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Scientists have found life in an ecosystem trapped underneath a glacier in Antarctica for nearly 2 million years. The microbes, they suggest, are surviving the dark, oxygen-free waters by drawing energy from sulfur and iron. The findings provide insight into how life may have survived "Snowball Earth" and hint at the possibility of life in other inhospitable environments, such as Mars and Jupiter's icy moon Europa. |
在南极冰川下被封存了将近200万年之久的一个生态系统中，科学家们发现了生命。他们提出，这些微生物通过硫和铁来吸收能量，在黑暗和无氧的水域中生存下来。这些发现为科学家们提供了新的认识，使他们了解到生命是如何度过“冰雪地球”时期的，同时也为他们提供了线索，表明在其他不可生存的环境中，如：在火星上以及被冰覆盖的木星卫星——木卫二上，也有可能存在生命。 |
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Researchers have found microbial life surviving in the most unusual places: the depths of cold and dark oceans, seething geothermal vents, and the deepest layers of permafrost. And ever since scientists discovered Antarctica's dark and mysterious subglacial lakes in the late 1960s and early 1970s, they've wondered if microbes could make a life for themselves there too. But the challenges of drilling through kilometers of ice and concerns about contaminating these pristine lakes have curtailed previous efforts to find out. |
研究人员已经发现微生物生存在最不同寻常的地方，如：寒冷黑暗的海洋深处，火热的地热出口处，以及永久冻结带的最深层。自从科学家们在二十世纪六十年代后期和七十年代初期发现了南极洲黑暗而神秘的冰下湖泊之后，他们一直想知道微生物是否也能够独自生存在那里。然而，由于钻透厚厚的冰层所面临的挑战，以及担心对这些原始湖泊会造成污染，以前寻找生命的努力受到限制。 |
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Blood Falls, a small, saltwater outflow from Taylor Glacier's subglacial lake in Antarctica's Dry Valleys, offers an alternative. The lake sits beneath 400 meters of ice and trickles out at the glacier's end, painting an orange stain across the ice as its iron-rich waters rust upon contact with air. The subglacial lake was originally part of a marine fjord system that became trapped as Taylor Glacier enclosed it between 1.5 million and 2 million years ago. Its sporadic outflow allows researchers to explore the lake without drilling or risking contamination of the isolated environment. |
南极干谷中泰勒冰川下面的湖泊流出细小的咸水流，被称为“血色瀑布”，为研究人员提供了一个可以利用的研究方法。该湖泊位于冰面以下400米处，从冰川的末端流出，其富铁的水质遇到空气后生锈，流经冰面时染上一片橘红色的痕迹。这个冰下湖泊起初是一个海洋峡湾系统的一部分，在150万至200万年以前，泰勒冰川将其封闭起来，一直被封存在冰下。湖水的偶尔外流使研究人员不用钻探、不用冒险污染这个隔离的环境，就可以进行探索。 |
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Geomicrobiologist Jill Mikucki, now at Dartmouth College, collected water samples from Blood Falls over 6 years. A battery of tests revealed that its waters contained almost no oxygen and hosted a community of at least 17 different types of microorganisms. But how could they have survived for so long, with no light or oxygen? Mikucki and her team uncovered three main clues. First, a genetic analysis of the microbes showed that they were closely related to other microorganisms that use sulfate instead of oxygen for respiration. Second, isotopic analysis of sulfate's oxygen molecules revealed that the microbes were modifying sulfate in some form but not using it directly for respiration. Third, the water was enriched with soluble ferrous iron, which would happen only if the organisms had converted ferric iron, which is insoluble, to the soluble ferrous form. The best explanation, the team reports in tomorrow's issue of Science, is that the organisms use sulfate as a catalyst to "breathe" with ferric iron and metabolize the limited amounts of organic matter trapped with them years ago. Lab experiments have suggested this might be possible, but it has never been observed in a natural environment. |
目前供职于达特茅斯学院的地球微生物学家吉尔·米库基在六年的时间里采集了血色瀑布的水样。多次实验表明，水中几乎没有氧气，却拥有一个至少包含17种不同微生物的生态群落。然而，在没有光线、没有氧气的情况下，它们何以存活了如此之久呢？米库基及其研究小组发现了三个主要线索。首先，对这些微生物的遗传分析表明，它们跟利用硫酸盐而不用氧气进行呼吸的其他微生物密切相关；其次，对硫酸盐中的氧分子所进行的同位素分析显示，这些微生物不断地将某种形式的硫酸盐进行转化，并没有直接用来呼吸；第三，水中富含可溶解的亚铁，只有当这种微生物将不能溶解的三价铁转化为可溶于水的亚铁形式时，才会发生这种情况。研究小组在明天出版的《科学》杂志中报道：最好的解释是，这些微生物拿硫酸盐作为一种催化剂，以便利用三价铁进行呼吸，代谢多年前封存于其中的少量有机质。实验表明这种情况是有可能发生的，但是在自然环境中从未观察到。 |
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"I think this is a fantastic study," says Alan Kaufman, a biogeochemist at the University of Maryland, College Park. It presents "a spectacular new environment that we can explore to understand life on the edge," he says. "A place like this ... would be probably as close of an analog as we can find on this planet for subpermafrost life habitats on Mars," says glaciologist Slawek Tulaczyk of the University of California, Santa Cruz. Ultraviolet radiation and other hazards would most likely lock life away beneath the surface of the Red Planet, he notes. |
“我认为这是一项非常有意义的研究，”马里兰大学帕克分校的生物地球化学家艾伦·考夫曼说。他指出：“该研究展示出一个奇妙的新环境，我们可以通过探索这个环境来了解边缘地带的生命。”“我们在地球上所发现的象这样的地方很可能跟火星冻土以下的生命栖息地最为类似，”加州大学圣克鲁兹分校的冰川学家斯拉维克·图拉吉克说。他指出，紫外辐射和其他危害很可能将生命封锁在那颗红色行星的表面以下 |
