PBS高端访谈:火星首次发现液态水湖（在线收听）

JUDY WOODRUFF: Finally, some tantalizing new findings about water on Mars. Naturally, it raises more questions about the possibility of some kind of extraterrestrial life there. It's a perfect fit for our Miles O'Brien and our weekly segment on the Leading Edge of science. Amna Nawaz caught up with him.

AMNA NAWAZ: They may have long suspected it, but scientists have finally found for the first time a large watery reservoir, possibly a lake, beneath the southern ice cap of Mars. Radar suggests the reservoir is more than 12-miles-wide and similar in some ways to lakes found beneath the Greenland and Antarctic ice sheets on Earth. It's salty and buried nearly a mile below the three-billion-year-old ice cap. For many, it's a huge moment. And that includes Miles, who's long been covering the latest on the Red Planet, and joins me now. Miles, for those of us who haven't been following the Red Planet all the years, why is this such a big deal?

MILES O'BRIEN: Well, Amna, I guess scientists, myself, and anyone who watches this closely would have been surprised if they didn't find liquid water beneath the surface. But it's not an easy thing to do. You know, really, when you think about this, this is the culmination of about 150 years of work that began with an Italian astronomer by the name of Schiaparelli, who trained his telescope on Mars and saw what he called canali, which, translated, should mean channels, but got mistranslated into canals, and really started off a whole trend which led us to "The War of the Worlds" and the idea that there were really Martians. This has gone on recently with NASA missions, including the Pathfinder missions, the Curiosity, Spirit, and Opportunity missions, where there was all kinds of inferences of past water, mineralogical data, that sort of thing. Finally, the discovery of water ice at the poles. So, think about it for a moment. You have got all this evidence of distant, ancient water. You have got water ice at the poles. You know you have a hot core in the middle. So if there's a hot core in the middle, water ice at the poles, somewhere along the way, there has got to be water. And that's what they discovered. And the significance of that is, on this planet, wherever we find liquid water, no matter where it is, bottom the ocean, in a hot acidic bath in Yellowstone, underneath a glacier in Antarctica, wherever that may be, you find life.

AMNA NAWAZ: It's a huge moment. Let's talk about how we got here in the first place. What have they been looking at? What did they use? How do we know that the water is there?

MILES O'BRIEN: It's a European orbiter by the name of Mars Express. It's been an orbit for 15 years. And it has a radar device. It has this long-wave radar. It's kind of ground-penetrating radar that's been looking, analyzing beneath the surface of Mars for all this time. The data goes back really about a decade. And the scientists have just been trying very carefully to make sure what they thought they saw is what they thought. And, in fact, after all these years of going through all the possibilities of what it might or might not be, they have come to the conclusion it just has to be water. And scientists I have talked to today say it's a very elegant piece of science. There's a radar return about a mile-and-a-half below the surface of the south pole ice that is clear-cut signs of liquid water.

AMNA NAWAZ: OK, so let's hear from one of the scientists who was actually the lead on this research. He's a planetary scientist in Italy.

This is him talking about exactly what they did find there. Take a listen.

ROBERTO OROSEI, National Institute of Astrophysics: The radar data tell us that this water must contain a large amount of salts. This is because the ice above it is very transparent. And this wouldn't be possible if the ice was too warm, too close to the melting point. So, we have to conclude that the water in contact with the ice must be at least minus-10, minus-20, maybe minus-30 Celsius.

AMNA NAWAZ: So, Miles, very salty water, very cold water. You mentioned life where there is water. What can actually live in these conditions?

MILES O'BRIEN: Well, your tiny, microscopic things, but that might be the extent of what we ultimately find and it won't be easy to do, but maybe down the road in the way of Martians. It's important to understand that, you know, at that temperature, you would think it'd be solid.

But if it's a briny solution, if it's a salty solution, and under pressure, which is what you would have in this case, it can stay at liquid form at much lower temperatures. And that part of Mars is a very cold place, indeed. The question is, how would you ever verify if there were microbes there? That would require some drilling. And when I say that, some significant drilling, more than a mile-and-a-half deep at the south pole.

AMNA NAWAZ: So is that what's next? We're going to possibly see missions to drill on Mars?

MILES O'BRIEN: Well, the devil is in the details on that one, for sure, Amna....

MILES O'BRIEN: because, if you think about what it takes to do, you know, "Armageddon"-style drilling with Bruce Willis on Mars, it involves a lot of very heavy machinery and drill bits, which is very expensive and way beyond our capabilities right now to get to Mars. One of the scientists I was talking to today, the principal investigator on Spirit and Opportunity, Steve Squyres said, you know, if there's water there, it's very likely it is in the mid-latitude regions, which would be a better place for humans to go anyway. And it might be at a shallower depth, because it's warmer there. So maybe, just maybe, they could do some drilling mid-latitudes, and it would be not as deep. But, either way, it's not an easy mission. So it'll be we will have to sort of stay tuned as to whether there are microbes in this underwater lake in on Mars.

AMNA NAWAZ: We will be staying tuned, indeed. We know you will as well. Miles O'Brien, always great to talk to you.

MILES O'BRIEN: Amna, it's a pleasure.

