Meteoritics is the science that deals with

meteor A meteor, known colloquially as a shooting star, is a glowing streak of a small body (usually meteoroid) going through Earth's atmosphere, after being heated to incandescence by collisions with air molecules in the upper atmosphere, creating a ...

meteorite A meteorite is a rock (geology), rock that originated in outer space and has fallen to the surface of a planet or Natural satellite, moon. When the original object enters the atmosphere, various factors such as friction, pressure, and chemical ...

s, and

meteoroid A meteoroid ( ) is a small rocky or metallic body in outer space. Meteoroids are distinguished as objects significantly smaller than ''asteroids'', ranging in size from grains to objects up to wide. Objects smaller than meteoroids are classifie ...

s. It is closely connected to

cosmochemistry Cosmochemistry () or chemical cosmology is the study of the chemical composition of matter in the universe and the processes that led to those compositions. This is done primarily through the study of the chemical composition of meteorites and ot ...

mineralogy Mineralogy is a subject of geology specializing in the scientific study of the chemistry, crystal structure, and physical (including optical mineralogy, optical) properties of minerals and mineralized artifact (archaeology), artifacts. Specific s ...

and

geochemistry Geochemistry is the science that uses the tools and principles of chemistry to explain the mechanisms behind major geological systems such as the Earth's crust and its oceans. The realm of geochemistry extends beyond the Earth, encompassing the e ...

. A specialist who studies meteoritics is known as a ''meteoriticist''. Scientific research in meteoritics includes the

collection Collection or Collections may refer to: Computing * Collection (abstract data type), the abstract concept of collections in computer science * Collection (linking), the act of linkage editing in computing * Garbage collection (computing), autom ...

, identification, and classification of meteorites and the analysis of samples taken from them in a

laboratory A laboratory (; ; colloquially lab) is a facility that provides controlled conditions in which scientific or technological research, experiments, and measurement may be performed. Laboratories are found in a variety of settings such as schools ...

. Typical analyses include investigation of the

mineral In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid substance with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure form.John P. Rafferty, ed. (2011): Mi ...

s that make up the meteorite, their relative locations, orientations, and chemical compositions; analysis of isotope ratios; and

radiometric dating Radiometric dating, radioactive dating or radioisotope dating is a technique which is used to Chronological dating, date materials such as Rock (geology), rocks or carbon, in which trace radioactive impurity, impurities were selectively incorporat ...

. These techniques are used to determine the age, formation process, and subsequent history of the material forming the meteorite. This provides information on the

history of the Solar System There is evidence that the formation of the Solar System began about 4.6 billion years ago with the gravitational collapse of a small part of a giant molecular cloud. Most of the collapsing mass collected in the center, forming the Sun, while the ...

, how it formed and evolved, and the process of

planet formation The nebular hypothesis is the most widely accepted model in the field of cosmogony to explain the formation and evolution of the Solar System (as well as other planetary systems). It suggests the Solar System is formed from gas and dust orbiting t ...

History of investigation

Before the documentation of

L'Aigle L'Aigle is a commune in the Orne department in Normandy in northwestern France. Before 1961, the commune was known as ''Laigle''. According to Orderic Vitalis, the nest of an eagle (''aigle'' in French) was discovered during the construction ...

it was generally believed that meteorites were a type of superstition and those who claimed to see them fall from space were lying. In 1960 John Reynolds discovered that some meteorites have an excess of ¹²⁹Xe, a result of the presence of ¹²⁹I in the solar nebula.

Methods of investigation

Mineralogy

The presence or absence of certain minerals is indicative of physical and chemical processes. Impacts on the parent body are recorded by impact-breccias and high-pressure mineral phases (e.g.

coesite Coesite () is a form (polymorphism (materials science), polymorph) of silicon dioxide (silicon, Sioxide, O2) that is formed when very high pressure (2–3 gigapascals), and moderately high temperature (), are applied to quartz. Coesite was first ...

akimotoite Akimotoite is a rare silicate mineral in the ilmenite group of minerals, with the chemical formula . It is polymorphous with pyroxene and with bridgmanite, a natural silicate perovskite that is the most abundant mineral in Earth's silicate mantle. ...

