Geology of solar terrestrial planets of heavier elements contained in the solar nebula. The four inner or terrestrial planets have dense, rocky compositions, few or no moons, and no ring systems. They are composed largely of minerals with high melting points, such as the silicates which form their solid crusts and semi-liquid mantles, and metals such as iron and nickel, which form their cores. The Mariner 10 mission (1974) mapped about half the surface of Mercury. On the basis of that data, scientists have a first-order understanding of the geology and history of the planet. Mercury's surface shows intercrater plains, basins, smooth plains, craters, and
Solar System in fiction and that Mars could hardly support any macroscopic life forms on its surface, much less an advanced civilization. In the 1980s it was shown that the surfaces of Jupiter's moons were just as hostile to life. More recent fiction focused on the Solar System has thus tended to address its exploration for purposes such as terraforming, the engineering of planets for human habitation, than the possibility of any existing life. The following works or series use multiple planets and other locations within the Solar System as their primary settings: Solar System in fiction The Solar System and its various bodies