Editing Hot spring (section)

=== Hot spring hypothesis ===
In contrast with "[[black smokers]]" (hydrothermal vents on the ocean floor), hot springs similar to terrestrial hydrothermal fields at Kamchatka produce fluids having suitable pH and temperature for early cells and biochemical reactions. Dissolved organic compounds were found in hot springs at Kamchatka .<ref>{{Cite journal |last=Kompanichenko |first=Vladimir N. |date=May 16, 2019 |title=Exploring the Kamchatka Geothermal Region in the Context of Life's Beginning |journal=Life |language=en |volume=9 |issue=2 |pages=41 |doi=10.3390/life9020041 |pmid=31100955 |pmc=6616967 |bibcode=2019Life....9...41K |issn=2075-1729|doi-access=free }}</ref><ref name=":1" /> Metal sulfides and silica minerals in these environments would act as photocatalysts.<ref name=":1">{{Cite journal |last1=Mulkidjanian |first1=Armen Y. |last2=Bychkov |first2=Andrew Yu. |last3=Dibrova |first3=Daria V. |last4=Galperin |first4=Michael Y. |last5=Koonin |first5=Eugene V. |date=2012-04-03 |title=Origin of first cells at terrestrial, anoxic geothermal fields |journal=Proceedings of the National Academy of Sciences |volume=109 |issue=14 |pages=E821-30 |doi=10.1073/pnas.1117774109 |pmc=3325685 |pmid=22331915|doi-access=free }}</ref> They experience cycles of wetting and drying which promote the formation of biopolymers which are then encapsulated in vesicles after rehydration.<ref>{{Cite journal |last1=Damer |first1=Bruce |last2=Deamer |first2=David |date=March 15, 2015 |title=Coupled Phases and Combinatorial Selection in Fluctuating Hydrothermal Pools: A Scenario to Guide Experimental Approaches to the Origin of Cellular Life |journal=Life |volume=5 |issue=1 |pages=872–887 |doi=10.3390/life5010872 |pmid=25780958 |pmc=4390883 |bibcode=2015Life....5..872D |doi-access=free }}</ref> Solar UV exposure to the environment promotes synthesis to monomeric biomolecules.<ref>{{Cite journal |last1=Patel |first1=Bhavesh H. |last2=Percivalle |first2=Claudia |last3=Ritson |first3=Dougal J. |last4=Duffy |first4=Colm D. |last5=Sutherland |first5=John D. |date=March 16, 2015 |title=Common origins of RNA, protein and lipid precursors in a cyanosulfidic protometabolism |journal=Nature Chemistry |language=en |volume=7 |issue=4 |pages=301–307 |doi=10.1038/nchem.2202 |pmid=25803468 |pmc=4568310 |bibcode=2015NatCh...7..301P |issn=1755-4349}}</ref> The ionic composition and concentration of hot springs (K, B, Zn, P, O, S, C, Mn, N, and H) are identical to the cytoplasm of modern cells and possibly to those of the [[Last universal common ancestor|LUCA]] or early cellular life according to phylogenomic analysis.<ref>{{Cite journal |last1=Van Kranendonk |first1=Martin J. |last2=Baumgartner |first2=Raphael |last3=Djokic |first3=Tara |last4=Ota |first4=Tsutomu |last5=Steller |first5=Luke |last6=Garbe |first6=Ulf |last7=Nakamura |first7=Eizo |date=2021-01-01 |title=Elements for the Origin of Life on Land: A Deep-Time Perspective from the Pilbara Craton of Western Australia |url=https://www.liebertpub.com/doi/abs/10.1089/ast.2019.2107 |journal=Astrobiology |volume=21 |issue=1 |pages=39–59 |doi=10.1089/ast.2019.2107 |pmid=33404294 |bibcode=2021AsBio..21...39V |s2cid=230783184}}</ref><ref name=":1" /> For these reasons, it has been hypothesized that hot springs may be the place of origin of life on Earth.{{sfn|Farmer|2000}}{{sfn|Des Marais|Walter|2019}} The evolutionary implications of the hypothesis imply a direct evolutionary pathway to land plants. Where continuous exposure to sunlight leads to the development of photosynthetic properties and later colonize on land and life at hydrothermal vents is suggested to be a later adaptation.<ref name=":2">{{Cite journal |last1=Damer |first1=Bruce |last2=Deamer |first2=David |date=2020-04-01 |title=The Hot Spring Hypothesis for an Origin of Life |journal=Astrobiology |volume=20 |issue=4 |pages=429–452 |doi=10.1089/ast.2019.2045 |issn=1531-1074 |pmc=7133448 |pmid=31841362|bibcode=2020AsBio..20..429D }}</ref>

