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。

词汇表

asteroid 小行星
striking 撞击
catastrophic 灾难性的
deflect 转向，偏离轨道
spacecraft 航天器
telescopes 太空望远镜
orbit （天体）运行轨道
impact 撞击
path 路径
notice 事先注意

阅读理解：请在读完上文后，回答下列问题。

1. How often do large asteroids strike the planet?

2. What is this Nasa mission hoping to find out?

3. What is needed if scientists are to stop an asteroid hitting Earth?

4. By how much does the asteroid need to be knocked off its path?

答案  

1. How often do large asteroids strike the planet?
It is very unlikely – a large asteroid striking our planet is an extremely rare event.

2. What is this Nasa mission hoping to find out?
Nasa is launching this mission to find out whether it's possible to deflect an asteroid heading for Earth.

3. What is needed if scientists are to stop an asteroid hitting Earth?
Scientists need enough notice to prevent a dangerous space rock from striking Earth.

4. By how much does the asteroid need to be knocked off its path?
It only needs to alter its path by a small amount.