新的模型表明，我們對地球上第一次大規(guī)模的氧氣爆發(fā)的認識可能是錯誤的

新的模型表明，我們對地球上第一次大規(guī)模的氧氣爆發(fā)的認識可能是錯誤的

These days, Earth's atmosphere is perfectly suited for us to breathe - but the air on our planet wasn't always this way.

如今，地球的大氣層非常適合我們呼吸，但地球上的空氣并不總是這樣。

Now, researchers have put forward a new explanation for the events that dramatically shifted that crucial composition of gasses.

現(xiàn)在，研究人員提出了一種新的解釋，來解釋那些劇烈改變氣體關鍵成分的事件。

According to the new study, a critical event in Earth's atmospheric history may have come in the form of volcanic eruptions, caused by shifting tectonic plates.

根據(jù)這項新的研究，地球大氣史上的一個關鍵事件可能以火山爆發(fā)的形式出現(xiàn)，這是由移動的構造板塊引起的。

The planet's crust and mantle moved in a way that set off particular chemical reactions, resulting in a spike in oxygen production and laying the foundation for complex life on our planet.

地球的地殼和地幔以一種引發(fā)特殊化學反應的方式移動，導致氧氣產(chǎn)量激增，為我們星球上復雜的生命奠定了基礎。

The new model put forward by a Rice University-led team could help to explain not one, but two long-standing geological mysteries.

由萊斯大學領導的研究小組提出的新模型有助于解釋兩個長期存在的地質謎團，而不是一個。

First, there's the Great Oxidation Event (GOE) of around 2.4 billion years ago, where oxygen levels rose sharply; then, the Lomagundi event, a significant shift in carbon isotope balances that happened about 100 million years later.

首先是大約24億年前的大氧化事件(GOE)，當時氧含量急劇上升;然后是Lomagundi事件，大約1億年后，碳同位素平衡發(fā)生了重大變化。

Carbon has three naturally occurring isotopes - variants that can be distinguished based on the number of neutrons they contain. The ratio of carbon-12 and carbon-13 isotopes is a useful tool for studying natural systems and the atmosphere, since the two variants tend to come from different sources.

碳有三種天然存在的同位素——根據(jù)它們所含的中子數(shù)可以區(qū)分它們的變體。碳-12和碳-13同位素的比例是研究自然系統(tǒng)和大氣的有用工具，因為這兩種同位素往往來自不同的來源。

The vast majority of carbon on Earth is carbon-12, but during the Lomagundi event there was a sudden spike in carbon-13 isotopes. Before now, researchers have found it tricky to fit the GOE and the Lomagundi event together in one coherent hypothesis.

地球上絕大多數(shù)的碳是碳12，但是在Lomagundi事件中，碳13的同位素突然激增。在此之前，研究人員發(fā)現(xiàn)很難把GOE和Lomagundi事件放在一個連貫的假設中。

What makes this unique is that it's not just trying to explain the rise of oxygen, says geoscientist James Eguchi, from the University of California, Riverside.

來自加州大學河濱分校的地球科學家James Eguchi說:“這一發(fā)現(xiàn)的獨特之處在于，它不僅試圖解釋氧氣的產(chǎn)生。”

It's also trying to explain some closely associated surface geochemistry, a change in the composition of carbon isotopes, that is observed in the carbonate rock record a relatively short time after the oxidation event.

“它還試圖解釋一些密切相關的表面地球化學，即碳同位素組成的變化，這是在氧化事件發(fā)生后較短時間內從碳酸鹽巖記錄中觀察到的。”

We're trying to explain each of those with a single mechanism that involves the deep Earth interior, tectonics and enhanced degassing of carbon dioxide from volcanoes."

“我們試圖用一種單一的機制來解釋每一種機制，它涉及到地球深處的內部構造和火山釋放的二氧化碳。”

Before now, photosynthesis was thought to be the main driver of the GOE, as cyanobacteria pumped oxygen out as a waste product of just being alive. That still played a big part, the new research suggests, but much more was going on in our planet's interior.

在此之前，光合作用被認為是GOE的主要驅動力，因為藍藻細菌把氧氣作為活著的廢物排出體外。新的研究表明，這仍然發(fā)揮了很大的作用，但更多的是在我們星球的內部。

Based on detailed modelling, the scientists think that increased tectonic activity produced hundreds of new volcanoes ahead of the GOE, pumping masses of CO2 into the air. This warmed the climate, increasing rainfall and subsequent weathering, leading to more minerals being washed off rocks and into the ocean.

基于詳細的模型，科學家們認為，構造活動的增加在GOE之前產(chǎn)生了數(shù)百座新火山，將大量的二氧化碳排放到空氣中。這使得氣候變暖，增加了降雨量和隨后的風化，導致更多的礦物質從巖石中被沖刷到海洋中。

In turn, this triggered a boom in cyanobacteria and carbonates, with this extra organic and inorganic carbon getting recycled from the ocean floor into Earth's mantle. The rise in oxygen is accounted for in both the growth of cyanobacteria numbers (therefore increasing photosynthesis) and in the carbon being taken out of the atmosphere as it gets buried deep underground.

反過來，這引發(fā)了藍藻和碳酸鹽的繁榮，這些額外的有機和無機碳從海底回收到地球的地幔。氧氣的增加既可以解釋藍藻數(shù)量的增長(因此增加了光合作用)，也可以解釋碳被從大氣中抽出并深埋地下的過程。

It's kind of a big cyclic process, says Eguchi.

“這是一個大的循環(huán)過程，”Eguchi說。

Crucially for the Lomagundi event calculations, the different chemical make-up of organic and inorganic carbon means they reappeared at different times, explaining the increase in carbon-13 with a 100-million-year gap.

對Lomagundi事件的計算至關重要的是，有機碳和無機碳的不同化學組成意味著它們會在不同的時間重新出現(xiàn)，這解釋了碳13的增加與1億年的時間差距。

The research has been published in Nature Geoscience.

這項研究發(fā)表在《自然地球科學》雜志上。