Moon Fact Sheet


[Global view of Moon]

Moon/Earth Comparison


Bulk parameters

                                   Moon         Earth      Ratio (Moon/Earth)
Mass (1024 kg)                    0.07342       5.9726     0.0123    
Volume (1010 km3)                 2.1958      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)        1737.1        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)                 0.0049        0.3986     0.0123 
Bond albedo                       0.11          0.306      0.360
Visual geometric albedo           0.12          0.367      0.330    
Visual magnitude V(1,0)          +0.21         -3.86          -
Solar irradiance (W/m2)            1367.6        1367.6    1.000      
Black-body temperature (K)          270.7         254.3    1.064      
Topographic range (km)               16            20      0.800      
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)        1.076
Min. orbital velocity (km/s)        0.964
Inclination to ecliptic (deg)       5.145
Inclination to equator (deg)       18.28 - 28.58                    
Orbit eccentricity                  0.0549              
Sidereal rotation period (hrs)    655.728                
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     

* These represent mean apogee and perigee for the lunar orbit.  
The orbit changes over the course of the year so the distance 
from the Moon to Earth roughly ranges from 357,000 km to 407,000 km. 

Lunar Atmosphere

Diurnal temperature range: >100 K to <400 K  (roughly -250 F to +250 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 (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.

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

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


bullet Moon Home Page
bullet Directory to other Planetary Fact Sheets

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


NASA Official: Ed Grayzeck, edwin.j.grayzeck@nasa.gov
Last Updated: 25 April 2014, DRW