NASA's Double Asteroid Redirection Test (DART) mission is the world's first full – scale planetary defense test against potential asteroid impact on Earth.
NASA's Double Asteroid Redirection Test (DART) mission is the world's first full – scale planetary defense test against potential asteroid impact on Earth. Scientists are now showing that instead of leaving a relatively small crater behind, the impact of the DART spacecraft on its target can make the asteroid almost unrecognizable.
66 million years ago, a giant asteroid impact on Earth probably caused the extinction of dinosaurs. At present, no known asteroid poses an immediate threat. However, should a large asteroid one day be spotted on a collision course with Earth, it may need to be deflected from its orbit to prevent catastrophic consequences.
In November last year, the DART spacecraft from the US space agency NASA was launched as the first full-scale experiment of such a maneuver: Its mission is to collide with an asteroid and divert it from its orbit, to provide valuable information for the development of such a planetary defense system.
In a new study published in The Planetary Science Journal, researchers at the University of Bern and the National Center for Competence in Research (NCCR) PlanetS have simulated this impact using a new method. Their results suggest that it may deform its target much more severely than previously thought.
Gravel instead of solid stone
“Contrary to what one might imagine when imagining an asteroid, direct evidence from space missions such as the Japanese Space Agency's (JAXA) Hayabusa2 probe shows that the asteroid may have a very loose internal structure – similar to a pile of debris – held together by gravitational interactions and small cohesive forces “, says the study's lead author Sabina Raducan from the Institute of Physics and the National Center of Competence in Research PlanetS at the University of Bern.
Nevertheless, previous simulations of the impact of the DART mission mostly assumed a much more solid interior of its asteroid target Dimorphos. “This could drastically change the outcome of the collision of DART and Dimorphos, which is scheduled to take place in the coming September,” Raducan points out. Instead of leaving a relatively small crater on the 160-meter-wide asteroid, DART's impact at a speed of about 24,000 km / h can completely deform Dimorphos. The asteroid could also be deflected much more strongly and larger amounts of material could be ejected from the impact than previously estimated.
An award-winning new approach
“One of the reasons why this scenario with a loose internal structure has not been studied carefully so far is that the necessary methods were not available,” says the study's lead author Sabina Raducan.
“Such shock conditions cannot be recreated in laboratory experiments and the relatively long and complex process of crater formation after such an impact – a matter of hours in the case of DART – made it impossible to realistically simulate these impact processes to date,” according to the researcher.
“With our new modeling method, which takes into account the propagation of the shock waves, the compression and the subsequent flow of material, we were able to model for the first time the entire crater process that is the result of impact on small asteroids like Dimorphos,” reports Raducan. For this achievement, she was rewarded by ESA and by the Mayor of Nice at a workshop on the DART follow-up mission HERA.
Widen the horizon of expectations
In 2024, the European Space Agency ESA will send a space probe to Dimorphos as part of the HERA space mission. The purpose is to visually examine the aftermath of the impact of the DART probe. “To get the most out of the HERA mission, we need to have a good understanding of the potential outcomes of the DART effect,” said study co-author Martin Jutzi of the Institute of Physics and the National Center of Competence in Research PlanetS. “Our work on impact simulations adds an important potential scenario that requires 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 in our understanding of asteroids in general,” he said. concludes Jutzi.
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