Silicon Based Life forms????

William Bains william at
Tue Apr 15 07:27:30 EST 1997

In article <3349933C.391F at>, Rob <rchapman at> wrote:

>  What if life forms were silicon based rather than carbon bases? Silicon
> is much more abundant on earth than carbon its atoms can bond to 4 other
> atoms.  Bonds between silicon are unstable in the presence of 02 but
> bonds between silicon and oxygen are extremely stable and difficult to
> break. I was wondering what implications would these properties have for
> these life forms.
>                             Please reply by April 7, but if you cant its
> no problem.
>                              Thanks, Justin

One explanation is that carbon forms bonds with many other atoms that are
stable, but not too stable. By contrast, silicon forms bonds with oxygen
which are very stable, but only comparatively labile bonds with other
elements. (This is related to Silicon's extra shell of electrons, which
enables a range of reaction paths and intermediates which are not
available to carbon under 'physiological' conditions.) So carbon can form
amines, amides, sulphides, hydroxides and oxides, phosphates, sulphates
and so on, and of course the range of hydrocarbons, all of which are
stable enough to exist in each other's presence but not stable enough to
be unbreakable. Silicon chemistry does not support this complexity.

One speculative idea (I think attributable to Larry Niven, following
Cairns' ideas on the mineral origins oflife) is that life *was* originally
silicon based, but was eradicated by the oxygen-producing carbon biosphere
we have today. Under this scenario, oxygen was originally produced as a
toxic secondary metanolite, and its central role in energy metabolism is a
relatively recent adaptation. This, of course, does not address any of the
problems with using silicon in the first place.

William Bains

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