81P/Wild
Encyclopedia
Comet 81P/Wild, also known as Wild 2 (icon ), is a comet
named after Swiss
astronomer Paul Wild
, who discovered it in 1978 using a 40-cm Schmidt telescope at Zimmerwald
.
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
, whose strong gravitational pull 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 AU (astronomical unit
).
, 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. 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).
As of 2006, the composition of the dust has contained a wide range of organic compounds, including two that contain biologically usable nitrogen. Indigenous aliphatic hydrocarbons were found with longer chain lengths than those observed in the diffuse interstellar medium. No hydrous silicates or carbonate minerals were detected, which suggests a lack of aqueous processing of Wild 2 dust. Very few pure carbon (CHON) particles were found in the samples returned. A substantial amount of crystalline silicates such as olivine
, anorthite
and diopside
were found, materials only formed at high temperature. This is consistent with previous observations of crystalline silicates both in cometary tails and in circumstellar disks at large distances from the star. Possible explanations for this high temperature material at large distances from Sun were summarised before the Stardust sample return mission by van Boekel et al.:
Results from a study reported in the September 19, 2008 issue of the journal Science has revealed an oxygen isotope signature in the dust that suggests an unexpected mingling of rocky material between the center and edges of the solar system. Despite the comet’s birth in the icy reaches of outer space beyond Pluto, tiny crystals collected from its halo appear to have been forged in the hotter interior, much closer to the Sun.
In April 2011, scientists from the University of Arizona
discovered evidence for the presence of liquid water. They have found iron and copper sulfide
minerals that must have formed in the presence of water. The discovery shatters the existing paradigm that comets never get warm enough to melt their icy bulk.
Comet
A comet is an icy small Solar System body that, when close enough to the Sun, displays a visible coma and sometimes also a tail. These phenomena are both due to the effects of solar radiation and the solar wind upon the nucleus of the comet...
named after Swiss
Switzerland
Switzerland name of one of the Swiss cantons. ; ; ; or ), in its full name the Swiss Confederation , is a federal republic consisting of 26 cantons, with Bern as the seat of the federal authorities. The country is situated in Western Europe,Or Central Europe depending on the definition....
astronomer Paul Wild
Paul Wild (Swiss astronomer)
Professor Paul Wild of Berne, Switzerland, is an astronomer who discovered numerous comets and asteroids.- Career :Professor Wild was director of the Astronomical Institute of the University of Berne from 1980 to 1991...
, who discovered it in 1978 using a 40-cm Schmidt telescope at Zimmerwald
Zimmerwald Observatory
Observatorium Zimmerwald is an astronomical observatory owned and operated by the Astronomisches Institut der Universität Bern . Built in 1956, it is located 10 kilometers south of Bern, Switzerland near Zimmerwald.The 1 meter aperture ZIMLAT telescope was inaugurated in 1997.-External links:*...
.
For most of its 4.5 billion-year lifetime, Wild 2 probably had a more distant and circular orbit
Orbit
In physics, an orbit is the gravitationally curved path of an object around a point in space, for example the orbit of a planet around the center of a star system, such as the Solar System...
. In September 1974, it passed within one million kilometers of the planet Jupiter
Jupiter
Jupiter is the fifth planet from the Sun and the largest planet within the Solar System. It is a gas giant with mass one-thousandth that of the Sun but is two and a half times the mass of all the other planets in our Solar System combined. Jupiter is classified as a gas giant along with Saturn,...
, whose strong gravitational pull perturbed
Perturbation (astronomy)
Perturbation is a term used in astronomy in connection with descriptions of the complex motion of a massive body which is subject to appreciable gravitational effects from more than one other massive body....
the comet's orbit and brought it into the inner Solar System
Solar System
The Solar System consists of the Sun and the astronomical objects gravitationally bound in orbit around it, all of which formed from the collapse of a giant molecular cloud approximately 4.6 billion years ago. The vast majority of the system's mass is in the Sun...
. Its orbital period
Orbital period
The orbital period is the time taken for a given object to make one complete orbit about another object.When mentioned without further qualification in astronomy this refers to the sidereal period of an astronomical object, which is calculated with respect to the stars.There are several kinds of...
changed from 43 years to about 6 years, and its perihelion is now about 1.59 AU (astronomical unit
Astronomical unit
An astronomical unit is a unit of length equal to about or approximately the mean Earth–Sun distance....
).
Nucleus parameters
- Dimensions: 5.5×4.0×3.3 km
- Density: 0.6 g/cm³
- Mass: 2.3 kg
Stardust mission
NASA's Stardust Mission launched a spacecraftSpacecraft
A spacecraft or spaceship is a craft or machine designed for spaceflight. Spacecraft are used for a variety of purposes, including communications, earth observation, meteorology, navigation, planetary exploration and transportation of humans and cargo....
