Mercury, Venus, Earth, and Mars, the first four planets in order from the Sun to the asteroid belt, are called the inner planets or terrestrial planets.
The inner planets all have hard, solid surfaces, terra means “earth” in Latin.
They share a few other characteristics of Earth that partially result from their proximity to the sun.
The four inner or terrestrial planets have dense, rocky compositions of mainly silicates and metals, few or no moons, and no ring systems.
