1. Rocky Composition: All inner planets are primarily composed of rock and metal, giving them a solid surface.
2. Smaller Size and Mass: Compared to the gas giants, the inner planets are significantly smaller and less massive.
3. Closer to the Sun: They orbit much closer to the Sun than the outer planets.
4. Fewer Moons (or none): None of the inner planets have a large number of moons, with Earth having one, Mars having two, and Mercury and Venus having none.