majorite Majorite is a mineral found in the mantle of the Earth. Its chemical formula is Mg3(MgSi)(SiO4)3. It is a type of garnet, distinguished from other garnets in having silicon in octahedral as well as tetrahedral coordination. Majorite was first d ...

ringwoodite Ringwoodite is a high-pressure phase of Mg2SiO4 (magnesium silicate) formed at high temperatures and pressures of the Earth's mantle between depth. It may also contain iron and hydrogen. It is polymorphous with the olivine phase forsterite (a ...

stishovite Stishovite is an extremely hard, dense tetragonal form ( polymorph) of silicon dioxide. It is very rare on the Earth's surface; however, it may be a predominant form of silicon dioxide in the Earth, especially in the lower mantle. Stishovite w ...

wadsleyite Wadsleyite is an orthorhombic mineral with the formula β-(Mg,Fe)2SiO4. It was first found in nature in the Peace River meteorite from Alberta, Canada. It is formed by a phase transformation from olivine (α-(Mg,Fe)2SiO4) under increasing press ...

Water Water is an inorganic compound with the chemical formula . It is a transparent, tasteless, odorless, and Color of water, nearly colorless chemical substance. It is the main constituent of Earth's hydrosphere and the fluids of all known liv ...

bearing minerals, and samples of liquid water (e.g., Zag, Monahans) are an indicator for hydrothermal activity on the parent body (e.g.

clay mineral Clay minerals are hydrous aluminium phyllosilicates (e.g. kaolin, Al2 Si2 O5( OH)4), sometimes with variable amounts of iron, magnesium, alkali metals, alkaline earths, and other cations found on or near some planetary surfaces. Clay minera ...

s).

Radiometric dating

Radiometric methods can be used to date different stages of the history of a meteorite. Condensation from the

solar nebula There is evidence that the formation of the Solar System began about 4.6 bya, billion years ago with the gravitational collapse of a small part of a giant molecular cloud. Most of the collapsing mass collected in the center, forming the Sun, whil ...

is recorded by

calcium–aluminium-rich inclusion A calcium–aluminium-rich inclusion or Ca–Al-rich inclusion (CAI) is a submillimeter- to centimeter-sized light-colored calcium- and aluminium-rich inclusion found in carbonaceous chondrite meteorites. The four CAIs that have been dated using ...

s and

chondrule A chondrule (from Ancient Greek χόνδρος ''chondros'', grain) is a round grain found in a chondrite. Chondrules form as molten or partially molten droplets in space before being Accretion (astrophysics), accreted to their parent asteroids ...

s. These can be dated by using radionuclides that were present in the solar nebula (e.g. ²⁶Al/²⁶Mg, ⁵³Mn/⁵³Cr, U/Pb, ¹²⁹I/¹²⁹Xe). After the condensed material accretes to

planetesimal Planetesimals () are solid objects thought to exist in protoplanetary disks and debris disks. Believed to have formed in the Solar System about 4.6 billion years ago, they aid study of its formation. Formation A widely accepted theory of pla ...

s of sufficient size melting and differentiation take place. These processes can be dated with the U/Pb, ⁸⁷Rb/⁸⁷Sr, ¹⁴⁷Sm/¹⁴³Nd and ¹⁷⁶Lu/¹⁷⁶Hf methods. Metallic core formation and cooling can be dated by applying the ¹⁸⁷Re/¹⁸⁷Os method to

iron meteorite Iron meteorites, also called siderites or ferrous meteorites, are a type of meteorite that consist overwhelmingly of an iron–nickel alloy known as meteoric iron that usually consists of two mineral phases: kamacite and taenite. Most iron me ...

s. Large scale impact events or even the destruction of the parent body can be dated using the ³⁹Ar/⁴⁰Ar method and the ²⁴⁴Pu fission track method. After breakup of the parent body meteoroids are exposed to cosmic radiation. The length of this exposure can be dated using the ³H/³He method, ²²Na/²¹Ne, ⁸¹Kr/⁸³Kr. After impact on earth (or any other planet with sufficient cosmic ray shielding) cosmogenic radionuclides decay and can be used to date the time since the meteorite fell. Methods to date this terrestrial exposure are ³⁶Cl, ¹⁴C, ⁸¹Kr.

History of investigation

Methods of investigation

Mineralogy

Radiometric dating

See also

Notes & references

Notes

References

Further reading