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
The Science of Aliens possibilities for alien life. The second section explores the variety of life on Earth and the extreme conditions in which it can survive. It looks at recent missions to moons and planets in the Solar System and what they can tell us about alien life before going on to examine some extra-solar planets. The next section presents two fictional planets, Aurelia and Blue Moon and their ecosystems as imagined by scientists. These are used to explore the factors and parameters governing life on other planets and are presented as two large interactive landscapes. The exhibition concludes by looking at the