HowarditeOne type of meteorite in the HED (Howardite, Eucrite, Diogenite) achondrite group. Howardites are named after the English chemist Edward Howard (1774-1816), one of the pioneers of meteoritics. Consisting mostly of eucritic and diogenitic clasts and fragments, howardites are polymict breccias. However, they can also contain dark clasts of carbonaceous Click on Term to Read More
Fragmental brecciaWork in Progress ... A rock that is a mechanical mixture of different minerals and/or rock fragments (clasts). A breccia may also be distinguished by the origin of its clasts: (monomict breccia: monogenetic or monolithologic, and polymict breccia: polygenetic or polylithologic). The proportions of these fragments within the unbrecciated material Click on Term to Read More
Fell December 16, 1813
61° 19′ N., 27° 32′ E.
Around 10:00 at night a meteorHow long Sonic booms Of the several 10s of tons of cosmic material entering Earth's atmosphere each day, only about one ton reaches the surface. An object's chance of survival depends on its initial mass, speed and angle of entry, and friability (tendency to break up). Micrometeoroids radiate heat so Click on Term to Read More
exploded over Viborg, Finland, and many fragments fell onto an ice-covered lake near the village of Luotolahti. The fallMeteorite seen to fall. Such meteorites are usually collected soon after falling and are not affected by terrestrial weathering (Weathering = 0). Beginning in 2014 (date needs confirmation), the NomComm adopted the use of the terms "probable fall" and "confirmed fall" to provide better insight into the meteorite's history. If Click on Term to Read More
was witnessed by two farmers who later recovered some fragments, the largest of which weighed 843 g. Some stones were acquired by Count Fabian Steinheil, who donated the only presently preserved mass of ~556 g to the Helsingfors Universitet, Finland.
The basaltic achondriteAn achondrite is a type of stony meteorite whose precursor was of chondritic origin and experienced metamorphic and igneous processes. They have a planetary or differentiated asteroidal origin where the chondritic parent body reached a sufficient size that through heating due to radioactive decay of 26Al (aluminum isotope) and gravitational Click on Term to Read More
group is a complicated one to classify due to the diversity in the structural and mineralogical relationships among its members. This group is composed of brecciated and unbrecciated, monomict and polymict eucritesMost common type of achondrite meteorite and a member of the HED group. Eucrites are basalts composed primarily of pigeonite and anorthite (An60-98). Eucrites have been placed into three subgroups based on mineralogical and chemical differences. • Non-cumulate eucrites represent the upper crust that solidified on a magma ocean after Click on Term to Read More
, diogenitesDiogenites belong to the evolved achondrite HED group that also includes howardites and eucrites. They are named after the Greek philosopher Diogenes of Apollonia, of the 5th century BCE, who was the first to suggest that meteorites come from outer space (a realization forgotten for over 2,000 years). They are Click on Term to Read More
, and howardites, and has recently undergone a redefinition. The monomict subgroup containing eucrites, cumulateIgneous rock composed of crystals that have grown and accumulated (often by gravitational settling) in a cooling magma chamber. Click on Term to Read More
eucrites, and diogenites is further subdivided into brecciated and unbrecciated members. The polymict subgroup samples a compositional and textural continuum of regolithMixture of unconsolidated rocky fragments, soil, dust and other fine granular particles blanketing the surface of a body lacking an atmosphere. Regolith is the product of "gardening" by repeated meteorite impacts, and thermal processes (such as repeated heating and cooling cycles). Click on Term to Read More
and surface breccias consisting of eucrites, cumulate eucrites, diogenites, and howardites. Those meteorites containing more than 90% of a single component are given the prefix ‘polymict’ attached to their present description (e.g.
, polymict eucrites contain less than 10% non-eucritic material, and polymict diogenites contain more than 90% orthopyroxeniteA rock composed primarily of orthopyroxene. Non-terrestrial orthopyoxenites include diogenites and a single martian meteorite, ALH 84001, that was found in the Allan Hills region of Antarctica in 1984. ALH 84001 is a cumulate rock consisting of 97% coarse-grained, Mg-rich orthopyroxene, with small amounts of plagioclase, chromite, and carbonate. It Click on Term to Read More
or hypersthene). Those meteorites that contain less than 90% of any single component are defined as howardites. While this 10% level is still an arbitrary dividing line based simply on mineralInorganic substance that is (1) naturally occurring (but does not have a biologic or man-made origin) and formed by physical (not biological) forces with a (2) defined chemical composition of limited variation, has a (3) distinctive set of of physical properties including being a solid, and has a (4) homogeneous Click on Term to Read More
proportions, it represents an amount of orthopyroxeneOrthorhombic, low-Ca pyroxene common in chondrites. Its compositional range runs from all Mg-rich enstatite, MgSiO3 to Fe-rich ferrosilite, FeSiO3. These end-members form an almost complete solid solution where Mg2+ substitutes for Fe2+ up to about 90 mol. % and Ca substitutes no more than ~5 mol. % (higher Ca2+ contents occur Click on Term to Read More
that can easily be detected by X-ray diffractionAnalytical technique used to determine the structures of crystalline solids. A monochromatic beam of X-rays (usually Cu-Kα) is diffracted off repeating planes of atoms in crystalline samples to produce a diffraction pattern. Through analysis of the diffraction pattern, atomic structures can often be determined.
techniques. An additional tool to distinguish between polymict eucrites and howardites involves pyroxenes in the basaltic clasts; in howardites pyroxenes are mostly unzoned whereas in polymict eucrites they are usually zoned.
Luotolax has an unusually long CRE age for a howardite, 81 (±8) m.y., which is second only to the ~110 m.y. CRE age of Lohawat (Mahajan et al., 2000). Because these ages deviate significantly from the much lower CRE age clusters that comprise most howardites, and since no eucriteMost common type of achondrite meteorite and a member of the HED group. Eucrites are basalts composed primarily of pigeonite and anorthite (An60-98). Eucrites have been placed into three subgroups based on mineralogical and chemical differences. • Non-cumulate eucrites represent the upper crust that solidified on a magma ocean after Click on Term to Read More
or diogeniteDiogenites belong to the evolved achondrite HED group that also includes howardites and eucrites. They are named after the Greek philosopher Diogenes of Apollonia, of the 5th century BCE, who was the first to suggest that meteorites come from outer space (a realization forgotten for over 2,000 years). They are Click on Term to Read More
samples with comparable CRE ages have been identified, the possibility that Luotolax and Lohawat might have originated from a separate HED-like parent bodyThe body from which a meteorite or meteoroid was derived prior to its ejection. Some parent bodies were destroyed early in the formation of our Solar System, while others like the asteroid 4-Vesta and Mars are still observable today. Click on Term to Read More
deserves consideration. In support of this, a Mössbauer analysis of Lohawat has revealed that it possesses certain mineralogical differences when compared to Kapoeta, consistent with a different petrogenetic history on its parent asteroid (Tripathi et al., 2000). The specimen of Luotolax shown above is a 0.44 g cut fragment, previously acquired from the Helsingfors Universitet. Some of the information utilized on this page, as well as the photo of the Luotolax main massLargest fragment of a meteorite, typically at the time of recovery. Meteorites are commonly cut, sliced or sometimes broken thus reducing the size of the main mass and the resulting largest specimen is called the "largest known mass". Click on Term to Read More
shown below, was was made available courtesy of Jarmo Moilanen—Finnish Meteorites.