Scientists have leveraged images from NASA’s DART mission to gain deeper insights into the binary asteroids Didymos and Dimorphos. The Double Asteroid Redirection Test (DART) impacted Dimorphos, the smaller asteroid in the pair, while data collected from both the DART and the Light Italian Cubesat for Imaging of Asteroids (LICIACube) missions provided a detailed look at both celestial bodies.
Led by Olivier Barnouin of Johns Hopkins University Applied Physics Laboratory, the research team analyzed Didymos, discovering its rugged surface with boulders ranging from 33 to 525 feet and numerous craters at high elevations, while smoother terrain with fewer craters characterizes its lower elevations. The smaller moonlet, Dimorphos, features a range of rock sizes and several cracks but is mostly crater-free.
The team’s analysis indicates that Dimorphos likely formed from debris ejected from Didymos and coalesced under gravity. They estimated Didymos to be about 12.5 million years old, significantly older than Dimorphos, which they placed at around 0.3 million years.
Further studies led by Maurizio Pajola from INAF – Astronomical Observatory of Padova revealed that boulders on Dimorphos formed at different times, supporting the idea that moonlets in binary systems originate from material shed by their larger counterparts. This process also accounts for a notable ridge on Didymos.
Another team, led by Naomi Murdoch from the Université de Toulouse, examined boulder tracks on Didymos and found its surface to be composed of loose material, less capable of supporting weight compared to terrestrial sand or lunar soil.
Alice Lucchetti from INAF-Astronomical Observatory of Padova identified rapid “thermal fatigue” on Dimorphos, where temperature fluctuations cause micro-fractures in rocks over about 100,000 years. This rapid fatigue is unprecedented in silicate and nickel-iron asteroids.
Comparative studies by Colas Robin from Université de Toulouse of 34 boulders on Dimorphos with those on other “rubble-pile” asteroids, like Itokawa, Ryugu, and Bennu, suggested a shared formation and evolution mechanism among these bodies.
These findings offer a comprehensive view of the Didymos system before the DART impact and will aid the European Space Agency’s upcoming Hera mission, set to launch in October 2024. Hera will arrive at Didymos and Dimorphos in September 2026 to gather high-resolution data on the system post-DART collision, further illuminating the mission’s aftermath.
The research was published on July 30 in the journal Nature.