Read the section entitled "Formation of Inner Planets." What could be an explanation for why the inner planets are all terrestrial?

To provide an explanation for why the inner planets are all terrestrial, we can consider several factors related to their formation and the conditions in the early solar system: 1. **Proximity to the Sun**: The inner planets (Mercury, Venus, Earth, and Mars) are located closer to the Sun compared to the outer planets. The intense heat from the Sun in this region caused lighter gases, such as hydrogen and helium, to be blown away, leaving behind heavier elements and compounds. 2. **Material Composition**: The inner solar system was primarily composed of heavier materials, such as metals and silicates, which are conducive to forming rocky planets. These materials were able to condense and solidify at the higher temperatures found closer to the Sun. 3. **Accretion Process**: During the formation of the solar system, dust and gas began to coalesce into larger bodies. In the inner solar system, the accretion process favored the formation of solid, rocky bodies due to the availability of solid materials and the lack of lighter gases. 4. **Solar Wind**: The solar wind, a stream of charged particles emitted by the Sun, played a significant role in shaping the composition of the inner solar system. It stripped away lighter elements from the inner regions, further promoting the formation of terrestrial planets. 5. **Differentiation**: As these planets formed, they underwent differentiation, where denser materials sank to the center, forming a metallic core, while lighter materials formed the crust. This process is characteristic of terrestrial planets. In summary, the inner planets are terrestrial due to their formation in a region of the solar system where higher temperatures and solar wind conditions favored the accumulation of heavy, solid materials, leading to the development of rocky planets.