Meteorites, hydrocarbons

This resemblance is highly significant if one considers that 10,359 structural isomers exist for saturated hydrocarbons with 16 C atoms (Lederberg, 1972). Apparently the meteoritic hydrocarbons were made by FTT reactions, or some other process of the same extraordinary selectivity. The Miller-Urey reaction, incidentally, shows no such selectivity. Gas chromatograms of hydrocarbons made by electric discharges in methane show no structure whatsoever in the region around Cjg (Ponnamperuma et al., 1969). Apparently all 10 possible isomers are made in comparable yield, as expected for random recombination of free radicals. 

Studier M. H., Hayatsu R., and Anders E. (1972) Origin of organic matter in Early Solar System—V Further studies of meteoritic hydrocarbons and discussion of their origin. Geochim. Cosmochim. Acta 36, 189—215. 

McCollom, T.M. Formation of meteorite hydrocarbons from thermal decomposition of siderite (FeCOs). Geochim. Cosmochim. Acta 2003, 67(2), 311-317. 

Aromatic hydrocarbons were found in more recent analyses pyrene, fluoran-threne, phenanthrene and naphthalene in the ratio of 10 10 5 1 (Cronin, 1998). The majority (around 70%) of the hydrocarbons extracted from the Murchison meteorite are polar compounds such as ... 

Now and then, projectiles from outer space cause excitement and surprises, as in January 2000, when a meteorite impacted the frozen surface of Lake Targish in Canada. It was a new type of C-chondrite with a carbon concentration of 4-5%, and probably came from a D-type asteroid (Hiroi et al., 2001). More exact analysis of the Targish meteorite showed the presence of a series of mono- and dicarboxylic acids as well as aliphatic and aromatic hydrocarbons (Pizzarello et al., 2001). Aromatic compounds and fullerenes were detected in the insoluble fraction from the extraction this contained planetary helium and argon, i.e., the 3He/36Ar ratio was... 

Thus, the question is whether such classes of molecules were present on the young Earth. The only witnesses capable of giving an answer to this question are meteorites (Deamer, 1988). The group of David Deamer studied Murchison material after extraction and hydropyrolysis (at 370-570 K, with reaction times of several hours or days). GC and MS analyses showed the presence of a series of organic compounds, including significant amounts of amphiphilic molecules such as octanoic (C ) and nonanoic acids (C9) as well as polar aromatic hydrocarbons. 

Krishnamurthy RV, Epstein S, Cronin JR, Pizzarello S, Yuen GU (1992) Isotopic and molecular analyses of hydrocarbons and monocarboxyUc acids of the Murchison meteorite, Geochim Cosmochim Acta 56 4045 058... 

Knenvolden, K., Lawless, J. G., Pering, K., et al. (1970). Evidence for extraterrestrial amino acids and hydrocarbons in the Murchison meteorite. Nature, 228, 923-6. 

The presence of organic molecules in samples of extraterrestrial matter has been known for more than a century. Some of the greatest chemists of the nineteenth century were involved in the analysis of samples of meteoritic material. They were able to show that carbonaceous chondrites (as they are now named) contain organic molecules. The first to detect carbon in a meteoritic sample was Thenard, in 1806, by analysis of a sample of the Alais meteorite. This result was confirmed in 1834 by Berzelius, who was also the first to detect the presence of water of crystallisation. Working on a sample of the Kaba meteorite, Wohler (1858) confirmed the presence of organic matter, and in a paper dated 1859 said, I am still convinced that besides free carbon this meteorite contains a low-melting point, carbon containing substance which seems to be similar to certain fossil hydrocarbon-like substances... . 

Working on a sample of the Orgueil chondrite, in 1868 Berthelot detected the presence of hydrocarbons after the hydrogenation of a meteorite sample. This... 

Fig. 3. Hydrocarbons from Murchison meteorite and Fischer-Tropsch synthesis. BP = branched paraifin BO = branched olefin

A pattern of this sort does not form directly in the primary Fischer-Tropsch reaction. It does, however, develop when a primary Fischer-Tropsch mixture remains in contact with the catalyst, for a day or so at 35(MOO °C (Fig. 3, bottom), or longer times at lower temperatures (Studier et al., 1968, 1972 Galwey, 1972). Under such conditions, a metastable equilibrium is approached, with methane and aromatic hydrocarbons forming at the expense of ethane and heavier alkanes (Dayhoff et al, 1964 Eck et al, 1966). The kinetics and mechanism of such aro-matization on the catalyst surface has been discussed by Galwey (1972). Of the 61 hydrocarbons in the meteorite, 42 (underlined) are also seen in the synthetic sample, though often not in the same amount. It remains to be seen whether the match can be made more quantitative by changes in the reheating conditions. 

Fig. 9. Mass spectra of polymeric materials from the Murchison meteorite and a Fischer-Tropsch synthesis extended over 6 months. The principal peaks are due to ardmatic hydrocarbons, their alkyl derivatives, and alkenes (Hayatsu et al., 1977)...

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