🌙 The MoonA separate category: everything about Earth's only natural satellite, and above all what it is made of
The Moon is the fifth-largest moon in the solar system and the only place beyond Earth that humans have walked. It is a dry, airless, ancient world, about a quarter of Earth's width, and it is probably what is left of a planet-sized collision about 4.5 billion years ago. It holds a record of the early solar system that Earth's active surface erased long ago. The sections below cover its makeup, interior, surface, ice and atmosphere, origin, orbit, quakes and magnetism, exploration and a map. The Moon's home planet has its own site: Planet Earth.
Earth and the Moon compared
Values are rounded from NASA's planetary fact sheets. Differences in the last digit between sources are normal.
🧪 What the Moon Is Made Of Elements, minerals, rocks and soil
We know the Moon's makeup better than that of any other world besides Earth, thanks to 382 kg of rock and soil brought back by the six Apollo landings, about 300 g from three Soviet Luna robots, and over 3.6 kg from China's Chang'e-5 and Chang'e-6, plus orbiter measurements and hundreds of lunar meteorites found on Earth. Overall the Moon looks like Earth's mantle and crust without most of the iron and without the easily vaporised elements, because it formed from the hot debris of a giant impact.
Highlands vs. maria: what the rocks contain
Typical analyses of soil samples, in percent by weight of oxides, rounded: highlands (Apollo 16), high-titanium mare (Apollo 11) and low-titanium mare (Apollo 12). Other sites differ.
🧅 Inside the Moon Crust, mantle and a small core
Seismometers left by Apollo, plus orbiting gravity (GRAIL) and laser-ranging data, show the Moon is layered like Earth, but its core is very small. Select a layer.
Cross-section drawn to scale by radius (1,737 km). The crust is slightly exaggerated.
Interior values come from models and are uncertain; they are revised as new analyses of Apollo seismic data and GRAIL gravity data appear.
Bulk properties
Why it differs from Earth
🏔️ The Lunar Surface Highlands, maria, craters and regolith
The Moon's face has two main kinds of terrain: bright, old, heavily cratered highlands and dark, smooth, younger maria (Latin for "seas", though they are solidified lava plains). The whole surface is covered by a blanket of powdery regolith made by billions of years of meteorite impacts.
🧊 Water, Ice, Atmosphere & Temperature Almost no air, but not quite dry
The Moon has no breathable air and no liquid water, but there is more water there than scientists expected before 2009, mostly as ice trapped in permanently shadowed craters near the poles and as tiny amounts bound into minerals and glass.
Temperatures
Typical values measured by NASA's Diviner instrument and Apollo probes; exact numbers vary with place and season.
💥 Where the Moon Came From The giant-impact hypothesis
The leading explanation is that a Mars-sized body, often called Theia, struck the young Earth about 4.5 billion years ago. The debris formed a disc that quickly clumped into the Moon. It is the best fit to the evidence, though details are still debated.
Evidence for the giant impact
Older ideas and open questions
🔄 Orbit, Phases & Tides Earth's partner in motion
The Moon circles Earth every 27.3 days, but because Earth moves around the Sun in that time, it takes 29.5 days to return to the same phase. It is tidally locked: it turns once per orbit, so the same side, the near side, always faces us.
The eight phases
As seen from the northern hemisphere; the lit part is on the right while the Moon is waxing and on the left while it is waning. The same half of the Moon is always lit by the Sun; only our view of it changes.
📳 Moonquakes, Magnetism & Gravity A quiet but not dead world
🚀 Exploring the Moon From Luna 2 to Artemis
Dozens of missions from the United States, the Soviet Union, Japan, India, Europe, China, Israel and private companies have studied the Moon. Only the six Apollo missions between 1969 and 1972 have put people on the surface.
Crewed Moon missions tap a mission for its ship names and crew
Timeline
Samples brought back to Earth
Masses are approximate. Apollo returned about 382 kg in total from 2,196 separate samples (NASA). Most of it is stored at the Lunar Sample Laboratory at Johnson Space Center in Houston, and is lent to scientists worldwide.
Why go back?
Next steps
Mission schedules change often. Check the space agencies (NASA, CNSA, ISRO, ESA, JAXA) for the latest.
🗺️ Moon Map Landing sites, maria, basins and craters
An interactive map of the Moon built from NASA's Lunar Reconnaissance Orbiter Wide Angle Camera mosaic. Zoom in and tap a pin. The near side is on the left half of the map (longitudes −90° to +90°) and the far side is at the edges.
Imagery: NASA / GSFC / Arizona State University (LRO WAC global mosaic), served by NASA's Moon Trek. Positions are approximate. If the imagery does not appear, check your connection and reload.