Mars Fact Sheet


[Global view of Mars]

Mars/Earth Comparison


Bulk parameters

                                   Mars           Earth     Ratio (Mars/Earth)
Mass (1024 kg)                     0.64174         5.9726         0.107
Volume (1010 km3)                 16.318         108.321          0.151  
Equatorial radius (km)	           3396.2         6378.1          0.532
Polar radius (km)                  3376.2         6356.8          0.531
Volumetric mean radius (km)        3389.5         6371.0          0.532
Core radius (km)                   1700           3485            0.488
Ellipticity (Flattening)           0.00589         0.00335        1.76
Mean density (kg/m3)               3933           5514            0.713 
Surface gravity (m/s2)             3.71            9.80           0.379
Surface acceleration (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                        0.250           0.306          0.817
Visual geometric albedo            0.170           0.367          0.463
Visual magnitude V(1,0)           -1.52           -3.86             -
Solar irradiance (W/m2)          589.2          1367.6            0.431
Black-body temperature (K)       210.1           254.3            0.826
Topographic range (km)               30             20            1.500
Moment of inertia (I/MR2)          0.366           0.3308         1.106
J2 (x 10-6)                     1960.45         1082.63           1.811 
Number of natural satellites          2              1
Planetary ring system                No             No

Orbital parameters

                                   Mars           Earth     Ratio (Mars/Earth)
Semimajor axis (106 km)          227.92          149.60           1.524
Sidereal orbit period (days)     686.980         365.256          1.881
Tropical orbit period (days)     686.973         365.242          1.881
Perihelion (106 km)              206.62          147.09           1.405       
Aphelion (106 km)                249.23          152.10           1.639
Synodic period (days)            779.94             -               -
Mean orbital velocity (km/s)      24.07           29.78           0.808 
Max. orbital velocity (km/s)      26.50           30.29           0.875
Min. orbital velocity (km/s)      21.97           29.29           0.750
Orbit inclination (deg)            1.850           0.000            -
Orbit eccentricity                 0.0935          0.0167         5.599
Sidereal rotation period (hrs)    24.6229         23.9345         1.029
Length of day (hrs)               24.6597         24.0000         1.027
Obliquity to orbit (deg)          25.19           23.44           1.075

Mars Observational Parameters

Discoverer:      Unknown
Discovery Date:  Prehistoric

Distance from Earth
        Minimum (106 km)           55.7
        Maximum (106 km)          401.3
Apparent diameter from Earth
        Maximum (seconds of arc)   25.1
        Minimum (seconds of arc)    3.5
Mean values at opposition from Earth
        Distance from Earth (106 km)         78.39    
        Apparent diameter (seconds of arc)   17.9
        Apparent visual magnitude            -2.0
Maximum apparent visual magnitude            -2.91      

Mars Mean Orbital Elements (J2000)

Semimajor axis (AU)                  1.52366231  
Orbital eccentricity                 0.09341233   
Orbital inclination (deg)            1.85061   
Longitude of ascending node (deg)   49.57854  
Longitude of perihelion (deg)      336.04084   
Mean Longitude (deg)               355.45332

North Pole of Rotation

Right Ascension: 317.681 - 0.106T
Declination    :  52.887 - 0.061T
Reference Date : 12:00 UT 1 Jan 2000 (JD 2451545.0)
T = Julian centuries from reference date 

Martian Atmosphere


Surface pressure:  6.36 mb at mean radius (variable from 4.0 to 8.7 mb depending on season)  
                   [6.9 mb to 9 mb (Viking 1 Lander site)]
Surface density: ~0.020 kg/m3
Scale height:  11.1 km
Total mass of atmosphere: ~2.5 x 1016 kg
Average temperature:  ~210 K (-63 C)
Diurnal temperature range: 184 K to 242 K (-89 to -31 C) (Viking 1 Lander site)
Wind speeds:  2-7 m/s (summer), 5-10 m/s (fall), 17-30 m/s (dust storm) (Viking Lander sites)
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
Semi-major axis* (km)                9378          23459
Sidereal orbit period (days)        0.31891        1.26244
Sidereal rotation period (days)     0.31891        1.26244
Orbital inclination (deg)            1.08           1.79
Orbital eccentricity                0.0151         0.0005
Major axis radius (km)                13.4            7.5
Median axis radius (km)               11.2            6.1
Minor axis radius (km)                 9.2            5.2
Mass (1015 kg)                       10.6            2.4
Mean density (kg/m3)                 1900           1750 
Geometric albedo                      0.07           0.08
Visual magnitude V(1,0)             +11.8          +12.89     
Apparent visual magnitude (V0)        11.3           12.40      

*Mean orbital distance from the center of Mars.

bullet Notes on the factsheets - definitions of parameters, units, notes on sub- and superscripts, etc.

bullet Planetary Fact Table - metric units
bullet Planetary Fact Table - U.S. units
bullet Planetary Fact Table - Earth ratio


bullet Mars Home Page
bullet Directory to other Planetary Fact Sheets

[NASA Logo]
Author/Curator:
Dr. David R. Williams, dave.williams@nasa.gov
NSSDC, Mail Code 690.1
NASA Goddard Space Flight Center
Greenbelt, MD 20771
+1-301-286-1258


NASA Official: Ed Grayzeck, edwin.j.grayzeck@nasa.gov
Last Updated: 25 April 2014, DRW