Written by: Leonard Parker | solar news | March 30, 2021
The permanent rise of oxygen in the Earth's atmosphere, which fundamentally changed the subsequent nature of Earth's habitability, occurred much later than thought, according to new research.
And the study, from an international team led by the University of Leeds and including researchers from the University of California-Riverside, Harvard University, the University of Southern Denmark and the University of St Andrews, also provides an explanation for some of the most extreme climate episodes to have affected the Earth, when the planet was repeatedly covered with ice.
The first time oxygen was significantly present in the atmosphere was about 2.43 billion years ago, and this marks the start of the Great Oxidation Event - a pivotal period in Earth's history.
Although the Great Oxidation Event led to oxygen levels that were still much lower than today, it dramatically changed the chemical composition of the planet's surface and set the stage for the subsequent course of biological evolution on Earth, which ultimately led to a planet teaming with animal life.
By analysing rocks from South Africa, which were deposited in the ocean at the time of the Great Oxidation Event, the researchers discovered that early atmospheric oxygenation was short-lived, and oxygen did not become a permanent feature of the atmosphere until much later.
Professor Simon Poulton, of Leeds' School of Earth and Environment, led the research.
He said: "The Great Oxidation Event fundamentally changed Earth's environment and habitability. This early period of oxygenation was thought to have occurred between about 2.43 and 2.32 billion years ago.
"However, our research shows that, in fact, oxygenation of the atmosphere was highly unstable over a period of about 200 million years, with permanent atmospheric oxygenation occurring about 100 million years later that previously thought."
Their findings, published in the journal Nature, also suggest a direct link between fluctuations in atmospheric oxygen concentration and greenhouse gas concentrations.
Professor Andrey Bekker of the University of California-Riverside, who co-authored the study, said: "These findings help explain four widespread glaciations that occurred coincident with the Great Oxidation Event, some of which were likely to have covered the whole of the Earth in ice for millions of years.
"Our new data show that the permanent rise of oxygen actually occurred after the final major glaciation of the period and not before it, which had previously been a major puzzle in our understanding of links between early atmospheric oxygenation and intense climatic instability."
The research team has re-labelled this period the Great Oxidation Episode. It ushered in a 1.5 billion year period of subsequent climatic and environmental stability, which remained until a second major period of rising oxygen and climate instability at the end of the Precambrian period.
Professor David Johnston, a co-author from Harvard University said: "The rise of atmospheric oxygen was a key factor in Earth's habitability.
"Unravelling the history of atmospheric oxygenation ultimately allows us to understand how oxygen rose to levels that were sufficient to allow the evolution of animals.
"The Great Oxidation Episode, when atmospheric oxygen first rose to appreciable levels, represents a pivotal step in this history."
Professor Poulton added: "We cannot begin to understand the causes and consequences of atmospheric oxygenation, the most significant control on Earth's habitability, if we do not know when permanent atmospheric oxygenation actually occurred. Now at last we have that piece of the puzzle."
Research Report: A 200-million-year delay in permanent atmospheric oxygenation
University Of Leeds
