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Mars has long been thought of as dry and barren – unable to harbour life. But research over the past few years indicates that there is most likely some briny water present there today, including a possible subsurface lake. This has led to new hopes that there could actually be life on the red planet after all, depending on what the conditions are like in the water.

长久以来,火星一直被认为是干燥贫瘠的,无法维持生命。但是过去几年的研究表明,今天那里很可能存在一些盐水,包括一个可能的地下湖。这带来了新的希望,即这个红色星球上可能存在生命,这取决于水里的环境如何。

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Mounting evidence

越来越多的证据

We now know that there are traces of methane on Mars, however, as discovered by Mars Express and the Curiosity rover. The source of this methane might be either hydrothermal activity (the movement of heated water), or microbial life. On Earth, flatulent cows alone produce some 25% to 30% of the methane in the atmosphere. Either of these possibilities challenges our current understanding of the red planet, but if the source is life that would obviously be an amazing discovery. The joint European and Russian ExoMars Trace Gas Orbiter is currently investigating the source of this methane.

但是,正如火星快车和好奇号探测器所发现的,我们现在知道火星上有甲烷的痕迹。这种甲烷的来源可能是水热活动(热水的运动),或者是微生物。在地球上,仅胀气的牛就产生大气中大约25%到30%的甲烷。这两种可能性中的任何一种都挑战了我们目前对这个红色星球的理解,但如果来源是生命,那显然将是一个惊人的发现。欧洲和俄罗斯联合的ExoMars示踪气体轨道飞行器目前正在调查这种甲烷的来源。

The NASA Mars Reconnaissance Orbiter also discovered seasonal features called “recurrent slope lineae” – streak-like patterns which may indicate briny water seeping to the surface. However there are alternative explanations. Some scientists suggest that these may also just be movements of sand. That said, rovers and landers have found substances including calcium and magnesium perchlorates near the suspected water seeps and at other locations on Mars – and these indicate the presence of brine.

美国宇航局的火星勘测轨道飞行器还发现了称为“周期性斜坡线”的季节特征——可能表明咸水渗入地表的条纹状图案。然而,还有其他解释。一些科学家认为这些也可能是沙子的运动。美国宇航局说探测器和登陆器已经在疑似渗漏水附近和火星上的其他地点发现了包含钙和镁在内的高氯酸盐物质——这些表明存在盐水。



Most recently, the ESA Mars Express mission found radar evidence for liquid water underneath the south polar region on Mars – potentially a subsurface lake. This water, which also appears to be briny, would be a whopping 20km wide and be situated 1.5km under the surface.

最近,欧洲航天局的火星快车在火星南极地区下发现了液态水的雷达证据——可能是一个地下湖。这些水似乎也是咸的,它的宽度达到庞大的20公里,并且位于地表下面1.5公里。

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However, the NASA rovers are designed to drill only five centimetres under the surface. The rover that is part of the ESA-Russia ExoMars 2020 mission that we are working on will be able to drill up to two metres below it. This will get below where ultraviolet, cosmic and solar radiation can penetrate and harm life – providing our best hope of finding life on Mars of any planned mission. The ExoMars rover landing site will be decided in November from two current candidates – Mawrth Vallis and Oxia Planum, both of these were ancient water-rich environments.

然而,美国宇航局的探测器被设计成仅能钻探到表面以下5厘米。作为欧洲航天局-俄罗斯ExoMars 2020计划的一部分,我们正在研制的探测器将能够在火星表面往下钻探两米。这将低于紫外线、宇宙和太阳辐射能穿透并伤害生命的地方——为在火星上发现生命提供我们的最佳希望。ExoMars探测器的着陆点将在11月决定,将在 Mawrth Vallis和 Oxia Planum这两个地方选择一个,它们在古代都水量丰富。



Although the current strategy is to search for signs of ancient life on Mars, current life should be detectable too if present. We will have to wait for the ExoMars results to see if signs of either past or present biomarkers are present, and in the longer term analyse the returned samples. While the rover won’t go to the lake or the water seeps, there is evidence for brines at other locations too, so there is a good possibility that they may be present at the ExoMars candidate sites.

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Another obstacle is the planetary protection rules, which state that you shouldn’t risk contaminating an area where there may be extra-terrestrial life with bacteria from Earth. However, the hope is that any Martian life would be hardy enough to populate other areas and that our missions, designed and built with strict planetary protection guidelines, will find it.

另一个障碍是行星保护规则,它规定你不应该冒险用来自地球的细菌污染可能存在外星生命的区域。火星上的任何生命都难以在其它地方居住,而希望就是我们基于严格的行星保护方针设计和建造的任务能够找到它们。