美国宇航局“藏宝图”展示了火星上的水

美国宇航局“藏宝图”展示了火星上的水

The evidence of water on Mars continues to grow. And because water is so important for life as we know it, this bodes well for our efforts both to send humans farther from home and to search for signs of extraterrestrial life.

火星上有水的证据在不断增加。因为水对于我们所知道的生命是如此重要，这对我们把人类送到离家更远的地方以及寻找外星生命的迹象来说是个好兆头。

This map shows underground water ice on Mars. Cool colors are closer to the surface, and the outlined box represents the ideal region to send astronauts for them to dig up water ice. (Photo: NASA/JPL-Caltech/ASU)

Liquid water can't last very long in the thin Martian air, instead quickly evaporating when exposed to the atmosphere, NASA explains. Scientists have found evidence of frozen water deeper underground at the planet's mid-latitudes, but this new image maps out shallower — and thus more accessible — water ice. Rather than trying to move large amounts of water from Earth, any human missions to Mars will likely need to harvest this kind of ice for drinking water and other purposes.

美国宇航局解释说，液态水在稀薄的火星空气中不能维持很长时间，而是在暴露于大气中时迅速蒸发。科学家们已经在火星中纬度地区的地下深处发现了冰冻水的证据，但这张新的图像描绘出了更浅的水冰，因此也更容易接近。人类前往火星的任何任务都可能需要收集这种冰，以供饮用和其他用途，而不是试图从地球上转移大量的水。

Underground lakes

地下湖

Craters on Mars hint at a system of interconnected lakes running underground. (Photo: NASA)

Earlier in 2019, researchers from the European Space Agency (ESA) and the Mars Express project announced they had not only found historical evidence of water flowing in craters around Mars' northern hemisphere, but also that a system of ancient, interconnected lakes lurks underground.

2019年早些时候，欧洲航天局(ESA)和火星快车项目的研究人员宣布，他们不仅发现了火星北半球环形山中有水流动的历史证据，而且还发现了一个古老的相互连接的湖泊系统潜伏在地下。

"Findings like this are hugely important; they help us to identify the regions of Mars that are the most promising for finding signs of past life," said Dmitri Titov, ESA’s Mars Express project scientist.

“这样的发现非常重要;它们帮助我们识别火星上最有希望发现过去生命迹象的区域。欧洲航天局火星快车项目的科学家德米特里·提托夫说。

Polar ice caps

极地冰盖

NASA/ESA Hubble Space Telescope snapped this portrait of Mars, which shows the southern polar ice cap at the bottom. (Photo: NASA/ESA, J. Bell (Cornell U.) and M. Wolff (SSI))

In 2018, the Italian Space Agency announced evidence of liquid water underneath Mars' southern polar ice cap. Using the Mars Advanced Radar for Subsurface and Ionosphere Sounding instrument (MARSIS) aboard the ESA's Mars Express spacecraft, radar detected a subglacial lake roughly 20 km (12.5 miles) wide and 1.6 km (1 mile) below the surface.

2018年，意大利航天局公布了火星南部极地冰盖下液态水的证据。在欧空局火星快车上利用火星先进雷达探测地下和电离层测深仪(MARSIS)，雷达探测到一个冰下湖泊，大约20公里(12.5英里)宽，1.6公里(1英里)深。

Other experts, however, were not immediately able to confirm MARSIS' findings.

然而，其他专家并不能立即证实MARSIS的发现。

Liquid water or flowing sand?

液态水还是流动的沙子?

These dark streaks, called recurring slope lineae (RSL), flow downhill at several locations on the surface of Mars. Initially thought to be signs of liquid water, they may also be caused by 'granular flows' of sand and dust, research suggests. (Photo: NASA/JPL/University of Arizona)

In 2015, NASA announced evidence of liquid, flowing seasonal water on the red planet, although further research later cast doubt on that interpretation, suggesting what seemed like evidence of flowing water might actually be caused by "granular flows" — i.e., sand or dust. NASA acknowledged this in a statement, although it noted the clues behind these dueling conclusions "remain puzzling."

2015年，美国国家航空航天局(NASA)公布了在这颗红色星球上存在流动的季节性液体水的证据，尽管后来的进一步研究对这一解释提出了质疑，沙子还是灰尘。美国国家航空航天局在一份声明中承认了这一点，尽管它指出这些结论背后的线索“仍然令人费解”。

This image shows RSL on the walls of Garni crater, where the dark streaks are up to a few hundred meters in length. (Photo: NASA/JPL/University of Arizona)

The news was based on research published in Nature Geoscience, which showed how scientists were able to study RSL on the planet's surface. These streaks had been previously seen in photos, but because the streaks are only about 5 meters (16 feet) across, researchers couldn't get a good enough look to determine what was causing them. Eventually, however, they found a way to analyze data from the Mars Reconnaissance Orbiter by extracting data from the pictures on a per pixel level. This let scientists study smaller details on the red planet's surface, and those details provided the new information.

这一消息是基于发表在《自然地球科学》上的一项研究，该研究表明，科学家们能够在地球表面研究RSL。这些条纹以前在照片中出现过，但是因为这些条纹只有5米(16英尺)宽，研究人员无法得到足够好的观察来确定是什么导致了这些条纹。然而，最终他们找到了一种分析火星勘测轨道飞行器数据的方法，即从图片中按像素提取数据。这使得科学家们可以研究这颗红色星球表面的更小的细节，这些细节提供了新的信息。