What can we learn about asteroids from planetary radar observations?
Planetary radar observations of asteroids, such as those obtained by the Arecibo Observatory and Goldstone Solar System Radar, provide critical information about asteroid sizes, shapes, and rotation periods. The effects of surface physical properties, such as roughness, particle size/abundance, and composition, on the scattering mechanisms producing the observed radar echoes are less well understood. NASA’s OSIRIS-REx mission to near-Earth asteroid 101955 Bennu has obtained high resolution topographic measurements of the surface, providing a rare opportunity to ground-truth Earth-based radar observations.
We are using shape models of the surface of Bennu obtained by OSIRIS-REx to perform numerical simulations of radar scattering from the surface. By comparing these simulations to observations, we will improve our understanding of radar scattering from complex asteroidal surfaces, which will facilitate better interpretation of radar observations of hundreds of other asteroids in addition to Bennu. This work will improve our understanding of solar system formation and evolution, and improve our planetary defense capabilities.
Top: NAIC Arecibo Observatory, a facility of the National Science Foundation (Courtesy: National Science Foundation); Bottom: Delay-Doppler radar images of Bennu obtained by the Goldstone Solar System Radar (Courtesy NASA/JPL-Caltech).