Extraterrestrial materials

Peroxonitrite is beHeved to be present in the crystals of nitric acid trihydrate that form in the stratosphere and in Martian soil (see Extraterrestrial materials). Peroxonitrous acid may be present in mammalian blood and other biochemical systems. However, peroxonitric acid, HNO, is not known. Before the chemistry of peroxonitrous acid was understood, these two acids were sometimes confused. 

Occurrence and Recovery. Rhenium is one of the least abundant of the naturally occurring elements. Various estimates of its abundance in Earth s cmst have been made. The most widely quoted figure is 0.027 atoms pet 10 atoms of silicon (0.05 ppm by wt) (3). However, this number, based on analyses for the most common rocks, ie, granites and basalts, has a high uncertainty. The abundance of rhenium in stony meteorites has been found to be approximately the same value. An average abundance in siderites is 0.5 ppm. In lunar materials, Re, when compared to Re, appears to be enriched by 1.4% to as much as 29%, relative to the terrestrial abundance. This may result from a nuclear reaction sequence beginning with neutron capture by tungsten-186, followed by p-decay of of a half-hfe of 24 h (4) (see Extraterrestrial materials). 

Tritium has also been observed in meteorites and material recovered from sateUites (see also Extraterrestrial materials). The tritium activity in meteorites can be reasonably well explained by the interaction of cosmic-ray particles and meteoritic material. The tritium contents of recovered sateUite materials have not in general agreed with predictions based on cosmic-ray exposure. Eor observations higher than those predicted (Discoverer XVII and sateUites), a theory of exposure to incident tritium flux in solar flares has been proposed. Eor observations lower than predicted (Sputnik 4), the suggested explanation is a diffusive loss of tritium during heating up on reentry. 

The Analysis of Extraterrestrial Materials. By Isidore Adler Chemometiics. By Muhammad A. Sharaf, Deborah L. Illman, and Bruce R. Kowalski Fourier Transform Infrared Spectrometry. By Peter R. Griffiths and James A. de Haseth Trace Analysis Spectroscopic Methods for Molecules. Edited by Gary Christian and James B. Callis... 

Alexander von Humboldt (1769-1859) recognised meteorites as being a source of extraterrestrial material. Several well-known chemists carried out analyses of material from meteorites, starting at the beginning of the nineteenth century. Thus Louis-Jacques Thenard (1777-1857) found carbon in Alais meteorites these results were confirmed in 1834 by Jons Jacob Berzelius, who by dint of very careful work was also able to detect water of crystallisation in meteoritic material. 

Birck JL (2004) An overview of isotopic anomalies in extraterrestrial materials and their nucleosynthetic heritage. Rev Mineral Geochem 55 25-64... 

An Overview of Isotopic Anomalies in Extraterrestrial Materials and Their Nucleosynthetic Heritage... 

The high precision with which Mg isotope ratios can be measured using MC-ICPMS opens up new opportunities for using Mg as a tracer in both terrestrial and extraterrestrial materials. A key advance is the ability to resolve kinetic from equilibrium mass-dependent fractionation processes. From these new data it appears that Mg in waters is related to mantle and crustal reservoirs of Mg by kinetic fractionation while Mg in carbonates is related in turn to the waters by equilibrium processes. Resolution of different fractionation laws is only possible for measurements of Mg in solution at present laser ablation combined with MC-ICPMS (LA-MC-ICPMS) is not yet sufficiently precise to measure different fractionation laws. 

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