專家:地球曾有兩個月亮
日本作家村上春樹的小說《1Q84》模擬了一個虛幻的場景：虛幻場景中天空會出現兩個月亮，近日，某雜誌以《地球曾擁有兩個月亮》作爲標題宣告了兩個月亮可能不是幻想，因爲美國聖克魯茲大學行星科學家和瑞士伯恩大學的一組科學家提出了新的觀點：地球早期確實存在兩個月亮，現在我們在地球上看到的“一輪獨月”其實是一個大月亮“吞噬”了小月亮最終形成的，兩個月亮的撞擊行程瞭如今月球坑坑窪窪的表面，以及略小的那個月亮最終被“吞噬”的事實。科學家還發現，如今月球靠近地球的表面相對比較平坦、光滑；而遠離地球的表明地勢起伏不定，有着較厚的地殼。
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'.
據悉，“雙月撞擊”發生於距今大約44億年前，我們古代巴比倫的先知們在當時早已經描繪出月蝕的團，這與現在印度宇航員的推論不謀而合。據悉，在地球上還尚未出現生命時，一顆星球與地球相撞，飄散在太空中的物質逐漸形成了今天月球的主體。不過，撞擊，其實還形成了另一個較小的星球。這個較小的“月亮”直徑只有約1000公里，是今天月球體積的約三十分之一。它存在了數千萬年，這段時間裏，能在地球上看見兩個月亮。不過，這兩個月亮最終相撞，結果合二爲一。而計算機模型顯示，這次撞擊就發生在當今月球的背面，並因此造成了月球遠地一側更加起伏不平的地貌，這次撞擊還將大量的鉀、磷和稀土等元素推向了月球的近地一側。
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.
不管是中國人對月亮“詩情畫意”的情結，似乎全世界各個國家的人對於月亮都“情有獨鍾”。從1969年美國國家航空和宇宙航行局在人類歷史上首次將兩名宇航員成功登上月球開始，人類從未停止“探月”的步伐，儘管阿波羅登月計劃最終在1972年宣告結束，在月球上，我們的科學家們還留下許多未得出結論的證據尚待繼續分析才能得出結論。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.
“第二個月亮”的理論獲得許多科學家的認同，據《自然》雜誌稱，兩個月亮碰撞過程相對緩慢。此外，月球的年齡大約有46億年，和地球同歲，也有殼、幔、核等分層結構。然而，月球永遠都是一面朝向我們，這一面習慣上被稱爲“正面”。另外一面，除了在月面邊沿附近的區域因天秤動而中間可見以外，絕大部分不能從地球看見。在沒有探測器的年代，月球的“背面”一直是個未知的世界。各種猜測、各種推測層出不窮。專家Erik Asphaug說：“我們當今的工作就是模擬月球撞擊時的景象，並預測在碰撞軌道上還有可能遺留地球或者月球的殘骸。”
