Space experts deliver their verdict on NASA’s DART mission to knock an asteroid off course

Tonight, NASA may just pull off one of its most ambitious feats in its 64-year history. 

A NASA spacecraft called DART is due to crash into an asteroid that’s about 6.8 million miles away from Earth. 

DART was launched from California last November – and finally completes its 10-month journey in the early hours of Tuesday, UK time. 

DART’s target is the small asteroid Dimorphos, which orbits a larger asteroid called Didymos, around 6.8 million miles away from our planet. 

DART will hit the space rock at 15,000mph and be destroyed upon impact, while Dimorphos will merely receive a ‘small nudge’ to alter its trajectory by a fraction. 

If this sounds like the plot from a sci-fi disaster movie, rest assured – neither Dimorphos nor Didymos pose any danger to Earth. 

The $325 million (£298 million) mission is merely a rehearsal of what may be required if a space rock does one day threaten our planet.

If a large asteroid was to hit Earth, it could wipe out the human race – much like the demise of the dinosaurs 66 million years ago. 

MailOnline has spoken to experts about how the DART mission will be judged a success – and any implications for Earthlings if it fails. 

DART – which is being referred to as a planetary defence mission – marks humanity’s first attempt at deflecting an asteroid. 

The impact is due to take place on Monday (September 26) at 19:14 ET (00:14 BST Tuesday) and can be watched live on NASA TV and the agency’s YouTube channel. 

Professor Alan Fitzsimmons from Queen’s University Belfast, told MailOnline that completion of the DART mission will give experts ‘a much better idea how to protect ourselves against a catastrophic impact’. 

‘I’ve been waiting 20 years for a planetary defence test to be performed,’ he said. 

‘DART will give us our first proof that we have the technology to prevent a small asteroid hitting Earth.’  

Colin Snodgrass, an astronomer at the University of Edinburgh, said there is the possibility it won’t work, but that if this is the case ‘there is no real problem’.

‘This has never been tried before, it is an experiment,’ he told MailOnline. ‘So there is always a risk that it doesn’t work.

‘That is why we do these tests now rather than waiting until we found an asteroid that was actually a danger and we need to do it for real. 

‘If the mission fails, for example by missing the target, there is no real problem as it is just a test – and NASA would learn from analysis of what went wrong to be able to make sure a future mission would succeed.’ 

Dr Jonathan McDowell, an astronomer at the Harvard-Smithsonian Center for Astrophysics, highlighted potential issues that could occur tonight. 

‘The worst case scenario is that we don’t get any information back from the mission, due to a communications system failure or something like that,’ Dr McDowell told MailOnline. 

‘The other main way the mission can fail is if there’s a problem in the targeting system and DART misses Dimorphos instead of hitting it, in which case it will sail on around the sun.’ 

DART did not travel alone – it carried with it LICIACube, a shoebox-size mini spacecraft developed by the Italian Space Agency. 

The mini satellite weighs just 31 pounds and measures roughly the length of an adult’s hand and forearm.

After piggybacking on DART for almost the entire journey, LICIACube was released from DART on September 11 and is now travelling on its own to witness the impact at a safe distance of 34 miles (55km). 

Using its cameras, LICIACube will capture images of the impact, as well as images of the ejecta plume produced by the impact itself. 

It is possible that there is smaller debris orbiting Didymos, and if either DART or LICIACube were to run into such debris they could be destroyed before completing their mission, according to Dr McDowell. 

But the impact will also be observed from Earth using telescopes, which means the mission doesn’t rely on LICIACube to be a success, Professor Snodgrass added. 

‘DART is designed so that observations from telescopes on the ground will give the key results of the mission, by monitoring how the asteroid changes after the impact,’ Professor Snodgrass told MailOnline.  

While $325 million is a hefty amount, researchers were in agreement that the money will be worth it if the mission goes to plan. 

Dr McDowell told MailOnline: ‘Some day we may have to deal with an asteroid that’s heading towards the Earth, and this practice shot will give us invaluable experience for that day.’

Professor Snodgrass also said the mission will ‘undoubtedly’ be worth it and that $325 million is ‘a tiny fraction of the cost of the damage that an asteroid impact could cause’.

‘It makes sense to make the investment in technology that could prevent such a disaster in the future,’ he said. ‘Asteroid impact is the one kind of major natural disaster that we can actually prevent.’   

Dr Stefania Soldini, a lecturer in space engineering at the University of Liverpool, said it could take weeks for LICIACube to send all the images back to Earth.

‘This period will be utterly nerve wracking – waiting for good news from a spacecraft is always an emotional time for an engineer,’ she wrote for The Conversation. 

In the run-up to the impact, LICIACube has already successfully tested its camera, sending back images of Earth and the Pleiades star cluster. 

The two images, released by NASA at the weekend, were each taken by one of LICIACube’s two cameras – LUKE and LEIA, named in reference to heroes from Star Wars. 

After tonight’s impact, LICIACube will hopefully capture images of the newly formed impact crater and the opposite hemisphere of Dimorphos that DART will never see.  

Paul Wiegert, an asteroid expert at Western University’s Institute for Earth and Space Exploration in Canada, also said some pieces of debris could even reach Earth. 

‘I suspect the amount of DART-ejected material that will reach the Earth is very small,’ he said.

Both Didymos and the smaller Dimorphos were discovered relatively recently; Didymos in 1996 and the smaller Dimorphos in 2003. 

The year it was discovered, Dimorphos came within 3.7 million miles of Earth – 15 times farther away than the Moon. 

This is even closer that the current close approach of around 6.8 million miles.  

Currently, scientists are not entirely certain how porous the asteroids are, or much about their composition at all. 

‘We actually know very little of the asteroids’ composition,’ said Dr Soldini. 

‘The great uncertainty around how strong Dimorphosis is has made designing a bullet spacecraft a truly enormous engineering challenge. 

‘Based on ground observation, the Didymos system is suspected to be a rubble-pile made up of lots of different rocks, but its internal structure is unknown.’