評論
打印
The broad basis of life on Earth iscarbon-based and requires water. Carbon is much more versatile as a buildingblock for complex molecules than, say, silicon, the favourite element forspeculations about alternative alien biochemistries.
地球上生命的廣泛基礎是基于碳和需要水。碳作為復雜分子的構建元素，比諸如硅這樣在推測另類的外星人生化組成時最受青睞的元素要全能得多。
As well as sugars, life on Earth needed aminoacids, the building blocks of proteins. But we know that these can be formed inouter space too, because they have been found in "primitive"meteorites. They might be made from some variation of a chemical reactioncalled the Strecker synthesis, after the 19th-Century German chemist whodiscovered it. The reaction involves simple organic molecules called ketones oraldehydes, which combine with hydrogen cyanide and ammonia. Alternatively,light-driven chemistry triggered by ultraviolet light will do the job.
和需要糖一樣，地球上的生命也需要蛋白質的構成元素氨基酸。但我們知道這些也可在外太空形成，因為在“原始的”隕石中發現過它們。它們可以從被稱為“斯特雷克合成反應”的化學反應的一些變化中產生，這個化學反應是19世紀德國化學家斯特雷克發現的。該反應涉及簡單的有機分子酮或醛，它們與氰化氫和氨結合?；蛘?，紫外線觸發的光驅動化學反應也可以做這個工作。
It looks at first as though these reactionsshould not take place in deepest space, without a source of heat or light todrive them. Molecules encountering one another in frigid, dark conditions donot have enough energy to get a chemical reaction started.
乍一看，這些反應似乎不會在幽深的沒有熱源或光源驅動的太空發生。分子在寒冷黑暗的環境中相遇并沒有足夠的能量引發化學反應。
However, in the 1970s the Soviet chemistVitali Goldanski showed otherwise. Some chemicals could react even when chilledto just four degrees above absolute zero. They just needed a bit of help fromhigh-energy radiation such as gamma-rays or electron beams –like thecosmic rays that whizz through all of space.
然而，20世紀70年代，蘇聯化學家戈爾丹斯基證明情況并非如此。一些化學物質甚至被冷卻至只有絕對零度以上4度時，也能發生反應。它們只需要伽瑪射線或電子束等高能射線助一臂之力- 這些射線就像嗖嗖穿過太空的宇宙射線。
Under these conditions, Goldanski foundthat the carbon-based molecule formaldehyde, which is common in molecularclouds, could link up into polymer chains several hundred molecules long.
戈爾丹斯基發現，在這種情況下，常見于分子云中的碳基分子甲醛可聯結成長達幾百個分子的聚合物鏈。
Goldanski believed that such space-basedreactions might have helped the molecular building blocks of life assemble fromsimple ingredients like hydrogen cyanide, ammonia and water.
戈爾丹斯基認為，這種以太空環境為基礎的反應或可幫助生命的構建分子從氰化氫，氨和水等簡單成分中形成。
But it is far more difficult to coax suchmolecules to combine into more complex forms. Ultraviolet and other forms ofradiation can induce reactions. But they are just as likely to smash moleculesas they are to form them. Potential biomolecules – progenitors of proteins andRNA, say –would be broken apart faster than they were being produced.
但誘使這類分子結合成更復雜的形態要困難得多。紫外線和其它形式的射線可誘導產生化學反應。但它們打碎分子的幾率和形成分子的幾率一樣高。潛在的生物分子- 比如蛋白質和核糖核酸的祖細胞- 被分解比被制造出來要快得多。
Ultimately the question is whether othercompletely alien environments would give rise to self-replicating chemicalsystems that can evolve.
最終，問題在于其它完全陌生的環境是否會產生能夠進化的自我復制的化學系統。
