Astronomical Data

  mercury venus earth mars
traditional
symbol
mass
(1024 kg)
0.3302 4.8685 5.9736 0.64185
mean radius
(km)
2439.7 6051.8 6371.0 3390
equatorial radius (km) 2439.7 6051.8 6378.1 3397
polar radius
(km)
2439.7 6051.8 6356.8 3375
flattening
factor
0.0000 0.0000 0.00335 0.00648
moment of inertia constant 0.33 0.33 0.3308 0.366
obliquity of
axis (°)
0.01 177.36 23.45 25.19
semimajor axis
(106 km)
57.91 108.21 149.60 227.92
perihelion
(106 km)
46.00 107.48 147.09 206.62
aphelion
(106 km)
69.82 108.94 152.10 249.23
orbital
eccentricity
0.2056 0.0067 0.0167 0.0935
orbital
inclination (°)
7.00 3.39 0
(by definition)
1.850
siderereal
orbit (days)
87.969 224.701 365.256 686.980
tropical
orbit (days)
87.968 224.695 365.242 686.973
sideral period
(hours)
1407.6 −5832.5 23.9345 24.6229
length of day
(hours)
4222.6 2802.0 24.0000 24.6597
mean surface
pressure (kPa)
10−12 9,200 101.325
(by convention)
0.638
mean surface
temperature (K)
440 737 288 210
blackbody
temperature (K)
442.5 231.7 254.3 210.1
natural
satellites
none none 1 2
planetary
ring system
none none none none
The Inner Planets (Terrestrial Planets)