Earth's Moon

From lighting up our skies to preserving evidence of our solar system’s history, Earth’s closest neighbor plays a pivotal role in the study of our planet and beyond.

Lunar science, space weather, astronaut health, and more.

Moon Composition & Structure

Like Earth, the Moon consists of three main layers: a crust, a mantle, and a core.

Billions of years ago, the Moon was a molten world. As it solidified, the heaviest materials (metals like iron) sank down into the Moon’s center, and the lighter materials (lower density rocks) rose towards the surface. The result is a structure a bit like a chocolate-dipped cherry – solid core, mostly solid/partly liquid mantle, and thin outer crust.

In contrast to Earth’s thick layers of air, the Moon’s exosphere is a bit like the haze you get when you whack a dirty rug with a broom: it includes a sampling of particles knocked free by impact. But instead of a rug, these particles come from the lunar surface. Instead of flying through the air, they’re ejected into near-emptiness. And instead of a broom, the Moon is pummeled by space debris.

Earthrise photographed by Apollo 8 astronaut William Anders, December 1968, with Earth at gibbous phase as seen from the Moon.

Lunar Craters

Earth's Moon is covered in craters.

Lunar craters tell us the history not only of the Moon, but of other worlds, too. On the Moon, where there’s no liquid water or wind, evidence of our solar system's impact history has been preserved for billions of years.

Pierazzo crater imaged by NASA's Lunar Reconnaissance Orbiter. It is located within the north-northwestern extent of ejecta surrounding the Orientale impact basin.

NASA/GSFC/Arizona State University

Moon Phases

Earth's view of the half-sunlit Moon shifts throughout the month.

As our perspective changes, we observe a pattern known as lunar phases: new moon, waxing crescent, first quarter, waxing gibbous, full moon, waning gibbous, third quarter, and waning crescent.

There are several theories about our Moon’s formation, but almost all share this point in common. Our early solar system was the scene of violent smashups that could end in obliteration or new, larger objects. Those mashed-together objects make up the planets, moons, asteroids and other solar system objects we know today.

Earth’s Moon is thought to have formed in a tremendous collision.

Uncovering Lunar Water

There’s water on the Moon.

Ancient ice hidden deep in permanently shadowed craters. H20 molecules on the sunlit lunar surface. Humanity's search for water on the Moon began hundreds of years ago. Here's a brief history of discoveries leading up to the confirmation of its presence.

Areas of the Moon’s south pole with possible deposits of water ice, shown in blue. The map is based on data taken by NASA’s Lunar Reconnaissance Orbiter.

September 19: Observe the Moon with NASA

You're invited to International Observe the Moon Night! Join our worldwide community in celebrating Earth's Moon through direct observations, hands-on activities, lunar-themed music, artwork, readings, and more.

The Moon is a 4.5-billion-year-old time capsule, pristinely preserved by the cold vacuum of space.

Artemis II carried its crew farther from Earth and closer to the Moon than any human has been in over half a century. The astronauts on board were both scientists and subjects as they flew around the far side of the Moon and back.