Meteoritics

For the 1953 journal, see Meteoritics & Planetary Science.

Meteoritics is a science that deals with meteorites and other extraterrestrial materials that further our understanding of the origin and history of the Solar System. A specialist who studies meteoritics is known as a meteoriticist.

History of investigation

Before the documentation of L'Aigle 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, akimotoite, majorite, ringwoodite, stishovite, wadsleyite). Water bearing minerals are an indicator for hydrothermal activity on the parent body (e.g. clay minerals).

Radiometric dating

Radiometric methods can be used to date different stages of the history of a meteorite. Condensation from the solar nebula is recorded by calcium-aluminium-rich inclusions and chondrules. 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 planetesimals 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 meteorites. 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.

See also

• Glossary of meteoritics
• Meteor
• Meteoroid
• Meteorite