Seismic resurfacing of 433 Eros indicative of a highly dissipative interior for large near-Earth asteroids

An asteroid’s interior dictates how its space environment changes its shape and surface, which provides a record of the collisional and dynamical evolution of the Solar System. Knowledge of asteroid interiors also enables the formulation of mitigation strategies against hazardous asteroids. Despite this importance, asteroid interiors remain poorly understood. Asteroids between 0.2 km and 10 km in diameter are thought to have rubble-pile interiors, transitioning to fractured interiors at 10 km scales, then to coherent and differentiated interiors at ≳100 km scales. The asteroid 433 Eros, the only 10-km-scale asteroid explored by a rendezvous mission, is an exemplar of asteroids at intermediate scales. Recent exploration of smaller rubble piles has provided insight into physical properties that are shared with Eros-sized objects. Here we quantify the seismic and physical properties of Eros’ interior through measurements and modelling of crater degradation and erasure from the impact that formed the 7.5-km-diameter Shoemaker crater on Eros. Our results indicate that Eros’ deep interior has a seismic wave scattering length of 0.5 ± 0.1 km and effective quality factor ^EQ < \({63}_{-13}^{+18}\) at frequencies >0.06 Hz. Contrary to the established view of Eros as a fractured shard, our findings suggest that Eros’ interior properties are consistent with those of a rubble-pile asteroid.