The origin, physical and chemical properties of asteroids, and their association with defense

Asteroids are direct relics of early Solar system materials, whose composition, structure, and orbital distribution preserve crucial physical and chemical information about the evolutionary process from the primitive solar nebula to the planetary system. Significant differences exist in the formation conditions and evolutionary pathways reflected by different types of asteroids, making them important research objects for reconstructing Solar system material distribution, early planetary embryo accretion, and planetary differentiation processes. In recent years, based on multi-wavelength spectroscopic observations, thermal radiation characteristic analysis, dynamical simulations, and meteorite analog studies, systematic understanding has been gained regarding the mineral composition, internal structure, thermal history, and surface weathering of asteroids. The success of sample-return missions such as Hayabusa, Hayabusa2, and OSIRIS-REx has further advanced in-depth research on the structure of primitive planetary materials, volatile preservation mechanisms, and the origin of organic molecules, laying a solid foundation for the interdisciplinary development of planetary science and cosmochemistry. Meanwhile, the continuous advancement of global asteroid exploration has led to the identification of a large number of near-Earth asteroids (NEAs) and potentially hazardous asteroids (PHAs). Although the short-term probability of these celestial bodies impacting Earth is low, their potential impacts could trigger severe regional damage or even global climate catastrophes. Therefore, research on asteroid impact risk assessment and deflection technologies is becoming a common focus in the international fields of planetary science and space engineering. NASA’s 2022 DART (Double Asteroid Redirection Test) mission successfully validated the kinetic impact deflection strategy on a real celestial body for the first time, significantly altering the orbital period of the target asteroid and marking the transition of active planetary defense technologies from conceptual research to an in-orbit experimental phase. China officially launched the construction of its near-Earth asteroid defense system in 2024, planning to conduct an in-orbit impact deflection verification mission for small targets in the future, which is of great significance for promoting the systematic layout of China in the field of planetary defense. The effectiveness of asteroid defense strategies relies heavily on the accurate understanding of the target celestial body’s physical and chemical properties, including density, porosity, internal structure, rotational state, mineral composition, and space weathering degree. Asteroids with different compositions and structures exhibit significant differences in their responses to deflection methods such as kinetic impact, gravity tractor, and laser ablation. Therefore, a systematic understanding of asteroid formation mechanisms, evolutionary processes, and orbital variation laws is the foundation for advancing impact risk assessment, mission planning, and engineering scheme design. Based on systematically sorting out the origin, late evolution, spatial distribution, and dynamical characteristics of asteroids, this paper focuses on summarizing the intrinsic links between asteroid material properties and planetary defense technologies, and proposes the needs and development directions of future asteroid scientific research in supporting impact risk assessment and defense engineering. It aims to provide a reference for scientific exploration and technological layout in related fields in China.