Meteorites isotopic measurements

Amino acid measurements in ALH84001 are almost certainly the result of Antarctic ice contamination. Amino acids are readily soluble in water but PAHs are practically insoluble. Isotopic measurements of 14C show that terrestrial carbon is incorporated into the meteorite during extended stays in the Antarctic ice fields. In addition, microbial activity on the exposed surfaces provides an additional source of biogenic organic material that may be incorporated over time. 

Since the IM-20 had not previously been used for high precision isotopic measurements and since previous isotopic measurements with other ion microprobes [24,25] were characterized by percent level relative errors, we carried out an extensive series of Mg isotopic analyses of terrestrial samples. Terrestrial standards were especially emphasized prior to the study of meteoritic samples, but were also periodically interspersed with later meteoritic analyses as a check on the performance of the ion probe. Terrestrial standards included Ceylon spinel (MgAl204), Madagascar hibonite (CaA112019), a suite of olivines (Fo 100 to Fo 5) used in... 

Kehm K, Hauri EH, Alexander CMOD, Carlson RW (2003) High precision iron isotope measurements of meteoritic material by cold plasma ICP-MS. Geochim Cosmochim Acta 67 2879-2891... 

Nittler LR, Alexander CMOD (2003) Automated isotopic measurements of micron-sized dust application to meteoritic presolar silicon carbide. Geochim Cosmochim Acta 67 4961-4980 Nuth JA(1987) Small-particle physics and interstellar diamond. Nature 329 589... 

Figure 4. Correlation between the excesses of of the different classes of meteorites, as measured by their A 0 and their 5 Cu values. The volatile-depleted carbonaceous chondrites (CV) show a deficit in the heavier isotope Cu, which led Luck et al. (2003) to suggest that the observed correlations result from a nucleosynthetic excess of Cu.

Mass-independent isotopic fractionations are widespread in the earth s atmosphere and have been observed in O3, CO2, N2O, and CO, which are all linked to reactions involving stratospheric ozone (Thiemens 1999). For oxygen, this is a characteristic marker in the atmosphere (see Sect. 3.9). These processes probably also play a role in the atmosphere of Mars and in the pre-solar nebula (Thiemens 1999). Oxygen isotope measurements in meteorites demonstrate that the effect is of significant importance in the formation of the solar system (Clayton et al. 1973a) (Sect. 3.1). 

Ag2S was mixed with cuprous oxide and converted to SO2 by heating at 900 C (2). BaSC>4 was directly converted to SO2 by thermal decomposition in quartz at 1600 C (3). Product SO2 was freed from water and COo> before isotopic measurement on a Micromass 602D mass spectrometer. S/ S ratios are reported to a precision of 0.2%o relative to troilite from the Canyon Diablo meteorite using the normal 8 S%o notation. 

Figure 7 Isotopic patterns measured in bulk samples of SiC extracted from the Murchison meteorite. Isotopic ratios are relative to the reference isotope plotted as a solid circle and are normalized to the solar isotopic ratios. Data are from Lewis et al. (1994) (Kr and Xe), Podosek et al. (2003) (Sr), Prombo et al. (1993) (Ba), Richter et al. (1993)...

Pillinger C. T. (1987) Stable isotope measurements of meteorites and cosmic dust particles. Phil. Trans. Roy. Soc. London A 323, 313-322. 

Yurimoto H, Nagasawa H, Mori Y, Matsubaya O (1994) Micro-distribution of oxygen isotopes in a refractory inclusion from the Allende meteorite. Earth Planet Sci Lett 128 47-53 Zinner E (1989) Isotopic measurements with the ion microprobe. In WCI Shanks, RE Criss (eds) New Frontiers in Stable Isotope Research Laser Probes, Ion Probes, and Small-Sample Analysis, U S Geol SurvBull 1890 145-162... 

The one-time presence of superheavy elements in meteorites has been inferred from the anomalous xenon effect. The ratios of xenon isotopes measured in some meteorites are very different from those found in terrestrial xenon. This was thought to be due to the former presence of Pu which had produced fission-product xenon as it decayed out. This theory was confirmed in part recently when xenon isotope ratios from Pu were measured and were found to be identical with ratios from one group of meteorites, the achondrites. On the other hand, the chondrite meteorites still do not fit. It had been shown that an element heavier than Cf was needed to give the required ratio, ° and Anders and Heymann and Dakowski suggested independently that extinct superheavy elements could be the cause. Rao indicated that excess Kr could be explained similarly. Schramm has calculated that if fission of a superheavy element is the cause, its half-life would lie in the surprisingly narrow range of 1.6 x lO" —6.8 x 10 yr. 

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