[TML] Alien ecologies

[Robert O'Connor]

Jerry Barrington wrote:
> Remember that the height of the solar spectrum has been squished by a factor
> of 10.55, so differences are way more then this makes clear.

So what?

You seem to have unrealistic expectations of how efficient an absorber
can be without deliberate effort and/or some *very* unusual - probably
impossible - chemistry. Chlorophyll's really not that bad in what it does.

To recap:
> Having very broad absorption spectra is unlikely for plausible energy transducing
> compounds (e.g. organic heterocycles with transition metal or group 2 metal
> ion reactive centres).

An overview of the problem:
1. The stellar spectrum is going to be a function of its temperature
(black body radiator, Planck's modification to Wien's law).

2. Atmospheric 'transparency' is a function of the absorptive and
scattering properties of its components. For most worlds of interest in
Traveller these are nitrogen-oxygen atmospheres of varying optical
depth; the Bougeur-Lambert law applies regardless, but it's very easy to
extrapolate from the characteristics of Earth's atmosphere.

3. The components of the spectrum available for interception by a
chromogen will be limited by its chemical structure and composition. It
is currently difficult to predict the absorption spectrum of a given
heterocyclic organic structure. As far as I can recall, organic and 
biochemists are at the 'synthesize and see' stage.

4. As a world's atmosphere evolves from anaerobic (CO2, N2, methane, CO
predominant) to oxygen containing there will be significant changes to
the atmosphere's absorption spectrum.

However, there are evolutionary constraints on the potential energy
transduction 'receptors' - the basic chemical elements in the
biosphere's repertoire and structural motifs have probably been largely
'fixed' by the indigenous microbial life.

5. What color the local plants end up being is governed by the
wavelengths reflected (emitted!) by their tissues. Chromogens like
chlorophyll will be the primary determinant of this.


Robert O'Connor
medico, gamer