Eagle Station grouplet

Eagle Station grouplet
	— Grouplet —
	Eagle Station meteorite, type specimen for the grouplet.
Type	Stony-iron
Class	Pallasite
Composition	Meteoric iron, silicates
Total known specimens	4

Last updated April 10, 2019

The Eagle Station grouplet (abbreviated PES - Pallasite Eagle Station) is a set of pallasite meteorite specimen that don't fit into any of the defined pallasite groups. In meteorite classification five meteorites have to be found, so they can be defined as their own group.^[1] Currently only four Eagle Station type meteorites have been found.^[2]

The pallasites are a class of stony–iron meteorite.

The ultimate goal of meteorite classification is to group all meteorite specimens that share a common origin on a single, identifiable parent body. This could be a planet, asteroid, Moon, or other current Solar System object, or one that existed some time in the past. However, with a few exceptions, this goal is beyond the reach of current science, mostly because there is inadequate information about the nature of most Solar System bodies to achieve such a classification. Instead, modern meteorite classification relies on placing specimens into "groups" in which all members share certain key physical, chemical, isotopic, and mineralogical properties consistent with a common origin on a single parent body, even if that body is unidentified. Several meteorite groups classified this way may come from a single, heterogeneous parent body or a single group may contain members that came from a variety of very similar but distinct parent bodies. As such information comes to light, the classification system will most likely evolve.

Naming and history

The Eagle Station grouplet is named after the Eagle Station meteorite, the type specimen of the grouplet. It is in turned named after Eagle Station, Carroll County Kentucky where it was found.^[3]

The Eagle Station meteorite is a pallasite and type specimen of the Eagle Station grouplet.

Carroll County is a county located in the U.S. state of Kentucky. As of the 2010 census, the population was 10,811. Its county seat is Carrollton. The county was formed in 1838 and named for Charles Carroll of Carrollton, the last living signer of the Declaration of Independence. It is located at the confluence of the Kentucky and Ohio Rivers.

Kentucky, officially the Commonwealth of Kentucky, is a state located in the east south-central region of the United States. Although styled as the "State of Kentucky" in the law creating it, (because in Kentucky's first constitution, the name state was used) Kentucky is one of four U.S. states constituted as a commonwealth. Originally a part of Virginia, in 1792 Kentucky became the 15th state to join the Union. Kentucky is the 37th most extensive and the 26th most populous of the 50 United States.

Description

The Eagle Station grouplet has a composition similar to Main group pallasites. Diagnostic differences are that the olivine is richer in iron and calcium. The grouplet also has a distinct oxygen isotope signature.^[1]

Olivine Magnesium iron silicate solid solution series mineral

The mineral olivine is a magnesium iron silicate with the formula (Mg²⁺, Fe²⁺)₂SiO₄. Thus it is a type of nesosilicate or orthosilicate. It is a common mineral in Earth's subsurface but weathers quickly on the surface.

Iron is a chemical element with symbol Fe and atomic number 26. It is a metal, that belongs to the first transition series and group 8 of the periodic table. It is by mass the most common element on Earth, forming much of Earth's outer and inner core. It is the fourth most common element in the Earth's crust.

Calcium is a chemical element with symbol Ca and atomic number 20. As an alkaline earth metal, calcium is a reactive metal that forms a dark oxide-nitride layer when exposed to air. Its physical and chemical properties are most similar to its heavier homologues strontium and barium. It is the fifth most abundant element in Earth's crust and the third most abundant metal, after iron and aluminium. The most common calcium compound on Earth is calcium carbonate, found in limestone and the fossilised remnants of early sea life; gypsum, anhydrite, fluorite, and apatite are also sources of calcium. The name derives from Latin calx "lime", which was obtained from heating limestone.

The meteoric iron is similar to the IIF iron meteorites. This might indicate that Eagle station grouplet and IIF formed close to each other in the solar nebula.^[1]

Meteoric iron, sometimes meteoritic iron, is a native metal found in meteorites and made from the elements iron and nickel mainly in the form of the mineral phases kamacite and taenite. Meteoric iron makes up the bulk of iron meteorites but is also found in other meteorites. Apart from minor amounts of telluric iron, meteoric iron is the only naturally occurring native metal of the element iron on the Earth's surface.

Parent body

The trace elements in the phosphates of the Eagle Station grouplet are distinct from other pallasites. Most pallasites are believed to be derived from the core-mantle boundary. Trace elements indicate that the Eagle Station grouplet came from shallower depths of their parent body.^[4]

A trace element is a chemical element whose concentration is very low. The exact definition depends on the field of science:

The planetary core consists of the innermost layer(s) of a planet. Cores of specific planets may be entirely solid or entirely liquid, or may be a mixture of solid and liquid layers as is the case in the Earth. In the Solar System, core size can range from about 20% (Moon) to 85% of a planet's radius (Mercury).

A mantle is a layer inside a planetary body bounded below by a core and above by a crust. Mantles are made of rock or ices, and are generally the largest and most massive layer of the planetary body. Mantles are characteristic of planetary bodies that have undergone differentiation by density. All terrestrial planets, a number of asteroids, and some planetary moons have mantles.

