Re: Nothing like oil?

On Mar 17, 9:51 pm, "Keith F. Lynch" <k...@xxxxxxxxxxxxxx> wrote:

Interesting. Why is that ratio different in living things? And where
is the *non*-biogenic carbon that has a different ratio? Hasn't all
the carbon on our planet cycled through the biosphere many times?

Probably it has. But life does not alter the total inventory of C12
relative to C13. When living things incorporate an excess of C12
relative to background, the background becomes slightly richer in C13.

When formerly living tissues oxidize, they pull the background ratio
closer to the norm. But as long as organic carbon is a small fraction
of the total, the background is essentially constant.


What's the ratio on other planets?

I do not believe we know this. It does not seem reasonable to me to
assume no fractionation in either the solar nebula or in
differentiation of the earth. So other planets might well have a
different ratio.

People are looking at the carbon isotope ratios in meteorites,
including those from Mars, but with what results, if any, I do not
know.


William Hyde
.

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