Scientists are seeking to find out what is producing the slow release of methane gas on Mars.

科学家们正在寻找火星上甲烷气体缓慢释放的原因。

Methane often results from biological processes. On Earth, most of the gas comes from living creatures. For this reason, the American space agency NASA has been investigating methane levels on Mars in a search for signs of current or past life. So far, no evidence has been found.

甲烷通常是生物过程产生的。在地球上，大部分气体来自生物。出于这个原因，美国宇航局一直在调查火星上的甲烷水平，以寻找现在或过去生命的迹象。到目前为止，还没有发现任何证据。

But a new study is providing fresh details about methane on Mars. NASA's Curiosity explorer, or rover, has repeatedly measured methane levels on the Martian surface. The rover arrived on Mars in 2012 and has been exploring areas around Gale Crater. This area is believed to have contained a lake at one time and has also shown other evidence of flowing water in the past.

但一项新的研究提供了火星上甲烷的新细节。美国宇航局的好奇号探测器已经多次测量了火星表面的甲烷含量。该探测器于2012年抵达火星，并一直在探索盖尔环形山周围的地区。这个地区被认为曾经有过一个湖泊，也有证据表明过去有流动的水。

NASA says Gale Crater is the only place where methane has been discovered. Even a spacecraft sent to collect data on the Martian atmosphere has not identified the presence of methane. That spacecraft, the ExoMars Trace Gas Orbiter, is operated by the European Space Agency.

美国宇航局表示，盖尔陨石坑是唯一发现甲烷的地方。即使是用来收集火星大气数据的航天器也没有发现甲烷的存在。这艘名为ExoMars Trace Gas Orbiter的航天器由欧洲航天局运营。

In addition to only being discovered, or detected, around Gale Crater, the observations of methane happen only at night, NASA researchers recently reported. Levels also go up and down during different seasons and at times, rise sharply for short periods.

美国宇航局的研究人员最近报告说，除了只在盖尔环形山附近发现或探测到甲烷外，对甲烷的观测只发生在夜间。在不同的季节，浓度也会上下波动，有时会在短时间内急剧上升。

The mysterious methane releases leave scientists considering "a lot of plot twists," said Curiosity project leader Ashwin Vasavada. But a NASA research group recently proposed a possible explanation for how the gas behaves on Mars.

“好奇号”项目负责人阿什温·瓦萨瓦达说，神秘的甲烷释放让科学家们考虑了“很多曲折的情节”。但美国宇航局的一个研究小组最近提出了一种可能的解释，解释了这种气体在火星上的行为。

The researchers theorize that all detected methane could be trapped, or sealed, underneath hardened pieces of salt in Martian regolith. Regolith describes soil that contains rock and dust that sits on or below the surface.

研究人员推测，所有检测到的甲烷都可能被困住或密封在火星风化层中硬化的盐块下面。风化层指的是位于地表或地表以下的含有岩石和灰尘的土壤。

The scientists say increases in temperature might explain the differences in gas release. During certain seasons or times of day warmer temperatures could weaken the seal on the methane, causing gas to be released.

科学家们表示，温度的升高可能解释了气体释放的差异。在某些季节或一天中的某些时候，温度升高会削弱甲烷的密封，导致气体被释放出来。

NASA said the research was led by Alexander Pavlov, a planetary scientist at the agency's Goddard Space Flight Center in Maryland. He said small amounts of methane could also be released when the regolith seal is broken by weight from above, for example, when the Curiosity rover drives over the area.

美国宇航局表示，这项研究是由马里兰州戈达德太空飞行中心的行星科学家亚历山大·巴甫洛夫领导的。他说，当风化层的封条被上方的重量打破时，也会释放出少量的甲烷，例如，当好奇号火星车在该地区行驶时。

Pavlov said this theory could help explain why methane levels have only been discovered in the Gale Crater area. It is the only place on Mars where NASA's Curiosity rover is currently active.

巴甫洛夫说，这一理论可以帮助解释为什么甲烷水平只在盖尔环形山地区被发现。这是美国宇航局好奇号火星车目前在火星上唯一活跃的地方。

NASA has another rover working on Mars, Perseverance. But it has been exploring the Jezero Crater area on another part of the planet. Jezero Crater is also believed to have contained large water bodies in the distant past. But Perseverance is not equipped with a methane-detecting instrument.

美国宇航局还有另一个在火星上工作的探测器毅力号。但它一直在探索火星另一端的耶泽罗陨石坑。据信，在遥远的过去，耶泽罗陨石坑也含有大量的水体。但是毅力号并没有配备甲烷探测仪器。

Pavlov noted that the latest theory came from his memories of an unrelated experiment carried out in 2017. The experiment involved growing microorganisms in a simulated Martian environment that included frozen soil that contained salt.

巴甫洛夫指出，最新的理论来自他对2017年进行的一项无关实验的记忆。该实验涉及在模拟的火星环境中培养微生物，其中包括含有盐的冻土。

During that experiment, researchers observed that the collection of soil on top formed an icy, salty crust. Changes in conditions caused the ice to melt, turning the solid material into a gas and leaving the salt behind.

在那次实验中，研究人员观察到，顶部的土壤形成了一层冰冷、含盐的外壳。环境的变化导致冰融化，把固体物质变成气体，留下了盐。

Pavlov's team tested five samples of frozen soil containing different kinds of salt material commonly found on Mars. A new set of Earth-based experiments was carried out in which the frozen material was exposed to different temperatures and air pressures inside an environment at Goddard that was designed to be like Mars.

巴甫洛夫的研究小组测试了五个冻土样本，这些样本含有火星上常见的不同种类的盐物质。一组新的基于地球的实验进行了，在戈达德的一个类似火星的环境中，冷冻的物质暴露在不同的温度和气压下。

The team was able to repeatedly copy the salt sealing process in Mars-like conditions during laboratory testing. The researchers said they plan to keep carrying out experiments under different conditions and using salt minerals to confirm their theory.

在实验室测试中，该团队能够在类似火星的条件下反复复制盐封过程。研究人员表示，他们计划继续在不同条件下进行实验，并使用盐矿物来证实他们的理论。

But the researchers noted that to carry out more detailed methane investigations, they will likely need a whole new generation of sensitive instruments. These would be designed to measure methane continuously from many places on Mars.

但研究人员指出，要进行更详细的甲烷调查，他们可能需要全新一代的敏感仪器。这些将被设计用来连续测量火星上许多地方的甲烷。