Scientists have discovered that the target asteroid in NASA’s Double Asteroid Redirection Test (DART) may have been reshaped by the impact. A new study of the impact’s aftermath found that the asteroid, the smaller component of the binary asteroid system, exhibited a loose “rubble” composition.
DART crashed into the moonlet Dimorphos orbiting the larger space rock Didymos on September 26, 2023. The purpose of this cosmic attack was to see if a kinetic impact could change an asteroid’s orbit around a larger object, and to verify whether this method worked. It could one day be used to deflect a space rock if it lands on a collision course with Earth.
Six months after the crash, NASA confirmed that the mission was a success; The time required for Dimorphos to enter orbit of its larger asteroid companion was reduced by 33 minutes. After the impact, one of Dimorphos’ orbits around Didymos takes approximately 11 hours and 23 minutes to complete. And now, new research shows that this effect could also have major impacts on the world. shape It belongs to Dimorphos.
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A team led by scientist Sabina Raducan from the University of Bern used state-of-the-art computer modeling to first determine that Dimorphos is a loose, debris-filled asteroid. This also means that the moonlet may have formed from material ejected from its larger asteroid partner Didymos.
Simulations closest to the impact observations show that Dimorphos has only weak cohesiveness and no large rocks on its surface.
“We didn’t know what to expect before DART arrived at Dimorphos. Because the system was so far from Earth, Dimorphos couldn’t be properly resolved. So we may have encountered anything from a monolithic body (essentially a large rock),” Raducan told Space.com. “From Dimorphos to a pile of rubble that couldn’t hold on, or anything in between,” he said. “So, while the impact outcome was a surprise to most, it was one of the predicted scenarios.”
Raducan added that being prepared the rubble nature of Dimorphos wasn’t too surprising, but DART revealed other things that caught the team off guard.
“Dimorphos has a very different composition from asteroids Ryugu and Bennu, but their responses to collisions appear to be quite similar and were surprising,” Raducan said. said. “For all these asteroids, cratering occurs in the low-gravity, low-adhesion regime, where the crater grows many times larger than the projectile.
Additionally, according to the team’s calculations, the DART impact appears to have completely reshaped Dimorphos, rather than simply creating an impact crater. This may have occurred through a process called spherical deformation. In turn, the reshaping appears to have caused the outer surface of the moonlet to be re-covered by material from its interior.
The team’s simulations showed that as a result of the DART impact, 0.5% to 1% of Dimorphos’ mass was ejected, while 8% of its mass was redistributed, causing the asteroid to significantly reshape and resurface. Raducan added that these findings suggest that the structural integrity of small asteroids and their response to impacts are likely deeply influenced by their internal composition and the distribution of their constituent materials.
The team’s results could help scientists better understand the Dimorphos and Didymos asteroid system and study the dynamics of other binary asteroids in the solar system.
“The material properties and structure of Dimorphos obtained in this study indicate that the little moon probably formed through rotational mass loss and reaccumulation from Didymos,” Raducan said. said. “These findings provide clues about the prevalence and properties of similar binary systems in our solar system, contributing to our broader understanding of their formation history and evolution.”
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DART’s primary purpose was to test planetary defense methods, and Raducan said the mission certainly succeeded in that regard. He explained that these results will inform the development of future asteroid exploration missions and guide the design of future planetary defense initiatives by influencing asteroid impact mitigation strategies.
“What this means from a planetary defense perspective is that small, rubble asteroids like Dimorphos are very effective at deflecting, and a kinetic impact technique would be a suitable deflection mechanism,” Raducan said. “However, before attempting deflection, a reconnaissance mission will likely be required to accurately assess the asteroid’s properties.”
The researchers now plan to compare the simulation results with data collected by the European Space Agency’s (ESA) mission Hera, which will visit Dimorphos, to validate and improve their model.
“The findings of the Hera mission will be instrumental in validating our models and transforming the kinetic impactor into a reliable asteroid deflection mechanism,” Raducan concluded. “We also plan to expand our analysis to a broader range of asteroid types and/or shapes, such as Dinkinesh recently imaged by the Lucy mission.
“These studies will increase the robustness of our predictions for planetary defense and contribute to a more comprehensive understanding of asteroid mechanics and composition.”
The team’s research was published Monday, February 26, in the journal Nature Astronomy.