Planet Needs To Be Redefined (Again)

摘要

What we understand to be 'planetary' largely relates to our experi-ences of the ultimate planet, Earth. Across the solar system we study the chemistry and dynamics of atmospheres, non-impact surface structures that reveal something about processes underneath the surface, and magnetic fields that reveal processes even deeper beneath the surface. We study erosion due to winds and the flow of liquids. We study geysers and volcanism. On some worlds we search for signs of past and even present life.