Iltkatastrofen

O₂ opbygning i jordens atmosfære. Den røde og grønne linje repræsenterer estimationsintervallet – og tiden måles i milliarder af år før nu (Ga – Giga-anno – dansk Giga-år).
* Trin 1 (3,85–2,45 Ga): O₂ antages ikke at blive produceret. Dog har Professor Minik Rosing og Professor Robert Frei fundet spor af fotosyntetiserende mikrober fra ca. 3,7 milliarder år siden.^[1] Professor Kenichiro Sugitani og en medarbejder har fundet mikrofossiler med noget, der ligner fotosyntetiserende plankton - og som er fra ca. 3 milliarder år siden.^[2] Geologer ved Trinity College Dublin har fundet tegn på at iltproducerende liv fandtes for 3 milliarder år siden.^[3]
* Trin 2 (2,45–1,85 Ga): O₂ produceres,^[4] men bindes grundet kemiske reaktioner med opløste stoffer i verdenshavet og uopløste stoffer (fx mineraler) i oceanbundplader.
* Trin 3 (1,85–0,85 Ga): O₂ starter med at udgasse fra verdenshavet, men bindes grundet kemiske reaktioner med mineraler i kontinentalpladerne (landfladerne - undtagen kontinentalsoklerne) og danner ozonlaget.
* Trin 4 og 5 (0,85–0,54 Ga) og (0,54 Ga–nu): O₂ dræn er fyldte og iltgassen akkumulerer. I trin 4 hævdes jorden at have lignet en sneboldjord i den sidste del af Proterozoikum; Neoproterozoikum. Fra ca. 600 Ma dukker flercellede eukaryote organismer op – Ediacara-faunaen. Fra ca. 543 Ma siden sker den Kambriske Eksplosion.

Den store Iltkatastrofe (forkortelse GOE fra eng. Great Oxygenation Event), iltkatastrofen eller oxygenkatastrofen var en væsentlig miljøændring på jorden, som menes at have fundet sted for ca. mellem 3,8-2,45 milliarder år siden i æonen Prækambrium^[5], da cyanobakterier udviklede evnen til at udskille ilt som et restprodukt fra omdannelse af CO₂ ved fotosyntese. Den store mængde dannede ilt medførte en økologisk krise.

^ 17 December, 2003, BBCNews: Oldest evidence of photosynthesis Citat: "...Scientists claim to have found the oldest evidence of photosynthesis – the most important chemical reaction on Earth – in 3.7-billion-year-old rocks....If their findings are correct, life was very sophisticated, very early on in Earth history," said Buick...But life may be older and more robust than we thought..."
^ Penn State (2013, June 6). Three-billion-year-old microfossils include plankton. ScienceDaily Citat: "...However, the researchers not only showed that these inclusions in the rocks were biological in origin, but also that they were likely planktonic autotrophs..."
^ Trinity College Dublin. (2014, September 4). Life forms appeared at least 60 million years earlier than previously thought. ScienceDaily Citat: "...Geologists from Trinity College Dublin have rewritten the evolutionary history books by finding that oxygen-producing life forms were present on Earth some 3 billion years ago -- a full 60 million years earlier than previously thought...There was virtually no atmospheric O2 present 3.4 billion years ago, but recent work from South African paleosols suggested that by about 2.96 billion years ago O2 levels may have begun to increase..."
^ University of Zurich (2013, January 17). Great Oxidation Event: More oxygen through multicellularity. ScienceDaily Citat: "...multicellular cyanobacteria emerged much earlier than previously assumed. "Multicellularity developed relatively early in the history of cyanobacteria, more than 2.3 billion years ago," Schirrmeister explains in her doctoral thesis, written at the University of Zurich..."
^ 26. sep 2013, ing.dk: Ilt og udbredt liv på Jorden 700 millioner år tidligere end hidtil antaget Citat: "...En analyse af jordbunden placerer ilt i atmosfæren allerede for tre milliarder år siden, hvilket viser, at det vrimlede med liv på Jorden...Livet på Jorden opstod for omkring 3,8 milliarder år siden. Her eksisterede bakterier, som kunne omdanne sol og vand til kulstof og ilt..."

[1] 17 December, 2003, BBCNews: Oldest evidence of photosynthesis Citat: "...Scientists claim to have found the oldest evidence of photosynthesis – the most important chemical reaction on Earth – in 3.7-billion-year-old rocks....If their findings are correct, life was very sophisticated, very early on in Earth history," said Buick...But life may be older and more robust than we thought..."

[2] Penn State (2013, June 6). Three-billion-year-old microfossils include plankton. ScienceDaily Citat: "...However, the researchers not only showed that these inclusions in the rocks were biological in origin, but also that they were likely planktonic autotrophs..."

[3] Trinity College Dublin. (2014, September 4). Life forms appeared at least 60 million years earlier than previously thought. ScienceDaily Citat: "...Geologists from Trinity College Dublin have rewritten the evolutionary history books by finding that oxygen-producing life forms were present on Earth some 3 billion years ago -- a full 60 million years earlier than previously thought...There was virtually no atmospheric O2 present 3.4 billion years ago, but recent work from South African paleosols suggested that by about 2.96 billion years ago O2 levels may have begun to increase..."

[4] University of Zurich (2013, January 17). Great Oxidation Event: More oxygen through multicellularity. ScienceDaily Citat: "...multicellular cyanobacteria emerged much earlier than previously assumed. "Multicellularity developed relatively early in the history of cyanobacteria, more than 2.3 billion years ago," Schirrmeister explains in her doctoral thesis, written at the University of Zurich..."

[5] 26. sep 2013, ing.dk: Ilt og udbredt liv på Jorden 700 millioner år tidligere end hidtil antaget Citat: "...En analyse af jordbunden placerer ilt i atmosfæren allerede for tre milliarder år siden, hvilket viser, at det vrimlede med liv på Jorden...Livet på Jorden opstod for omkring 3,8 milliarder år siden. Her eksisterede bakterier, som kunne omdanne sol og vand til kulstof og ilt..."

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Iltkatastrofen

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