Argon solar abundance

Natural isotopes of argon and their solar abundances... 

Noble gases and nitrogen in martian meteorites reveal several interior components having isotopic compositions different from those of the atmosphere. Xenon, krypton, and probably argon in the mantle components have solar isotopic compositions, rather than those measured in chondrites. However, ratios of these noble gas abundances are strongly fractionated relative to solar abundances. This decoupling of elemental and isotopic fractionation is not understood. The interior ratio in martian meteorites is similar to chondrites. 

The Zag meteorite fell in the western Sahara of Morocco in August 1998. This meteorite was unusual in that it contained small crystals of halite (table salt), which experts believe formed by the evaporation of brine (salt water). It is one of the few indications that liquid water, which is essential for the development of life, may have existed in the early solar system. The halite crystals in the meteorite had a remarkably high abundance of 128Xe, a decay product of a short-lived iodine isotope that has long been absent from the solar system. Scientists believe that the iodine existed when the halite crystals formed. The xenon formed when this iodine decayed. For this reason, the Zag meteorite is believed to be one of the oldest artifacts in the solar system. In this lab, you will use potassium-argon radiochemical dating to estimate the age of the Zag meteorite and the solar system. 

Murer, Ch. A., Baur, H., Signer, P., Wider, R. (1997) Helium, neon, and argon abundances in the solar wind In vacuo etching of meteoritic iron-nickel. Geochim. Cosmochim. Acta, 61, 1303-14. 

Argon is the third mostabundant of the noble gases. From the isotopic decomposition of solar-wind Ar one finds that the mass-38 isotope,38 Ar, is the second mostabundant of Ar isotopes in the universe. In the Earth s atmosphere,40 Ar happens to be the most abundant owing to its peculiar origin on Earth as the daughter of radioactive 4°K. 3 Ar comprises 15.8% of all the Ar isotopes in the Sun. Using the total abundance of elemental Ar = 1.01 x lo5 per million silicon atoms in the Sun, this isotope has... 

For most of the chemical elements, the relative abundances of their stable isotopes in the Sun and solar nebula are well known, so that any departures from those values that may be found in meteorites and planetary materials can then be interpreted in terms of planet-forming processes. This is best illustrated for the noble gases neon, argon, krypton, and xenon. The solar isotopic abundances are known through laboratory mass-spectrometric analysis of solar wind extracted from lunar soils (Eberhardt et al., 1970) and gas-rich meteorites. Noble gases in other meteorites and in the atmospheres of Earth and Mars show many substantial differences from the solar composition, due to a variety of nonsolar processes, e.g., excesses of " Ar and... 

Figure 5 The relative abundances of noble gases in gas-rich MORE (Moreira et al, 1998), as calculated for the upper mantle (see text), air (Tables 2 and 3), and in the solar composition (see Ozima and Podosek, 2001). The upper mantle is enriched in neon and xenon, relative to argon, compared to the air composition.

On Venus, the noble gases do not appear to have greatly evolved from solar characteristics. The heavy rare-gas elemental abundances are similar to solar values, although this similarity does not extend to neon, since the e/ Ar ratio is low. Nonetheless, the je/ Ne ratio is closer to the solar value. Venus is also gas rich, with the absolute abundance of argon on Venus exceeding... 

Kumagai H, Kaneoka 1 (1998) Variations in noble gas abundances and isotope ratios in a single MORB pillow. Geohys Res Lett 25 3891-3894 Kunz J (1999) Is there solar argon in the Earth s mantle Nature 399 649-650... 

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