This second volume of Frontiers articles contains a broad array of fascinating topics. The first four
papers focus on the Sun, the origin of the solar system and the early history of the Earth. The fifth, on komatiites, is also relevant to the early Earth but also forms a nice transition to three articles that focus on subduction and mantle processes. The final three articles focus on changes in our surface environment including biogeochemical cycles, the evolution of hominids and, finally, the future threat posed by near Earth asteroids.