From lighting up our skies to preserving evidence of our solar system’s historyEarth’s closest neighbor plays a pivotal role in the study of our planet and beyond.
Moon Composition & Structure
Like Earththe Moon consists of three main layers: a crusta mantleand a core.
Billions of years agothe Moon was a molten world. As it solidifiedthe heaviest materials (metals like iron) sank down into the Moon’s centerand the lighter materials (lower density rocks) rose towards the surface. The result is a structure a bit like a chocolate-dipped cherry – solid coremostly solid/partly liquid mantleand thin outer crust.
In contrast to Earth’s thick layers of airthe 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 rugthese particles come from the lunar surface. Instead of flying through the airthey’re ejected into near-emptiness. And instead of a broomthe Moon is pummeled by space debris.
Earthrise photographed by Apollo 8 astronaut William AndersDecember 1968with Earth at gibbous phase as seen from the Moon.
NASA
Lunar Craters
Earth's Moon is covered in craters.
Lunar craters tell us the history not only of the Moonbut of other worldstoo. On the Moonwhere there’s no liquid water or windevidence 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 changeswe observe a pattern known as lunar phases: new moon, waxing crescent, first quarter, waxing gibbous, full moon, waning gibbous, third quarterand waning crescent.
There are several theories about our Moon’s formationbut almost all share this point in common. Our early solar system was the scene of violent smashups that could end in obliteration or newlarger objects. Those mashed-together objects make up the planetsmoonsasteroids and other solar system objects we know today.
Earth’s Moon is thought to have formed in a tremendous collision.
NASA
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 iceshown in blue. The map is based on data taken by NASA’s Lunar Reconnaissance Orbiter.
NASA
Featured Video
Moon Phases 2025
This visualization shows the Moon's phase at hourly intervals throughout 2025as viewed from the Northern Hemisphere.
The Moon's far side gets as much sunlight as its near side.
Like Earththe Moon has a day side and a night sidewhich change as the Moon rotates. The Sun always illuminates half of the Moon while the other half remains dark.
NASA’s Lunar Reconnaissance Orbiter (LRO) mission has mapped the entire lunar surfaceincluding the Moon’s near and far sidesdown to a scale of one meter.
Lunar Reconnaissance Orbiter ImagE:
Far Side of the Moon
Observe the Moon
Daily Moon Guide
NASA’s interactive map for observing the Moon each day of the year.
Moon Observation Journal
Spend the next month getting to know the Moon.
International Observe the Moon Night
You're invited! Learn more and see how people around the world #ObserveTheMoon together.
