radioisotope dating造句

• Radioisotope dating of the impact - melt samples ? rocks that melted when an asteroid or comet struck the moon , therefore revealing when an impact occurred ? shows that all these basins formed in a narrow interval between 3 . 9 billion and 3 . 8 billion years ago
  利用放射性同位素为撞击熔融物（在小行星或彗星撞击月球时熔化的岩石，因此它们能显示撞击发生的时间）定年，显示这些盆地都在39 ~ 38亿年前一个很短的时间内形成。