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"Kama ilivyotangazwa na ""Solar News"" mnamo Machi 30, 2021, ongezeko la kudumu la oksijeni katika anga la Dunia, ambalo lilibadilisha asili ya baadaye ya kuishi kwa Dunia, lilitokea baadaye kuliko ilivyodhaniwa, kulingana na utafiti mpya." Utafiti huo uliofanywa na timu ya kimataifa inayoongozwa na Chuo Kikuu cha Leeds na pamoja na watafiti kutoka Chuo Kikuu cha California-Riverside, Chuo Kikuu cha Harvard, Chuo Kikuu cha Kusini mwa Denmark na Chuo Kikuu cha St Andrews, pia hutoa ufafanuzi wa baadhi ya matukio ya hali ya hewa ya hali ya juu zaidi ambayo yameathiri Dunia, wakati sayari ilifunikwa mara kwa mara na barafu. Oksijeni ilionekana kwa mara ya kwanza katika anga ya dunia miaka bilioni 2.43 iliyopita, na hii ilikuwa mwanzo wa tukio la Great Oxidation, kipindi muhimu katika historia ya dunia. Ingawa tukio la Great Oxidation lilisababisha viwango vya oksijeni kuwa chini sana kuliko leo, lilibadilisha sana muundo wa kemikali ya uso wa sayari na kuweka hatua kwa mwendo wa baadaye wa mageuzi ya kibiolojia duniani, ambayo hatimaye ilisababisha sayari ya wanyama. Kwa kuchunguza miamba kutoka Afrika Kusini, ambayo ilichukuliwa katika bahari wakati wa tukio kubwa la oksijeni, watafiti waligundua kwamba oksijeni ya angahewa ya mapema ilikuwa ya muda mfupi, na oksijeni haikuwa kipengele cha kudumu cha angahewa hadi baadaye. Profesa Simon Poulton, wa Shule ya Dunia na Mazingira ya Leeds, aliongoza utafiti huo. Alisema hivi: "Tukio Kuu la Oksidation lilibadili kabisa mazingira ya Dunia na uwezo wake wa kuishi. Kipindi hiki cha kwanza cha oksijeni kilidhaniwa kutokea kati ya miaka bilioni 2.43 na 2.32 iliyopita. "Hata hivyo, utafiti wetu unaonyesha kwamba, kwa kweli, oksijeni ya angahewa ilikuwa isiyo na uthabiti sana kwa kipindi cha miaka milioni 200 hivi, na oksijeni ya kudumu ya angahewa ilitokea miaka milioni 100 hivi baadaye kuliko ilivyodhaniwa hapo awali.""" Utafiti huo, uliochapishwa katika jarida la Nature, unaonyesha kwamba kuna uhusiano wa moja kwa moja kati ya kuongezeka kwa kiasi cha oksijeni katika angahewa na kuongezeka kwa kiasi cha gesi zinazosababisha uharibifu wa mazingira. "Profesa Andrey Bekker wa Chuo Kikuu cha California-Riverside, ambaye ni mwandishi mwenza wa utafiti huo, alisema: ""Ugunduzi huu unasaidia kuelezea barafu nne zilizotokea wakati huo huo, ambazo zingine zilihitaji kufunika Dunia nzima kwa barafu kwa mamilioni ya miaka." "Tunaona kwamba ongezeko la kudumu la oksijeni lilitokea baada ya barafu kuu ya mwisho ya kipindi hicho, na sio kabla yake, ambayo hapo awali ilikuwa fumbo kubwa katika uelewa wetu wa uhusiano kati ya oksijeni ya anga ya mapema na ukosefu mkubwa wa hali ya hewa. """ Timu ya watafiti imeita kipindi hiki Kipindi Kikuu cha Oksidation. Katika kipindi cha miaka bilioni 1.5 ya hali ya hewa na mazingira ya kudumu, ambayo ilibaki hadi kipindi cha pili cha kuongezeka kwa oksijeni na hali ya hewa ya kutokuwa na utulivu mwishoni mwa kipindi cha Precambrian. "Profesa David Johnston, mwandishi mwenza kutoka Chuo Kikuu cha Harvard, alisema: ""Kuongezeka kwa oksijeni katika angahewa kulikuwa sababu kuu ya kuishi duniani." "Kufunua historia ya oksijeni ya angahewa hatimaye inatuwezesha kuelewa jinsi oksijeni ilivyopanda hadi viwango vilivyotosha kuruhusu mageuzi ya wanyama.""" "Kisa cha Oksidation Kubwa, wakati oksijeni ya angahewa ilipopanda kwa mara ya kwanza hadi viwango vyenye kutokeza, huwakilisha hatua muhimu katika historia hii". "Profesa Poulton aliongeza: ""Hatuwezi kuanza kuelewa sababu na matokeo ya oksijeni ya angahewa, udhibiti muhimu zaidi juu ya kuishi kwa Dunia, ikiwa hatujui wakati oksijeni ya angahewa ya kudumu ilitokea kweli.""" Sasa hatimaye tuna kipande hicho cha fumbo". "Kulingana na ripoti ya utafiti wa ""Ucheleweshaji wa miaka milioni 200 katika oksijeni ya kudumu ya angahewa"" Chuo Kikuu cha Leeds, ""Kwa kuongezeka kwa ad blockers na Facebook, vyanzo vyetu vya jadi vya mapato kupitia matangazo ya ubora wa mtandao vinaendelea kupungua.""" Na tofauti na tovuti nyingine nyingi za habari, hatuna paywall - na majina ya watumiaji na nywila hizo zenye kukasirisha. Utangazaji wa habari unahitaji wakati na juhudi ili kuchapishwa siku 365 kwa mwaka. Kama unaona tovuti zetu za habari kuwa zenye kuelimisha na muhimu basi tafadhali fikiria kuwa msaidizi wa kawaida au kwa sasa fanya mchango wa mara moja.