University of Bern researchers simulate planetary defense.
The world’s first comprehensive planetary defense test against potential asteroid impacts on Earth is being conducted by NASA as part of the Double Asteroid Redirection Test (DART) project. Researchers from the University of Bern and the National Centre of Competence in Research (NCCR) PlanetS have now shown that the impact of the DART spacecraft on its target might render the asteroid almost unrecognizable rather than leaving behind a relatively tiny crater.
The extinction of the dinosaurs is thought to have occurred 66 million years ago as a result of a massive asteroid collision on Earth. No known asteroid presents an immediate danger right now. But if a large asteroid were to be found one day headed straight for Earth, it might need to be diverted off its route to avoid disastrous consequences.
The DART space probe, developed by NASA in the US, was launched last November as the first full-scale test of such a maneuver. Its goal is to hit an asteroid and divert it off its orbit in order to gather important data for the creation of a planetary defense system.
Researchers from the University of Bern and the National Centre of Competence in Research (NCCR) PlanetS used a new method to model this impact in a recent study that was published in The Planetary Science Journal. According to their findings, it may damage its target far more severely than previously believed.
Rubble instead of solid rock
“Contrary to what one might imagine when picturing an asteroid, direct evidence from space missions like the Japanese space agency’s (JAXA) Hayabusa2 probe demonstrates that an asteroid can have a very loose internal structure – similar to a pile of rubble – that is held together by gravitational interactions and small cohesive forces”, says study lead-author Sabina Raducan from the Institute of Physics and the National Centre of Competence in Research PlanetS at the University of Bern.
Yet, previous simulations of the DART mission impact 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 around 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 the previous estimates predicted.
A prize-winning new approach
“One of the reasons that this scenario of a loose internal structure has so far not been thoroughly studied is that the necessary methods were not available”, study lead-author Sabina Raducan says.
“Such impact conditions cannot be recreated in laboratory experiments and the relatively long and complex process of crater formation following such an impact – a matter of hours in the case of DART – made it impossible to realistically simulate these impact processes up to now”, according to the researcher.
“With our novel modeling approach, which takes into account the propagation of the shock waves, the compaction, and the subsequent flow of material, we were for the first time able to model the entire cratering process resulting from impacts on small, asteroids like Dimorphos”, Raducan reports. For this achievement, she was awarded by ESA and by the mayor of Nice at a workshop on the DART follow-up mission HERA.
Widen horizon of expectations
In 2024, the European Space Agency ESA will send a space probe to Dimorphos as part of the space mission HERA. The aim is to visually investigate the aftermath of the DART probe impact. “To get the most out of the HERA mission, we need to have a good understanding of potential outcomes of the DART impact”, says study co-author Martin Jutzi from the Institute of Physics and the National Centre of Competence in Research PlanetS.
“Our work on the impact simulations adds an important potential scenario that requires us to widen 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.
Reference: “Global-scale Reshaping and Resurfacing of Asteroids by Small-scale Impacts, with Applications to the DART and Hera Missions” by Sabina D. Raducan and Martin Jutzi, 1 June 2022, The Planetary Science Journal.