Solar wind noble gases

Schwarzmiiller, J. Stettler, A. (1970). Trapped solar wind noble gases, exposure age and K/Ar-age in Apollo 11 lunar fine material. Proc. Apollo 11 Lunar Sci. Conf, 2,1037-70. 

Eberhardt, E, Geiss, X, Graf, H., Grogler, N., Mendia, M. D., Morgeli, M. U., Schwaller, H., Stettler, A. (1972) Trapped solar wind noble gases in Apollo 12 lunar fines 12001 and Apollo 11 breccia 10046. Proc. Third Lunar Science Conf., 2, 1821-56. 

Figure 7. The solid line shows the cahbiation curve for the antiquity indicator "" Ar/ Ar for lunar soils, proposed by Eugster et al. (2001). The antiquity (abscissa) is the time when a sample has trapped its solar wind noble gases at the immediate lunar surface. The ordinate shows the ratio (" °Ar/ Ar)tr of Ar trapped on grain surfaces. Filled and open symbols represent calibrabon data of higher and lower quality, respectively. The dashed line is an exponential curve illustrating the decay of the parent isotope of " °Ar. [Used by permission of The Meteoritical Society, from Eugster et al. 2001), Meteoritics and Planetary Sciences, Vol. 36, Fig. 4, p 1107.]...

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. 

Noble gas abundances in lunar soils and chondrites, (a) Elemental abundance patterns for trapped solar wind in lunar soils, normalized to solar system abundances, (b) Elemental abundance patterns for planetary trapped noble gases, normalized to solar system abundances. This diagram is intended to illustrate patterns only vertical positions are arbitrary. Modified from Ozima and Podosek (2002). 

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.

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... 

The observed noble-gas abundances and isotopic ratios on Venus are summarized in Tables 3 and 4. The helium mixing ratio is a model-dependent extrapolation of the value measured in Venus upper atmosphere, where diffusive separation of gases occurs. The main differences between Venus and Earth are that Venus is apparently richer in He, Ar, and Kr than the Earth, and the low " Ar/ Ar ratio of — 1.1 on Venus, which is —270 times smaller than on Earth. The low " Ar/ Ar ratio may reflect more efficient solar-wind implantation of Ar in solid grains accreted by Venus and/or efficient early outgassing that then stopped due to the lack of plate tectonics. Wieler (2002) discusses the noble-gas data. Volkov and Frenkel (1993) and Kaula (1999) describe implications of the " Ar/ Ar ratio for outgassing of Venus. 

Figure 15 Noble-gas elemental ratios in IDPs compared with Cl meteorites and solar-wind (star) noble gas compositions are also plotted. Closed and open diamonds represent unheated IDPs and Zn-depleted IDPs, respectively. Square and circle represent lunar mineral separates (Singer et a/. 1977) and planetary bulk Cl chondrite (Jeffery and Anders, 1970), respectively (data courtesy of K. Kehm). See also Kehm et al. (2002).

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. 

Models of a solar-wind source for noble gases on the terrestrial planets have been proposed in various contexts by WetheriU (1981), Donahue et al. (1981), and McEkoy and Prather (1981). Assuming that sufficient abundances of noble gases were accumulated in solid materials, it would be expected that due to gravitational scattering gas-bearing materials would be dispersed throughout the inner solar system and... 

The atmosphere of Mars has several features that are distinct from that of the Earth and require a somewhat different planetary history. At likely nebular temperatures and pressures at its radial distance. Mars is too small to have condensed a dense early atmosphere from the nebula even in the limiting case of isothermal capture (Hunten, 1979 Pepin, 1991). Therefore, regardless of the plausibility of gravitational capture as a noble-gas source for primary atmospheres on Venus and Earth, some other way is needed to supply Mars. This may include solar-wind implantation or comets. An important feature is that, in contrast to Earth, martian xenon apparently did not evolve from a U-Xe progenitor, but rather from SW-Xe. This requires that accreting SW-Xe-rich materials that account for martian atmospheric xenon are from sources more localized in space or time and so have not dominated the terrestrial-atmospheric xenon budget. There are insufficient data to determineif the martian C/N ratio is like the terrestrial value, but it appears that the initial C/H2O ratio may have been. Further constraints on the sources of the major volatUes are required. 

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