Scientists have discovered that the target asteroid of NASA’s Double Asteroid Redirection Test (DART) may have been reshaped by the impact. A new study of the aftermath of the collision revealed that the asteroid, the smaller part of a binary asteroid system, exhibits a loose “mess” composition.
On September 26, 2023, DART collided with the moon Dimorphos, which orbits the larger space rock Didymos. The purpose of this cosmic strike was to see if a kinetic impact could shift the trajectory of an asteroid around a larger object and to verify that this method could do that. be used to one day shunt a space rock as its path falls on a collision course with Earth.
Six months after the impact, NASA confirmed that the mission had been successful, with the time required for Dimorphos to orbit its larger asteroid companion reduced by 33 minutes. After impact, one of Dimorphos’ orbits around Didymos lasts approximately 11 hours and 23 minutes. And now new research shows that the impact may also have had major consequences for the form of Dimorphos.
Related: Scientists applaud DART’s success six months after historic asteroid crash
A team led by scientist Sabina Raducan of the University of Bern used state-of-the-art computer modeling to first determine that Dimorphos is a loose asteroid with debris clusters. This also means that the moon may have formed from material ejected from its larger asteroid partner, Didymos.
The closest simulations to the observations of the impact suggest that Dimorphos is only weakly coherent and has no large boulders on its surface.
“Before DART’s arrival at Dimorphos, we didn’t know what to expect. Because the system is so far from Earth, Dimorphos was not well resolved. Therefore, we could have encountered anything from a monolithic body – essentially a large boulder as big as Dimorphos – to a coherent mess or something in between,” Raducan told Space.com. “So while the impact outcome was a surprise to most, it was one of the predicted scenarios.”
Raducan added that while the preparedness meant Dimorphos’ mess nature wasn’t too surprising, DART revealed other things that did catch the team off guard.
“Dimorphos have a very different composition than the asteroids Ryugu and Bennu, but their response to impacts, which appeared to be very similar, was surprising,” Raducan said. ‘For all these asteroids, cratering occurs in a low-gravity, low-cohesion regime, with the crater becoming many times larger than the projectile.
Furthermore, according to the team’s calculations, rather than just creating an impact crater, the DART collision appears to have completely reshaped Dimorphos. This would have happened through a process called global distortion. In turn, the reform appears to have resulted in the exterior of the moonlet being re-covered with material from the interior.
The team’s simulations showed that between 0.5% and 1% of Dimorphos’ mass was ejected as a result of the DART impact, while 8% of its mass was redistributed, leading to significant reform and revival of the asteroid. Raducan added that these findings suggest that the structural integrity and responses to impacts of small asteroids are likely profoundly affected by their internal composition and the distribution of their constituent materials.
The team’s results could help scientists better understand the asteroid system Dimorphos and Didymos and parse the dynamics of other binary asteroids in the solar system.
“The material properties and structure of Dimorphos, as inferred in this study, suggest that the small moon was likely formed by the loss of rotational mass and the reaccumulation of Didymos,” Raducan said. “These findings provide clues about the prevalence and characteristics of similar binary systems in our Solar System, and contribute to our broader understanding of their formation history and evolution.”
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— DART asteroid crash seen by James Webb, Hubble Space Telescopes (photos)
— DART impact gave asteroid Dimorphos a debris tail thousands of miles long (stunning photo)
DART’s primary purpose was to test planetary defense methods, and Raducan said the mission certainly delivered results in this regard. She explained that these results will inform the development of future asteroid exploration missions and impact asteroid collision mitigation strategies, guiding the design of future planetary defense initiatives.
“The implication for planetary defense is that small asteroids with debris clusters, such as Dimorphos, can deflect very efficiently, and the kinetic impactor technique would be a suitable deflection mechanism,” Raducan said. “However, before attempting a deflection, a reconnaissance mission would likely be necessary 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) upcoming Dimorphos visiting mission, Hera, to validate and refine their models.
“The findings from the Hera mission will play an important role in validating our models and transforming a kinetic impactor into a reliable asteroid deflection mechanism,” Raducan concluded. ‘We also plan to extend our analysis to a wider range of asteroid types and/or shapes, such as Dinkinesh, as recently imaged by the Lucy mission.
“These studies will increase the robustness of our planetary defense predictions and contribute to a more comprehensive understanding of asteroid mechanics and composition.”
The team’s research was published Monday (Feb. 26) in the journal Nature Astronomy.