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 Mercury Fact Sheet
Index
See also: Notes On The Fact Sheets 

Mercury Fact Sheet

Mercury/Earth Comparison

Bulk parameters

                                   Mercury        Earth      Ratio (Mercury/Earth)
Mass (1024 kg)                      0.3302        5.9736     0.0553    
Volume (1010 km3)                   6.083       108.321      0.0562  
Equatorial radius (km)            2439.7        6378.1     0.383      
Polar radius (km)                   2439.7        6356.8     0.384      
Volumetric mean radius (km)         2439.7        6371.0     0.383
Ellipticity (Flattening)            0.0000        0.00335    0.000     
Mean density (kg/m3)                5427          5515       0.984       
Surface gravity (eq.) (m/s2)        3.70          9.78       0.378     
Escape velocity (km/s)              4.3          11.2        0.384     
GM (x 106 km3/s2)                   0.02203       0.3986     0.0553  
Bond albedo                         0.056         0.385      0.145
Visual geometric albedo             0.106         0.367      0.289    
Visual magnitude V(1,0)            -0.42         -3.86         -  
Solar irradiance (W/m2)             9126.6        1367.6     6.673     
Black-body temperature (K)           442.5         247.3     1.789
Moment of inertia (I/MR2)           0.33          0.3308     0.998      
J2 (x 10-6)                          60.         1082.63     0.055

Orbital parameters

                                   Mercury        Earth      Ratio (Mercury/Earth)
Semimajor axis (106 km)             57.91        149.60       0.387     
Sidereal orbit period (days)        87.969       365.256      0.241
Tropical orbit period (days)        87.968       365.242      0.241 
Perihelion (106 km)                 46.00        147.09       0.313 
Aphelion (106 km)                   69.82        152.10       0.459
Synodic period (days)              115.88          -            -     
Mean orbital velocity (km/s)        47.87         29.78       1.607     
Max. orbital velocity (km/s)        58.98         30.29       1.947
Min. orbital velocity (km/s)        38.86         29.29       1.327
Orbit inclination (deg)              7.00          0.00         -   
Orbit eccentricity                   0.2056        0.0167    12.311    
Sidereal rotation period (hrs)    1407.6          23.9345    58.785      
Obliquity to orbit (deg)             0.01         23.45       0.0004

Mercury Observational Parameters

Discoverer:      Unknown
Discovery Date:  Prehistoric

Distance from Earth
        Minimum (106 km)            77.3
        Maximum (106 km)           221.9
Apparent diameter from Earth
        Maximum (seconds of arc)    13.
        Minimum (seconds of arc)     4.5
Maximum visual magnitude            -1.9      
Mean values at inferior conjunction with Earth
        Distance from Earth (106 km)         91.70    
        Apparent diameter (seconds of arc)   11.0

Mercury Mean Orbital Elements (J2000)

Semimajor axis (AU)                  0.38709893  
Orbital eccentricity                 0.20563069   
Orbital inclination (deg)            7.00487    
Longitude of ascending node (deg)   48.33167     
Longitude of perihelion (deg)       77.45645  
Mean Longitude (deg)               252.25084

Mercurian Magnetosphere

    Dipole field strength: 0.0033 gauss-Rh3
    Dipole tilt to rotational axis: 169 degrees
    Longitude of tilt: 285 degrees (from Mercury  I flyby)
                       115 degrees (from Mercury III flyby)

Note: Rh denotes Mercurian radii, 2,439 km

Mercury Atmosphere

Surface Pressure: ~10-15 bar (0.001 picobar)  
Average temperature: 440 K (590-725 K, sunward side)

Atmospheric composition: 42% Oxygen (O2), 29% Sodium (Na), 
22% Hydrogen (H2), 6% Helium (He), 0.5% Potassium (K),
possible trace amounts of Argon (Ar), Carbon Dioxide (CO2), 
Water (H2O), Nitrogen (N2), Xenon (Xe), Krypton (Kr), Neon (Ne)

(Compositional values not well constrained, values from "Mercury" Vilas, 
Chapman, and Matthews, eds., University of Arizona Press, 1988)
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