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.

地球上生命的广泛基础是基于碳和需要水。碳作为复杂分子的构建元素，比诸如硅这样在推测另类的外星人生化组成时最受青睐的元素要全能得多。

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.

和需要糖一样，地球上的生命也需要蛋白质的构成元素氨基酸。但我们知道这些也可在外太空形成，因为在“原始的”陨石中发现过它们。它们可以从被称为“斯特雷克合成反应”的化学反应的一些变化中产生，这个化学反应是19世纪德国化学家斯特雷克发现的。该反应涉及简单的有机分子酮或醛，它们与氰化氢和氨结合。或者，紫外线触发的光驱动化学反应也可以做这个工作。

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，这些反应似乎不会在幽深的没有热源或光源驱动的太空发生。分子在寒冷黑暗的环境中相遇并没有足够的能量引发化学反应。

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世纪70年代，苏联化学家戈尔丹斯基证明情况并非如此。一些化学物质甚至被冷却至只有绝对零度以上4度时，也能发生反应。它们只需要伽玛射线或电子束等高能射线助一臂之力- 这些射线就像嗖嗖穿过太空的宇宙射线。

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.

戈尔丹斯基发现，在这种情况下，常见于分子云中的碳基分子甲醛可联结成长达几百个分子的聚合物链。

Goldanski believed that such space-basedreactions might have helped the molecular building blocks of life assemble fromsimple ingredients like hydrogen cyanide, ammonia and water.

戈尔丹斯基认为，这种以太空环境为基础的反应或可帮助生命的构建分子从氰化氢，氨和水等简单成分中形成。

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.

但诱使这类分子结合成更复杂的形态要困难得多。紫外线和其它形式的射线可诱导产生化学反应。但它们打碎分子的几率和形成分子的几率一样高。潜在的生物分子- 比如蛋白质和核糖核酸的祖细胞- 被分解比被制造出来要快得多。

Ultimately the question is whether othercompletely alien environments would give rise to self-replicating chemicalsystems that can evolve.

最终，问题在于其它完全陌生的环境是否会产生能够进化的自我复制的化学系统。