From: CurtAdams@aol.com
Date: Wed Nov 24 1999 - 19:34:23 MST
In a message dated 11/24/99 18:25:21, you wrote:
>Right, but biota aren't based on heavy metals. Most carbon and oxygen
>are produced by *much* slower processes, principally planetary
>nebula ejection and white-dwarf novas. These events happen
>gigayears or tens of gigayears after star formation.
More relevant might be concentrations of elements whose concentrations often
limit on earth; nitrogen and phosphorus spring to mind. (Iron can be
limiting in the ocean but that's more of a solubility issue.) Life uses a
lot of trace elements: I wouldn't think concentrations of things like
selenium would be limiting but I'm not really sure.
I think nitrogen is the most limiting element since life uses a lot of it,
it's relatively rare, and since it's mostly gas it's very prone to get lost.
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