Complementary, double- and single-resonance solid-state (H-1 and C-13) nuclear magnetic resonance (NMR) experiments were performed on a solvent extracted and demineralized sample of Murchison meteorite organic macromolecule. These NMR data provide a consistent picture of a complex organic solid composed of a wide range of organic (aromatic and aliphatic) functional groups, including numerous oxygen-containing functional groups. The fraction of aromatic carbon within the Murchison organic residue (constrained by three independent experiments) lies between 0.61 and 0.66. The close similarity in cross-polarized and single-pulse spectra suggests that both methods detect the same distribution of carbon. With the exception of interstellar diamond (readily detected in slow magic angle spinning single-pulse NMR experiments), there is no evidence in the solid-state NMR data for a significant abundance of large laterally condensed aromatic molecules in the Murchison organic insoluble residue. Given the most optimistic estimation, such carbon would not exceed 10%, and more likely is a fraction of this maximum estimate. The fraction of aromatic carbon directly bonded to hydrogen is low (similar to30%), indicating that the aromatic molecules in the Murchison organic residue are highly substituted. The bulk hydrogen content, H/C, derived from NMR data, ranges from a low of 0.53 +/- 0.06 and a high of 0.63 +/- 0.06. The hydrogen content (H/C) determined via elemental analysis is 0.53. The range of oxygen-containing organic functionality in the Murchison is substantial. Depending on whether various oxygen-containing organic functional groups exist as free acids and hydroxyls or are linked as esters and ethers results in a wide range in O/C (0.22 to 0.37). The lowest values are more consistent with elemental analyses, requiring that oxygen-containing functional groups in the Murchison macromolecule are highly linked. The combined H-1 and C-13 NMR data reveal a high proportion of methine carbon, which requires that carbon chains within the Murchison organic macromolecule are highly branched. Copyright (C) 2002 Elsevier Science Ltd.

Lead isotopes are compared in two equivalent diagrams. With a range in U/Pb, a closed system that evolved its radiogenic Pb in a single stage yields data that define a line of exactly the same age in the two presentations. This strict reproducibility (within +/- a few 10(6) yr, at most) is the crux of the concept of Pb-isotope synchronism. In contrast, an open system produces data that disperse variably in the two diagrams, yielding ages which are often different by much greater than 107 yr. However, because an age-calculation reconciles uncertainty in the age with the degree of dispersion in the data, a highly disturbed system yields false ages (from both diagrams), which nevertheless overlap within the calculated errors.

By using accelerator mass spectrometry we have measured the Be-10 concentrations of 86 Australasian tektites. Corrected to the time of tektite production similar to0.8 My ago, the Be-10 concentrations (10(6) atom/g) range from 59 for a layered tektite from Huai Sai, Thailand, to 280 for an australite from New South Wales, Australia. The average value is 143 +/- 50. When tektites are sorted by country, their average measured Be-10, concentrations increase slowly with increasing distance from Southeast Asia, the probable location of the tektite producing event, from 59 +/- 9 for 6 layered tektites from Laos to 136 +/- 20 for 20 splash-form tektites from Australia. The lowest Be-10 concentrations for tektites fall on or within a contour centered off the shore of Vietnam, south of the Gulf of Tonkin (107degreesE; 17degreesN), but also encompassing two other locations in the area of northeastern Thailand previously proposed for the site of a single tektite-producing impact. The Be-10 concentrations of layered tektites show only a weak anticorrelation (R similar to -0.3) with the numbers of relief crystalline inclusions.

An approach aiming at a summation-depiction of the isotopic characteristics of a planet is attempted. The approach, Lead Isotope Planetary Profiling (LIPP), is a thematic derivation from the general field of planetary geochemistry. Specifically, the recently developed methodology of Pb isotope synchronism, which often allows the accurate dating of disturbed geologic systems, has been applied to a large body of terrestrial Pb isotopic data in the literature. The exercise resulted in 26 Pb/Pb lines most of which appear to be highly precise isochrons.