Chapter 5: Geography and Environment of Mars

Mars is the fourth planet from the Sun in the solar system, with an average distance from the Sun of approximately 1.52 astronomical units (AU), or about 227 million kilometers. Mars's orbital period is approximately 687 Earth days, equivalent to 1.88 Earth years, meaning that seasonal changes on Mars are about twice as long as those on Earth. Mars's diameter is about half that of Earth, its volume is about 15% of Earth's, and its mass is about 11% of Earth's (Mars's diameter is 6,779 kilometers, while Earth's is 12,742 kilometers; Mars's volume is approximately 1.63118 × 10¹¹ cubic kilometers, and its mass is approximately 6.4171 × 10²³ kilograms). Mars's surface gravity is about 38% of Earth's, meaning that a person weighing 100 kilograms on Earth would weigh only about 38 kilograms on Mars. Mars has a thin atmosphere composed primarily of carbon dioxide (about 95.3%), along with small amounts of nitrogen (about 2.7%) and argon (about 1.6%), with trace amounts of oxygen and water vapor. The atmospheric pressure on Mars's surface is only about 0.6% of Earth's, which is insufficient to support human survival without pressurized equipment. Mars's surface temperature ranges widely, from approximately -140°C in polar winter to about 20°C at the equator during summer, with an average temperature of about -63°C. This extreme temperature variation poses a significant challenge for human settlement. Mars has some distinctive surface features, the most notable being Olympus Mons, the tallest volcano in the solar system, rising approximately 21.9 kilometers above the surrounding terrain, about 2.5 times the height of Mount Everest. Valles Marineris, a vast canyon system, stretches approximately 4,000 kilometers in length, up to 200 kilometers in width, and reaches depths of up to 7 kilometers, dwarfing Earth's Grand Canyon. These distinctive geological features demonstrate Mars's complex geological history and provide abundant subjects for scientific research. Mars also has two small moons, Phobos and Deimos, both of which are irregularly shaped and likely captured asteroids. Phobos has a diameter of approximately 22.2 kilometers and orbits Mars at a distance of about 9,378 kilometers, while Deimos has a diameter of approximately 12.6 kilometers and orbits at about 23,459 kilometers from Mars.