Mars is the fourth planet from the Sun, the third largest terrestrial planet, and the seventh largest planet in the Solar System (only Mercury is smaller).
- Distance from the Sun: 1.5 AU
- Solar Day equivalent to 24.5 Earth hours
- Tropical Year (how long it takes to complete one orbit around the Sun: 687 Earth days
- Inclination of 5.65° from the Solar equator and 1.85° from the ecliptic
- Martian density is 3.9 g/cm³ or about 3.9 times that of water
- Mass is 10.7% of Earth and Radius is 53.2% of Earth
- Gravity on Mars is 0.376 times that of Earth (a 100-lb person would weigh 37.6 lbs on Mars)
Mars has a geography that you would find on Earth, but to a larger scale. Mars boasts the largest mountain in the solar system, the longest and deepest canyon, and strange polar caps. Mars is also well known for its reddish color, which you can see above, but is also apparent when seeing it in the sky. Another strange feature is that Mars is criss-crossed by a multitude of channels, has high spots and low spots, and has features that on Earth, were created by flowing water.
Mars has two satellites that did not form in the same location as Mars. Phobos and Deimos were probably captured by Mars and will be discussed in a later post.
Mars has an atmosphere, which can be seen as the bluish ring in the above photo of Mars. The major component of its atmosphere is carbon dioxide, like Venus, but that is where the similarities end. It has an atmospheric pressure at the surface of 0.636 kPa, compared to Earth's surface pressure of 101.3 kPa and Venus' surface pressure of 9.2 MPa (9,200 kPa). Despite the low pressure, the surface of Mars can reach 35°C (95°F) in direct sunlight, but drops to as low as -143°C (-225.4°F) at night. Unlike Earth and Venus, it does not retain heat as well because of its thin atmosphere. The average surface temperature of Mars is -63°C (-81.4°F) so liquid water does not really exist on the surface.
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