链接：http://www.astronomy.com/asy/default.aspx?c=a&id=7764
Where did Venus' water go?
The solar wind strikes the upper atmosphere of Venus and carries off particles into space. Planetary scientists think the planet has lost part of its water in this way.
太阳风冲击金星的上层大气，并将粒子带入太空，行星学家们认为金星一直是这样丢失其部分水的。
Provided by ESA, Noordwijk, The Netherlands
December 18, 2008
Venus Express has made the first detection of an atmospheric loss process on Venus' dayside. Last year the spacecraft revealed that most of the lost atmosphere escapes from the nightside. Together, these discoveries bring planetary scientists closer to understanding what happened to the water on Venus, which is suspected to have once been as abundant as on Earth.
金星快车首次在金星的向日面探测到大气的遗失过程，加上去年该探测器发现大气逃逸大多数发生在背日面，使得行星学家们更进一步了解金星上的水发生了什么，而之前一直认为金星上的水同地球上的一样含量巨大。
The spacecraft's magnetometer instrument (MAG) detected the unmistakable signature of hydrogen gas being stripped from the dayside. "This is a process that was believed to be happening at Venus, but this is the first time we measured it," said Magda Delva, Austrian Academy of Sciences, Graz, who leads the investigation.
探测器上的磁力仪探测到氢气从向日面被拉走的明显的迹象。“我们一直相信这样的事会发生在金星上，但这是第一次测量到。”格拉茨奥地利科学院Magda Delva说。Magda Delva调查中的负责人。
Thanks to its carefully chosen orbit, Venus Express is strategically positioned to investigate this process. The spacecraft travels in a highly elliptical path that sweeps over the poles of the planet.
得益于精心选择的轨道，金星快车被用于调查这个过程。探测器的运行轨道是一个高偏心率的椭圆轨道，并且扫过金星的两极。
Water is a key molecule on Earth because it makes life possible. With Earth and Venus approximately the same size and having formed at the same time, astronomers believe both planets likely began with similar amounts of the liquid. Today, however, the proportions on each planet are extremely different. Earth's atmosphere and oceans contain 100,000 times the total amount of water on Venus. In spite of the low concentration of water on Venus, Delva and colleagues found that Venus' dayside was losing some 2x1024 hydrogen nuclei, a constituent atom of the water molecule, every second.
由于水使生命变得可能，所以水成为地球上的一个关键组成要素。地球和金星无论在大小还是形成时间上都极其的相近，天文学家们由此相信这两颗行星可能最初有相近含量的液体。然而如今表明，两颗行星上的比例却相差甚大，地球大气和海洋所含的水是金星上的100,000倍。尽管金星上水的聚集程度很低，Delva和他的同事发现其向日面正以每秒大约2x1024个的速度丢失氢原子，氢原子正是水分子的组成部分。
Last year, the Analyzer of Space Plasma and Energetic Atoms (ASPERA) aboard Venus Express showed that there was a great loss of hydrogen and oxygen on the nightside. Roughly twice as many hydrogen atoms as oxygen atoms were escaping. Because water is made of two hydrogen atoms and one oxygen atom, the observed escape indicates that water is being broken up in the atmosphere of Venus.
去年，金星快车上的空间等离子体和能量原子分析器显示，金星背日面有大量的氢原子和氧原子的丢失，氢原子的遗失量大致是氧原子的两倍。水分子由两个氢原子和一个氧原子组成，那么观察到的遗失足以表明金星上的水在大气层中被分解了。
The Sun not only emits light and heat into space, but it also constantly spews out solar wind, a stream of charged particles. This solar wind carries electrical and magnetic fields throughout the solar system and "blows" past the planets.
太阳不仅向太空中散发光和热，同时不停地喷发带电粒子流组成的太阳风。太阳风将这些电磁场带入太阳系，“吹过”各个行星。
Unlike Earth, Venus does not generate a magnetic field. This is significant because Earth's magnetic field protects its atmosphere from the solar wind. At Venus, however, the solar wind strikes the upper atmosphere and carries off particles into space. Planetary scientists think the planet has lost part of its water in this way over the 4½ thousand million years since the planet's birth.
金星不能像地球一样产生磁场，这至关重要，因为地球磁场可以保护大气免受太阳风的摧残。因此，太阳风冲击着金星的上层大气并将粒子带离金星，行星学家们由此认为，自金星诞生之后过去的45亿年里，部分水一直是这样丢失的。
"We do see water escaping from the nightside. But the question remains: How much has been lost in the past in this way?" said Stas Barabash, Swedish Institute of Space Physics, Kiruna and Principal Investigator of ASPERA, who looked at nightside data.
“我们确实看到了水从背日面遗失，但问题在于：过去有多少水是这样遗失的？”Stas Barabash一边看着背日面的数据一边说。Stas Barabash是瑞典空间物理研究所空间等离子体和能量原子分析器的kiruna and Principal调查员。
The discovery takes scientists a step toward understanding the details, but it does not provide the last piece of the puzzle. To be certain that the hydrogen is coming from water, Delva and colleagues also must detect the loss of oxygen atoms on the dayside and verify that there are approximately half as many leaving Venus as hydrogen.
这项发现让科学家们在了解细节的路上向前走了一步，但这并不意味着揭开谜底。为了肯定那些氢原子来自水，Delva和他的同事们必须探测从向日面遗失的氧原子量，并确认其大约有遗失的氢原子量的一半。
So far, this has not been possible. "I keep looking at the magnetometer data but so far I can't see the signature of oxygen escaping on the dayside," said Delva.
到目前为止，这看起来不太可能。“我一直研究着磁力仪的数据，但至今也没看到氧从向日面逃逸的迹象。”Delva说。
It also highlights a new mystery. "These results show that there could be at least twice as much hydrogen in the upper atmosphere of Venus than we thought," said Delva. The detected hydrogen ions could exist in atmospheric regions high above the surface of the planet, but scientists don't know the source of these regions.
这样一个新的谜显现出来了。“这些结果显示在金星的上层大气中的含氢量至少是我们估计的两倍。”Delva说。探测到的氢离子可能存在于行星表面以上很高的大气区域，但这些区域源自何处科学家们尚未得知。
So like a true lady, Venus still retains some of her mystery.
就像真正的女士，金星依然有许多谜有待发现。
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