Characteristics of asteroids and comets: implications of Tianwen-2 radar observations

A recent online publication in Earth and Planetary Physics by researchers Shibang Du and Chunyu Ding from Shenzhen University presents a comprehensive review of the internal characteristics of asteroids and comets, as well as their radar exploration. The study highlights the profound significance of the Tianwen-2 mission's radar in probing the internal structures of the near-Earth asteroid 2016 HO₃ (Kamo'oalewa) and the active asteroid 311P/PANSTARRS. These investigations are expected to yield critical data supporting our understanding of the interior properties of small bodies and the early evolution of the solar system.

Asteroids and comets preserve primitive solar system materials, having undergone no severe planetary-scale surface-atmospheric weathering. This renders them "fossils of the solar system," whose internal structural characteristics reflect cumulative collisional evolution and trace the early solar system’s dynamical environment. To achieve these objectives, China launched the Tianwen-2 mission in late May 2024, equipped with the Asteroid Internal Structure Detection Radar (AISDR). This instrument operates dual-frequency channels: the 130-150 MHz band enables electromagnetic wave penetration >50 m into asteroid interiors, while the 300-1500 MHz band achieves high-resolution subsurface imaging.

For primary target 2016 HO₃—a rapidly rotating body (period ≈28 minutes) with small dimensions (diameter ~40-80 m)—proposed origins include main-belt derivation or lunar ejecta. Tianwen-2’s AISDR will conduct penetrating radar observations, analyzing echo signals to resolve potential internal structures and constrain formation mechanisms. Regarding active asteroid 311P/PANSTARRS, its multi-tailed activity (distinct from typical cometary behavior) may originate from collisions or rotational instability. AISDR will investigate subsurface properties through the Looyenga-Landau-Lifshitz dielectric mixing model, quantifying dust-to-ice ratios and macroporosity to classify internal architectures (e.g., rubble-pile, pebble-pile, or layered structures). These measurements will elucidate volatile preservation mechanisms and advance understanding of snowline evolution in the solar system.

See the article:

Research progress on internal characteristics of asteroids and comets: implications of Tianwen-2 radar observations

http://doi.org/10.26464/epp2025023