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Process that might have led to first organic molecules

可能導致首個有機分子出現的過程

New research could have relevance to search for extraterrestrial life, green chemistry

新研究可能會涉及尋找地球外生物和綠色化學

New research led by the American Museum of Natural History and funded by NASA identifies a process that might have been key in producing the first organic molecules on Earth about 4 billion years ago, before the origin of life. The process, which is similar to what might have occurred in some ancient underwater hydrothermal vents, may also have relevance to the search for life elsewhere in the universe. Details of the study are published this week in the journal Proceedings of the National Academy of Sciences.

由美國自然歷史博物館牽頭并由NASA資助的新研究發現了一項過程。該過程可能在40億年前，也就是生命起源之前，在地球上產生首個有機分子方面發揮著重要作用。該過程與某些古代深海熱泉中發生的反應類似，其可能還與在宇宙中尋找地球外生物有關。研究的詳細內容于本周發表于《美國國家科學院院刊》中。

All life on Earth is built of organic molecules -- compounds made of carbon atoms bound to atoms of other elements such as hydrogen, nitrogen and oxygen. In modern life, most of these organic molecules originate from the reduction of carbon dioxide (CO2) through several "carbon-fixation" pathways (such as photosynthesis in plants). But most of these pathways either require energy from the cell in order to work, or were thought to have evolved relatively late. So how did the first organic molecules arise, before the origin of life?

地球上的所有生命都由有機分子構成-有機分子是由與其他諸如氫、氮和氧原子所聯接在一起的碳原子構成。在現代生命中，絕大多數此類有機分子來自于二氧化碳的還原，即通過數個“碳素固定”路徑（比如植物中的光合作用）。但是絕大多數這類路徑要么需要從細胞中獲取能量以發揮作用，要么被認為進化相對較晚。那么第一個有機分子是如何在生命起源之前出現的呢？

To tackle this question, Museum Gerstner Scholar Victor Sojo and Reuben Hudson from the College of the Atlantic in Maine devised a novel setup based on microfluidic reactors, tiny self-contained laboratories that allow scientists to study the behavior of fluids -- and in this case, gases as well -- on the microscale. Previous versions of the reactor attempted to mix bubbles of hydrogen gas and CO2 in liquid but no reduction occurred, possibly because the highly volatile hydrogen gas escaped before it had a chance to react. The solution came in discussions between Sojo and Hudson, who shared a lab bench at the RIKEN Center for Sustainable Resource Science in Saitama, Japan. The final reactor was built in Hudson's laboratory in Maine.

為了解決這一問題，博物館的Gerstner學者Victor Sojo和來自緬因州大西洋學院的Reuben Hudson提出了一個新穎的方法。該方法以微型流體反應器為基礎，微型流體反應器是一個微型的設施齊全的實驗室。科學家可以在其中從微觀的角度研究流體以及氣體的特性。之前的反應器試圖將氫氣泡泡和液狀的二氧化碳混合起來，但結果沒有發生任何反應，這可能是由于極度易揮發的氫氣在有機會發生反應之前就已經揮發了。Sojo和Hudson通過討論確定了這一解決方案。Sojo和Hudson與日本琦玉的可持續資源科學RIKEN中心共享一個實驗臺。最終的反應器在Hudson位于緬因的實驗室內建造。

"Instead of bubbling the gases within the fluids before the reaction, the main innovation of the new reactor is that the fluids are driven by the gases themselves, so there is very little chance for them to escape," Hudson said.

Hudson表示：“與在反應發生之前在液體內使氣體變成泡泡不同，新反應器的主要創新之處在于流體由氣體本身產生，因此氣體基本沒有機會揮發。”

The researchers used their design to combine hydrogen with CO2 to produce an organic molecule called formic acid (HCOOH). This synthetic process resembles the only known CO2-fixation pathway that does not require a supply of energy overall, called the Wood-Ljungdahl acetyl-CoA pathway. In turn, this process resembles reactions that might have taken place in ancient oceanic hydrothermal vents.

研究人員利用他們的設計裝置將氫氣和二氧化碳相結合并產生一種叫做甲酸（HCOOH）的有機分子。這一過程和唯一已知的CO2-固定路徑類似。該路徑不需要提供能量并被稱為Wood-Ljungdahl acetyl-CoA 路徑。反之，該過程和可能出現在古代海洋深海熱泉的反應相似。

"The consequences extend far beyond our own biosphere," Sojo said. "Similar hydrothermal systems might exist today elsewhere in the solar system, most noticeably in Enceladus and Europa -- moons of Saturn and Jupiter, respectively -- and so predictably in other water-rocky worlds throughout the universe."

Sojo表示：“這一結果遠遠超過我們自己的生物圈。同樣的熱液體系可能在今天存在于太陽系的其他地方，可能性最大的是在土衛二和木衛二中（土星和木星的衛星），因此也可以存在于宇宙中其他由水和巖石組成的世界中。”

"Understanding how carbon dioxide can be reduced under mild geological conditions is important for evaluating the possibility of an origin of life on other worlds, which feeds into understanding how common or rare life may be in the universe," added Laurie Barge from NASA's Jet Propulsion Laboratory, an author on the study.

NASA 噴氣推進實驗室的Laurie Barge，同樣也是該研究的作者補充表示：“理解二氧化碳如何在溫和的地質條件下進行還原對于評估其他世界中生命起源的可能性非常重要。其有助于理解普通或稀有的生命如何存在于宇宙中。”

The researchers turned CO2 into organic molecules using relatively mild conditions, which means the findings may also have relevance for environmental chemistry. In the face of the ongoing climate crisis, there is an ongoing search for new methods of CO2reduction.

研究人員利用相對溫和的條件將二氧化碳轉變為有機分子，這意味著研究結果可能還與環境化學有關聯。面對著持續不斷的氣候危機，尋找新的二氧化碳還原方法將會繼續下去。

以上內容摘自《科學日報》并由質控部Susan翻譯并編輯