搜了论坛N遍,也没有找到大家讨论以下这个问题,估计实在是太低级了。。。 我只想问: 140. Rock samples taken from the remains of an asteroid about twice thesize of the 6-mile-wide asteroid that eradicated the dinosaurs have beendated at 3.47 billion years old and thus are evidence of the earliest knownasteroid impact on Earth.