Linking NEAs to their main belt source regions

Abstract

Asteroids preserve information about the earliest times in solar system history, information long lost from planets that have have evolved significantly since then. The best known is the population of near-Earth asteroids (NEAs), the objects that occasionally come close to the Earth. This is because a typical near-Earth asteroid is much easier to reach than a typical main-belt asteroid. There is obvious interest in NEAs in order to understand the threat they pose and the resources they promise, but they carry a rich bounty of scientific information as well. Dynamical calculations show that lifetimes of NEAs are typically about 10 million years, eventually meeting their ultimate fate by crashing into the Sun, being ejected from the solar system, or impacting one of terrestrial planets. With such short lifetimes, NEAs observed today cannot be residual bodies that have remained orbiting among the inner planets since the beginning of the solar system. Instead, the NEA population must have some source of resupply. Thus, objects formed at a variety of solar distances currently find themselves in near-Earth space. As it was confirmed by numerous dynamical studies, most NEAs originated in the main-asteroid belt, between Mars and Jupiter. Moreover, the most important transport routes are identified and well known. In the recent years, advances in ground-based and mission work open possibility to link a specific NEA to a potential source region in the main belt. A current orbit of an asteroid, combined with physical properties, can give a good sense of where this object originated. In turn, this allows study of these nearby objects to gain insight into the outer reaches of the solar system and vice-versa. A few such links has been already established, but many more are expected to be settled in the coming years.