by Scientists discovered that the target asteroid of NASA’s Double Asteroid Redirect Test (DART) may have been reshaped by the impact. A new investigation into the aftermath of the collision has revealed that the asteroid has the composition of a loose “debris pile”, which is the smallest component of a binary asteroid system.
DART crashed into the moonlet Dimorphos, which orbits the larger space rock Didymos, on September 26, 2023. The aim of this cosmic attack was to see if the kinetic impact could shift the trajectory of an asteroid around a larger object and verify that the this method. could be used to shunt a space rock someday should its path fall on a collision course with Earth.
Six months after the impact, NASA confirmed that the mission was successful, and the time it takes to put Dimorphos into the orbit of its larger asteroid companion reduced by 33 minutes. After impact, one of Dimorphos’ orbits around Didymos takes about 11 hours and 23 minutes. And now, new research shows that the impact on the shape of Dimorphos.
Related: Scientists welcome DART success 6 months after historic asteroid crash
A team led by University of Bern scientist Sabina Raducan used state-of-the-art computer modeling to first determine that Dimorphos is a loose, rubble-like asteroid. This also means that the moon may have been made of material ejected from its larger asteroid partner, Didymos.
The simulations closest to the impact observations suggest that Dimorphos is only weakly cohesive and lacks large boulders on its surface.
“Before DART came to Dimorphos, we didn’t know what to expect. Because the system is so far away from Earth, Dimorphos was not properly resolved. So, we could have come anything from a monolithic body — basically a big boulder the size of Dimorphos — to a pile of uncohesed rubble or anything in between,” Raducan told Space.com. “So, while the outcome was a surprise to most, it was one of those situations that was predicted.”
Raducan added that while preparedness meant the nature of the Dimorphos rubble pile wasn’t too surprising, DART has revealed other things that have thrown the team off guard.
“Dimorphos has a very different composition from asteroids Ryugu and Bennu, but their reaction to impacts was surprising, they seem very similar,” said Raducan. “For all of these asteroids, cratering occurs in a low-center-of-gravity, low-cohesion regime, where the crater grows much larger than the missile.
Furthermore, according to the team’s calculations, rather than just creating an impact crater, Dimorphos appears to have been completely reshaped by the DART collision. This would happen through a process called global deformation. Apparently, the reshaping seems to have resulted in the outer surface of the moon’s bottom being resurfaced with material from its interior.
The team’s simulations showed that between 0.5% and 1% of Dimorphos’ mass was expelled as a result of the DART impact, and 8% of its mass was redistributed, resulting in significant reshaping and resurfacing of the asteroid. Raducan added that these findings suggest that their internal composition and distribution of constituents are likely to have profound effects on structural integrity and responses to small asteroid impacts.
The team’s findings could help scientists better understand the Dimorphos and Didymos asteroid system as well as decipher the dynamics of other binary asteroids in the solar system.
“The material properties and structure of Dimorphos as derived in this study indicate that the small moon was probably formed by rotational mass shedding and re-accumulation from Didymos,” said Raducan. “These results provide clues to the prevalence and characteristics of similar binary systems in our solar system, contributing to our broader understanding of their formation history and evolution.”
Related stories:
— Asteroid impact: This is the last thing NASA’s DART spacecraft saw before it crashed
— DART asteroid crash seen by James Webb, Hubble space telescope (photos)
— DART’s impact sent a tail of debris on asteroid Dimorphos thousands of miles long (great photo)
DART’s main purpose was to test planetary defense methods, and Raducan said the mission has definitely delivered in this regard. She explained that these findings will inform the development of future asteroid exploration missions and influence asteroid impact mitigation strategies, guiding the design of future planetary defense initiatives.
“The implication for planetary defense is that small debris asteroids, like Dimorphos, are very effective at deflection, and the kinetic impactor technique would be an appropriate deflection mechanism,” said Raducan. “However, before attempting a deflection, a reconnaissance mission would probably be necessary to accurately assess the properties of the asteroid.”
The researchers now plan to compare simulation results with data collected by the European Space Agency’s (ESA’s) upcoming Dimorphos visit mission, Hera, to validate and refine their models.
“The results of the Hera mission will be key to validating our models and turning a kinetic collider into a reliable asteroid deflection mechanism,” Raducan said. “We also plan to extend our analysis to a wider range of asteroid types and/or shapes, like Dinkinesh, as recently imaged by the Lucy mission.
“These studies will improve the robustness of our predictions for planetary protection and contribute to a more comprehensive understanding of asteroid mechanics and composition.”
The team’s research was published on Monday (February 26) in the journal Nature Astronomy.
