Extraterrestrial matter

The analysis of extraterrestrial matter is concentrated on the detection of nucleic acid and protein building blocks, i.e., N-heterocycles and amino acids. The search for such compounds began immediately after the fall of the Murchison meteorite. Twenty-two amino acids were detected in it as early as 1974 eight of them pro-teinogenic, ten which hardly ever occurred in biological material, and four which were unknown in the biosphere. Up to now, about 70 amino acids have been identified (Cronin, 1998), the most common being glycine and a-aminoisobutyric acid. The latter is a branched-chain amino acid with the smallest possible number of carbon atoms. The most frequently found amino acids occur in concentrations of... 

In this article, we first discuss basic dating principles and then studies based on isotopes produced by cosmic radiation in extraterrestrial matter and in the earth s atmosphere. The discussions are intended to illustrate how analytical physical and chemical studies contribute to the understanding of processes in the environmental system and their history. 

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... . 

The mass of the earth increases daily due to falls of extraterrestrial material. The estimates by different authors of the flux of extraterrestrial matter vary by many orders of magnitude, depending on the estimation method used. In his recent book, Dodd 5) gives an estimation of 102-103 tons per day, the largest part being in the shape of dust particles (or micrometeorites). 

The fall of a carbonaceous chondrite in September 1969 near Murchison (85 miles north of Melbourne, Australia) was an event of great importance for scientists involved in meteoritic research. In 1969, many laboratories were well equipped to analyse the lunar samples, and interest in extraterrestrial matter was at its height when suddenly 83 kg of a carbonaceous chondrite were available. The biggest fragment... 

The configuration of natural amino acids has led to studies on the possibility that homochirality emerged at a prebiotic stage, which may be supported by the presence of amino acids as non-racemic mixtures in meteorites (32). This enantiomeric excess may have resulted from the exposition of extraterrestrial matter to circularly polarized light (42). Whatever the origin of this enantiomeric excess, it may have initiated stereoselective processes through different catalytic pathways (7). Symmetry breaking may also have resulted from reactivity in connection with other processes such as crystallization or interfacial chemistry (43, 44) and polymerization of amino acids (45). 

The concern of cosmochemistry is the investigation of extraterrestrial matter (sun, moon, planets, stars and interstellar matter) and their chemical changes. Meteorites are an object of special interest in cosmochemistry, because of the nuclear reactions induced by high-energy protons in cosmic radiation ( (p) up to about 10 GeV) and by other particles, such as a particles and various heavy ions. Measurement of the radionuclides produced in meteorites by cosmic radiation gives information about the intensity of this radiation in interstellar space and about the age and the history of meteorites. 

A key goal of ionospheric modeling efforts is to determine from meteor observations the influx of extraterrestrial matter, and how the matter that is deposited between altitudes of 80 and 120 km couples to ionospheric disturbances such as sporadic E layers that seriously affect communications... 

Michel R., Leya 1., and Borges L. (1996) Production of cosmogenic nuclides in meteoroids accelerator experiments and model calculations to decipher the cosmic ray record in extraterrestrial matter. Nucl. Instr. Meth. Phys. Res. B 113,... 

Farley K. A. (2001) Extraterrestrial helium in seafloor sediments identification, characteristics and accretion rates over geologic time. In Accretion of Extraterrestrial Matter throughout Earth s History (eds. B. Peucker-Ehrenbrinck and B. Schmitz). Kluwer, New York, pp. 179-204. 

Peucker-Ehrenbrink B. (1996) Accretion of extraterrestrial matter during the last 80 million years and its effect on the marine osmium isotope record. Geochim. Cosmochim. Acta 60, 3187-3196. 

Flynn GJ (2001) Atmospheric entiy heating of interplanetary dust. In Accretion of extraterrestrial matter throughout Earth s history. Peucker-Ehrenbrink B, Schmitz (eds) Kluwer, New York, p 107-127 Galer SJG, Mezger K (1998) Metamorphism, denudation and sea level in the Archean and cooling of the Earth. Precamb Res 92 389-412... 

Extraterrestrial He. Polar ice also archives the influx of extraterrestrial matter in the form of interplanetary dust particles (IDPs), similar to the ocean sediments (see Schlosser and Winckler 2002 in this volume). Ice cores may provide less ambiguous results for the IDP flux than ocean sediments, as accumulation rates and time scales are well known in this archive. By analyzing He isotopes in particles separated from polar ice. Brook et al. (2000) demonstrated the utility of the ice core record to study the IDP flux and found similar results as obtained from marine sediments. 

Farley KA (2001) Extraterrestrial helium in seafloor sediments Identification, characteristics, and accretion rate over geological time. In Accretion of extraterrestrial matter throughout Earth s history. B Peucker-Ehrenbrink, B Schmitz (eds) Kluwer Academic/Plenum Pubhsheis, p 179-204 Farley KA, Patterson DB (1995) A 100-kyr periodicity in the flux of extraterrestrial e to the sea floor. Nature 378 600-603... 

Mason, B., 1969. Composition of stony meteorites. In C.A. Randall, Jr. (Editor), Extraterrestrial Matter. Northern Illinois University Press, DeKalb, 111., pp. 3—22. 

Bland P (2001) Quantification of meteorite infall rates from accumulations in deserts, emd meteorite accumulations on Mars. In Peucker-Ehrenbrink B, Schmitz B (eds) Accretion of extraterrestrial matter throughout earth s history. Kluwer Academic/Plenum, New York, pp 267-298 Bogard DD (ed) (1983) A meteorite from the Moon. Geophys Res Lett 10 733-840... 

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