Origin and evolution of light elements

The light elements (D to B, apart from 4He) have such fragile nuclei (see Table 9.1) that they tend to be destroyed, rather than created, in thermonuclear burning, although certain special processes can lead to stellar production of 3 He, 7Li and nB. 

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The prevailing theory of the origin and evolution of the Universe is the Big Bang theory. According to this theory, about 14 billion years ago the Universe expanded to its present enormous volume from an initial volume, which was effectively zero. Three sets of observations have profoundly shaped the way in which we think about our Universe and led to the Big Bang theory. First was the discovery that our Universe is expanding. Second, there were predictions about the abundances of the light elements H, He, and Li in the Universe, and third was the discovery made by Penzias and Wilson (1965) that our part of the Universe is filled with microwave radiation. 

The molecules found to date are composed of the elements H, C, N, O, Si, S, and Cl with the bulk of the molecules containing H, C, N, and O. The light elements H, D, and He are of cosmological origin and are therefore tracers of the early universe. On the other hand the heavier elements C, N, O,... are produced in stars by the processes of stellar nucleosynthesis. In addition to the most abundant isotopic forms many stable isotopes such as D, 13C, 170, lsO, 15N, 30Si, 33S, and 34S have been detected (see Appendix 1). The detailed determination of isotopic ratios — though often beset with formidable difficulties — has become a useful indicator of the chemical evolution of molecular clouds and the past chemical history of the galaxy. 

Martian (SNC) meteorites, remote sensing, and spacecraft exploration have provided insights into the origin, evolution and interaction of several light-element reservoirs on Mars including the lithosphere, hydrosphere and atmosphere. Beyond Earth, Mars is certainly the most exhaustively investigated body from a stable isotopic perspective. 

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