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科学美国人60秒: 火星中的气候周期

所属教程:科学美国人60秒科学系列 更新:01-15
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Climate Cycles Could Have Carved Canyons on Mars

火星中的气候周期

The surface of Mars is etched with ancient river valleys and lake basins. Which makes researchers think that liquid water once flowed on the Red Planet. But how? Today, Mars is too cold for much, if any, liquid water to exist. And 3.8 billion years ago, when the flowing water features formed, the sun was fainter than it is today, making it even harder to imagine a balmy Martian climate. That’s why many researchers think Mars may have gone in and out of deep freezes.

火星表面蚀刻古代的河谷以及湖泊盆地的印记。这让研究人员认为这个红色的行星表面曾经有液态水存在。但是,液态水是如何存在的?现在,火星太冷了,不适合液态水的存在。38亿年前,当流动水特征形成的时候,阳光强度比现在弱,因此火星想形成一个温和的气候也非常的难。这就是为什么很多研究人员会认为火星曾经经历了深度冻结的过程。

“The real questions have been: for how long was it warm, and what was the mechanism for warming it up.”

真正的问题是:火星温暖持续的时间,以及其变暖的机制。

James Kasting, a geologist at Penn State University. He shared his take on the problem at the December meeting of the American Geophysical Union in San Francisco, and in the journal Earth and Planetary Science Letters.

詹姆斯·卡斯丁是宾夕法尼亚大学的地质学家。他在12月份在旧金山举行的《美国地球联合会》会议上分享了关于此问题的见解,并发表在《地球与行星科学通讯》杂志上。

Some researchers have suggested that early Mars only thawed out when large asteroid impacts or volcanic eruptions temporarily warmed the planet. But Kasting and others think warm windows from such dramatic events would have been too brief to carve the vast canyons that exist on Mars. Now, Kasting and his colleagues have come up with an alternative explanation: they think Mars may have experienced a series of climate cycles caused by changes in the strength of the greenhouse effect.

一些研究人员认为初期只有大型行星的影响或者火山爆发会暂时使火星温度升高。但是卡斯丁和其他人认为这些戏剧性事件所产生的热量加温火星上存在的大峡谷时间太短暂。现在卡斯丁和同事们提出了另外一种解释方法:他们认为由于温室气体强度的影响,由此火星经历了一系列的气候周期。

The idea goes like this: when Mars was cold and frozen, volcanoes continued to belch out the greenhouse gases carbon dioxide and hydrogen into the atmosphere. There, the gas blanket trapped heat and warmed the planet up until liquid water began to flow, forming Mars’ rivers and lakes. However, warm temperatures and abundant water would also have sped up certain chemical reactions that consumed carbon dioxide, reducing the greenhouse effect and cooling the planet back down again. Then the cycle would repeat.

具体的想法是这样的:在火星天寒地冻的时候,火山持续向大气中喷发温室气体二氧化碳和氢气。大气层就会把热量包住,然后使得火星的温度上升直到液态水开始流动,由此形成火星上的河流和湖泊。然而,温暖的温度以及充足的水分加速了二氧化碳某些化学过程,由此减少了温室效应并由此让火星的温度再度下降。之后这种循环持续进行。

“Which is similar to what the impact people have been arguing, except that when it gets warm, it can stay warm for millions of years instead of thousands of years.”

这就类似于人们一直在争论的影响,但是不包括火星何时变暖以及这种变暖将持续数万年而不是数千年。

So far, Kasting’s team has only shown that such an explanation is possible, according to climate models. But the researchers say NASA’s Curiosity rover and other future Mars missions could help test the idea by looking for evidence of multiple warm events, and their durations. Perhaps, hidden in the dry Martian dust lie clues to a surprisingly soggy past.

到目前为止,卡斯丁的团队仅仅表示,根据气候模型,上述的解释是可能的。但是研究人员表示NASA好奇流浪者号以及其他未来火星任务可以通过调查多起温暖的气候事件以及它们的持续时间来帮助验证上述的想法。可能,干燥的火星尘埃会为火星沉闷的过去提供线索。

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