Introduction to the “Planetary Exploration, Horizon 2061” foresight exercise

This introductory chapter describes the science base, objectives, and methods of the “Planetary Exploration, Horizon 2061” foresight exercise. It first describes the class of astrophysical objects whose future investigation and improved understanding are the objective of the Horizon 2061 foresight: planetary systems. It then introduces the four “pillars” of science-driven planetary exploration: (1) the science of planetary systems—six key science questions about planetary systems, their origins, evolution, workings, and habitability, which can be addressed via in situ exploration only in the solar system; (2) the space missions needed to perform the observations that can inform these questions; (3) the technologies needed to fly these challenging space missions; (4) the space-based and ground-based infrastructures and services needed to support these missions to all destinations in the Solar System. It then describes the method followed by the “Horizon 2061” exercise to successively build these four “pillars,” and how this method and work flow are reflected in the structure of the book and translated into each of its seven chapters.