Interstellar molecules, organic matter

In 1981, Geiss and Reeves 100) suggested that the deuterium enrichment observed in the organic macromolecular compounds could be explained on the basis of a suggestion made by the same authors in 1972 101 , i.e. the survival of interstellar molecules [synthesised at low temperatures (10—50 K) by ion-molecule gas-phase reaction] in chondritic matter. 

Interstellar clouds, tlie birthplace of stars and planetary systems, are rich in simple organic materials and radicals in tlie gas phase and may contain more complex molecules and even macromolecular organic matter on grains. Although these complicated molecules have not been observed in interstellar... 

Organic-rich extraterrestrial samples such as meteorites, micrometeorites, interplanetary dust particles (IDPs) and samples returned by spacecraft provide a unique record of the chemical processes in the early solar system and in the interstellar medium. In particular, detailed structural and isotopic analyses of carbonaceous meteorites have revealed a rich organic inventory and provided evidence of the synthesis of complex organic molecules in the interstellar medium and on the asteroidal parent bodies of meteorites [1,2], The organic matter in carbonaceous meteorites is present at levels of up to 5% and can be divided into solvent-soluble (l%-25%) and insoluble (75%-99%) fractions, the former characterized by considerable structural, isomeric, and isotopic diversity [2,3], and the latter characterized by a high molecular weight and complex aromatic network [4]. 

However, the detection of radio spectral lines in the frequency range of about 22 to 23 GHz from the polyatomic molecules NH3 and H20 (in 1968 and 1969) by Cheung et al. and the discovery of the organic molecule H2CO (in 1969) by Snyder et al. marked the beginning of a long series of discoveries. From these and all subsequent discoveries it became evident that dense and cool condensations of the interstellar matter are particularly rich in molecules. 

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