Noble gases solar wind components

Figure 3.5 Radically anomalous noble gas isotopic compositions in extrasolar materials isolated from undifferentiated meteorites (from Anders Zinner, 1993). Stepwise heating of whole-rock meteorites liberates slightly more or less of components such as Xe-HL and Ne-E, relative to other noble gas reservoirs in the rock, leading to the modest isotopic variations (e.g., Xe compositions as illustrtated in Figure 3.4, or Ne compositions to the lower-left of the air-spallation-solar wind triangle in Figure 3.3) from which the presence of anomalies was originally inferred.

To resolve the primordial terrestrial noble gas, it would be useful to examine major noble gas reservoirs in the early solar system, which could have supplied noble gases to the Earth. As we discussed in Chapter 3, two major noble gas components occur very widely in the solar system and can be a potential source for the terrestrial noble gas. They are solar noble gas (representative of the sun), which is generally assumed to be best represented by solar wind noble gas implanted on Al-foil target plates on the moon (elemental ratio) and on lunar breccia (isotopic ratio) (e.g., Ozima et al., 1998), and Q phase noble gas (see Wieler, 1994, for a review), which occurs very widely in various chondrites. Next we will compare the bulk Earth noble gas, which we assume to be represented by atmospheric noble gas with these two major noble gas components in the solar system. 

Marti K. and Mathew K. (1998) Noble-gas components in planetary atmospheres and interiors in relation to solar wind and meteorites. Proc. Indian Acad. Sci. Earth Planet Sci. 107, 425-431. 

Note that in the next subsection and in XbtMoon section we will discuss a noble gas component in lunar samples also dubbed SEP, as it is thought to be of solar origin and implanted at higher energies than the solar wind. This component seems, however, not to represent the same energy range as SEPs detected in space. 

Figure 8. Ne data from 4 lunar and 2 meteoritic samples containing solar noble gases. Gases were released by in vacuo etching, except for samples 10084 (stepwise heating) and 61501 (total fusion of aliquot samples previously etched off-line). Besides solar wind Ne (SW), all samples appear to contain a second solar component, labeled SEP. This is indicated e. g. by the many points on the mixing line SEP-GCR, where GCR represents the composition of Ne produced by Galactic Cosmic Rays. The Ne/ Ne ratios above the SW point in the first release fractions of 10084 (inset) indicate isotopic fractionation during gas extraction, which is not observed in the etch-experiments. Data sources listed in Wieler (1998). [Used by permission of Kluwer Academic Publishers, from Wieler (1998), Space Sci. Rev., Vol. 85, Fig. 1, p 304.]...

Figure 3. Isotopic ratios °Ne/ Ne and Ar/ Ar as determined for various trapped noble gas components (Table 3). Not shown are Ne isotopic ratios for the nucleogenic G [Ne-E(H)] and R [Ne-E(L)] components, which are almost or (probably) entirely pure Ne (see discussion in text). Also not shown is the (theoretical) value for Ar-G. HE may contain small contributions from P6. Obvious are the similarities between the Q and ureilite compositions as well as the similarity in Ar/ Ar between solar wind and the subsolar component. Both ratios (maybe by coincidence) decrease in the order from left to right.

Meteorites contain a variety of trapped noble gas components other than the solar wind. In many cases their compositions have not been measured in pure form, but have been determined from measured (i.e., not pure) compositions based correlation / mixing lines involving assumptions about one isotopic ratio in the end-member. Some of the components established in this way are of nucleosynthetic origin and carried by presolar grains (diamond, SiC, graphite). Their isotopic compositions are testament to the nuclear processes by which elements are made in the interior of the stars around which those carrier grains formed. 

Martel DJ, Deak J, Dovenyi P, Horvath F, O Nions RK, Oxbmgh ER, Stegna L, State M (1989) Leakage of helium from the Patmonian Basin. Nature 432 908-912 Marti K, Mathew KJ (1998) Noble-gas components in planetary atmospheres and interiors in relation to solar wind and meteorites. Proc Indian Acad Sci (Earth Planet Sci) 107 425-431 Marty B, Alle P (1994) Neon and argon isotopic constraints on Earth-atmosphere evolution. In Noble gas geochemistry and cosmochemistry. Matsuda J-1 (ed) Terra Scientific Publishing Co., Tokyo, p 191-204. 

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