Mercury Fact Sheet

All this information came from a employee of NASA: David R Willams

Mercury/Earth Comparison

Bulk parameters

                                   Mercury        Earth      Ratio (Mercury/Earth)

Mass (1024 kg)                      0.3302        5.9736     0.0553    

Volume (1010 km3)                   6.085       108.321      0.0562  

Equatorial radius (km)              2440          6378       0.383      

Polar radius (km)                   2440          6356       0.384      

Volumetric mean radius (km)         2440          6371       0.383

Ellipticity                         0.0000        0.0034     0.000     

Mean density (kg/m3)                5427          5520       0.983       

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             0.11          0.367      0.300    

Visual magnitude V(1,0)            -0.42         -3.86         -  

Solar irradiance (W/m2)             9214          1380       6.677     

Black-body temperature (K)           442.5         247.3     2.531

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)             57.9         149.6        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)                 46.0         147.1        0.313 

Aphelion (106 km)                   69.8         152.1        0.459

Synodic period (days)              115.88          -            -     

Mean orbital velocity (km/s)        47.87         29.79       1.607     

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)            ~0.1          23.45       0.004

Mercury Observational Parameters

Discoverer:      Unknown

Discovery Date:  Prehistoric



Apparent diameter from Earth

        Maximum (seconds of arc)    13.

        Minimum (seconds of arc)     4.5

Distance from Earth

        Minimum (106 km)            77.3

        Maximum (106 km)           221.9

Apparent magnitude near opposition  -1.9

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)