Media release

From: Springer Nature

Dimorphos may have been reshaped following DART impact

The asteroid moon Dimorphos may have been reshaped following the impact from NASA’s Double Asteroid Redirection Test (DART), according to a paper published in Nature Astronomy. This result indicates that Dimorphos is potentially a weak rubble pile made up of material shed from its asteroid Didymos.

The DART planetary defence demonstrator accomplished its mission on September 26, 2022, when it impacted Dimorphos, the moon of near-Earth asteroid Didymos, and shortened its orbital period around the asteroid by 33 minutes. DART has important planetary defence applications, but the spacecraft also provided information on the internal structure of asteroids and the effect of an impact on their properties.

Sabina Raducan and colleagues modelled the DART impact with a state-of-the-art shock physics code, using realistic constraints on Dimorphos’s 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 authors suggest that Dimorphos may be a rubble pile formed from rotational shedding and re-accumulation of ejected material from Didymos. The 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 authors conclude that their findings offer additional insights into the formation and characteristics of binary asteroids and may have implications for future explorations, such as ESA’s upcoming Hera mission, and asteroid deflection efforts.