Moon Fact Sheet (original) (raw)

Moon

Moon/Earth Comparison

Bulk parameters

| | Moon | Earth | Ratio(Moon/Earth) | | | --------------------------- | ------- | ----------------- | ------ | | Mass (1024 kg) | 0.07346 | 5.9724 | 0.0123 | | Volume (1010 km3) | 2.1968 | 108.321 | 0.0203 | | Equatorial radius (km) | 1738.1 | 6378.1 | 0.2725 | | Polar radius (km) | 1736.0 | 6356.8 | 0.2731 | | Volumetric mean radius (km) | 1737.4 | 6371.0 | 0.2727 | | Ellipticity (Flattening) | 0.0012 | 0.00335 | 0.36 | | Mean density (kg/m3) | 3344 | 5514 | 0.606 | | Surface gravity (m/s2) | 1.62 | 9.80 | 0.165 | | Surface acceleration (m/s2) | 1.62 | 9.78 | 0.166 | | Escape velocity (km/s) | 2.38 | 11.2 | 0.213 | | GM (x 106 km3/s2) | 0.00490 | 0.39860 | 0.0123 | | Bond albedo | 0.11 | 0.294 | 0.37 | | Geometric albedo | 0.12 | 0.434 | 0.28 | | V-band magnitude V(1,0) | -0.08 | -3.99 | - | | Solar irradiance (W/m2) | 1361.0 | 1361.0 | 1.000 | | Black-body temperature (K) | 270.4 | 254.0 | 1.065 | | Topographic range (km) | 13 | 20 | 0.650 | | Moment of inertia (I/MR2) | 0.394 | 0.3308 | 1.191 | | J2 (x 10-6) | 202.7 | 1082.63 | 0.187 |

Orbital parameters (for orbit about the Earth)

| | Moon | | | ---------------------------------- | ------------- | | Semimajor axis (106 km) | 0.3844 | | Perigee (106 km)* | 0.3633 | | Apogee (106 km)* | 0.4055 | | Revolution period (days) | 27.3217 | | Synodic period (days) | 29.53 | | Mean orbital velocity (km/s) | 1.022 | | Max. orbital velocity (km/s) | 1.082 | | Min. orbital velocity (km/s) | 0.970 | | Inclination to ecliptic (deg) | 5.145 | | Inclination to Earth equator (deg) | 18.28 - 28.58 | | Orbit eccentricity | 0.0549 | | Sidereal rotation period (hrs) | 655.720 | | Obliquity to orbit (deg) | 6.68 | | Recession rate from Earth (cm/yr) | 3.8 |

Mean values at opposition from Earth Distance from Earth (equator, km) 378,000
Apparent diameter (seconds of arc) 1896 Apparent visual magnitude -12.74

Lunar Atmosphere

Diurnal temperature range (equator): 95 K to 390 K (~ -290 F to +240 F) Total mass of atmosphere: ~25,000 kg Surface pressure (night): 3 x 10-15 bar (2 x 10-12 torr) Abundance at surface: 2 x 105 particles/cm3

Estimated Composition (night, particles per cubic cm): Helium 4 (4He) - 40,000 ; Neon 20 (20Ne) - 40,000 ; Hydrogen (H2) - 35,000 Argon 40 (40Ar) - 30,000 ; Neon 22 (22Ne) - 5,000 ; Argon 36 (36Ar) - 2,000 Methane - 1000 ; Ammonia - 1000 ; Carbon Dioxide (CO2) - 1000 Trace Oxygen (O+), Aluminum (Al+), Silicon (Si+) Possible Phosphorus (P+), Sodium (Na+), Magnesium (Mg+)

Composition of the tenuous lunar atmosphere is poorly known and variable, these are estimates of the upper limits of the nighttime ambient atmosphere composition. Daytime levels were difficult to measure due to heating and outgassing of Apollo surface experiments.

For information on the Earth, see the Earth Fact Sheet.

If no sub- or superscripts appear on this page - for example, if the "Mass" is given in units of "(1024 kg)" - you may want to check the notes on the sub- and superscripts.

Notes on the factsheets- definitions of parameters, units, notes on sub- and superscripts, etc.

Planetary Fact Table- metric units
Planetary Fact Table- U.S. units
Planetary Fact Table- Earth ratio

Moon Home Page
Directory to other Planetary Fact Sheets

NASA

Author/Curator:
Dr. David R. Williams, dave.williams@nasa.gov
NSSDCA, Mail Code 690.1
NASA Goddard Space Flight Center
Greenbelt, MD 20771
+1-301-286-1258

NASA Official: Dave Williams, david.r.williams@nasa.gov

Last Updated: 11 January 2024, DRW