Solar System all have impact craters and tectonic surface features, such as rift valleys and volcanoes. The term "inner planet" should not be confused with "inferior planet", which designates those planets that are closer to the Sun than Earth is (i.e. Mercury and Venus). Asteroids except for the largest, Ceres, are classified as small Solar System bodies and are composed mainly of refractory rocky and metallic minerals, with some ice. They range from a few metres to hundreds of kilometres in size. Asteroids smaller than one meter are usually called meteoroids and micrometeoroids (grain-sized), depending on different, somewhat arbitrary definitions. The asteroid
Max Planck Institute for Solar System Research Research offers the PhD programme "International Max-Planck Research School (IMPRS) for Solar System Science" together with the University of Göttingen. The Solar System School offers a three-year course of study emphasizing actual research. The curriculum covers the entire area of the solar system from small bodies to the planets and the Sun. The goal is a broad, interdisciplinary, and solid scientific education, extended with courses in numerical physics, space technology, project management, scientific writing, and presentation techniques. There are always about 50 graduate students studying at the Solar System School. Two thirds are from abroad from over 30 different countries.