Water trickles down gullies and crater walls on the surface of Mars, raising intriguing questions about whether life could exist on the red planet。

水流沿着火星表面的火山口壁和山壑流淌而留下的痕迹，又一次将“火星上是不是有生命存在”这一问题抛了出来。

The findings are the strongest evidence yet that liquid water darkens the Martian surface today; we've known for years that water flowed on Mars long ago。

如今，这一发现是证明液态水使火星表面变得暗沉的最有利证据。其实，多年前我们就知道，很久以前火星上是有水存在的。

Described Monday in Nature Geoscience, the observations suggest that this water appears seasonally, forming dark lines as it tumbles down steep Martian slopes. But scientists still don’t know where the water is coming from, or if the chemistry is even right for supporting life。

《自然地球科学》星期一发布的文章中称，这一发现表明这些水迹的出现是季节性的，水沿着陡峭的火星山壁一泻而下，形成了许多深色的水流线条。但是科学家还是不知道水源在哪，或这一化学物是否能够维持生命。

For now, the find solves the mystery of dark streaks that appear and disappear seasonally, called recurring slope lineae。

目前，这一发现解释了为什么火星表面总会季节性出现或消失深色线纹，这种线段的学名叫做“季节性斜坡纹线”。

The streaks were first spotted in 2010 by Lujendra Ojha, then an undergraduate at the University of Arizona. Ojha was studying images returned to Earth from the HiRISE camera, aboard NASA’s Mars Reconnaissance Orbiter. At the time, he says, he had no clue how important his observation would be。

2010年，一位亚利桑那大学的学生——卢金德拉·欧嘉首次发现了这种深色线纹。他一直在研究从装在美国国家航空暨太空总署火星侦察卫星上的照相机发回地球的照片。欧嘉说，那时候的他一点都不知道这个发现有这么重要。

Is Mars Sweating?

火星是流汗了吗？

A big question swirls around the origin of that water: Where is it coming from? One possibility is that the seeps are fueled by an aquifer or melting subsurface ice. These scenarios would have Mars essentially sweating, with saltwater seeping from its pores and trickling down slopes as the planet warms。

问题在于水源：这些水从哪里来？一种可能是由含水层渗透、或地下冰融化造成的。这些现象导致火星“流汗”——由于星球变暖，地下的盐水从地表空隙渗透出来，并沿着表面斜坡流淌下来。

The water might also be atmospheric in origin, which is the hypothesis the team seems to favor. In this scenario, surface salts absorb water vapor in the Martian atmosphere。

水也有可能是来源于大气，这一说法也有人认可。这种假设是说，火星表面盐分吸取了大气中的水蒸气。

But until now, evidence has been scarce for flowing water at the surface today. What it means, in the bigger picture of planetary exploration and the search for life beyond Earth, is still a mystery。

目前为止，能证明火星表面有流动的水存在的证据还是微不足道的。也就是说，在星球探索中，地球外的生命研究还仍只是一个谜。