The Origin of the Moon

The Moon and the Earth

Where did the moon come from?

Although some planets have many moons, Earth has just one. Our moon is about one quarter the size of Earth. Scientists estimate that the moon is just a little younger than Earth, about 4.51 billion years old compared to 4.54 billion years for Earth.

In fact, what we know about the moon suggests that it is made of material that broke off from Earth when a huge object—some say a planet—crashed into our planet when it was very young. The impact destroyed the object and also knocked a huge amount of material from Earth into space. That material seems to have formed our moon.

In July, 1969, humans stepped foot on the moon for the first time. What an exciting moment that was! Those astronauts, and others who landed on the moon later, scooped up rocks to study back on Earth. By measuring the age of these rocks, scientists determined how old the moon is. Analysis of the moon rocks also confirmed that the moon is very similar in composition to the Earth.

Written by Laura McCamy

Edited by Beth Geiger, MS Geology

Illustrated by Renee Barthelemy