| Mars may have been wet for a billion years longer than previously thought, new water-related opal evidence from NASA's Mars Reconnaissance Orbiter suggests. The findings have implications for the possibility that Mars once supported life. |
从美国国家航空航天管理局的火星侦探卫星获得了跟水相关的蛋白石新证据，证据表明：火星的湿润阶段可能比以前所认为的要长10亿年。这个发现意味着，火星可能一度支持生命的存在。 |
| Scientists have known for some time that the 4.5 billion-year-old planet once harbored liquid water because of the many features on its surface that were likely created by flowing water. Hydrated, or water-containing, mineral deposits also provide telltale signs of where and when water was present on ancient Mars. |
科学家们已经了解到，这个45亿岁的行星上有一段时间曾经拥有水，因为其表面上许多地貌特征好象是由于流水造成的。含水沉积层也提供了明确的迹象，可以说明古代火星曾经在何时何地出现过水。 |
| Until now, only two major groups of hydrated minerals, phyllosilicates and hydrated sulfates, have been observed by spacecraft orbiting the red planet. (The clay-like phyllosilicates formed more than 3.5 billion years ago where igneous rock encountered water. Hydrated sulfates formed until about 3 billion years ago from the evaporation of salty and sometimes acidic water.) |
此前，环绕这颗红色星球的太空船观察过两种主要的含水矿物——层状硅酸盐和含水硫酸盐。35亿多年以前，粘土状的层状硅酸盐形成于火成岩遇到水的地方；直到大约30亿年前，由于含有盐分的、有时呈酸性的水蒸发而形成了含水硫酸盐。 |
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But a new hydrate mineral has now entered the picture: hydrated silica, commonly known as opal. These opaline silicates were detected by MRO's Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) and are the youngest of the three types of hydrated minerals. They formed where liquid water altered materials created by volcanic activity or meteorite impacts on the Martian surface. |
但是，现在一种新的水合矿物进入了视野：水合二氧化硅，俗称蛋白石。这些蛋白石硅酸盐是由火星侦探卫星上搭载的专用小型侦察影像频谱仪（CRISM）发现的，是三种含水矿物中最年轻的一种。火山活动或陨星在火星表面的撞击所产生的物质，被液态水改变之后就形成了蛋白石硅酸盐。 |
| "This is an exciting discovery because it extends the time range for liquid water on Mars, and the places where it might have supported life," said CRISM principal investigator Scott Murchie of the Johns Hopkins Applied Physics Laboratory in Laurel, Md. "The identification of opaline silica tells us that water may have existed as recently as 2 billion years ago." |
“这是个令人兴奋的发现，因为该发现延长了水在火星上的存在时间，也扩大了可能支持生命存在的范围，”专用小型侦察影像频谱仪的主要研究人员、马里兰州劳瑞尔市约翰霍普金斯应用物理实验室的斯科特·默基说，“蛋白石硅酸盐的发现使我们可以断定：仅仅20亿年前，火星上仍有水存在。” |
| Some of the opaline deposits were also associated with iron sulfates, which study team member Ralph Milliken of NASA's Jet Propulsion Laboratory in Pasadena, Calif., said is "the exact sort of minerals you would expect to see if you had really acidic water." |
一些蛋白石沉积层也跟硫酸铁和硫酸亚铁有关。研究小组成员、加州帕萨迪纳市美国国家航空航天管理局空气推进实验室的拉尔夫·米利肯说：“这些硫酸盐跟存在酸性水的情况下你所期望看到的那种矿物一模一样。” |
| And not only do the deposits indicate the past presence of liquid water, but that the water "was there long enough to alter some of the rocks," Milliken told SPACE.com. "It wasn't an overnight process." |
米利肯告诉《太空网》：“这些沉积层不但证说明了过去存在液态水，而且还说明液态水存在的时间很长，足以使某些岩石发生改变。这个改变过程不是一夜之间所能完成的。” |
| One particular location where the opaline silicates were found was the large canyon system Valles Marineris. "We see numerous outcrops of opal-like minerals, commonly in thin layers extending for very long distances around the rim of Valles Marineris and sometimes within the canyon system itself," Milliken said. |
发现蛋白石硅酸盐的一个特殊地点是大型山谷系统——水手谷。“我们看到了许多路出地面的蛋白石状矿物层，通常呈薄层状，在水手谷周围的凸缘上延伸出很远的距离，有时也在该山谷系统之内延伸，”米利肯说。 |
| The minerals were also recently found in Gusev Crater by NASA's Mars rover Spirit. |
美国国家航空航天管理局的“勇气”号火星探测器最近在古瑟夫环形山中也发现了这种矿物。 |
| Another recent study, which Milliken co-authored, looked at images of the same deposits taken by MRO's HiRISE camera. |
不久前，由米利肯跟其他研究人员共同发起的另外一项研究，在图像中观察到了同样的沉积层。这些图像是由火星侦探卫星上搭载的高分辨率科学实验成像仪（HiRISE）拍摄的。 |
| The new study, detailed in the November issue of the journal Geology, reveals that opaline silicates are widespread and occur in relatively young terrain. |
这项新研究详细地记录在11月份出版的《地质学》杂志上。该研究显示：蛋白石硅酸盐分布广泛，并出现在相对年轻的岩体中。 |
| "What's important is that the longer liquid water existed on Mars, the longer the window during which Mars may have supported life," Milliken said. "The opaline silica deposits would be good places to explore to assess the potential for habitability on Mars, especially in these younger terrains." |
“重要的是，液态水在火星上存在的时间越长，火星可能适合生命存在的时间也就越长，”米利肯说，“若要评估火星上潜在的可居住性，这些蛋白石硅酸盐沉积层，特别是较为年轻岩体中的沉积层，将会是理想的研究地点。” |
