What is Nasa's DART? Watch how a spacecraft will save the Earth by smashing into an asteroid

Some of the world's leading scientists believe that a monumental­­ asteroid collision with Earth is highly likely in the future. However, Nasa is not merely theorizing about such a possibility. The space agency has revealed how it plans to protect the Earth from potential asteroid impacts in the future.

Nasa's DART (Double Asteroid Redirection Test) is the space agency's "first-ever mission to demonstrate an asteroid deflection technique for planetary defense."

Nasa's new asteroid defense mission will involve the "refrigerator-sized" DART spacecraft targeting an asteroid (not heading toward Earth) as part of a dry-run test. The DART spacecraft will be designed to smash into the asteroid "at a speed about nine times faster than a bullet, approximately 3.7 miles per second (6 kilometers per second)," effectively altering the asteroid's orbit.

The DART spacecraft's target will be an asteroid called Didymos – the name in Greek means twin. The asteroid was named such as it's a binary system that actually consists of two bodies. Didymos A and a smaller asteroid orbiting it called Didymos B. Nasa's spacecraft's actual target is Didymos B, the smaller of the two bodies.

"DART is a critical step in demonstrating we can protect our planet from a future asteroid impact," Andy Cheng of The Johns Hopkins Applied Physics Laboratory, the DART investigation co-lead said in a statement. "Since we don't know that much about their internal structure or composition, we need to perform this experiment on a real asteroid. With DART, we can show how to protect Earth from an asteroid strike with a kinetic impactor by knocking the hazardous object into a different flight path that would not threaten the planet."

Nasa is yet to announce a launch date for DART, however, the space agency did mention that the spacecraft's target asteroid Didymos, will make distant approaches toward Earth in 2022 and 2024, indicating that DART may be launched in that period.

Nasa says that the Earth is hit by small asteroids on a daily basis that "harmlessly" break up in the upper atmosphere. However, for a collision to cause actual damage to Earth, the planetary object has to be larger than 1km in diameter. The space agency said that around 93% of such sized objects have already been found.

"DART would test technologies to deflect objects in the intermediate size range—large enough to do regional damage, yet small enough that there are many more that have not been observed and could someday hit Earth. NASA-funded telescopes and other assets continue to search for these objects, track their orbits, and determine if they are a threat," the space agency said.