Notable specimen

Only four specimen have been found so far:^[2]

Cold Bay meteorite
Eagle Station meteorite (type specimen)
Itzawisis meteorite
Karavannoe meteorite

Related Research Articles

Chondrites are stony (non-metallic) meteorites that have not been modified due to melting or differentiation of the parent body. They are formed when various types of dust and small grains that were present in the early solar system accreted to form primitive asteroids. They are the most common type of meteorite that falls to Earth with estimates for the proportion of the total fall that they represent varying between 85.7% and 86.2%. Their study provides important clues for understanding the origin and age of the Solar System, the synthesis of organic compounds, the origin of life and the presence of water on Earth. One of their characteristics is the presence of chondrules, which are round grains formed by distinct minerals, that normally constitute between 20% and 80% of a chondrite by volume.

Carbonaceous chondrites or C chondrites are a class of chondritic meteorites comprising at least 8 known groups and many ungrouped meteorites. They include some of the most primitive known meteorites. The C chondrites represent only a small proportion (4.6%) of meteorite falls.

Iron meteorite meteorite composed of iron-nickel alloy called meteoric iron

Iron meteorites are meteorites that consist overwhelmingly of an iron–nickel alloy known as meteoric iron that usually consists of two mineral phases: kamacite and taenite. Iron meteorites originate from cores of planetesimals.

Pallasovka is a pallasite meteorite found in 1990 near the town of Pallasovka, Russia.

Mbozi is an ungrouped iron meteorite found in Tanzania. It is one of the world's largest meteorites, variously estimated as the fourth-largest to the eighth-largest, it is located near the city of Mbeya in Tanzania's southern highlands. The meteorite is 3 metres (9.8 ft) long, 1 metre high, and weighs an estimated 16 metric tons.

Winonaites are a group of primitive achondrite meteorites. Like all primitive achondrites, winonaites share similarities with chondrites and achondrites. They show signs of metamorphism, partial melting, brecciation and relic chondrules. Their chemical and mineralogical composition lies between H and E chondrites.

The Brachina meteorite is the type specimen of the brachinites class of the asteroidal achondrites.

IAB meteorites are a group of iron meteorites according to their overall composition and a group of primitive achondrites because of silicate inclusions that show a strong affinity to winonaites and chondrites.

IIICD meteorites are a group of primitive achondrites. They are classified in a clan together with the IAB meteorites and the winonaites.

IVB meteorites are a group of ataxite iron meteorites classified as achondrites. The IVB group has the most extreme chemical compositions of all iron meteorites, meaning that examples of the group are depleted in volatile elements and enriched in refractory elements compared to other iron meteorites.

Brachinites are a group of meteorites that are classified either as primitive achondrites or as asteroidal achondrites. Like all primitive achondrites, they have similarities with chondrites and achondrites. Brachinites contain 74 to 98% (Volume) olivine.

IIG meteorites are a group of iron meteorites. The group currently has six members. They are hexahedrites with large amounts of schreibersite. The meteoric iron is composed of kamacite.

The Bellsbank meteorite is a hexahedrite iron meteorite with abundant schreibersite. It is classified as a member of the IIG group. It was found in Bellsbank, South Africa in 1955.

The Vermillion meteorite is a pallasite (stony-iron) meteorite and one of two members of the pyroxene pallasite grouplet.

The pyroxene pallasite grouplet is a subdivision of the pallasite meteorites (stony-irons).

This is a glossary of terms used in meteoritics, the science of meteorites.

IIAB meteorites are a group of iron meteorites. Their structural classification ranges from hexahedrites to octahedrites. IIABs have the lowest concentration of nickel of all iron meteorite groups. All iron meteorites are derived from the metallic planetary cores of their respective parent bodies, but in the case of the IIABs the metallic magma separated to form not only this meteorite group but also the IIG group.

References

1 2 3 D.S. Lauretta, H.Y. McSween, Jr., editors ; foreword by Richard P. Binze; M. K. Weisberg; T. J. McCoy, A. N. Krot (2006). "Systematics and Evaluation of Meteorite Classification". Meteorites and the early solar system II (PDF). Tucson: University of Arizona Press. pp. 19–52. ISBN 978-0816525621 . Retrieved 15 December 2012.CS1 maint: Multiple names: authors list (link)
1 2 "Meteoritical Bulletin Database". Meteoritical Society.
↑ "Eagle Station". Meteoritical Society.
↑ Davis, Andrew M.; Olsen, Edward J. (17 October 1991). "Phosphates in pallasite meteorites as probes of mantle processes in small planetary bodies". Nature. 353 (6345): 637–640. doi:10.1038/353637a0.

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[Weisberg_2006-1] 1 2 3 D.S. Lauretta, H.Y. McSween, Jr., editors ; foreword by Richard P. Binze; M. K. Weisberg; T. J. McCoy, A. N. Krot (2006). "Systematics and Evaluation of Meteorite Classification". Meteorites and the early solar system II (PDF). Tucson: University of Arizona Press. pp. 19–52. ISBN 978-0816525621 . Retrieved 15 December 2012.CS1 maint: Multiple names: authors list (link)

[Meteoritical_Bulletin_Database-2] 1 2 "Meteoritical Bulletin Database". Meteoritical Society.

[Met_Eagle_Station-3] "Eagle Station". Meteoritical Society.

[Davis_1991-4] Davis, Andrew M.; Olsen, Edward J. (17 October 1991). "Phosphates in pallasite meteorites as probes of mantle processes in small planetary bodies". Nature. 353 (6345): 637–640. doi:10.1038/353637a0.