Earth
Mars
Diameterkm
12,742
6,779
Mass (Earth = 1)x
1.00
0.11
Surface Gravitym/s²
9.81
3.72
Mean Temperature°C
+15
-65
Distance from SunAU
1.00
1.52
Orbital Perioddays
365.25
687
Day Lengthhours
24.00
24.66
Known Moons
1
2
Axial Tilt°
23.44
25.19
Orbital Velocitykm/s
29.78
24.07
Quick Facts
Earth
- -Earth is the only planet not named after a Greek or Roman deity.
- -Earth's rotation is gradually slowing -- days are getting about 1.4 milliseconds longer per century.
- -About 71% of Earth's surface is covered by water, but 96.5% of that water is in the oceans.
- -Earth's magnetic field has flipped its polarity hundreds of times over millions of years.
Mars
- -Olympus Mons on Mars is about 21.9 km tall -- nearly three times the height of Mount Everest.
- -A Martian day (sol) is 24 hours and 37 minutes, remarkably similar to an Earth day.
- -Mars has seasons like Earth because its axial tilt (25.19°) is very similar to Earth's (23.44°).
- -Dust storms on Mars can grow large enough to engulf the entire planet and last for months.