An unprecedented and long-awaited deep-space venture will take place on Monday night when a Nasa spacecraft will be deliberately crashed into an asteroid in an attempt to show humans can avert an Armageddon-style impact to Earth.
What is happening and why.
The Double Asteroid Redirection Test is the first planetary defense experiment conducted by the US space agency to see if it can change the trajectory of an asteroid if it ever comes close to Earth.
The asteroid Didymos and its moon Dimorphos have been targeted by the agency in order to crash a small craft into them. The asteroid and its moon are close enough to pose no threat to our planet before or after they collide.
If you have watched the recent comedy Don't Look Up, you will know that there is a chance of an asteroid hitting Earth. If that ever happens, Nasa wants to know if it has the ability to protect us.
The plan is that the 15,000mph impact of the Dart spaceship will cause Dimorphos to change course and go somewhere else. The goal of Asteroids was to change the direction of menacing space rocks in order to destroy them, which is not the goal of Dart. There are no flying saucers that kill people.
The mission is being broadcasted on the internet with commentary and video. Mission managers will hold a press conference after the impact. You can follow the developments on the Guardian's live blogs.