Nasa spacecraft collision with asteroid expelled over 1,000 tons of dust

Nasa scientists estimate momentum transfer from Dart’s roughly 22,530 km/h collision

The deliberate collision of Nasa’s Dart spacecraft with the asteroid moonlet Dimorphos is estimated to have displaced over 1,000 tonnes of rock into space.

Material from the collision altered Dimorphos’ orbit by about 33 minutes, according to research presented during the American Geophysical Union’s Fall Meeting in Chicago.

History was made by September’s collision, which was the first time humans have altered the course of a heavenly body.

Nasa hoped to find out if future asteroids threatening Earth could be diverted by a deliberate collision, saving the planet from potentially deadly impacts of the kind that once wiped out the dinosaurs.

Dart, or Double Asteroid Redirection Test, was launched in November 2021 and spent months traveling to target Dimorphos – a companion asteroid of the larger Didymos – that was travelling through space at a distance of about 6.8 million miles from Earth.

Scientists used new data on the composition of Dimorphos and the characteristics of the ejected material, gained from telescope observations and images from Dart’s ride-along Light Italian CubeSat for Imaging of Asteroids contributed by the Italian Space Agency.

Based on the data, scientists could learn how much Dart’s initial hit moved the asteroid and how much came from the recoil.

“We know the initial experiment worked. Now we can start to apply this knowledge. Studying the ejecta made in the kinetic impact – all of it derived from Dimorphos – is a key way of gaining further insights into the nature of its surface,” said Andy Rivkin, Dart investigation team co-lead at the Johns Hopkins Applied Physics Lab (APL).

The research also revealed that Dimorphos and Didymos have a similar makeup and are composed of the same material.

Scientists said predicting the momentum transfer would be central to planning a future kinetic impact mission, including estimating the size of the impactor spacecraft.

It would also help to determine the amount of lead time that would be needed to ensure that a small deflection would move a potentially dangerous asteroid off its path in the future, Nasa said.

In the analysis, the space agency found the momentum transfer onto Dart was roughly 3.6 times greater than if the asteroid had simply absorbed the spacecraft and produced no ejecta at all, indicating the ejecta contributed to moving the asteroid more than the spacecraft did.

“Momentum transfer is one of the most important things we can measure, because it is information we would need to develop an impactor mission to divert a threating asteroid,” said Andy Cheng, Dart investigation team lead from Johns Hopkins APL.

“Understanding how a spacecraft impact will change an asteroid’s momentum is key to designing a mitigation strategy for a planetary defense scenario,” he added.