The collision between the DART spacecraft and the asteroid Dimorphos ejected 1 to 10 million kilograms of material into space, demonstrating the effectiveness of the experiment.
The Double Asteroid Redirection Test (DART) spacecraft from NASA crashed into the small asteroid Dimorphos at the end of September, preparing for a future scenario where humanity may need to divert a hazardous asteroid threatening Earth. The DART team reported that the impact shortened the time it takes for Dimorphos to complete an orbit around the larger asteroid Didymos by 32 minutes, exceeding initial expectations.
The large tail of Didymos approximately two months after the DART impact. (Photo: Magdalena Ridge Observatory/NM Tech)
Scientists shared new findings about the collision at the annual meeting of the American Geophysical Union held in Chicago from December 12-16. Many new results focused on the comet-like tail formed by debris from the collision. Additionally, the research team shared two significant figures they calculated.
First, they estimated that at least 1 million kilograms, potentially up to 10 million kilograms, of debris was ejected from the asteroid. The total mass of Dimorphos is approximately 5 billion kilograms, meaning the asteroid could have lost only 0.2% of its material.
The second figure is the “momentum transfer coefficient,” or beta, which is central to the DART mission’s objectives. Scientists use this important number to assess the effectiveness of a collision with an asteroid. If a spacecraft were to collide head-on with an asteroid without creating any debris, the asteroid would only gain the momentum that the spacecraft had at the moment of impact, making beta equal to 1.
Debris ejected from the asteroid into space adds additional momentum to the asteroid, gradually increasing the beta coefficient of the collision. The research team calculated that DART’s beta coefficient is 3.6. This figure indicates that Dimorphos gained more than three times the momentum, and the debris created by the impact affected the asteroid more than the spacecraft itself did.
“This is very good news for kinetic impactor technology. At least in the case of DART, the collision was indeed effective in changing the target’s orbit,” said Andy Cheng, the DART investigation team leader at the Johns Hopkins University Applied Physics Laboratory.
The calculations also provide scientists with real data to understand how the characteristics of the asteroid affect momentum transfer. This essential data helps determine the size of a spacecraft needed to prevent a disaster. The “successor” to DART, the Hera spacecraft from the European Space Agency (ESA), is scheduled for launch in 2024 and will play a crucial role after it approaches the Dimorphos and Didymos asteroid pair for close-up study.
