Moon
The Moon is Earth's only natural satellite and the fifth-largest moon in the Solar System. Tidally locked to Earth, its cratered, airless surface drives our tides and stabilises Earth's axial tilt.
Key facts
Science
Physical
- Mass
- 7.34 × 10²² kg · 0.0123 M⊕
- Radius
- 1,737 km · 27% of Earth's radius
- Density
- 3,342 kg/m³ · 3.3× water
- Surface gravity
- 1.62 m/s² · 17% of Earth's
- Escape velocity
- 2.38 km/s · 21% of Earth's
- Axial tilt
- 6.68 °
Orbit around Earth
- Distance from Earth
- 851,552 km
- Orbital period
- 27.3 days
- Eccentricity
- 0.0554
- Inclination
- 5.16 °
Rotation
- Rotation period
- 27.3 days
- Tidal locking
- Tidally locked to its parent
Temperature
- Minimum
- 100 K (-173 °C)
- Mean
- 250 K (-23 °C)
- Maximum
- 390 K (117 °C)
Composition
- Bulk composition
- Anorthosite highlands and basaltic maria; small iron core
Radiation & temperature
- Insolation
- 0.977 S⊕ · ≈ the sunlight Earth receives
- Bond albedo
- 0.11 · reflects 11% of incoming sunlight
- Equilibrium temperature
- 269 K (-4 °C)
- Measured mean temperature
- 250 K (-23 °C)
Discovery & history
- First known
- Known since antiquity
- Name
- Old English 'mōna'; Latin 'Luna'. Its name predates written history.
The Moon has guided calendars, tides and myth for all of human history. Galileo's 1609–10 telescope sketches revealed mountains and craters, ending the idea of a perfect celestial sphere. It remains the only world beyond Earth that humans have visited: twelve astronauts walked its surface during the Apollo programme (1969–72), and robotic missions continue to study and sample it.
- 1959Luna 2Impactor
First human-made object to reach another celestial body.
- 1966Luna 9Lander
First soft landing on the Moon; returned the first photographs from the surface.
- 1966Surveyor 1Lander
First US lunar soft landing; proved the surface was firm and returned over 11,000 images.
- 1968Apollo 8Crewed landing
First crewed flight to leave Earth orbit and circle the Moon — ten orbits on Christmas Eve 1968.
- 1969Apollo 11 — ColumbiaOrbiter
Michael Collins flew the Command Module Columbia in lunar orbit while Eagle descended to the surface.
- 1969Apollo 11 — EagleCrewed landing
First crewed landing — Armstrong and Aldrin walked at Tranquility Base and returned 21.5 kg of samples.
- 1970Luna 16Sample return
First robotic sample return from the Moon — 101 g of soil from Mare Fecunditatis.
- 1970Lunokhod 1Rover
First roving robot on another world; driven from Earth across ~10 km of Mare Imbrium over ten months.
- 1972Apollo 17Crewed landing
Last crewed landing; geologist Harrison Schmitt collected samples from deep in the regolith.
- 1973Lunokhod 2Rover
Second Soviet Moon rover; drove a record ~39 km across the Le Monnier crater.
- 2004SMART-1Orbiter
ESA's ion-drive demonstrator reached lunar orbit, then was steered to a controlled impact in 2006.
- 2009Lunar Reconnaissance OrbiterOrbiter
Mapping the Moon in fine detail since 2009 and scouting landing sites for the Artemis era.
- 2013Chang'e 3Lander
China's first soft landing on the Moon, delivering the Yutu rover to Mare Imbrium.
- 2019Chang'e 4Lander
First soft landing on the lunar far side.
- 2020Chang'e 5Sample return
Returned the first lunar samples since 1976.
- 2023Luna 25Impactor
Russia's first lunar mission since 1976; lost during the descent toward the south pole.
- 2024SLIMLander
Japan's 'Moon Sniper' landed within ~55 m of its target and survived multiple lunar nights.
- 2024IM-1 OdysseusLander
First US soft landing since Apollo and the first ever by a private company.
Images
Images from open archives · credit shown per image