一艘航天器已发射升空，以测试一种可以令危险小行星偏离轨道的技术。美国国家航空航天局将该任务称为 “ 双小行星重定向试验（Double Asteroid Redirection Test ）”，希望借此了解阻止一块巨大的太空岩石与地球相撞有多困难。

A large asteroid striking our planet is an extremely rare event, but the consequences of a direct hit could be catastrophic. A rock measuring 150 metres across could release the energy of several nuclear bombs. Even larger objects could affect life across the world.  

大型小行星撞击地球是一件极其罕见的事情，但直接相撞的后果可能是灾难性的。一块直径150米的岩石可能释放出相当于几枚原子弹的能量。更大的物体则可能影响全世界范围内的生命。

So, Nasa is launching this mission to find out whether it's possible to deflect an asteroid heading for Earth. In late 2022, the Dart spacecraft will crash into a space rock called Dimorphos, allowing scientists on the ground to use telescopes to measure the change in its orbit.

因此，美国国家航空航天局开展这次任务，以查明是否有可能使飞向地球的小行星偏离其运行轨道。2022年底，“双小行星重定向试验” 航天器将撞向一块叫 Dimorphos 的太空岩石，从而让地面科学家用太空望远镜测量其运行轨道的变化。

The impact should only alter the object's speed and path by a small amount, but over long distances that may be enough to prevent a dangerous space rock from striking Earth, if we spot it with enough notice.

撞击只会稍微改变物体的速度和路径，但如果距离够长的话，可能就足以防止危险的太空岩石撞向地球，前提是我们要有足够的时间提前注意到它。