New research shows that ‘deadly’ asteroids could subject Earth to meteoroid bombardment

NASA's Double Asteroid Redirection Test (DART) mission, which successfully impacted the asteroid Dimorphos on September 26, 2022, has provided valuable insights into an asteroid defense strategy for Earth. A new study has now used these insights to map possible trajectories of ejecta that could be created should humanity ever need to “kill” more asteroids.

The European team of astronomers and scientists used complex computer simulations to map the trajectory of the ejected material and found that any asteroid debris could potentially reach Mars and Earth, potentially creating a whole new set of problems.

The goal of NASA's DART mission was to test the effectiveness of “kinetic impact technology” to deflect potentially dangerous asteroids. Simply put, it is the science and art of ramming a spacecraft into an asteroid.

The mission's target was Dimorphos, the smaller member of the Didymos binary asteroid system. The star successfully changed its orbit by slamming a spacecraft into it at a speed of about 6.1 kilometers per second. Although Dimorphos posed no direct or immediate threat to Earth, its size and distance made it a good choice for a test.

The impact occurred 11 million kilometers from Earth. It was a milestone in planetary defense research and showed that if Earth ever found itself in the path of a giant space boulder, we would know how to change its trajectory.

Now some researchers have turned their attention to the obvious consequences of such a mission: If an asteroid is destroyed or even attempted to be moved a small distance, it creates huge amounts of debris.

Using modern numerical simulations, the researchers were able to model the behavior of the ejecta released by the DART impact and depict how it would spread from its place of origin, in this case Dimorphos. They took into account factors such as the initial velocity of the ejecta, its size distribution and the gravitational influence of various celestial bodies.

The simulations, which spanned a 100-year period, found that some of the 3 million small pieces of debris generated by the DART mission could reach the Martian vicinity within 7 to 13 years, depending on their initial speed. Particles ejected at a speed of about 770 meters per second were found to have the potential to reach Mars' Hill sphere, a region of gravitational influence, in about 7 years. The study also suggested that debris traveling at speeds over 1.5 kilometers per second could reach the Hill sphere of the Earth-Moon system within about 7 years.

The results of this study have significant implications for our understanding of asteroid deflection techniques and their potential consequences. While the DART mission demonstrated our ability to alter an asteroid's trajectory, this latest study underscores the importance of considering the fate of the ejecta created by such impacts.

According to the study, the size of each individual piece of debris in the case of the DART mission is relatively harmless to people on the planet, as it would burn up in the atmosphere. However, countless tiny space chunks could cause serious damage to our satellites or other spacecraft in orbit.

The possibility of debris reaching the vicinity of Mars and Earth raises questions about the potential risks associated with asteroid defense missions. This underscores the need for careful planning and risk assessment when developing future planetary defense strategies. In other words, we not only need to move an asteroid to ensure its safety, but we also need to map the consequences of the “kinetic impact.”

Another possibility is that the ejecta could potentially form a new meteor shower.

“Nevertheless, ongoing meteor observation campaigns will be crucial to determine whether DART has produced a new (and man-made) meteor shower: the Dimorphids,” study co-author Dr. Eloy Peña-Asensio, a DART mission research associate from the Politecnico of Milan, explained in a statement to Universe Today. “Meteor observation campaigns in the coming decades will have the final say. When these ejected Dimorphid fragments reach Earth, they pose no danger. Due to their small size and high speed, they will disintegrate in the atmosphere, creating a beautiful glowing streak in the sky.”

The DART mission was a resounding success and a necessary step forward in our efforts to protect Earth from the threat of asteroid impacts. But as this new study shows, in the future we'll have to dodge not only giant space chunks, but many small ones as well.

“There is probably no other planetary-scale impact where so much information is available about the impact body, the target, and the formation and early evolution of the ejecta,” says Peña-Asensio. “This allows us to test and improve our models and scaling laws of the impact process and ejecta evolution. These data provide the input data used by the ejecta evolution models.”

By studying such factors, we can hope to reduce the potential for surprise and the risks of future asteroid diversion or kill missions, should they ever be justified to protect life on Earth.