科学美国人60秒:Giant Tsunami Remnants Spotted on Mars

For as long as we’ve been sending spacecraft to Mars, we’ve been finding signs of water. The Red Planet’s sinuous river valleys, flood-carved canyons and buried glaciers all hint that it was wet billions of years ago.
自从我们人类发射飞船到火星，就一直能感觉到那上面有过水。这颗红色的星球上蜿蜒的河谷，有洪水冲击成的峡谷和深埋在地下的冰川都预示着几百亿年前这里可不是干燥的。

Some researchers think that the curiously flat and sparsely cratered northern lowlands are the remnants of a once-great ocean. But that ocean’s proposed coast varies in height by thousands of meters, which has made the idea controversial.
一些研究人员们认为这里那些异常平坦，罕见有火山坑的北部低洼地带就是曾经盛极一时的巨大海洋存在过的遗骸。但是，这个海洋中被推测出的海岸高低不同落差达到几千米，使得整个海洋的存在变得具有争议性。

Now, a team of researchers has found evidence for ancient tsunamis on Mars, evidence that supports the idea of a vanished Martian ocean and explains its vertically variable shoreline.
现在，有一组科研人员已经发现了火星上存在过海啸的证据，这点可以证明火星上现在消失的海洋曾经存在过，并且可以解释为什么它会出现竖直落差巨大的海岸线。

“We were trying to find shorelines on Mars like those we typically see on Earth, which is consistently distributed along a constant elevation. And that is not what we have found on Mars, because in the case of Mars the shorelines were buried beneath the tsunami deposits.”
我们曾尝试过寻找火星上海洋的海岸线，就像我们地球上典型存在的那种，在一个相对恒定的高度上持续分布。可是这并不是我们在火星上发现的那种，因为，就火星而言，海岸线被埋葬在海啸沉积物下面了。

Alexis Rodriguez of the Planetary Science Institute in Tucson. He led a team that used satellite images to identify thick deposits of boulders and silt apparently left by two separate tsunamis, a few million years apart, almost three-and-a-half billion years ago.
这是图森星球科学研究所的Alexis Rodriguez。他领导的研究小组采用卫星成像技术对厚厚的沉积大圆石和淤积沙进行确认，这些物质很明显就是两次不同的海啸过后残留下的，两次海啸的时间相差大约几百万年吧，距今大约有35亿年左右。

“The discovery of the tsunami deposits represents definite evidence for the existence of the early Martian ocean….the tsunamis were enormous. On average we estimate they were about 50 meters in height, but at some locations they could have reached as much as 120 meters...and the surface areas that the tsunamis covered within the study region are also huge…each tsunami had roughly the combined areas of California, Nevada and Oregon.”
这些海啸沉积物的发现可作为早期火星海洋存在过的明确证据。这些海啸规模还挺巨大的。平均上来看我们估计它们大约能有50米高，但某些位置甚至可达120米，而在这次研究中涉及到的海啸波及到的火星表面区域，也是巨大的，每一个海啸大概能有加州，内华达和俄勒冈州加起来那么大的范围。

The most plausible cause for such massive tsunamis was asteroids or comets slamming into the Martian ocean. The study is in the journalScientific Reports.
对形成如此巨大的海啸最合理的解释就是小行星或者彗星猛烈地撞击到了火星上的海洋。该研究已经发表在《科学报告》杂志上。

The tsunamis could provide crucial information about the habitability of ancient Mars. The first one occurred when the planet must have been relatively warm and amenable for life, because it carved out backwash channels as it returned to the sea. By contrast, the planet had become much cooler by the time the second tsunami hit—the waters apparently flash-froze after flowing onto the surface.
海啸能给我们带来很重要的，关于古老的火星上居住条件的信息。 第一次海啸一定这个星球上一定处于相对温暖的生命可承受的温度，因为当海啸撤回海洋时，会在沿途的渠道上刻下往复的痕迹。相比较，在第二次海啸发生的时间下，温度下降了不少——海水明显的就是在流过渠道表面后瞬间就结冰了。

Examining additional tsunami deposits could reveal much more data about Mars’s ancient climate changes. Someday, rovers—or astronauts—might even visit the deposits, looking for evidence of past marine life locked in frozen waves.
对海啸沉积物的检测可以提供大量的关于火星上古老的气候变化信息。将来某天，月球漫步车——或者说我们的宇航员——也许甚至能亲自察看这些沉积物，寻找一下在这些被冻存的海浪中隐藏的曾经那些海洋生命的残留痕迹。