Organic compounds in carbonaceous meteoritesMark A. SephtonPlanetary and Space Sciences Research Institute, Open University, Milton Keynes,UK MK7 6AA. E-mail: [email protected]; Fax: ⫹44 (0)1908 655910;Tel: ⫹44 (0)1908 659358Received (in Cambridge, UK) 11th January 2002First published as an Advance Article on the web 14th March 2002Covering: 1950s to the present dayThe carbonaceous chondrite meteorites are fragments of asteroids that have remained relatively unprocessed sincethe formation of the solar system 4.6 billion years ago. These carbon-rich objects contain a variety of extraterrestrialorganic molecules that constitute a record of chemical evolution prior to the origin of life. Compound classes includealiphatic hydrocarbons, aromatic hydrocarbons, amino acids, carboxylic acids, sulfonic acids, phosphonic acids,alcohols, aldehydes, ketones, sugars, amines, amides, nitrogen heterocycles, sulfur heterocycles and a relativelyabundant high molecular weight macromolecular material. Structural and stable isotopic characteristics suggestthat a number of environments may have contributed to the organic inventory, including interstellar space, thesolar nebula and the asteroidal meteorite parent body. This review covers work published between 1950 and thepresent day and cites 193 references.1 Introduction1.1 Carbonaceous chondrites and their origin1.2 Collection of meteorites1.3 Classification of carbonaceous chondrites2 Carbon in carbonaceous chondrites3 Stable isotopes and carbonaceous chondrites4 The organic compounds in carbonaceouschondrites4.1 Aromatic hydrocarbons4.1.1 Solvent and thermal extracts4.1.2 Laser desorption-mass spectrometry4.1.3 Stable isotopes and aromatic hydrocarbons4.2 Aliphatic hydrocarbonsMark Sephton was born in Merseyside in 1966. He obtained hisBSc in Geology from the University of Durham in 1991 and hisMSc in Organic Geochemistry, Organic Petrology and PetroleumGeochemistry from the University of Newcastle upon Tyne in1992. Between 1993 and 1996 he studied for a PhD in OrganicCompounds in Meteorites at the Open University and then spenttwo years investigating the molecular and isotopic record of thePermian–Triassic mass extinction at the Netherlands Institutefor Sea Research and University of Utrecht. Subsequently, hereturned to the Open University to develop stable isotope methodsfor the forensic detection of steroid abuse in association with theHoreseracing Forensic Laboratory in Newmarket. In 2000,he became a Lecturer inthe Planetary and SpaceSciences Research Instituteand Department of EarthSciences at the OpenUniversity. His currentresearch interests includemolecular and isotopicinvestigations of the extra-terrestrial organic matter inmeteorites and the causesand consequences of massextinctions in the geologicalrecord.4.2.1 Volatile aliphatics4.2.2 n-Alkanes4.2.3 Stable isotopes and aliphatic hydrocarbons4.3 Amino acids4.3.1 Amino acids in meteorites4.3.2 Enantiomeric excesses4.3.3 Origin of enantiomeric excess4.3.4 Amino acid precursors4.3.5 Stable isotopes and amino acids4.4 Carboxylic acids4.4.1 Monocarboxylic acids4.4.1.1 Short chain monocarboxylic acids4.4.1.2 Long chain monocarboxylic acids4.4.2 Dicarboxylic acids4.4.3 Hydroxycarboxylic and hydroxydicarboxylicacids4.4.4 Stable isotopes and carboxylic acids4.5 Sulfonic and phosphonic acids.4.6 Alcohols, aldehydes, ketones and sugars4.7 Amines and amides4.8 Nitrogen heterocycles4.9 Sulfur heterocycles4.10 Macromolecular material4.10.1 Elemental composition4.10.2 Aromatic and aliphatic hydrocarbons4.10.3 Oxygen, sulfur and nitrogen-containing moieties4.10.4 Stable isotopes and macromolecular materials5 Origin and evolution of organic matter inmeteorites5.1 Soluble compounds5.2 Macromolecular materials6 Meteoritic organic matter and the origin of life7 References1 IntroductionThis review covers the organic analyses of carbonaceous chon-drite meteorites performed during and since the second halfof the 20th century. The field lay inactive during the first halfof the 20th century but a rising interest in space science andthe development of new analytical methods led to its revival inthe 1950s and 1960s. Current theories rely heavily on analyses292 Nat. Prod. Rep., 2002, 19, 292–311 DOI: 10.1039/b103775gThis journal is © The Royal Society of Chemistry 2002Fig. 1 The journey from interstellar space to the laboratory illustrated in pictures: a) the Eagle Nebula (Photo courtesy of NASA) is a molecularcloud where stars are being born and a rich interstellar chemistry is taking place, b) Mathilde (Photo courtesy of NASA), a member of the C-typeasteroids that have remained relatively unchanged since the birth of the solar system and which may be the parent bodies for the carbonaceouschondrite meteorites, c) the Murchison (CM2) carbonaceous chondrite which fell in Australia in 1969 and contains a variety of organic molecules,d) a thin section of the Dar al Gani 186 carbonaceous chondrite showing spherical silicate chondrules surrounded by a matrix composed primarilyof clay minerals, oxides and organic matter.performed since 1969 when new contaminant free samplesbecame available and modern techniques were developed inanticipation of sample returns from spaceflight missions. Someolder results, however, are valuable when considered with mod-ern knowledge and this review examines and often re-interpretsmaterial presented in papers published both before and after1969. A number of key reviews have been published on theorganic analyses of carbonaceous chondrites over the last fortyyears.1–51.1 Carbonaceous chondrites and their originMeteorites are fragments of extraterrestrial material that fall tothe Earth’s surface. The Earth acquires 100 000 to 1 000 000 kgof such material each day, but only 1% or less arrives in pieceslarge enough for identification and recovery.6 The surface of themeteorite usually melts and emits a glowing tail and a trail ofsmoke, but the interior of the meteorite is unaffected by passagethrough the Earth’s atmosphere. It is generally agreed that mostmeteorites are fragments of asteroids propelled into Earth-crossing orbits by relatively recent collisions in the asteroid belt,initiated by the gravitational effects of Jupiter’s orbit.7 Theasteroids have escaped many of the geological processes experi-enced on the planets and they, and the meteorites derived fromthem, preserve some of the most primitive materials in the solarsystem. The carbonaceous chondrites are
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