Researchers simulate Earth’s defenses against asteroid impacts

NASA’s Double Asteroid Redirection Test (DART) mission is the world’s first full planetary defense test against possible asteroid impacts on Earth. Researchers from the University of Bern and the National Center of Competence in Research (NCCR) PlanetS now show that instead of leaving behind a relatively small crater, the impact of the DART spacecraft on its target could render the asteroid nearly unrecognizable. .

Sixty-six million years ago, a giant asteroid impact on Earth likely caused the extinction of the dinosaurs. Currently, no known asteroids pose an immediate threat. But if one day a large asteroid were discovered on a… collision course with Earth, it may need to be deflected from its orbit to avoid catastrophic consequences.

Last November, the DART room US space agency NASA probe was launched as a first full-scale experiment of such a maneuver: its mission is to collide with an asteroid and divert it from its orbit, providing valuable information for the development of such a maneuver. planetary defense system.

In a new study published in The Planetary Science Magazine, researchers from the University of Bern and the National Center of Competence in Research (NCCR) PlanetS simulated this impact with a new method. Their results indicate that it can distort its target much more severely than previously thought.

Debris instead of solid rock

“Contrary to what you might think when imagining an asteroid, direct evidence of space missions such as the Japan Space Agency’s (JAXA) Hayabusa2 probe shows that asteroid can have a very loose internal structure — similar to a pile of debris — that is held together by gravitational interactions and small cohesive forces,” said study lead author Sabina Raducan. Institute of Physics and the National Center of Competence in Research PlanetS at the University of Bern.

Still, previous simulations of the DART mission impact tended to assume a much sturdier interior of its asteroid target Dimorphos. “This could drastically change the outcome of the clash of DART and Dimorphos, which is scheduled for next September,” emphasizes Raducan. Rather than leaving a relatively small crater on the 160-meter-wide asteroid, the impact of DART at a speed of 24,000 km/h could completely deform Dimorphos. The asteroid could also be deflected much more strongly and larger amounts of material could be ejected from the impact than earlier estimates predicted.

“One of the reasons that this loose internal structure scenario has not been thoroughly studied until now is that the necessary methods were not available,” said study lead author Sabina Raducan. “Such impact conditions cannot be simulated in laboratory experiments and the relatively long and complex process of cratering after such an impact – a matter of hours in the case of DART – made it impossible to realistically simulate these impact processes until now,” he said. the researcher.

“With our new modeling approach, which takes into account shock wave propagation, compaction and subsequent material flow, we were able to model for the first time the entire crater process resulting from impacts on small asteroids such as Dimorphos,” reports Raducan For this achievement, she was honored by ESA and by the Mayor of Nice during a workshop on the DART follow-up mission HERA.

Broad horizon of expectations

In 2024, the European Space Agency will send a space probe to Dimorphos as part of the space mission HERA. The aim is to visually examine the aftermath of the DART probe impact. “To get the most out of the HERA missionwe need to have a good understanding of possible outcomes of the DART impact,” said co-author Martin Jutzi of the Institute of Physics and the National Center of Competence in Research PlanetS.

“Our work on the impact simulations adds an important potential scenario that forces us to broaden our expectations in this regard. This is not only relevant in the context of planetary defense, but also adds an important piece to the puzzle of our understanding of asteroids. in general,” Jutzi concludes.