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Mars Facts
Mars is the fourth planet from the Sun and derives its name from the Greek word Ares. Ares was the Greek god of war, and Mars was named Ares most likely because of its reddish color when seen from Earth. Mars is also sometimes referred to as the Red Planet. Mars more closely resembles the Earth than any other planet in our solar system. The Martian day is just slightly longer than the Earth's with temperatures that can reach as high as 25°C (77°F). The tilt of the planet is almost identical to Earth's, meaning Mars has four distinct seasons just as the Earth. However that is just about where the similarities end. The Martian atmosphere is unbreathable, it can very cold, -125°C (-193°F), and a Martian year is nearly twice as long as the Earth's. Of course that means if you were 34 years old on Earth, in Martians years, you would be 17!
Martian Day (or Sol): 24.6 Earth Hours The Martian atmosphere contains 95% carbon dioxide, 3% nitrogen, 1.5% argon, trace amounts of water, and no oxygen. Earth has 78% nitrogen, 21% oxygen, 1% argon, and 0.03% carbon dioxide.
Mars/Earth ComparisonBulk parameters
Mars Earth Ratio (Mars/Earth)
Mass (1024 kg) 0.64185 5.9736 0.107
Volume (1010 km3) 16.318 108.321 0.151
Equatorial radius (km) 3397 6378.1 0.533
Polar radius (km) 3375 6356.8 0.531
Volumetric mean radius (km) 3390 6371.0 0.532
Core radius (km) 1700 3485 0.488
Ellipticity (Flattening) 0.00648 0.00335 1.93
Mean density (kg/m3) 3933 5515 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 0.150 0.367 0.409
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) 24.13 29.78 0.810
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 23.45 1.074
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 RotationRight Ascension: 317.681 - 0.108T Declination : 52.886 - 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.
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