Challenges for the scientific exploitation of Gaia observations of solar system objects

In this introductory paper, we review the subjects addressed during the meeting “Solar System Science before and after Gaia”, which is at the origin of the content of this special issue. The several unknowns affecting our knowledge of the dynamical and physical properties of asteroids are briefly discussed, along with the perspectives opened by the availability of Gaia data and other surveys. The role of complementary observations is also stressed.