专家:地球曾有两个月亮

Earth may once have had two moons - the one that shines at night today and a smaller companion, according to a new theory. A slow-motion collision between the two is believed to have created the mountainous highlands on the moon's far side, as debris from the second, smaller moon piled up. The side of the moon facing the Earth and the side facing away have strikingly different topographies. While the near side is relatively low and flat, the far side is high and mountainous with a much thicker crust. 日本作家村上春树的小说《1Q84》模拟了一个虚幻的场景：虚幻场景中天空会出现两个月亮，近日，某杂志以《地球曾拥有两个月亮》作为标题宣告了两个月亮可能不是幻想，因为美国圣克鲁兹大学行星科学家和瑞士伯恩大学的一组科学家提出了新的观点：地球早期确实存在两个月亮，现在我们在地球上看到的“一轮独月”其实是一个大月亮“吞噬”了小月亮最终形成的，两个月亮的撞击行程了如今月球坑坑洼洼的表面，以及略小的那个月亮最终被“吞噬”的事实。科学家还发现，如今月球靠近地球的表面相对比较平坦、光滑；而远离地球的表明地势起伏不定，有着较厚的地壳。

The moon and how it was created has fascinated mankind since the earliest times. Records show that as early as the 5th century BC, civilisations in Babylon had mapped out lunar eclipses while Indian astronomers had worked out its monthly elongation. The Greek philosopher Anaxagoras argued that the moon reflected the sun's light and by the second century the moon's measurements had been accurately calculated. But there was little further development in our understanding of the moon until Galileo Galilei drew one of the first telescopic drawings of the moon and noted that it was not smooth but had mountains and craters. Telescopic mapping of the moon then developed throughout the 17th century. The Cold War between the U.S. and Soviet Union in the second half of the last century inspired further exploration of the moon, with the two superpowers competing to be the first to land a man on the lunar surface. By 1959, Russia had sent spacecraft to the moon and in 1966 Luna 9 achieved a 'soft landing'.

据悉，“双月撞击”发生于距今大约44亿年前，我们古代巴比伦的先知们在当时早已经描绘出月蚀的团，这与现在印度宇航员的推论不谋而合。据悉，在地球上还尚未出现生命时，一颗星球与地球相撞，飘散在太空中的物质逐渐形成了今天月球的主体。不过，撞击，其实还形成了另一个较小的星球。这个较小的“月亮”直径只有约1000公里，是今天月球体积的约三十分之一。它存在了数千万年，这段时间里，能在地球上看见两个月亮。不过，这两个月亮最终相撞，结果合二为一。而计算机模型显示，这次撞击就发生在当今月球的背面，并因此造成了月球远地一侧更加起伏不平的地貌，这次撞击还将大量的钾、磷和稀土等元素推向了月球的近地一侧。

But it was Nasa that won the space race by landing two astronauts on the moon in 1969. In all, six Apollo missions collected thousands of rock and soil samples to Earth. And although the Apollo programme wrapped up in 1972, many of the scientific instruments left on the moon are still being used today to gather further data about its surface.

不管是中国人对月亮“诗情画意”的情结，似乎全世界各个国家的人对于月亮都“情有独钟”。从1969年美国国家航空和宇宙航行局在人类历史上首次将两名宇航员成功登上月球开始，人类从未停止“探月”的步伐，尽管阿波罗登月计划最终在1972年宣告结束，在月球上，我们的科学家们还留下许多未得出结论的证据尚待继续分析才能得出结论。

The 'second' moon is also thought to have been generated by the giant impact, remaining in orbit for tens of millions of years. The two moons collided relatively slowly, according to the theory described today in the journal Nature. Such low velocity impacts do not produce craters or cause much melting. Instead, most of the colliding material is piled onto the impacted hemisphere as a thick new layer of solid crust. This could have formed the mountainous region now seen on the far side of the moon. 'Our model works well with models of the moon-forming giant impact, which predict there should be massive debris left in orbit about the Earth, besides the moon itself,' said lead researcher Professor Erik Asphaug, from the University of California at Santa Cruz.

“第二个月亮”的理论获得许多科学家的认同，据《自然》杂志称，两个月亮碰撞过程相对缓慢。此外，月球的年龄大约有46亿年，和地球同岁，也有壳、幔、核等分层结构。然而，月球永远都是一面朝向我们，这一面习惯上被称为“正面”。另外一面，除了在月面边沿附近的区域因天秤动而中间可见以外，绝大部分不能从地球看见。在没有探测器的年代，月球的“背面”一直是个未知的世界。各种猜测、各种推测层出不穷。专家Erik Asphaug说：“我们当今的工作就是模拟月球撞击时的景象，并预测在碰撞轨道上还有可能遗留地球或者月球的残骸。”