Mechanical properties of rubble pile asteroids (Dimorphos, Itokawa, Ryugu, and Bennu) through surface boulder morphological analysis

This material constitutes the dataset used for the computation of the results of the paper Mechanical properties of rubble pile asteroids (Dimorphos, Itokawa, Ryugu, and Bennu) through surface boulder morphological analysis by Robin & al. The folders "Bennu", "Dimorphos", "Itokawa" and "Ryugu" contains the raw images from PDS used for this study as well as the images with the outlined boulders made with segmentanygrains (https://github.com/zsylvester/segmenteverygrain), and the associated morphological descriptor values. The folder "ExtremeCases" contains the raw and outlined images for extreme roundness cases. This material also contains the main figures of the paper as well as the code to remake most the figures. Last version of this manuscript has been submitted to Nature Communications on May 14th, 2024 and accepted on May 17th, 2024. Abstract: Planetary defense efforts rely on estimates of the mechanical properties of asteroids, which are difficult to constrain accurately from Earth. The mechanical properties of asteroid material are also important in the interpretation of the Double Asteroid Redirection Test (DART) impact. Here we perform a detailed morphological analysis of the surface boulders on Dimorphos using images, the primary data set available from the DART mission. We estimate the bulk angle of internal friction of the boulders to be 32.7 ± 2.5° from our measurements of the roundness of the 34 best-resolved boulders ranging in size from 1.67 to 6.64 m. The elongated nature of the boulders around the DART impact site implies that they were likely formed through impact processing. Finally, we find striking similarities in the morphology of the boulders on Dimorphos with those on other rubble pile asteroids (Itokawa, Ryugu and Bennu). This leads to very similar internal friction angles across the four bodies and suggests that a common formation mechanism has shaped the boulders. Our results provide key inputs for understanding the DART impact and for improving our knowledge about the physical properties, the formation and the evolution of both near-Earth rubble-pile and binary asteroids.