朱蒂·伍德拉夫：最后，我们来看一些关于火星上水的新发现。当然，它提出了更多关于地外生命存在可能性的问题。它非常适合我们的迈尔斯·奥布赖恩以及我们每周的科学前沿部分。阿姆纳·纳瓦兹请到了他。

阿姆纳·纳瓦兹：他们可能长期以来一直怀疑它，但科学家们终于在火星南部冰盖下面首次发现了一个巨大的水库，可能还是一个湖泊。雷达探测表明，水库的宽度超过12英里，在某些方面类似于地球上格陵兰岛和南极冰盖下的湖泊。它水中含有盐份，埋在距今三十亿年之久的冰盖下方近一英里的地方。对许多人来说，这是一个重要的时刻。这其中也包括迈尔斯，他长期以来一直在报道这个红色星球上的最新消息，现在加入我。迈尔斯，对于我们这么多年来没有关注过这个红色星球的人来说，这个发现为何如此重要？

迈尔斯·奥布赖恩：嗯，阿姆纳，我猜，即使他们没有在地表下找到液态水，科学家们、我自己以及任何密切关注此事的人也都不会感到惊讶。但这不是一件容易的事。你知道，当你想想这个发现，150年前，一位意大利天文学家斯基亚帕雷利开始了火星观测，他用望远镜观测火星，看到了他所称的canali，翻译过来应该是指“水道”，但是被误译成了“运河”，但他真正开始了整个火星观测的大潮，由此引发了我们的“星球争霸战”，也让我们萌生了火星人真正存在的想法，而本次发现是这约150年工作的高潮。近年来，这些工作随着美国宇航局的科考任务逐步展开，这其中包括探路者号、好奇号、勇气号与机遇号，其中包含关于过去存在水源以及矿物数据等的各种推论。最后，他们在极地发现了水冰。所以，思考片刻。你得到了远古水源的所有证据。你发现两极都有水冰。你知道中间有一个热核。因此，如果中间有一个热核，而两极有水冰，那么沿途的某个地方，必然有水存在。这就是他们的发现。其重要性在于，在这个星球上，无论我们在哪里找到液态水，无论它在哪里，在海底，在黄石的炎热酸性浴中，在南极冰川之下，无论在哪里，你就找到了生命。

阿姆纳·纳瓦兹：这是一个重要的时刻。我们先来谈谈我们是如何发现它的。一直以来，他们在观测什么？他们用了什么？我们怎么知道水在那里？

迈尔斯·奥布赖恩：这是一个名为Mars Express的欧洲轨道飞行器。它已经在这个轨道上运行了15年。它有一个雷达设备。它有这种长波雷达。它是一种地面穿透式雷达，一直在对火星表面以下进行观测和分析。这些数据可以追溯到大约十年前。科学家们一直在非常仔细地确保他们所见就是所想。事实上，经过了这些年来所经历的所有可能与不可能之后，他们得出的结论是它必须是水。我今天与科学家们做了交谈，他们说，这是科学的优雅之处。在南极冰面下方约一英里半出现雷达回波，这是明确的液态水迹象。

阿姆纳·纳瓦兹：好的，让我们听听其中一位科学家的想法，他实际上是这项研究的领导者。他是一位意大利行星科学家。他在谈论他们在那里找到的确切内容。听一听。

罗伯托·奥罗赛，国家天体物理研究所：雷达数据告诉我们，这种水中一定含有大量的盐。这是因为它上面的冰非常透明。而如果冰太温暖，太接近融点，这是不可能的。因此，我们必须得出结论，与冰接触的水必须至少为-10℃，-20℃，可能为-30℃。

阿姆纳·纳瓦兹：所以，迈尔斯，非常咸的水，非常冷的水。你提到有水的地方即意味着生命。事实上，什么样的生命可以在这样的条件下存活？

阿姆纳·纳瓦兹：嗯，微小的和微观的东西，但这可能是我们最终找到的程度，而且这可能不容易做到，但可能将来会做到，以火星人的方式。重要的是要明白，在那个温度下，你会认为它是固态的。但如果它是一个咸水的解决方案，如果它是一个含盐的解决方案，并且在压力下，你在这种情况下会发现，它可以在更低的温度下保持液态。事实上，火星的那一地区是非常寒冷的。问题是，你如何验证那里是否有微生物？这需要一些钻探。当我这么说时，一些重要的钻探，在南极超过一英里半深的地方。

阿姆纳·纳瓦兹：接下来是什么？我们可能会看到在火星上执行钻探任务？

迈尔斯·奥布赖恩：嗯，魔鬼会专于那个细节，当然，阿姆纳。

迈尔斯·奥布赖恩：因为，如果你想一想它需要做些什么，你知道，在火星上进行《世界末日》风格的钻探与布鲁斯·威利斯一起，会需要很多非常重的机械和钻头，这是非常昂贵的，所以进行火星钻探，现在超出我们的能力。我今天正在和一位科学家，勇气号与机遇号的首席研究员史蒂夫·斯奎尔斯交谈，他说，你知道，如果那里有水，很可能是在中纬度地区，这对人类来说是一个更好的地方，无论如何要去。它可能处于较浅的位置，因为在那里更加温暖。也许，也许，只是也许，他们可以做一些中纬度钻探，而且不会那么深。但是，无论哪种方式，这都不是一件容易的事。因此，我们将不得不对火星上这个水下湖泊中是否存在微生物一事保有期待。

阿姆纳·纳瓦兹：我们将继续关注。我们知道您也会的。迈尔斯·奥布赖恩，与你搭档，精彩一如既往。

迈尔斯·奥布赖恩：阿姆纳，我很高兴。