Nasa is due to deliberately crash a spacecraft into an asteroid overnight to test if technology can prevent future asteroids from hitting Earth.
Bar a last minute cancellation, Nasa’s Double Asteroid Redirection Test (DART) mission is due to smash into the asteroid, Dimorphos, at over six kilometres per second with the intention of changing its path.
Asteroid Didymos and its small moonlet Dimorphos, which are about 11 million kilometres from Earth, make up a binary asteroid system, meaning the small moon, Dimorphos, orbits the larger body, Didymos.
Didymos, the larger asteroid of the two is about 780 metres in diameter while the moonlet, Dimorphos, is about 160 metres. Nasa's DART mission launched to Didymos on November 24, 2021, on a SpaceX Falcon 9 rocket from Vandenberg Air Force Base in California.
It is thought that the impact will be enough to slightly change the orbit of Dimorphos around the larger asteroid Didymos.
The collision is due to change the speed of Dimorphos by a fraction of one percent and alter the moonlet's orbital period around the larger asteroid by several minutes, enough to be observed and measured by telescopes on Earth.
Professor Alan Fitzsimmons, a Queen’s University Belfast professor and expert in the observation and measurement of asteroids and comets orbiting our sun, said that Nasa is doing “exactly what we need to do".'
Prof. Fitzsimmons has been working in the field of Planetary Defence for over 20 years and is a member of the Nasa DART Investigation Team.
Speaking in advance of the planned impact, Mr Fitzsimmons said: "This will give us our first proof that we have the technology to prevent a small asteroid from hitting Earth.”
Dimorphos and Didymos pose no threat. However, they were chosen as the target because they pass relatively close to Earth. Prof. Fitzsimmons said that it’s important to monitor asteroid activity.
“Asteroids the size of Dimorphos or larger hit our planet only once every 35,000 years or so, but we only know where a small fraction of them are. So, one could be heading our way in the near future, and smaller asteroids hit us much more frequently,” he said.
Prof. Fitzsimmons has supported the mission by making telescopic observations of the Dimorphos/Didymos system. He is also due to analyse telescope data of the impact itself.
Following tonight’s planned test, the next stage will involve the European Space Agency’s (ESA) post-impact survey. The mission, Hera, is due to launch in October 2024 and will reach the asteroid in December 2026.
It is hoped that Hera will turn the experiment into a well-understood and repeatable planetary defence technique. Prof. Fitzsimmons’s primary focus will now be the ESA Hera mission.
“Once the DART and follow-up Hera mission have been successfully completed, we’ll have a much better idea of how to protect ourselves against a catastrophic impact,” he said.