Wonders of the Solar System on the matter that composite the rings - a phenomenon called orbital resonance. The third episode looks at the atmosphere of the planets and moons of the Solar System, with Earth, Mars, and Venus being the main focus. The episode starts with Cox travelling to South Africa and taking a journey in an English Electric Lightning up to an altitude of 18 kilometres where the "thinness and fragility" of the atmosphere could be observed in the middle of the day. This is then contrasted with the planet-wide consequences of Mercury's depleted, and Venus' broiling greenhouse atmospheres. Later, the dunal morphology
Solar System icy objects. Astronomers sometimes informally divide this structure into separate regions. The inner Solar System includes the four terrestrial planets and the asteroid belt. The outer Solar System is beyond the asteroids, including the four giant planets. Since the discovery of the Kuiper belt, the outermost parts of the Solar System are considered a distinct region consisting of the objects beyond Neptune. Most of the planets in the Solar System have secondary systems of their own, being orbited by planetary objects called natural satellites, or moons (two of which, Titan and Ganymede, are larger than the planet Mercury), and, in