, named Stardust
Stardust (spacecraft)
Stardust is a 300-kilogram robotic space probe launched by NASA on February 7, 1999 to study the asteroid 5535 Annefrank and collect samples from the coma of comet Wild 2. The primary mission was completed January 15, 2006, when the sample return capsule returned to Earth...
, on February 7, 1999. It flew by Wild 2 on January 2, 2004, and collected particle samples from the comet's coma
Coma (cometary)
frame|right|The [[153P/Ikeya-Zhang|comet Ikeya-Zhang]] exhibiting a bright, condensed coma In astronomy, a coma is the nebulous envelope around the nucleus of a comet. It is formed when the comet passes close to the Sun on its highly elliptical orbit; as the comet warms, parts of it sublimate...
, 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. NASA is collaborating with The Planetary Society who will run a project called "Stardust@Home
Stardust@home
Stardust@home is a citizen science project that encourages volunteers to search images for tiny interstellar dust impacts. The project began providing data for analysis on August 1, 2006....
", using volunteers to help locate particles on the Stardust Interstellar Dust Collector (SIDC).
As of 2006, the composition of the dust has contained a wide range of organic compounds, including two that contain biologically usable nitrogen. Indigenous aliphatic hydrocarbons were found with longer chain lengths than those observed in the diffuse interstellar medium. No hydrous silicates or carbonate minerals were detected, which suggests a lack of aqueous processing of Wild 2 dust. Very few pure carbon (CHON) particles were found in the samples returned. A substantial amount of crystalline silicates such as olivine
Olivine
The mineral olivine is a magnesium iron silicate with the formula 2SiO4. It is a common mineral in the Earth's subsurface but weathers quickly on the surface....
, anorthite
Anorthite
Anorthite is the calcium endmember of plagioclase feldspar. Plagioclase is an abundant mineral in the Earth's crust. The formula of pure anorthite is CaAl2Si2O8.-Mineralogy :...
and diopside
Diopside
Diopside is a monoclinic pyroxene mineral with composition MgCaSi2O6. It forms complete solid solution series with hedenbergite and augite, and partial solid solutions with orthopyroxene and pigeonite. It forms variably colored, but typically dull green crystals in the monoclinic prismatic class...
were found, materials only formed at high temperature. This is consistent with previous observations of crystalline silicates both in cometary tails and in circumstellar disks at large distances from the star. Possible explanations for this high temperature material at large distances from Sun were summarised before the Stardust sample return mission by van Boekel et al.:
- Both in the Solar System and in circumstellar disks crystalline silicates are found at large distances from the star. The origin of these silicates is a matter of debate. Although in the hot inner-disk regions crystalline silicates can be produced by means of gas-phase condensation or thermal annealing, the typical grain temperatures in the outer-disk (2−20 au) regions are far below the glass temperature of silicates of approx 1,000 K. The crystals in these regions may have been transported outward through the disk or in an outward-flowing wind '. An alternative source of crystalline silicates in the outer disk regions is in situ annealing, for example by shocks or lightning. A third way to produce crystalline silicates is the collisional destruction of large parent bodies in which secondary processing has taken place. We can use the mineralogy of the dust to derive information about the nature of the primary and/or secondary processes the small-grain population has undergone.
Results from a study reported in the September 19, 2008 issue of the journal Science has revealed an oxygen isotope signature in the dust that suggests an unexpected mingling of rocky material between the center and edges of the solar system. Despite the comet’s birth in the icy reaches of outer space beyond Pluto, tiny crystals collected from its halo appear to have been forged in the hotter interior, much closer to the Sun.
In April 2011, scientists from the University of Arizona
University of Arizona
The University of Arizona is a land-grant and space-grant public institution of higher education and research located in Tucson, Arizona, United States. The University of Arizona was the first university in the state of Arizona, founded in 1885...
discovered evidence for the presence of liquid water. They have found iron and copper sulfide
Copper sulfide
Copper sulfides describe a family of chemical compounds and minerals with the formula CuxSy. Both minerals and synthetic materials comprise these compounds. Some copper sulfides are economically important ores....
minerals that must have formed in the presence of water. The discovery shatters the existing paradigm that comets never get warm enough to melt their icy bulk.
See also
Wild 2 shares a similar name with the other objects:- 1941 Wild1941 Wild1941 Wild is an outer main-belt asteroid discovered on October 6, 1931 by K. Reinmuth at Heidelberg.- External links :*...
- 63P/Wild
- 86P/Wild
- 116P/Wild116P/Wild-External links:*...
- C/1967 C2 (Wild)
- C/1968 U1 (Wild)