On September 26, 2022, NASA’s Double Asteroid Redirection Test (DART) mission successfully impacted Dimorphos, the natural satellite of the binary near-Earth asteroid Didymos. New numerical simulations indicate that the DART impact caused global deformation and resurfacing of Dimorphos.
DART was a planetary defense mission to demonstrate the feasibility of using a kinetic impactor to change the trajectory of an asteroid.
The impact was successful and highly effective, resulting in a reduction in Dimorphos’ orbital period around Didymos, which was initially 11 h and 55 min, by 33 min.
The LICIACube Unit Key Explorer (LUKE) instrument onboard the cubesat captured images of the system between 29 and 320 s after impact to reveal filamentary streams of ejecta and other complex patterns that expanded for several km from the impact site.
Moreover, the dramatic brightening of the Didymos system by solar illumination of released impact ejecta was observed by ground- and space-based telescopes for many weeks after the impact.
In new research, University of Bern scientist Sabina Raducan and her colleagues modeled the DART impact with a state-of-the-art shock physics code, using realistic constraints on Dimorphos’ mechanical and compositional properties informed by DART’s first results.
The simulations that were the closest match to observations of the impact suggest that Dimorphos is weak with a cohesive strength similar to the asteroids Bennu and Ryugu and has a lack of large boulders on its surface.
The researchers suggest that Dimorphos may be a rubble pile formed from rotational shedding and re-accumulation of ejected material from Didymos.
Their model also indicates that the DART impact may not have produced an impact crater but could have reshaped the moon in its entirety — a process known as global deformation — and caused resurfacing of Dimorphos with material from its interior.
The findings offer additional insights into the formation and characteristics of binary asteroids and may have implications for future explorations, such as ESA’s Hera mission, and asteroid deflection efforts.
“ESA’s upcoming Hera mission may find a reshaped asteroid rather than a well-defined crater,” the authors concluded.
Their paper was published in the journal Nature Astronomy.
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S.D. Raducan et al. Physical properties of asteroid Dimorphos as derived from the DART impact. Nat Astron, published online February 26, 2024; doi: 10.1038/s41550-024-02200-3
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