Earths, discussion whether elements

There is general agreement that theoretical predictions of nuclear stability, which we discuss briefly in the next paragraph, define a range of superheavy elements with sufficiently long half-fives to allow their study, provided they can be S3mthesized. What cannot be predicted is whether there exist nuclear reactions for such synthesis in detectable amounts on earth. 

The anthropomorphic question of the connection and relevance of interstellar chemistry to the existence and origin of life on earth is not touched on in this discussion, although a high premium has been placed on establishing this connection and thereby creating relevance. The earth has conditions and chemistries vastly different from those dealt with in this chapter. Whether the molecular forms synthesized by clearly abiotic pathways survive the condensation of the solar nebula, or whether molecular synthesis will occur essentially from the elements, is an interesting question on which to conclude. 

The accretion of a late veneer. Whether or not a late veneer was added to the Earth towards the end of accretion is not clear. The principal evidence comes from the elevated siderophile element chemistry of the mantle. If there was a late veneer, it had to happen after core formation. At present the evidence from the trace element chemistry is ambiguous, because these data can also be explained by the formation of the core at high pressures and temperatures in a magma ocean, or by continuous core formation with decreasing metal input. Currently, the best evidence for a late veneer comes from Os-isotope evidence, where there is a clear mismatch between the composition of the PUM and chondrite. However, even this is uncertain, as is discussed in the next chapter (Chapter 3, Section 3.2.3.4), for... 

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