Mars Fact Sheet


Mars

Mars/Earth Comparison


Bulk parameters

   
   Mars   
 
   Earth   
Ratio
(Mars/Earth)
Mass (1024 kg) 0.64169 5.9722 0.107
Volume (1010 km3) 16.312 108.321 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) 1830** 3485 0.525
Ellipticity (Flattening) 0.00589 0.00335 1.76
Mean density (kg/m3) 3934 5513 0.714
Surface gravity (mean) (m/s2) 3.73 9.82 0.380
Surface acceleration (eq) (m/s2) 3.69 9.78 0.377
Surface acceleration (pole) (m/s2) 3.73 9.83 0.379
Escape velocity (km/s) 5.03 11.19 0.450
GM (x 106 km3/s2) 0.042828 0.39860 0.107
Bond albedo 0.250 0.294 0.850
Geometric albedo 0.170 0.434 0.392
V-band magnitude V(1,0) -1.60 -3.99 -
Solar irradiance (W/m2) 586.2 1361.0 0.431
Black-body temperature (K) 209.8 254.0 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  

** Recent results indicate the radius of the core of Mars may only be 1650 - 1675 km.


Orbital parameters

   
   Mars   
 
   Earth   
Ratio
(Mars/Earth)
Semimajor axis (106 km) 227.956 149.598 1.524
Sidereal orbit period (days) 686.980 365.256 1.881
Tropical orbit period* (days) 686.972 365.242 1.881
Perihelion (106 km) 206.650 147.095 1.405
Aphelion (106 km) 249.261 152.100 1.639
Synodic period (days) 779.94 - -
Mean orbital velocity (km/s) 24.08 29.78 0.809
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) 1.848 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
Inclination of equator (deg) 25.19 23.44 1.075

* Mean value - the tropical orbit period for Mars can vary from this by up to 0.004 days depending on the initial point of the orbit.

Mars Observational Parameters

Discoverer:      Unknown
Discovery Date:  Prehistoric

Distance from Earth
        Minimum (106 km)           54.6
        Maximum (106 km)          401.4
Apparent diameter from Earth
        Maximum (seconds of arc)   25.6
        Minimum (seconds of arc)    3.5
Mean values at opposition from Earth
        Distance from Earth (106 km)         78.34    
        Apparent diameter (seconds of arc)   17.8
        Apparent visual magnitude            -2.0
Maximum apparent visual magnitude            -2.94      

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 
Atmospheric composition (by volume): 
    Major      : Carbon Dioxide (CO2) - 95.1% ; Nitrogen (N2) - 2.59%
                 Argon (Ar) - 1.94%; Oxygen (O2) - 0.16%; Carbon Monoxide (CO) - 0.06% 
    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   
Semimajor 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
Subplanetary axis radius (km) 13.0 7.8
Along-orbit axis radius (km) 11.4 6.0
Polar axis radius (km) 9.1 5.1
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.

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

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


Mars Home Page
Directory to other Planetary Fact Sheets

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


NASA Official: Dave Williams, david.r.williams@nasa.gov
Last Updated: 3 October 2024, DRW