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# 8: The Earth-Moon System

## Learning Objectives

• Describe the layers of the Earth and the geologic forces that shape the Earth's surface.
• Describe the composition and properties of the Earth's atmosphere.
• Explain the origin of the Moon.
• Describe the surface and interior of the Moon.

Our Solar System has four terrestrial planets. Of those, the most unique is the one most familiar to us. Earth is the largest of the terrestrial planets and the only one with ample liquid water on its surface. It is also the only one with an atmosphere made primarily of nitrogen and oxygen. It has the strongest magnetic field and the largest Moon. Indeed, the Earth-Moon system has the largest moon relative to the size of its primary. All of the other planets with moons, including Mars, have moons that are much smaller than their bodies.