DK Space: Mars
This rocky planet has a thin atmosphere and ice caps at its poles. Strong winds can whip up dust storms that cover the whole planet. All the water on Mars is frozen into rocks—primitive life may once have formed there.
Mars appears reddish in Earth’s night sky. The planet was named after the Roman god of war because its color symbolizes fire, blood, and war. Close-up photographs show that the Martian surface is a rusty red color. This is because there are iron compounds in the rocks and soil.
Table 8. MARS DATA
| Diameter (width) at equator | 4,222 miles (6,794 km) |
| Average distance from Sun | 141.6 million miles (227.9 million km) |
| Time to orbit Sun | 687 days |
| Time to spin around own axis | 24.63 hours |
| Mass | 0.11 x Earth’s mass |
| Gravity | 0.38 x Earth’s gravity |
| Average surface temperature | –81°F (–63°C) |
| Number of moons | 2 (Phobos and Deimos) |
Mars has polar ice caps, vast sandy deserts, heavily cratered regions, and high volcanic ridges. It boasts the biggest volcano in the Solar System, Olympus Mons, and the biggest canyon system, Valles Marineris.
