Asteroid shapes and hydration levels can serve as tracers of their history and origin. For instance, the asteroids (162173) Ryugu and (101955) Bennu have an oblate spheroidal shape with a pronounced equator, but contain different surface hydration levels. Here we show, through numerical simulations of large asteroid disruptions, that oblate spheroids, some of which have a pronounced equator defining a spinning top shape, can form directly through gravitational reaccumulation. We further show that rubble piles formed in a single disruption can have similar porosities but variable degrees of hydration. The direct formation of top shapes from single disruption alone can explain the relatively old crater-retention ages of the equatorial features of Ryugu and Bennu. Two separate parent-body disruptions are not necessarily required to explain their different hydration levels.
Michel, P.; Ballouz, R.-L.; Barnouin, O. S.; Jutzi, M.; Walsh, K. J.; May, B. H.; Manzoni, C.; Richardson, D. C.; Schwartz, S. R.; Sugita, S.; Watanabe, S.; Miyamoto, H.; Hirabayashi, M.; Bottke, W. F.; Connolly, Harold Jr.; Yoshikawa, M.; and Lauretta, D. S., "Collisional formation of top-shaped asteroids and implications for the origins of Ryugu and Bennu" (2020). School of Earth & Environment Faculty Scholarship. 42.
Creative Commons License
This work is licensed under a Creative Commons Attribution 4.0 License.
Michel, P., Ballouz, RL., Barnouin, O.S. et al. (2020). Collisional formation of top-shaped asteroids and implications for the origins of Ryugu and Bennu. Nature Communications 11, 2655. https://doi.org/10.1038/s41467-020-16433-z