PARIS - After NASA deliberately smashes a car-sized spacecraft into an asteroid next week, it will be up to the European Space Agency's Hera mission to investigate the "crime scene" and uncover the secrets of these potentially devastating space rocks.

NASA's Double Asteroid Redirection Test (DART) aims to collide with the asteroid moonlet Dimorphos on Monday night, hoping to slightly alter its trajectory - the first time such an operation has been attempted.

While Dimorphos is 11 million kilometres away and poses no threat to Earth, the mission is a test run in case the world someday needs to deflect an asteroid from heading our way.

Astronomers around the world will watch DART's impact, and its effect will be closely followed to see if the mission passed the test.

Then, the European Space Agency's Hera mission, named after the ancient Greek queen of the gods, will follow in its footsteps.

The Hera spacecraft is planned to launch in October 2024, aiming to arrive at Dimorphos in 2026 to measure the exact impact DART had on the asteroid.

But scientists are not only excited to see DART's crater, but also to explore an object that is very much out of this world.

Dimorphos, which orbits a larger asteroid Didymos as they hurtle together through space, provides not only a "perfect testing opportunity for a planetary defence experiment, but it is also a completely new environment," the ESA's Hera mission manager Ian Carnelli said.

Hera will be loaded up with cameras, spectrometers, radars and even toaster-sized nano-satellites to measure the asteroid's shape, mass, chemical composition and more.

NASA's Bhavya Lal said that it was critically important to understand the size and composition of such asteroids.

"If an asteroid is made up of, for example, loose gravel, approaches to disrupt it may be different than if it was metal or some other kind of rock," she told the International Astronautical Congress in Paris this week.

So little is known about Dimorphos that scientists will discover "a new world" at the same time as the public on Monday, Hera mission principal investigator Patrick Michel said.