This is the Web Edition of "A Trip Into Space", a Coimbra-based electronic book on space science. Both the texts and the photos are by courtesy of National Aeronautics and Space Administration.

A Trip Into Space Fact Sheets Moon Fact Sheet
Index
See also: Notes On The Fact Sheets, The Moon - By Hubble Space Telescope, The Moon - Full Moon As Seen From Apollo 11 

Moon Fact Sheet

Moon/Earth Comparison

Bulk parameters

                                   Moon         Earth      Ratio (Moon/Earth)
Mass (1024 kg)                    0.07349       5.9736     0.0123    
Volume (1010 km3)                 2.1968      108.321      0.0203
Equatorial radius (km)           1737.4        6378.1    0.2724      
Polar radius (km)                  1737.4        6356.8    0.2733
Volumetric mean radius (km)        1737.4        6371.0    0.2727
Ellipticity (Flattening)          0.000         0.00335    0.0    
Mean density (kg/m3)               3340          5515      0.605      
Surface gravity (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                       0.067         0.385      0.174
Visual geometric albedo           0.12          0.367      0.327    
Visual magnitude V(1,0)          +0.21         -3.86          -
Solar irradiance (W/m2)            1367.6        1367.6    1.000      
Black-body temperature (K)          274.5         247.3    1.110      
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)        1.023                  
Max. orbital velocity (km/s)        1.076
Min. orbital velocity (km/s)        0.964
Orbit inclination (deg)             5.145                    
Orbit eccentricity                  0.0549              
Sidereal rotation period (hrs)    655.728                
Equatorial inclination (deg)        6.68                   
Recession rate from Earth (cm/yr)   3.8

Mean values at opposition from Earth
        Distance from Earth (km)           384,467    
        Apparent diameter (seconds of arc)    1864.2
        Apparent visual magnitude              -12.74

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):
    4He - 40,000 ; 20Ne - 40,000 ; H2 - 35,000
    40Ar - 30,000 ; 22Ne - 5,000 ; 36Ar - 2,000 
    Methane - 1000 ; Ammonia - 1000 ; CO2 - 1000 
    Trace O+, Al+, Si+ 
    Possible P+, Na+, 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 are difficult to measure due to heating and 
outgassing of Apollo surface experiments.
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.

Last Update: 2004-Nov-27