[TML] Alien ecologies

[Jerry W Barrington]

On 8/20/08 12:40 PM, "darby eckles" <darbyeckles at yahoo.com> wrote:

> I had a dream lastnight that I was somplace where the vegetation was all
> shades of purple.  It got me thinking about how in most Traveller games I've
> been a player in the worlds we visited seemed to be either very Earth like,
> with green clorophyle based flora, or very arid/desert like.  When I run
> games, I like to have very alien planets.  I really liked the graphic book
> Expedition by Barlow, thre are some far out critters there...

In my own opinion, Barlowe generally goes a bit *too* far out.  He mostly
draws things that look interesting, with little regard to evolution.

> Anyways, I digress...
>  
> So, what I am wondering is: is it possible to have purple photosynthetic
> plants?  Is it just a matter of the chlorophyl/whatever processing UV spectrum
> light or reflect purple based colors, or would it necessitate some completely
> different system of light usage? 

Purple thing are reflecting both blue and red and absorbing the colors
between.  This is exactly opposite of chlorophyll.  (They may also absorb or
reflect IR or UV, but our eyes don't see that.)  Also, note that human
vision is most sensitive in the green, and that is also where the Sun's peak
emission is.  Actually makes it kind of odd that plants *aren't* purple, as
green is where the most energy is.  Although, they tend to be a *dark*
green, so apparently they still absorb a lot of the green.

Given the nature of sunlight and our eyes, even something that absorbed
moderately more green than not-green might still easily *look* green to us.

<http://en.wikipedia.org/wiki/Image:Chlorophyll_ab_spectra.png>

In any case, it's certainly *possible* for alien life to use something other
than or in addition to chlorophyll for photosynthesis.  How *likely* it is
needs study.

On the other hand, UV, and to a lesser extent blue, can cause damage, as
well as providing energy.  Check the function of anthocyanins:

<http://en.wikipedia.org/wiki/Anthocyanin>

> Also, what minierals have a purple hue?  Amethyst?  Can that be broken down
> and used by living creatures?

Amethyst is violet colored quartz.  Quartz is just silicon dioxide.  As
Bruce said, recent work has shown the violet color to be the result of iron
and aluminum impurities, and heat can easily turn it to yellow citrine.
Doesn't sound like any form of "digestion" would preserve the color.