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<title>Mercury Fact Sheet</title>
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<h3>Mercury Fact Sheet</h3>
<img src="../images/mercury">Mercury
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<h4>Mercury/Earth Comparison</h4>

<h5>Bulk parameters</h5>
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                                   Mercury        Earth  Ratio (Mercury/Earth)
Mass (10<sup>24</sup> kg)                      0.3302        5.9736     0.0553    
Volume (10<sup>10</sup> km<sup>3</sup>)                   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/m<sup>3</sup>)                5427          5520       0.983       
Surface gravity (eq.) (m/s<sup>2</sup>)        3.70          9.78       0.378     
Escape velocity (km/s)              4.3          11.2        0.384     
GM (x 10<sup>6</sup> km<sup>3</sup>/s<sup>2</sup>)                   0.02203       0.3986     0.0553  
Bond albedo                         0.056         0.385      0.145
V.Geo.Albedo             0.11          0.367      0.300    
Visual magnitude V(1,0)            -0.42         -3.86         -  
Solar irradiance (W/m<sup>2</sup>)             9214          1380       6.677     
Black-body temperature (K)           442.5         247.3     2.531
Moment of inertia (I/MR<sup>2</sup>)           0.33          0.3308     0.998      
J<sub>2</sub> (x 10<sup>-6</sup>)                          60.         1082.63     0.055
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<h5>Orbital parameters</h5> 
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                                   Mercury        Earth  Ratio (Mercury/Earth)
Semimajor axis (10<sup>6</sup> 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 (10<sup>6</sup> km)                 46.0         147.1        0.313 
Aphelion (10<sup>6</sup> km)                   69.8         152.1        0.459
Synodic period (days)              115.88          -            -     
Mean orbital velocity (km/s)        47.89         29.79       1.608     
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     
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<h4>Mercurian Magnetosphere</h4>
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Dipole field strength: 0.0033 gauss-Rh<sup>3</sup><br>
Dipole tilt to rotational axis: 169 degrees<br>
Longitude of tilt: 285 degrees (from Mercury  I flyby)<br>
                   115 degrees (from Mercury III flyby)
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<b>Note:</b> Rh denotes Mercurian radii, 2,439 km
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<h4>Mercury Atmosphere</h4>
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Surface Pressure: ~10<sup>-15</sup> bar (0.001 picobar)<br>
Average temperature: 440 K (590-725 K, sunward side)<br>
Atmospheric composition: 42% Oxygen (O<sub>2</sub>), 29% Sodium (Na),<br>
22% Hydrogen (H<sub>2</sub>), 6% Helium (He), 0.5% Potassium (K) <br>
possible trace amounts of Argon (Ar), Carbon Dioxide (CO<sub>2</sub>),<br> 
Water (H<sub>2</sub>O), Nitrogen (N<sub>2</sub>), Xenon (Xe), Krypton (Kr),<br>
Neon (Ne) <br>
(Numbers not well constrained)<br>
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