The Apollo moon missions ended almost 40 years ago. But for lunar scientists, they're ____1____. Researchers studying rocks brought back by astronauts have found that the moon's scarce water has a different chemical signature than Earth water. Which ____2____ that the water probably came from comets. The study appears in the journal Nature Geoscience.
The researchers used what's called an ion microscope to compare the amount of normal hydrogen in the moon rocks to the amount of the hydrogen isotope deuterium, which carries an extra neutron. They found deuterium at higher levels than it's found in Earth water — but at levels similar to the comets Hale-Bopp, Hyakutake and Halley. Which suggests comets ____3____ water on the ancient moon, shortly after its formation four-and-a-half billion years ago.
The finding could also explain a mystery of water on Earth — how the oceans got here. Because if comets ____4____ the moon, they probably hit the Earth, too. Ocean water does have more deuterium than water in the Earth's mantle. Maybe, the researchers say, that's because the oceans have ____5____.
【視聽版科學小組榮譽出品】
gifts that keep on giving leads to the conclusion deposited battered an extra dose of melted comet ice
月亮上的水跟地球上的不同 阿波羅登月任務大約在40年前就已完成。但對月球科學家而言，此次登月一直不斷地帶給他們新的研究成果。研究人員通過研究宇航員從月球上帶回的巖石發(fā)現(xiàn)月球上那少得可憐的水其化學成分跟地球上的水不同的。因此，他們得出這樣的結論：月球上的水可能來自彗星。這項研究發(fā)表在《自然地球科學》期刊上。 研究人員利用所謂的離子顯微鏡來比較月球巖石中正常的氫元素含量及同位素氘的含量，元素氘比卿多帶一個中子。他們發(fā)現(xiàn)，同地球上的水相比，氘的含量更高——但同海爾·波普彗星、哈庫塔克彗星和哈雷上的水有著相似的平。這表明,在45億年前月球剛剛形成其構造后不久，彗星就在古月球上留下了水。 這一發(fā)現(xiàn)也可以解釋地球上水的奧秘——海洋是如何在地球上形成的。因為如果彗星曾重重撞擊過月球，那它們很可能也造訪過地球，海洋里的水的確比地幔的水含有更多氘。研究人員說，也許這是因為海洋有著彗星上的冰融化而來的水。