Originally I sat down to write about the large-scale history of Earth, and line up the big developments that our biosphere has undergone in the last 4 billion years. But after writing about the reason that Earth is unique in our solar system (that is, photosynthesis being an option here), I guess I needed to explore photosynthesis and other forms of metabolism on Earth in a little more detail and before I knew it I’d written more than 3000 words about it. So, here we are, taking a deep dive into photosynthesis and energy metabolism, and trying to determine if the origin of photosynthesis is a rare event or likely anywhere you get a biosphere with light falling on it. Warning: gets a little technical.
https://thegreatatuin.wordpress.com/2016/10/17/energy-metabolism-and-photosynthesis/
In short, I think it’s clear from the fact that there are multiple origins of it that phototrophy, using light for energy, is likely to show up anywhere there is light and life. I suspect, but cannot rigorously prove, that even though photosynthesis of biomass only emerged once it was an early development in life on Earth emerging very near the root of the Bacterial tree and just produced a very strong first-mover advantage crowding out secondary origins of it, and would probably also show up where there is life and light. As for oxygen-producing photosynthesis, its origin from more mundane other forms of photosynthesis is still being studied. It required a strange chaining together of multiple modes of photosynthesis to make it work, and only ever happened once as well. Its time of emergence, early or late, is pretty unconstrained and I don’t think there’s sufficient evidence to say one way or another if it is likely to happen anywhere there is photosynthesis. It could be subject to the same ‘first mover advantage’ situation that other photosynthesis may have encountered as well. But once it got going, it would naturally take over biomass production and crowd out other forms of photosynthesis due to the inherent chemical advantages it has on any wet planet (that have nothing to do with making oxygen) and its effects on other forms of photosynthesis.
Oxygen in the atmosphere had some important side effects, one which most people care about being allowing big complicated energy-gobbling organisms like animals – all that energy that organisms can get burning biomass in oxygen lets organisms that do so do a lot of interesting stuff. Looking for oxygen in the atmospheres of other terrestrial planets would be an extremely informative experiment, as the presence of this substance would suggest that a process very similar to the process that created our huge diverse and active biosphere were underway.
Great article here on the latest deep bio, tho i can't read original..
Many Worlds, Subterranean Edition
http://www.manyworlds.space/index.php/2015/11/24/many-worlds-subterranean-edition/
and a panspermia update, with link in comments to a sweet little pdf
"And how was it that these sophisticated life processes emerged not all that long (in astronomical or geological terms) after Earth cooled enough to be habitable? “Either life developed here super-fast or it came full-on as DNA life from afar,” Ruvkun said."
http://www.manyworlds.space/index.php/2017/01/05/in-search-of-panspermia/
and a new paper in Nature on some new archeans, had a great takeaway that may def help the panspermia argument, as the little buggers seem to be primed to move up the chain in anerobic enviros.
"We found that Asgard archaea share many genes uniquely with eukaryotes, including several genes that are involved in the formation of structures that give eukaryotic cells their complex character. Such genes had thus far only been found in eukaryotes, indicating that these archaea were somehow primed to become complex.
http://astrobiology.com/2017/01/how-complex-cellular-life-may-have-emerged.html
I am continually confused as to why people find seven hundred million years (4.4 to 3.7 billion years ago, the date at which we have both the oldest intact rocks on earth and not coincidentally the oldest good evidence for living things) an insufficient time to develop biochemical complexity. The Hadean is more unknown (due to no solid rocks surviving from that era due to geological reprocessing) than hellish, at least to a microbe over evolutionary time. There was liquid water and hydrothermal systems, there was basalt, there was more granitic rock, the... (read more)