Re: Why Would Aliens Hide?
Wed, 24 Nov 1999 21:34:23 EST

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.