Chang'e 5 samples help rewrite moon's history
嫦娥五号带回的月球样品帮助改写了月球历史
Chinese scientists have discovered that lunar volcanism was still occurring about 800 million to 900 million years later than previously thought after analyzing lunar samples returned by the Chang'e 5 mission, suggesting the moon cooled down much more slowly.
在分析了由嫦娥五号任务返回的月球样品后，中国科学家发现月球岩浆活动停止的时间比原先认为的晚八到九亿年，表明月球冷却速度是慢得多的。
Researchers from the Chinese Academy of Sciences' Institute of Geology and Geophysics presented their results in three papers published in Nature on Tuesday.
中科院地质与地球物理所将研究结果以三篇论文形式于周二（10月19日）发表在了《自然》杂志上。
Their analysis of basalts, a type of rock formed during volcanic eruptions, not only indicated that the lunar samples were the youngest to be dated, but also provided new data on the composition and water content of the moon's interior, offering new insights on the moon's thermal evolution.
他们对火山喷发过程中形成的玄武岩进行了分析，结果不仅显示该月球样品是最“年轻”的，而且为月球内部成分和水含量提供了新数据，就月球热演化提供了新的见地。
The Chang'e 5 lunar mission returned with 1,731 grams of lunar samples on Dec 17, more than 40 years after the US Apollo and Soviet Union Luna missions retrieved their samples.
嫦娥五号任务于去年12月17日返回了1731克月球样品，晚于美国阿波罗任务和苏联月球任务取得其样品40多年。
The samples were then distributed to 13 research institutes on July 12, with the research team at the Institute of Geology and Geophysics receiving about 5 grams.
然后，该样品在7月12日被分发给13家科研机构，中科院地质与地球物理所被分得大约5克。
Volcanism is a sign that a celestial body is still dynamic, and studying planetary volcanism can reveal a planet's deep composition and thermal evolution.
火山活动标志着天体仍处于活跃状态，对行星火山活动的研究能够揭示行星的深层构造和热演进。
Lunar volcanism was most active on the near side of the moon, covering about 17 percent of the lunar surface.
月球火山活动在月球正面是最活跃的，覆盖了大约17%的月球表面。
Geochemist Li Xianhua, an academician at the Institute of Geology and Geophysics, said scientists have always been interested in figuring out exactly when the lunar volcanism started and ended, as well as the mechanism of formation of the most recent volcanism.
地球化学家李献华是中科院地质与地球物理所院士，他表示科学家们一直以来都对月球火山活动起止的精确时间以及月球最近一次火山活动形成的机制感兴趣。
Previous radioisotope dating of lunar samples brought back by the Apollo and Luna missions suggested that most lunar volcanic activities ceased by around 2.9 billion or 2.8 billion years ago.
此前对阿波罗任务和月球任务所返回的月球样品进行放射性同位素定年法，结果显示大部分的月球火山活动在29亿年前或28亿年前就停止了。
Those samples were collected within 30 degrees of the moon's equator and could not represent the large lunar surface.
这些样品都是在月球赤道上下30度的区域收集的，不能代表广袤的月球表面。
After studying the isotopes of the rocks, Li and his colleagues confirmed that the Chang'e 5 basalts came from the same eruption lava, which occurred around 2 billion years ago, delaying the end of the Moon's volcanic activity by 800 million to 900 million years.
在研究了岩石的同位素后，李献华和同事确认了嫦娥五号任务返回的玄武岩来自同样的20亿年前的火山喷发岩浆，该研究意味着月球火山活动截止的时间比之前所想的晚了八亿到九亿年。
Their finding also helps create a benchmark to better calibrate crater-counting chronology models.
他们的发现也帮助建立基准，从而更好地校准“撞击坑计数法”年表模型。
Meanwhile, the cause of the moon's most recent volcanic activity remained a puzzle.
与此同时，月球最近一次的火山活动成因还是个谜。
Li said the scientific community had proposed two possible explanations: a lunar mantle rich in radioactive elements to provide a heat source; or one rich in water to lower the melting point.
李献华表示科学界已经提出了两个可能的解释：月幔富含放射性元素来提供热源，或者月幔富含水分从而降低了熔点。
