Earth and Mars Comparison PIA02570
This composite image of Earth and Mars was created to allow viewers to gain a better understanding of the relative sizes of the two planets. The Earth image was aquired from the Galileo orbiter at about 6:10 a.m. Pacific Standard Time on Dec. 11, 1990, when the spacecraft was about 1.3 million miles from the planet during the first of two Earth flybys on its way to Jupiter. The Mars image was aquired by the Mars Global Surveyer in April of 1999.
Go to Full Text
Return to Planets Menu
Image Credit: JPL  
Planetary Facts Mars

Equatorial radius (km): 3396

Mass (relative to Earth): 0.107

Density (g/cm3): 3.91

Surface gravity: 0.38
(relative to Earth)

Rotation period: 24.62 hours

Axial inclination: 25.5°

Distance from the Sun: 1.52

Orbital period: 687 days

Orbital eccentricity: 0.093

Composition of surface: rocky

Mean surface temperature: -50°C

Composition of atmosphere: carbon dioxide (95%), nitrogen (2.7%), argon (1.6%), oxygen (0.13%), carbon monoxide (0.07%), water vapour (0.03%)

Number of satellites: 2		  
Return to top of page