Why did icy materials condense farther from the young Sun than rocky materials?

In the early solar nebula, the condensation of materials was dictated by a temperature gradient radiating from the young Sun. Close to the Sun, temperatures were too high for volatile substances—such as water, ammonia, and carbon dioxide—to transition from a gaseous state into ice.1

Because these volatiles have comparatively low freezing points, they could only condense into solid form at greater distances from the Sun, beyond a boundary known as the snow line. In contrast, metal-containing silicates, which have higher condensation temperatures, were able to solidify closer to the Sun, forming the basis of rocky bodies.1

This temperature-dependent distribution meant that objects forming in the outer solar system had access to a much larger reservoir of solid material. The ability to incorporate abundant ices allowed these outer bodies to grow massive enough to eventually attract and retain light gases like hydrogen and helium, leading to the formation of the giant planets.1