VASTWARDCelestial Atlas
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Object profile · MOON

Moon

Rocky natural satellite

Earth's nearest celestial neighbour, preserving a long record of impacts, volcanism and the early Solar System.

Atlas data reviewed
Editorial stage
Published
Visibility
Public
A sharp grayscale mosaic of the Moon's familiar near side, with dark maria, bright highlands and clearly defined craters.Direct observation
The Moon's near side assembled from about 1,300 LRO Wide Angle Camera observations acquired in December 2010.

Spacecraft data mosaic, not one exposure. LRO imaged separate strips as the Moon rotated beneath it, so illumination varies across the assembled disk and the view is not a single instant.

NASA/GSFC/Arizona State University ↗
Vastward explanation

What this world is

The Moon is a world, not just a light in the sky. It has mountains, plains, craters, a small metal core and an extremely thin exosphere. With almost no weather or liquid water at the surface, old impact scars remain visible for immense spans of time.

Why it looks this way now

A giant impact early in Solar System history is the leading formation model. The young Moon was much hotter and partly molten. As it cooled, dense material sank, lighter crust formed, lava flooded large basins and later impacts kept breaking the surface into regolith.

02

Where it sits

The Moon orbits Earth at an average distance of about 384,400 kilometres. Its orbit is elliptical and tilted, so distance, apparent size and position change through each month.

How to read this mapTwo-scale location · Solar System to the Earth moons

Swipe sideways to inspect the full map

Two-scale location · Solar System to the Earth moonsThe left panel places Earth in planetary order; the right places Moon among the profiled Earth moon orbits.Scale one · Solar SystemEarthPlanet 3 from the SunSunScale two · Earth moon systemEarthMoonProfiled orbit 1 of 1Mean distance · 384,400 km
Blue marks the current moon and orbit

Moon is 1 of 1 profiled Earth moons by distance, at a mean center distance of about 384,400 km.

Muted lines and dots show system context

The left panel locates Earth, dashed lines mark the scale change, and muted orbits and dots represent other profiled moons on the right. This is the innermost profiled moon in the system; it is the outermost profiled moon in the system.

The figure uses two linked scales and compares only the same-system moons currently profiled by Vastward; orbit spacing, body sizes and marker positions are compressed for teaching.
03

Read the numbers

Reference values retain their units, context, evidence state and published uncertainty.

Physical measurements

Mean radiusglobal mean
1,737.4kmCalculated measurementAbout 27 percent of Earth's mean radius.

A fitted global mean smooths over mountains and deep basins.

Published uncertainty: ± 0.1 km

JPL tabulated uncertainty for the adopted mean radius.

Massglobal mean
7.34579E22kgCalculated measurementAbout 1.23 percent of Earth's mass.

Calculated from the gravitational parameter, not weighed directly.

Approximate value

Derived from JPL's lunar gravitational parameter and a conventional gravitational constant, then rounded.

Mean densityglobal mean
3.344g/cm³Calculated measurementAbout 3.3 times the density of water.

Lower than Earth, consistent with a much smaller metal core.

Published uncertainty: ± 0.001 g/cm³

Calculated from the adopted mass and mean radius.

Reference gravitysurface
1.62m/s²Calculated measurementAbout one sixth of Earth's surface gravity.

A 60 kg person's mass stays 60 kg, but their weight force is much smaller.

Approximate value

Representative mean surface gravity. Local values vary with terrain and subsurface mass.

Temperaturesurface
-173°CDirect observationA representative lunar night value near the equator.

Some permanently shadowed polar terrain becomes colder.

Approximate value

NASA overview value for nighttime equatorial temperature; permanently shadowed polar regions can be colder.

Temperaturesurface
127°CDirect observationA representative sunlit equatorial value.

The surface heats and cools sharply because there is no thick atmosphere to spread heat.

Approximate value

NASA overview value for sunlit equatorial temperature.

Orbit and rotation

Average distancesystem reference
384,400kmCalculated measurementRoughly 30 Earth diameters.

The real distance changes by tens of thousands of kilometres each orbit.

Approximate value

Rounded average Earth-Moon distance. The elliptical orbit produces a large monthly variation.

Rotation periodrelative to distant stars
27.322Earth daysCalculated measurementOne turn relative to distant stars takes about 27.3 days.

Rotation and orbit stay synchronized, which keeps nearly the same side facing Earth.

Approximate value

Rounded sidereal rotation period.

Orbital periodrelative to distant stars
27.322Earth daysCalculated measurementAbout 27.3 days relative to distant stars.

