Another is that they are a surprising source of evidence for what happened in the solar system's earliest days.

另一个原因出人意料——它们是说明太阳系早期形成发展情况的来源之一。

For example, trackways are one of the best sources of evidence for establishing how fast extinct animals could move.

例如，轨道是确定灭绝动物移动速度的最佳证据来源之一。