Once DART has detected the much smaller Dimorphos, just 160 metres in diameter, it can make a last-minute course correction to collide with the moonlet. The larger Didymos has a diameter of 780 metres and thus, makes a better target for DART to aim for. This is still further away than our moon, but is very close in astronomical terms, so this is when DART will hit Dimorphos.ДART will spend about 10 months travelling towards Didymos and, when itвЂ™s close by, will change direction slightly to crash into Dimorphos at a speed of about 6.6 kilometres per second.ДЄlso Read - Russia's Prichal module docks at ISS However, NASA has also said there is a 99.943% chance the asteroid will miss us.ДЄt one point in their orbit around the Sun, Didymos and Dimorphos come within about 5.9 million kilometres of Earth. With a 500-metre diameter, Bennu is capable of creating a five-kilometre crater on Earth. The impacts that created the Barringer Crater, and the 1908 Tunguska event, both correspond to Torino Scale 8.Д¬urrently, NASA is keeping a close eye on asteroid Bennu, which is the object with the largest вЂњcumulative hazard ratingвЂќ right now. The Chicxulub impact (which is attributed to the extinction of non-avian dinosaurs) was a Torino Scale 10. It uses a scale from 0 to 10, wherein 0 means there is a negligible chance of collision, and 10 means imminent collision, with the impacting object being large enough to precipitate a global disaster. The Torino scale is a method for categorising the impact hazard associated with a near-Earth object (NEO). NASAвЂ™s DART mission has been sparked by the threat and fear of a major asteroid hitting Earth in the future. The 2013 Chelyabinsk meteoroid, which damaged buildings in six Russian cities and injured around 1,500 people, was estimated to be about 20 metres in diameter. Asteroids with an approximate five-kilometre diameter impact Earth about once every 20 million years.

The most вЂњrecentвЂќ impact of this size is thought to have formed the Tenoumer impact crater in Mauritania, around 20,000 years ago. This means we get hit much more frequently by small objects than larger ones - simply because there are many more smaller objects in space.ДЄsteroids with a 1-kilometre diameter strike the Earth every 500,000 years, on average. There is an inverse relationship between the size of these objects and the frequency of impact events. Almost all asteroids of this size disintegrate in the atmosphere and are usually harmless.ДЄlso Read - NASA InSight lander makes first underground map of Mars Well, Earth is actually bombarded frequently by small asteroids, ranging from 1-20 metres in diameter. WeвЂ™ve all seen disaster movies in which an asteroid hits Earth, creating an extinction event similar to the one that killed off the dinosaurs millions of years ago. This smaller half of the pair will be DARTвЂ™s target.ДЄre we facing an extinction threat from asteroids?

Every 12 hours Didymos is orbited by a mini-moon, or вЂњmoonletвЂќ, Dimorphos. The mission will travel to the asteroid Didymos, a member of the Amor group of asteroids. The Double Asteroid Redirection Test (DART) lifted off aboard a SpaceX rocket from California on November 23, and will arrive at the target asteroid system in September 2022. The test aims to demonstrate our technological readiness in case an actual asteroid threat is detected in the future. A NASA spacecraft the size of a golf cart has been directed to smash into an asteroid, with the intention of knocking it slightly off course.

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