Would we be helpless if a giant asteroid heads toward Earth? The answer is probably yes. However, humanity will not give up that easily. NASA and the European Space Agency (ESA) are planning their first attempt to knock an asteroid out of orbit. The project is named Double Asteroid Redirection Test (DART) and it should be conducted in October 2022.

The target for DART is an asteroid called Didymos (twin) – because it’s an asteroid binary system that consists of two bodies: Didymos A, about one-half mile (780 meters) in size, and a smaller asteroid orbiting it called Didymos B, about 530 feet (160 meters) in size. DART would impact only the smaller of the two bodies, Didymos B.

The spacecraft will also be accompanied by an ESA spacecraft called Hera, which will be responsible for gathering data about the asteroid. It will be also accompanied by two small CubeSats (nanosatellites) – that will record additional data, such as the gravitational field and the internal structure of the asteroid. They will be released around the asteroids and will land on the two space objects.

“DART would be NASA’s first mission to demonstrate what’s known as the kinetic impactor technique — striking the asteroid to shift its orbit — to defend against a potential future asteroid impact,” said Lindley Johnson, planetary defense officer at NASA Headquarters in Washington.

The refrigerator-sized spacecraft should strike the smaller body at a speed about nine times faster than a bullet, approximately 3.7 miles per second (6 kilometres per second). Earth-based observatories would be able to see the impact and the resulting change in the orbit of Didymos B around Didymos A, allowing scientists to better determine the capabilities of the kinetic impact as an asteroid mitigation strategy. The kinetic impact technique works by changing the speed of a threatening asteroid by a small fraction of its total velocity, but by doing it well before the predicted impact so that this small nudge will add up over time to a big shift of the asteroid’s path away from Earth.

“DART is a critical step in demonstrating we can protect our planet from a future asteroid impact,” said Andy Cheng of The Johns Hopkins Applied Physics Laboratory in Laurel, Maryland, the DART investigation co-lead. “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.”


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