Two cube-shaped probes will also study the make-up of the asteroid and its mass.
“We need to understand what are the physical properties of these asteroids? What are they made of? Are they blocks of rock? Are they made of sand inside?” says Naomi Murdoch, a scientist involved with the European Space Agency mission.
That should help scientists understand the best way to attempt to intercept other asteroids, which can be many different sizes and shapes, in the future.
Scientists do not believe that we are currently at risk of a dinosaur-style extinction caused by an asteroid hitting Earth. An asteroid of that size could be easily spotted in space.
The size of asteroid that DART and Hera are targeting are about 100-200m wide and are very difficult to see from our planet.
From time to time they hit Earth. On 2013 a house-sized asteroid exploded in the sky above the town of Chelyabinsk in Russia. The shock wave blew out windows for over 200 square miles and damaged buildings. Over 1,600 people were injured in the blast.
Scientists hope to one day be able to identify asteroids like this and knock them off course.
“It's not to avoid an extinction of the human race. It's to create a system to minimize the damage as much as we can. The dinosaurs didn't have a space program, but we do,” says Prof Murdoch.
But scientists warn that even though Nasa has proved it is possible to alter one asteroid’s course, it does not mean it can easily be done on all space rocks.
Intercepting an asteroid before it hits Earth also relies on being able to spot the incoming hazard in the first place.
