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Researchers recently said methane may be the first detectable sign of life outside of our planet.
研究人员最近表示，甲烷可能是在地球以外生命的第一种可探测到的迹象。
But the gas would only suggest the presence of life if discovered in the atmosphere of a rocky planet orbiting in the "habitable zone."
但这种气体只有在一颗环绕“可居住地带”运行的岩质行星的大气层中被发现时，才意味着生命的存在。
This area is neither too hot nor too cold for liquid water to exist.
这个区域既不太热也不太冷，适合液态水存在。
Scientists are working to understand the signs of life, known as biosignatures, that might be present in observations of planets in other solar systems.
科学家们正在努力了解生命的迹象，即所谓的生物标志，这些迹象可能存在于对其他太阳系行星的观测中。
The researchers, in a study published in Proceedings of the National Academy of Sciences, showed that atmospheric methane in the correct amount could be a sign of life if other conditions are met.
研究人员在《美国国家科学院院刊》上发表的一项研究中表明，如果其他条件都满足，大气层中恰当数量的甲烷可能是生命的迹象。
Methane is an important trace gas in Earth's atmosphere, at less than 2 parts per million by volume.
甲烷是地球大气层中一种重要的痕量气体，体积小于百万分之二。
Unlike other possible biosignatures such as atmospheric oxygen, methane is one of the few gases that could be detected by using the James Webb Space Telescope.
与大气中的氧气等其他可能的生物标志不同，甲烷是少数几种可以通过詹姆斯·韦伯太空望远镜探测到的气体之一。
The telescope was launched by NASA in December and is due to become operational within months.
该望远镜于去年12月由美国国家航空航天局发射，预计将在几个月内投入使用。
Study lead author Maggie Thompson, a graduate student at the University of California, Santa Cruz, said "On Earth, the ... majority of methane is produced by life."
该研究的主要作者麦琪·汤普森是加州大学圣克鲁斯分校的研究生，她说：“在地球上，大部分甲烷是由生命产生的。”
Most of the methane is created directly by life: methane-producing microbes in wetlands, rice fields or in the digestive system of large animals.
大部分甲烷是由生命直接产生的：湿地、稻田或大型动物消化系统中产生甲烷的微生物。
Methane is also produced through human activities such as burning fossil fuels including coal and oil, which are the remains of dead organisms.
甲烷也通过人类活动产生，比如燃烧化石燃料，包括煤和石油，它们是死亡的生物的遗骸。
The researchers made a three-part case for methane as a possible biosignature.
研究人员从三个方面论证了甲烷是一种可能的生物标志。
"First, it would be unsurprising for life elsewhere to produce methane," study co-writer Joshua Krissansen-Totton said.
该研究的合著者约书亚·克里桑森-托顿说：“首先，其他地方的生命产生甲烷不足为奇”。
Secondly, methane would not last for long in atmospheres of habitable rocky planets without constant replenishment, possibly by living organisms, the researchers said.
其次，研究人员表示，如果没有活的机体的持续补充，甲烷在可居住的岩质行星的大气层中不会存在很长时间。
Thirdly, they added, it would be difficult for other processes, such as chemical reactions, to maintain replenishment without leaving behind some kind of evidence.
第三，他们补充说，化学反应等其他过程很难在不留下某种证据的情况下保持补给。
This evidence would suggest the methane was not biologically produced.
这一证据表明甲烷不是生物产生的。
Gas-spewing volcanoes, for instance, would release carbon monoxide alongside methane.
例如，喷出气体的火山会在释放甲烷的同时释放一氧化碳。
But biological activity generally reduces carbon monoxide's atmospheric concentrations.
但生物活动通常会降低大气中一氧化碳的浓度。
Thus, the researchers explained, nonbiological processes cannot easily produce rocky planet atmospheres rich in both methane and carbon dioxide, as on Earth, but with little or no carbon monoxide.
因此，研究人员解释说，非生物过程不可能像在地球上那样轻易地产生富含甲烷和二氧化碳但几乎没有一氧化碳的岩质行星大气。
Scientists are expecting greater insight into exoplanet atmospheres using Webb and other new telescopes.
科学家期待着使用韦伯太空望远镜等新望远镜对系外行星的大气层有更深入的了解。
Oxygen, more plentiful in Earth's atmosphere than methane, is another possible biosignature.
在地球大气层中，氧气的含量比甲烷多，这是另一个可能的生物标志。
It is fed into Earth's atmosphere by biological processes--in this case photosynthesis by plants and microbes.
它通过生物过程，即植物和微生物的光合作用，进入地球大气层。
But oxygen could be difficult for Webb to detect.
但韦伯太空望远镜很难探测到氧气。
Krissansen-Totton explained that "it's important to note that the diversity of planetary environments elsewhere is probably" very large.
克里斯桑森-托顿解释说，“重要的是要注意到，其他地方的行星环境的多样性可能非常大”。
He added, "There could be other... methane-making .... processes that no one has yet considered."
他还说，“可能还有其他没有被人考虑过的制造甲烷的过程。”
I'm John Russell.
约翰·拉塞尔为您播报。
译文为可可英语翻译，未经授权请勿转载！
