Theoretical origin of life; hostile hot springs (Introduction)

by David Turell , Thursday, September 24, 2020, 20:02 (1521 days ago) @ David Turell

Another review:

https://www.sciencenews.org/article/life-earth-origins-hostile-hot-springs-microbes

"Microorganisms at hot springs can form communities called microbial mats. Made up of layers of microbes, mats have been found in geothermal areas all over the world, including in Yellowstone National Park, the Garga hot spring in southern Russia and Lassen — home to Bumpass Hell.

"Over time, microbial mats can form into stromatolites, structures of microbes and minerals that have accumulated on top of one another; the layered appearance of a stromatolite reflects the passage of time, like a tree’s growth rings. Researchers found evidence of stromatolites in the Dresser Formation, a 3.5-billion–year-old rock feature in the Western Australia outback, along with evidence of hot spring mineral deposits, describing the findings in 2017

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"These results, reported in December 2019 in Astrobiology, indicate that complex molecules can form at hot springs, supporting the hypothesis that life on Earth may have developed in such an environment.

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"In 2017, researchers found fossils in 3.77-billion-year-old rocks from Quebec that originated from the ancient ocean floor and had signs of hydrothermal activity (SN: 4/1/17, p. 6). The researchers claim that the distinct structures resemble those of microbes, suggesting that deep-sea environments may have supported some of the earliest life on Earth.

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"To Deamer, there are big barriers to putting life’s pieces together near underwater vents: The vastness of the ocean would dilute molecules so they wouldn’t be concentrated enough to drive chemical reactions. Also, there are “no wet-dry cycles underwater.” In his view, repeated evaporation is needed to pull together enough molecules to bump into each other and react to form longer chains. Plus, unlike a hot spring’s freshwater, salty ocean water inhibits the formation of membranes and reactions that link together molecules, he says.

"However, Deamer’s hot springs theory has its critics as well. DNA and RNA strands are composed of alternating phosphate and sugar molecules, but sugars “are profoundly unstable in hot spring environments,” says David Des Marais, an astrobiologist at NASA’s Ames Research Center.

"And it may be too soon to rule out wet-dry cycles underwater. “You can have a little bit of water get stuck in a pore,” says Bill Brazelton, a marine microbiologist at the University of Utah in Salt Lake City. And then, because the serpentinization reaction at a vent uses up water in making other molecules, “you can have these cycles of dehydration inside a rock underneath the ocean.'”

Comment: Still no clear cut theory. Hot springs or hot vents make an interesting proposal. Certainly not anything like lightning in a bottle, which started all of this.