So how big an impactor would it take to make a 180-kilometer diameter crater on the earth?

多大的撞击物才能在地球上留下直径180千米的陨石坑呢？

You can show that Mars was hit with an impactor, a comet or asteroid, about three billion years ago.

你可以证明火星在大约30亿年前被一个撞击物——彗星或小行星撞击过。

The Mars-sized impactor had been chosen because it could make the Moon and make the length of Earth's day.

选中火星大小的撞击物是因为它能够形成月球，并形成地球上一天的时长。

The size of the impactor isn't quite known, but we think it might be on the order of about 60 kilometers or so.

撞击物的大小并不确定，但我们认为大概是60千米（的直径）。

At that time, a 10-kilometre impactor is going to vaporize, melt and displace something like well over 10,000 cubic kilometers of the surface of the earth.

那时，这10千米的撞击物将要使地球表面上超过一万立方千米的东西被蒸发、融化和被撞飞。

Engineers tested the impactor in a controlled environment.

工程师在受控环境中测试了撞击器。

The mission's success depended on the accuracy of the impactor.

任务的成功取决于撞击器的准确性。

Scientists designed the impactor to study the composition of asteroids.

科学家设计了撞击器来研究小行星的成分。

The impactor hit the surface of the moon with great force.

撞击器以巨大的力量撞击了月球表面。

The impactor was launched from the spacecraft to create a crater.

撞击器从航天器发射出去以制造一个陨石坑。