* Composition: They are primarily composed of rock and metal, unlike the gas giants further out.
* Density: They have relatively high densities compared to the outer planets.
* Size: They are smaller in size and mass compared to the gas giants.
* Orbit: They have relatively close orbits to the Sun, resulting in shorter orbital periods.
* Surface: They have solid, rocky surfaces with craters, mountains, and valleys.
* Atmosphere: They have thin atmospheres, with the exception of Venus which has a thick, dense atmosphere.
* Moons: They have few or no moons, unlike the gas giants.
However, it's important to note that while these similarities exist, there are also significant differences between each inner planet. For example, Venus has a runaway greenhouse effect, making it incredibly hot, while Mars has a very thin atmosphere and is cold and dry.
