How does the temperature difference between inner and outer planets affect their composition during solar system formation?

During the early solar system, the Sun’s heat was strongest close to it, making the inner region very hot, while the outer region stayed cold. Because of this temperature gradient, volatile gases like water, methane, and ammonia could not survive near the Sun and instead condensed into metals and rocky material, giving the inner planets a dense, rocky makeup. Farther out, the cooler temperatures allowed those gases to freeze into ices, so the outer planets gathered large amounts of ice and gas, forming massive, gas‑rich worlds. For example, Earth’s iron and rocky crust form from hot, metal‑rich material, whereas Neptune’s atmosphere is rich in water ice and hydrogen because it formed in the cold outer zone. Thus, the temperature difference directly steered the types of materials that could accumulate where each planet formed.