The Sun-Earth-Moon geometry makes the visible phase cycle about 29.5 days.

Approximate value

Rounded sidereal orbit period. The phase cycle from full Moon to full Moon is longer, about 29.5 days.

04

Atmosphere and inside

Atmosphere

The Moon has a surface-bounded exosphere rather than an atmosphere that behaves like Earth's. Its particles are so sparse that collisions are rare, winds do not form and fractions change with time and location.

HeliumRelative abundance described; exact fraction not listed
NeonRelative abundance described; exact fraction not listed
ArgonRelative abundance described; exact fraction not listed

Surface and interior

Returned samples reveal surface materials directly. LRO maps the exterior in detail. The crust, mantle and small core are reconstructed by combining samples, gravity, rotation, heat flow and the Apollo seismic record.

  1. 1
    Small metallic core

    A compact iron-rich center inferred from Apollo seismology, rotation and other geophysical data.

    Scientific model
  2. 2
    Mantle

    A thick rocky layer that partly melted early in lunar history and supplied ancient volcanic plains.

    Scientific model
  3. 3
    Crust and regolith

    A rocky crust covered by impact-fragmented dust and rubble called regolith.

    Scientific model
05

How we know

Laser pulses time the Earth-Moon distance. Orbital tracking constrains gravity and mass. LRO laser altimetry maps shape, while infrared radiometry turns emitted energy into surface temperature estimates.

  1. 01

    Orbital laser altimetry

    LOLA times laser pulses reflected from the surface. Many tracks build a global elevation and shape model.

    Where this method stops

    A global radius is fitted from many uneven terrain heights and depends on the adopted reference figure.

    Direct observation
  2. 02

    Lunar laser ranging

    Earth observatories time laser pulses bounced from retroreflectors left on the Moon, tightly constraining distance and orbital motion.

    Where this method stops

    A range is measured along a particular line of sight. Orbital parameters come from fitting many measurements to a dynamical model.

    Calculated measurement
  3. 03

    Thermal radiometry

    Diviner measures emitted infrared energy to map how lunar surface temperatures change with sunlight, terrain and local time.

    Where this method stops

    The instrument measures radiance. Temperature is retrieved using calibration and assumptions about how the surface emits heat.

    Direct observation
06

Evidence key

Direct observation
An instrument or sample recorded the phenomenon, with processing still disclosed.
Calculated measurement
Observed motion or signal is converted into a physical quantity using equations and reference constants.
Scientific model
A tested interpretation that fits observations but is not directly imaged or sampled.
Vastward explanation
Original beginner-facing synthesis, traceable to the source records but not itself a measurement.
Artist visualization
An interpretive image, not observational evidence.
07

Missions and instruments

Active

Lunar Reconnaissance Orbiter

Since 2009 LRO has mapped lunar shape, temperature, composition, illumination and radiation at high resolution.

Official mission ↗
Instruments
  • Lunar Orbiter Laser AltimeterSurface elevation, slope, roughness and reflectance along orbital ground tracks.
  • Diviner Lunar RadiometerReflected solar radiation and emitted infrared radiation used to retrieve surface temperature.
Historical program

Apollo

Crewed landings returned samples and deployed instruments, including seismic stations and laser retroreflectors.

Official mission ↗
Instruments
  • Apollo laser retroreflectorsRound-trip light time between Earth observatories and fixed lunar surface arrays.
08

Official source trail

Links below are the exact records used for this profile. Access dates are retained with the content.

  1. 01

    NASA Jet Propulsion Laboratory, Solar System Dynamics · dataset

    Planetary Satellite Physical Parameters

    Source updated
    No source update date published
    Access checked
    2026-07-29
    Open official source ↗
  2. 02

    NASA Science · official-page

    Moon Facts

    Source updated
    2026-02-12
    Access checked
    2026-07-29
    Open official source ↗
  3. 03

    NASA Science · official-page

    Lunar Reconnaissance Orbiter

    Source updated
    No source update date published
    Access checked
    2026-07-29
    Open official source ↗
  4. 04

    NASA Science Photojournal · image

    Nearside Spectacular

    Source updated
    2025-09-23
    Access checked
    2026-07-30
    Open official source ↗
09

Continue exploring

Atlas is a starting point. Use these relationships to move into explanation, experiment and mission thinking.

Available now

Try one-sixth gravity

Keep mass fixed and predict how weight, jumping and falling change.

academyAvailable now

See orbit as continuous falling

Use the Moon to connect sideways motion, gravity and a closed orbit.

academy
Relationship reserved

Time a laser pulse

Convert round-trip light time into distance and inspect the error budget.

lab