Mars Fact Sheet

Mars/Earth Comparison

Bulk parameters

                                   Mars           Earth     Ratio (Mars/Earth)
Mass (10²⁴ kg)                     0.6419          5.9736         0.107
Volume (10¹⁰ km³)                 16.318         108.321          0.151  
Equatorial radius (km)	           3397           6378            0.533
Polar radius (km)                  3375           6356            0.531
Volumetric mean radius (km)        3390           6371            0.532
Core radius (km)                   1700           3485            0.488
Ellipticity                        0.0065          0.0034         1.912
Mean density (kg/m³)               3933           5520            0.713 
Surface gravity (m/s²)             3.69            9.78           0.377
Escape velocity (km/s)             5.03           11.19           0.450 
GM (x 10⁶ km³/s²)                  0.04283         0.3986         0.107
Bond albedo                        0.16            0.385          0.416
Visual geometric albedo            0.150           0.367          0.409
Visual magnitude V(1,0)           -1.52           -3.86             -
Solar irradiance (W/m²)             595           1380            0.431
Black-body temperature (K)       216.6           247.3            0.875
Topographic range (km)               36             20            1.800
Moment of inertia (I/MR²)          0.366           0.3308         1.106
J₂ (x 10^-6)                     1960.45         1082.63           1.811

Orbital parameters

                                   Mars           Earth     Ratio (Mars/Earth)
Semimajor axis (10⁶ km)          227.9           149.6            1.524
Sidereal orbit period (days)     686.980         365.256          1.881
Tropical orbit period (days)     686.930         365.242          1.881
Perihelion (10⁶ km)              206.6           147.1            1.404       
Aphelion (10⁶ km)                249.2           152.1            1.638
Synodic period (days)            779.94             -               -
Mean orbital velocity (km/s)      24.13           29.79           0.810
Orbit inclination (deg)            1.85            0.00             -
Orbit eccentricity                 0.0934          0.0167         5.593
Sidereal rotation period (hrs)    24.6229         23.9345         1.029
Obliquity to orbit (deg)          25.19           23.45           1.074

Martian Atmosphere

Surface Pressure:   6.9 mb to 9 mb (Viking Lander 1 site)
Surface Density: ~0.020 kg/m³
Scale height:  11.1 km
Average temperature:  ~210 K
Diurnal temperature range: 184 K to 242 K (Viking Lander 1 site)
Wind speeds:  2-7 m/s (summer), 5-10 m/s (fall), 17-30 m/s (dust storm) (Viking Lander sites)
Atmospheric composition:  95.3% Carbon Dioxide, 2.7% Nitrogen, 1.6% Argon, 0.4% Other
Mean molecular weight: 43.34 g/mole 
Atmospheric composition (by volume): 
    Major      : Carbon Dioxide (CO₂) - 95.32% ; Nitrogen (N₂) - 2.7%
                 Argon (Ar) - 1.6%; Oxygen (O₂) - 0.13%; Carbon Monoxide (CO) - 0.08% 
    Minor (ppm): Water (H₂O) - 210; Nitrogen Oxide (NO) - 100; Neon (Ne) - 2.5;
                 Hydrogen-Deuterium-Oxygen (HDO) - 0.85; Krypton (Kr) - 0.3; 
		 Xenon (Xe) - 0.08

Satellites of Mars

                                    Phobos         Deimos
Mean distance from Mars (km)         9377          23436
Sidereal orbit period (days)        0.31891        1.26244
Orbital inclination (deg)            1.08           1.79
Orbital eccentricity                0.0151         0.00033
Major axis radius (km)                13              8
Minor axis radius (km)                 9              5
Mass (10¹⁵ kg)                       10.8            1.8
Mean density (kg/m³)                 1900           1750 
Geometric albedo                      0.06           0.07
Visual magnitude V(1,0)             +11.8          +12.89

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.

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Questions and comments about this page should be addressed to:
Dr. David R. Williams, dwilliam@nssdc.gsfc.nasa.gov, (301) 286-1258
NSSDC, Mail Code 633, NASA/Goddard Space Flight Center, Greenbelt, MD 20771