The asteroid that hit the DART spacecraft is 300 thousand years old

MADRID (EUROPA PRESS) – Dimorphos, the asteroid that NASA’s DART mission hit with the aim of altering its trajectory, was formed 300,000 years ago, while its larger binary Didymos is 12.5 million years old.

By studying data collected by NASA’s Double Asteroid Redirection Test (DART) mission, which in 2022 sent a spacecraft to intentionally collide with the moon Dimorphos, the mission’s science team discovered new information about the origins of the target binary asteroid system and why the DART spacecraft was so effective at changing Dimorphos’ orbit.

In five papers recently published in Nature Communications, the team explored the geology of the binary asteroid system, comprising the moon Dimorphos and the parent asteroid Didymos, to characterize its origin and evolution and constrain its physical characteristics.

The authors infer that Dimorphos likely broke off from Didymos in a large mass-shedding event. There are natural processes that can speed up the rotation of small asteroids, and there is growing evidence that these processes may be responsible for reshaping these bodies or even forcing material off their surfaces.

The analysis suggested that both Didymos and Dimorphos have faint surface features, leading the team to postulate that Didymos has a surface age between 40 and 130 times older than Dimorphos, with the former estimated to be 12.5 million years old and the latter less than 300 thousand years old. Dimorphos’ low surface drag likely contributed to DART’s significant impact on its orbit.

“The images and data DART collected in the Didymos system provided a unique opportunity for a close-up geological look at a binary near-Earth asteroid system,” said Olivier Barnouin, senior author of the paper and a scientist at the Johns Hopkins Applied Physics Laboratory (APL), in a statement.

“From these images alone, we were able to infer a wealth of information about the geophysical properties of Didymos and Dimorphos and expand our understanding of the formation of these two asteroids. We also better understand why DART was so effective at moving Dimorphos.”