VOA慢速英语2019 火星上的甲烷之谜：它能代表生命吗？（在线收听）

Methane Mystery on Mars: Could It Mean Life?

The United States space agency, NASA, says its Mars exploration vehicle recently recorded a high level of methane gas on the planet.The discovery is exciting because the presence of methane gas could support the case for life on Mars.

美国宇航局（NASA）表示，他们的火星探测器最近在这个星球上记录到了高浓度的甲烷气体。这一发现令人兴奋，因为甲烷气体的存在可以支持火星上存在生命迹象的说法。

NASA’s Curiosity vehicle recently recorded the largest level of methane ever measured during its seven-year Mars mission.

美国宇航局的“好奇”号飞行器最近记录了其七年来火星任务期间探测到的最大甲烷含量。 

Methane has no color or smell.A special instrument on Curiosity’s Mars Science Laboratory recorded the increased gas level.The device, called a laser spectrometer, measures levels of chemical elements and gases in the Martian atmosphere.In addition to methane, the instrument can record levels of water and carbon dioxide.

甲烷无色无味。“好奇”号火星科学实验室的一个特殊仪器记录了甲烷含量的增加。这个被称为雷射光谱仪的装置观测火星大气中化学元素和气体的含量。除甲烷外，该装置还可以观测水和二氧化碳的含量。

Nearly all the methane gas found in Earth’s atmosphere is produced by biological activity.It usually comes from animal and plant life.But it can also be formed by geological processes, such as interactions between rocks and water.

地球大气中几乎所有的甲烷气体都是由生物活动产生的，通常来自动植物。但也可以通过地质作用形成，如岩石和水的相互作用。

NASA said the increased methane was measured to be about 21 parts per billion by volume (ppbv).One ppbv means that if you take a volume of air on Mars, one billionth of the volume of air is methane.

美国宇航局表示，测量到的甲烷的体积浓度比增加到21ppbv。1ppbv指如果你在火星上吸入1体积的空气，那么其中十亿分之一就是甲烷。

It was not the first time Curiosity has found methane gas in the Martian atmosphere.About a year ago, NASA announced that Curiosity had discovered sharp seasonal increases in the gas.

这并非“好奇”号第一次在火星大气中发现甲烷。大约一年前，美国宇航局就宣布“好奇”号发现甲烷含量季节性飙升。

This time, NASA said the measured methane gas level was clearly larger than any others observed in the past.NASA officials even temporarily stopped Curiosity’s other activities to investigate further.

这次，美国宇航局表示，这次测量到的甲烷浓度明显高于过去观测到的其他任何浓度。美国宇航局官员甚至暂停了“好奇”号的其他活动，从而进行进一步的调查。

“It’s exciting because microbial life is an important source of methane on Earth,” NASA said in a statement announcing the discovery.

“这令人感到兴奋，因为在地球上微生物是甲烷的重要来源，”美国宇航局在一份宣布其发现的声明中表示。

However, Curiosity’s team carried out a follow-up methane experiment that showed a sharp drop in levels of the gas.The second examination found the level was less than one part per billion by volume.That number was “close to the background levels Curiosity sees all the time,” NASA said.

然而，“好奇”号团队进行了后续的甲烷实验，其结果显示甲烷浓度急剧下降。第二次实验发现甲烷的体积浓度比低于1ppbv。美国宇航局表示，这个比例“接近好奇号探测到的历史平均水平”。

The rise and fall of the methane gas levels left NASA scientists with more questions than answers.The scientists are continuing to study possible causes for the sudden increase.

甲烷气体含量的上升和下降使美国宇航局的科学家们面临的问题多于答案。科学家们正在继续研究致使甲烷含量突然飙升的可能原因。

The methane mystery continues, said Ashwin Vasavada, Curiosity’s project scientist at NASA’s Jet Propulsion Laboratory in Pasadena, California.We’re more motivated than ever to keep measuring and put our brains together to figure out how methane behaves in the Martian atmosphere.

加利福尼亚州帕萨迪纳市的美国宇航局喷气推进实验室“好奇”号的项目科学家阿什文·瓦萨瓦达说：“甲烷之谜还在继续。我们比以往任何时候都更有动力去不断观测，发挥集体智慧来弄清火星大气中甲烷的动态。”

Curiosity does not have instruments that can exactly identify whether the source of the methane is biological or geological.One leading theory is that methane is being released from underground areas created by possible life forms that disappeared long ago.

“好奇”号没有仪器能够准确识别甲烷来自生物还是地质作用。一个主要的理论认为甲烷是从地下释放出来的，释放的甲烷可能是由很久以前消失的生命形态产生的。

Even though Mars has no active volcanoes, scientists believe it is also possible that methane is being produced by reactions involving carbon materials and water.

尽管火星上没有活火山，但科学家们相信甲烷也有可能是通过碳材料和水的反应产生的。 

A clearer understanding of methane levels over time “could help scientists determine where they’re located on Mars,” NASA said.Scientists hope this understanding will come as Curiosity continues to collect methane data in its search for possible life.

美国宇航局表示，更清楚地了解甲烷含量随着时间推移的改变“可以帮助科学家确定甲烷分布在火星上的位置”。科学家们希望，随着“好奇”号寻找生命迹象的过程中继续收集甲烷数据，这种了解也会实现。

Words in This Story

mission – n. an important task, usually involving travel somewhere

geological – adj. relating to the study of rocks, soil and the physical structure of the Earth

volume – n. the number of amount of something

microbial – adj. relating to microbes (very small living things)

motivate – v. to cause someone to behave in a particular way

determine – v. to control or influence directly

locate – v. find or discover the exact position of something