Ever since scientists first theorised that a meteor strike could have been possible for the extinction of the dinosaurs, the worry has been that a similar rogue accident could happen again. But what exactly can humanity do to protect itself from the wrath of Mother Nature.
Concept image of the DART spacecraft - NASA/JHUAPL
Now, NASA is putting together its first-ever mission to just that, by demonstrating a plan to deflect oncoming asteroids away from Earth. Called the Double Asteroid Redirection Test (DART), the planetary defence is finally moving from concept development to a preliminary design phase, following NASA approval on June 23.
¡°DART would be NASA¡¯s first mission to demonstrate what¡¯s known as the kinetic impactor technique ¨C striking the asteroid to shift its orbit ¨C to defend against a potential future asteroid impact,¡± said Lindley Johnson, planetary defence officer at NASA Headquarters in Washington. ¡°This approval step advances the project toward an historic test with a non-threatening small asteroid.¡±
DART¡¯s target is an asteroid that will be on a distant approach to Earth in October 2022, and again in 2024. Called Didymos, it¡¯s actually a binary asteroid system consisting of two bodies; Didymos A, about 780 m wide, and Didymos B, about 160 m wide. DART is intended to impact ad shift only the smaller of the two.
Didymos B is large enough to be a useful test, as it¡¯s determined to be the same size as an asteroid typically capable of devastating effect, should it hit Earth. ¡°A binary asteroid is the perfect natural laboratory for this test,¡± said Tom Statler, program scientist for DART at NASA Headquarters. ¡°The fact that Didymos B is in orbit around Didymos A makes it easier to see the results of the impact, and ensures that the experiment doesn¡¯t change the orbit of the pair around the sun.¡±
Once launched, the refrigerator-sized DART would fly to Didymos and use an on-board autonomous targeting system to aim itself at Didymos B. Then, it would strike the smaller body at about 6 kilometres per second, roughly nine times faster than a bullet. The idea isn¡¯t to try and shatter an asteroid or even bounce it away, but to preemptively make a minor course correction so it passes by Earth harmlessly over the course of its predicted passes.
While current law directs the development of the DART mission, it¡¯s not identified as a specific budget item in the Administration¡¯s Fiscal Year 2018 budget. However, the test is still important. ¡°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.¡±