Recent experimental studies at hot springs support this hypothesis. They show that fatty acids self-assemble into membranous structures and encapsulate synthesized biomolecules during exposure to UV light and multiple wet-dry cycles at slightly alkaline or acidic hot springs, which would not happen at saltwater conditions as the high concentrations of ionic solutes there would inhibit the formation of membranous structures.<ref name=":2" /><ref>{{Cite journal |last=Deamer |first=David |date= February 10, 2021 |title= Where Did Life Begin? Testing Ideas in Prebiotic Analogue Conditions |journal=Life |volume=11 |issue=2 |pages=134 |doi=10.3390/life11020134 |pmid= 33578711 |pmc= 7916457 |bibcode=2021Life...11..134D |issn=2075-1729|doi-access=free }}</ref><ref>{{Cite journal |last1=Milshteyn |first1=Daniel |last2=Damer |first2=Bruce |last3=Havig |first3= Jeff |last4= Deamer |first4=David |date=May 10, 2018 |title=Amphiphilic Compounds Assemble into Membranous Vesicles in Hydrothermal Hot Spring Water but Not in Seawater |journal= Life |volume=8 |issue=2 |pages=11 |doi=10.3390/life8020011 |pmid=29748464 |pmc=6027054 |bibcode=2018Life....8...11M |doi-access=free }}</ref> [[David W. Deamer|David Deamer]] and Bruce Damer note that these hypothesized prebiotic environments resemble [[Charles Darwin]]'s imagined "warm little pond".<ref name=":2"/> If life did not emerge at deep sea hydrothermal vents, rather at terrestrial pools, extraterrestrial quinones transported to the environment would generate redox reactions conducive to proton gradients. Without continuous wet-dry cycling to maintain stability of primitive proteins for membrane transport and other biological macromolecules, they would go through hydrolysis in an aquatic environment.<ref name=":2" /> Scientists discovered a 3.48 billion year old geyserite that seemingly preserved fossilized microbial life, stromatolites, and biosignatures.<ref>{{Cite journal |last1=Djokic |first1=Tara |last2=Van Kranendonk |first2=Martin J. |last3=Campbell |first3=Kathleen A. |last4=Walter |first4=Malcolm R. |last5=Ward |first5=Colin R. |date=2017-05-09 |title=Earliest signs of life on land preserved in ca. 3.5 Ga hot spring deposits |journal=Nature Communications |language=en |volume=8 |issue=1 |pages=15263 |doi=10.1038/ncomms15263 |pmid=28486437 |pmc=5436104 |bibcode=2017NatCo...815263D |issn=2041-1723}}</ref> Researchers propose pyrophosphite to have been used by early cellular life for energy storage and it might have been a precursor to pyrophosphate. Phosphites, which are present at hot springs, would have bonded together into pyrophosphite within hot springs through wet-dry cycling.<ref name=":3">{{Cite web |last=Marshall |first=Michael |date=April 2, 2013 |title= Meteorites could have been source of life's batteries |url=https://www.newscientist.com/article/mg21829114-800-meteorites-could-have-been-source-of-lifes-batteries/ |access-date=2022-11-01 |website=New Scientist |language=en-US}}</ref> Like alkaline hydrothermal vents, the Hakuba Happo hot spring goes through serpentinization, suggesting methanogenic microbial life possibly originated in similar habitats.<ref>{{Cite journal |last1=Suda |first1=Konomi |last2=Ueno |first2=Yuichiro |last3=Yoshizaki |first3=Motoko |last4=Nakamura |first4=Hitomi |last5=Kurokawa |first5=Ken |last6=Nishiyama |first6=Eri |last7=Yoshino |first7=Koji |last8=Hongoh |first8=Yuichi |last9=Kawachi |first9=Kenichi |last10=Omori |first10=Soichi |last11=Yamada |first11=Keita |last12=Yoshida |first12=Naohiro |last13= Maruyama |first13= Shigenori |date=2014-01-15 |title=Origin of methane in serpentinite-hosted hydrothermal systems: The CH4–H2–H2O hydrogen isotope systematics of the Hakuba Happo hot spring |url=https://www.sciencedirect.com/science/article/pii/S0012821X13006286 |journal=Earth and Planetary Science Letters |language=en |volume=386 |pages=112–125 |doi=10.1016/j.epsl.2013.11.001 |bibcode=2014E&PSL.386..112S |issn=0012-821X}}</ref>