Mars is the fourth planet from the Sun is sometimes called "the Red Planet" because it shines with a reddish color. Mars is a little more than half Earth's size and takes nearly twice as long to orbit the Sun. It's diameter measures 4,217 miles (6,787 km). It is located 1.5 Astronomical Units from the Sun.
With clouds, storms, and seasons, Mars is the most Earth-like of the Sun's family. Its year last 687 Earth days and its day is 24 hours, 37 minutes long. It has a 25-degree tilt on its axis thus giving the planet four distinct seasons. Other Earth-like features include tall mountains, deep canyons dust storms, dried riverbeds, and its many volcanoes. One of the largest, Olympus Mons, is more than twice as high as Mount Everest. The planet's red color comes from its rusty, oxidized rocks and dust. Mars' ruddy color is detectable with the naked eye.
The climate on Mars is brutal. The atmosphere is 95 percent carbon dioxide, which locks in heat, and helps keep the planet warm. But the Martian atmosphere is thin and offers only a small barrier to escaping heat. The temperature at the planet's surface climbs to a high of about 25 degrees Celsius at the equator at noon. At the north and south poles, which are covered with ice, it plunges to a low of –123 degrees Celsius. The polar ice is mostly "dry ice" or frozen carbon dioxide, with just a little water ice mixed in.
Mars has two moons that were discovered in 1877. They resemble asteroids (they look like potatoes) and are named Phobos and Deimos. Deimos is about 9 miles (15 km) long and Phobos is neary twice that size.
Life on Mars?
Science fiction has led us to believe stories about little green men from Mars. H.G. Wells' novel The War of the World had many Americans believing Martians had invaded the United States. However, recent discoveries of what appear to be fossil bacteria in a meteorite from Mars has reopened the discussion. At present, Mars probably cannot support life. However, Mars is the most Earth-like planet in our Solar System. Life may have begun on Mars and disappeared as the planet cooled and gave up most of its water in space. Future robotic space missions are designed to provide an understanding of Mars as a whole. Did life begin on Mars? By exploring our neighbor we may be able to answer this question.