From: Dan Clemmensen (dgc@cox.rr.com)
Date: Sun Jan 27 2002 - 08:49:13 MST
Spudboy100@aol.com wrote:
> Chlorophyll seems to be the best chemical that was randomly, successful for
> life; rather then rhodopsin, why argue the point? Perhaps posthumanity will
> lace the surfaces of different worlds with rhodopsin-engineered life? Not an
> objectionable idea, that.
>
> Dog Jones Opined:
> <<Curious but quite possibly pointless- that chlorophyll is the dominant
> photosynthetic compound on the surface of the earth today is an accident
> of history. If the green slime hadn't poisoned the atmosphere two
> billion years ago, rhodopsin would be *the* signature of a living
> planet. To expect that independently evolved life in another solar
> system would use the exact same chemical pathways as on earth is
> provincial thinking in the extreme.
>
It's possible that the test can be made insensitive to the specific
photochemical: Any life based on photosynthesis will leave a dark
spot in the spectrum. The tricky part is to figure out what a lifeless
spectrum should look like for planets of a particular star, so that you
can look for the difference. If someone works out a methodology, it
can be tested on the planets of the Solar system first.
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