E-type asteroids are

asteroid An asteroid is a minor planet of the Solar System#Inner solar system, inner Solar System. Sizes and shapes of asteroids vary significantly, ranging from 1-meter rocks to a dwarf planet almost 1000 km in diameter; they are rocky, metallic o ...

s thought to have

enstatite Enstatite is a mineral; the magnesium endmember of the pyroxene silicate mineral series enstatite (MgSiO3) – ferrosilite (FeSiO3). The magnesium rich members of the solid solution series are common rock-forming minerals found in igneous a ...

(MgSiO₃)

achondrite An achondrite is a stony meteorite that does not contain chondrules. It consists of material similar to terrestrial basalts or plutonic rocks and has been differentiated and reprocessed to a lesser or greater degree due to melting and recrystall ...

surfaces. They form a large proportion of asteroids inward of the

asteroid belt The asteroid belt is a torus-shaped region in the Solar System, located roughly between the orbits of the planets Jupiter and Mars. It contains a great many solid, irregularly shaped bodies, of many sizes, but much smaller than planets, called ...

known as Hungaria asteroids, but rapidly become very rare as the asteroid belt proper is entered. There are, however, some that are quite far from the inner edge of the asteroid belt, such as

64 Angelina Angelina ( minor planet designation: 64 Angelina) is an asteroid from the central region of the asteroid belt, approximately 50 kilometers in diameter. It is an unusually bright form of E-type asteroid. Discovery and naming Angelina was dis ...

. They are thought to have originated from the highly reduced mantle of a differentiated asteroid.

Description

E-type asteroids have a high

albedo Albedo (; ) is the measure of the diffuse reflection of solar radiation out of the total solar radiation and measured on a scale from 0, corresponding to a black body that absorbs all incident radiation, to 1, corresponding to a body that refl ...

(0.3 or higher), which distinguishes them from the more common M-type

s. Their

spectrum A spectrum (plural ''spectra'' or ''spectrums'') is a condition that is not limited to a specific set of values but can vary, without gaps, across a continuum. The word was first used scientifically in optics to describe the rainbow of color ...

is featureless flat to reddish. Probably because they originated from the edge of a larger parent body rather than a core, E-types are all small, with only three ( 44 Nysa,

55 Pandora Pandora (minor planet designation: 55 Pandora) is a fairly large and very bright asteroid in the asteroid belt. Pandora was discovered by American astronomer and Catholic priest George Mary Searle on September 10, 1858, from the Dudley Observato ...

) having diameters above 50 kilometres and no others above 25 kilometers (the biggest three also orbit atypically far, c. 3 AU, from the Sun). Aubrites (enstatite achondrite meteorites) are believed to come from E-type asteroids, because Aubrites could be linked to the E-type asteroid

3103 Eger 3103 Eger is an Apollo and Mars-crosser asteroid that was discovered in 1982, by Miklós Lovas. It was named after the city of Eger, Hungary. It has an albedo of 0.64, making it a highly reflective asteroid. Description It has made and will ...

. This grouping may be related to the Xe-type of the

SMASS classification An asteroid spectral type is assigned to asteroids based on their emission spectrum, color, and sometimes albedo. These types are thought to correspond to an asteroid's surface composition. For small bodies that are not internally differentiat ...

E-Belt

The E-type asteroids of the Hungaria family are thought to be the remains of the hypothetical E-belt asteroid population.Late, Late Heavy Bombardment - Bill Bottke
(SETI Talks) – Youtube.com The dispersal of most of that hypothetical E-Belt might have been caused by the outwards migration of the

gas giant A gas giant is a giant planet composed mainly of hydrogen and helium. Gas giants are also called failed stars because they contain the same basic elements as a star. Jupiter and Saturn are the gas giants of the Solar System. The term "gas giant" ...

s of the

Solar System The Solar System Capitalization of the name varies. The International Astronomical Union, the authoritative body regarding astronomical nomenclature, specifies capitalizing the names of all individual astronomical objects but uses mixed "Solar ...

according to simulations done under the Nice model – and these dispersed E-Belt asteroids might in turn have been the impactors of the

Late Heavy Bombardment The Late Heavy Bombardment (LHB), or lunar cataclysm, is a hypothesized event thought to have occurred approximately 4.1 to 3.8 billion years (Ga) ago, at a time corresponding to the Neohadean and Eoarchean eras on Earth. According to the hypoth ...

Exploration

On September 5, 2008, ESA's robotic spaceprobe

Rosetta Rosetta or Rashid (; ar, رشيد ' ; french: Rosette ; cop, ϯⲣⲁϣⲓⲧ ''ti-Rashit'', Ancient Greek: Βολβιτίνη ''Bolbitinē'') is a port city of the Nile Delta, east of Alexandria, in Egypt's Beheira governorate. The ...

visited the E-type asteroid

2867 Šteins 2867 Šteins (provisional designation ) is an irregular, diamond-shaped background asteroid from the inner regions of the asteroid belt, approximately in diameter. It was discovered on 4 November 1969 by Soviet astronomer Nikolai Chernykh at the ...

.H. U. Keller, et al. - E-Type Asteroid (2867) Steins as Imaged by OSIRIS on Board Rosetta - Science 8 January 2010: Vol. 327. no. 5962, pp. 190 - 193
Spectral data from the spacecraft confirmed the asteroid was composed mainly of iron-poor minerals such as

(magnesium-rich pyroxene),

forsterite Forsterite (Mg2SiO4; commonly abbreviated as Fo; also known as white olivine) is the magnesium-rich end-member of the olivine solid solution series. It is isomorphous with the iron-rich end-member, fayalite. Forsterite crystallizes in the ort ...

(magnesium-rich olivine) and

feldspar Feldspars are a group of rock-forming aluminium tectosilicate minerals, also containing other cations such as sodium, calcium, potassium, or barium. The most common members of the feldspar group are the ''plagioclase'' (sodium-calcium) feld ...

References

{{More citations needed, date=September 2008 Asteroid spectral classes *

Description

E-Belt

Exploration

See also

References