NASA to crash a spacecraft into an asteroid in humanity's first planetary defence test

While the mission may sound like the plot of the 90s cult-classic Armageddon, NASA is taking planetary defence very seriously.

NASA's Double Asteroid Redirection Test (DART) is the world's first full-scale mission to test technology for defending Earth against potential asteroid collisions.

On September 26, the DART spacecraft will intentionally collide with Dimorphos, the asteroid moonlet of Didymos, hoping to change the speed and path of the asteroid in space, according to NASA.

While the collision will take place at 7.14pm on Monday in the United States, Australians can watch the collision live on NASA TV at 9.14am Tuesday.

Scientists will then use ground-based telescopes to observe if Dimorphos' orbit has changed, and by how much.

In 2024, The European Space Agency will also launch the Hera mission, to survey the impact of the DART spacecraft on the asteroid and turn the mission into a "repeatable planetary defence technique".

Australian National University Professor Junichiro Kawaguchi, a former president of Japan's Society for Space and Astronautical Science, said the DART mission could help us understand how to deflect meteorites in the future.

Earth has been struck by many asteroids throughout history, with the most famous occuring 65 million years ago, Professor Kawaguchi said, when a 10km asteroid hit the Earth, wiping out the dinosaurs.

In 2013, a 15 to 20-metre meteorite exploded over southern Russia and caused a shockwave that injured more than 1600 people, an event which statistically happens once in a century, Professor Kawaguchi said

"Statistically, a 20-metre meteorite collides with the Earth every 100 years," Professor Kawaguchi said.

At that size, a collision with Earth would generate a 6.7 magnitude earthquake, he said.

If a meteorite the size of DART's target Dimorphos, measuring an estimated 160 metres, hit Earth, the generated earthquake would be "huge", Professor Kawaguchi said.

If successful, DART's mission technology could help deflect meteorite landing points to less populated, safer areas.

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"If such a hazardous body of Dimorphos class is discovered and deflection spacecraft is launched three years before collision, the small body trajectory may be deflected about 100 km, and the landing point is changed to a less populated and safe area," he said.

Professor Kawaguchi said ensuring DART hits its target would be "very difficult" but "theoretically possible".

A similar collision guidance was once performed during NASA's successful "Deep Impact" mission in 2005, when the space agency launched an impactor that collided with a comet, Professor Kawaguchi said.