Before the asteroid’s collision in a 2022 planetary defence test, NASA’s DART mission took high-resolution pictures of the asteroid Dimorphos and its companion Didymos. These photographs have allowed scientists to investigate the creation of binary asteroid systems, which consist of a parent asteroid and a secondary moonlet orbiting around it.
Didymos’ analysis indicates that it formed approximately 12.5 million years ago, most likely from the asteroid belt that lies between Mars and Jupiter. Dimorphos, on the other hand, formed about 300,000 years ago. Astronomer Maurizio Pajola claims that both asteroids are mountains of rubble composed of stony particles that were left over when a parent asteroid was destroyed. Didymos rotates so quickly that material is supposed to have been ejected from its equator, which is how Dimorphos formed.
Both Dimorphos and Didymos are considered near-Earth asteroids; Dimorphos is 560 feet broad, while Didymos is almost 0.5 miles wide. Didymos has stones the size of a football pitch, whereas Dimorphos has boulders the size of buses.
The DART mission of NASA effectively showed the use of kinetic impact to change an asteroid’s trajectory. Although neither asteroid is dangerous to Earth, the mission advanced knowledge of binary asteroids—which make up 10–15% of near-Earth asteroids—by shedding light on their origin and history.
