Abundances in Solar System

Figure 2 The s-process and r-process abundances in solar system matter (based upon the work by Kappeler et aL, 1989). Note the distinctive s-process signature at masses A —88, 138, and 208 and the corresponding r-process signatures at A — 130 and 195, all attributable to closed-shell effects on neutron capture cross-sections. It is the r-process pattern thus extracted from solar system abundances that can be compared with the observed heavy element patterns in extremely metal-deficient stars (the total solar system abundances for the heavy elements are those compiled by Anders and Grevesse, 1989), which are very similar to those from the compilation of Palme and Jones (see Chapter 1.03).

Figure 3 Map of the deuterium abundance in solar system objects, plotted as D/H mole fraction. The carrier molecules for which deuterium has been measured in each object are labeled. The protosolar value, derived from measurements of He products of deuterium fusion in the Sun, and deuterium in the local region of the galaxy, is given, as are values for a carbonaceous chondrite meteorite, the Earth s oceans, and comets (source...

Figure 2. Nitrogen isotope abundances in solar system materials upper scale gives absolute ratios lower scale gives relative to the terrestrial AIR standard. Heavy bars show observed ranges light bars show measurement...

Using the total abundance of elemental H = 2.79 x lo10 per million silicon atoms in solar-system matter and an initial isotope ratio in the Sun of D/H = 1.5 x 10-5, as determined in today s interstellar medium (ISM), the D isotope has... 

From the isotopic decomposition of normal He one finds that the mass-4 isotope, 4He, is 99.986% of all helium. It is the second most abundant nucleus in the universe Modern observations of the interstellar gas reveal it to be 10.3 times less abundant than hydrogen. The elemental abundance is He = 2.72 x 109 per million silicon atoms in solar-system matter. 

From the isotopic decomposition ofnormal lithium onefinds thatthemass-6 isotope, 6Li, is the lesser abundant of lithium s two isotopes 7.5% of terrestrial Li. Lithium presents some of the most interesting abundance questions in astrophysics (see also 7Li). Using the total abundance of elemental Li = 57.1 per million silicon atoms in solar-system matter, this isotope has... 

From the isotopic decomposition ofterrestrial nitrogen one finds thatthe mass-14 isotope, 14N, is 99.63% of all N isotopes, essentially the entire N abundance. (See 15N for evidence from Jupiter for an even smaller 15N fraction in the solar system.) Using the total abundance of elemental N = 3.13 million per million silicon atoms (he. 3.13 times more abundant than Si) in solar-system matter,... 

From the isotopic decomposition of normal silicon one finds thatthe mass-28 isotope, 2 Si, is the most abundant of the three stable Si isotopes 92.23 % of all Si. Using one million silicon atoms, the common cosmochemical standard in solar-system matter,... 

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