Near-Earth Asteroids and Comets: Opportunity and Risk
The asteroids and comets circling our Sun mostly remain in their orbits for billions of years, serving as reminders of conditions in the primordial solar nebula. However, some are occasionally perturbed out of these stable orbits and into Earth-crossing trajectories. The question of when the next major impact will occur can only be answered by surveying the skies to find, track, and characterize these objects. While much progress has been made in discovering the largest near-Earth asteroids, the vast majority of the population remains undiscovered.