, complementing isotopic and compositional analyses performed at the Max Planck Institute for Solar System Research and the University of Chicago. Comparisons have been made with volatile inventories of comets like C/1995 O1 (Hale–Bopp) and 103P/Hartley 2, and with models developed at Princeton University and Cornell University regarding sublimation-driven activity and dust ejection.
The orbit of 81P/Wild has been significantly altered by past encounters with Jupiter, most notably a close approach in 1974 that reduced its perihelion distance, an effect modeled using techniques refined from studies of Comet Encke and applied by researchers at NASA JPL Horizons and the European Space Agency. Numerical integrations by groups at Caltech and the University of Milan evaluate future perturbations and potential resonances with Jupiter and other planets, predicting continued evolution typical of Jupiter-family comets cataloged by the Minor Planet Center. Non-gravitational forces from asymmetric outgassing, studied in the context of missions like Rosetta and telescopic monitoring at the Keck Observatory, also affect its long-term trajectory.
The Stardust encounter elevated Wild 2 in public awareness through outreach by institutions such as the Smithsonian Institution, NASA, and the National Air and Space Museum, inspiring exhibits and educational materials used by universities like Stanford University and museums such as the American Museum of Natural History. Scientifically, Wild 2's returned samples reshaped theories of solar system formation and radial transport, influencing models developed at Caltech, MIT, Princeton University, and the Max Planck Society, and informing comparative studies with meteorites curated at the Natural History Museum, London and the Smithsonian Institution. The mission's success impacted policy and planning at agencies including NASA and the European Space Agency for subsequent sample-return missions and helped motivate projects like OSIRIS-REx and follow-on comet exploration concepts.
Category:Periodic comets