New Delhi: About 15 per cent of all asteroids, including Near Earth Asteroids (NEAs) are believed to be binary systems. Analysis of images captured by
the NASA’s Double Asteroid Redirection Test (DART) spacecraft in 2022, before it rammed into Dimorphos, the moonlet of Didymos have revealed an active exchange of rock and dust in gentle, slow collisions that reshape them over millions of years. The scientists identified fan-shaped streaks across the surface of the moonlet, which is the first direct visual evidence of material naturally travelling from one asteroid to another. The researchers were surprised by the discovery, and initially suspected something wrong with the camera and image processing algorithms.
After cleaning up the images, the patterns were consistent with low-velocity impacts. The researchers developed sophisticated techniques to remove shadows of boulders and lighting effects from the observations. The team was also able to confirm the Yarkovsky-O’Keefe-Radzievskii-Paddak effect, which predicted that sunlight makes small asteroids spin faster, until material flies off their surfaces. At times, this process can end up creating moons. It is likely that the moonlet Didymos spun out off Dimorphos, as evidenced by the cosmic snowballs left on the surface of Dimorphos. The trajectory of the kinetic impactor created unique challenges.
Lab experiments and computer simulations confirmed results
The spacecraft hurtled straight towards its target without any change in lighting or perspective, making it difficult to resolve surface features. The scientists proved the legitimacy of the streaks by mapping them back to their origin, to a single region near the edge of Dimorphos. The researchers also conducted laboratory experiments, by dropping marbles into sand scattered with painted gravel to simulate boulders, with high-speed cameras revealing that the impacts created ray-like patterns matching those found on Dimorphos. The results were also confirmed by computer simulations of loose clumps of dust, that also produced the ray-like patterns. A paper describing the results has been published in The Planetary Science Journal.
