‘What is special about Earth’s atmosphere?’ describes the several interconnected layers that make up Earth’s atmosphere before considering the atmospheres of other planets. Each layer has different characteristics determined by the density of air and their relative proximity to Earth’s surface and outer space. The lower atmosphere consists of the troposphere, which extends from the surface to the tropopause at 10–15 km. The middle atmosphere is comprised of the stratosphere, extending to the stratopause at 50 km, and the mesosphere that stretches to the mesopause at 100 km. Above this is the upper atmosphere divided into the thermosphere, which takes us to 500–1,000 km, and the exosphere, which extends to the near vacuum of outer space.