Space/Science — HabitableZone

Space/Science » in reply to Cool Green Hills of Earth an Anomoly?

re: Cool Green Hills of Earth an Anomoly?

I've mused on this topic before.

Rather than accept that it is an "accident" that Earth's plants absorb red light, rather than the more energetic yellow-blue light that dominates modern sunlight, maybe we should try to understand what the early Earth might have been like, and the conditions in which photosynthesis originated.

Let us assume that these early photosynthesisers got it RIGHT - they used the best energy spectrum that was available to them.

This would mean that the Early earth was lit by RED light. There are two wys to do this - by playing with the Sun, and by putting something in the way of sunlight.

An early sun MIGHT have been feeble and red, but this does not fit with what we know about main sequence stars. A star has never been observed in the moment of birth, so we're not sure, but there don't seem to be any young feeble red suns around.

Alternatively, we can interpose something to block and redden the sunlight. A thick and exotic/polluted atmosphere will do this - maybe a photochemical smog and every day the sun at noon is a dull red orb in a bronzed and dirty sky.

Or you could use interplanetary dust - but it's hard to keep this around with accreting planets and a young sun flaring off energetic solar winds - so I prefer the smog idea.

Later, once photosynthesis was "locked-in" as a basic biochemical process, the lighting conditions may have changed, but the fine-tuning of photosynthesis ensured that it would always be better than any de-novo chemical pathway, even if that one would be theoretically better, if it hung around long enough to get optimised.

Log in or register to post.

The whole thread (7 posts)