THE SOLAR SYSTEM AND OUTER SPACE
MARS

Mars
Photo courtesy of National Air and Space Museum

by Devon McGuigan and Cody McCarthy

Mars, called the red planet, is the fourth planet from the Sun, located in between Earth and Jupiter. Mars is much farther away from the Sun than Earth; the distance of Mars from the Sun is about 228,000,000 km. Mars travels around the Sun in an elliptical or egg-shaped orbit, with Mars being about 204 million km from the Sun at its closest and 246 million km away at its farthest. Since Mars is so much farther away from the Sun than Earth, a year on Mars, the time it takes to orbit the Sun, is about 687 Earth days. Mars rotates on its axis once every 24 hours and 37 minutes, a little longer than an Earth day. The diameter of Mars is only about 6,800 km, a little over half that of the Earth. Mercury and Pluto are the only planets smaller than Mars.

The average temperature on Mars is about 30 degrees Celsius; temperatures range from -125 degrees Celsius in the winter to 22 degree Celsius in the summer. Mars has permanent ice caps at both poles, and they are made of mostly carbon dioxide, which makes dry ice. These caps shrink in size during the spring and summer on Mars. Mars is much colder than Earth because of its distance from the Sun.

Much of the surface on Mars is very old and cratered, covered by different rocks, and a soil which is rich in iron-laden clay. The iron explains the planet's reddish color. There are many craters caused by meteors crashing into its surface. Mars also has canyons, deep gorges, and volcanoes. In fact, Mars has some of the largest volcanoes in the Solar System. The southern hemisphere on Mars has highlands, made of ancient, most heavily cratered crustal material, much like the Moon. The northern hemisphere is made of plains and they are not as old. Astronomers have evidence of erosion on many parts of Mars. At one time on Mars, millions of years ago, there was water and maybe even lakes or oceans that flowed across the now dry red planet. Some of the metoerites found on Earth are actually pieces of Mars. They are being examined by scientists for evidence of tiny bacteria and other signs that life may have once existed on the planet.

Mars has 2 small satellites or moons; they are very irregular in shape and are asteroids, which are small rocky fragments that are scattered throughout our Solar System. Millions of years ago, the two asteroids that are the moons came close enough to Mars that they were attracted or captured by Mars' gravitational field. The two moons are among the smallest moons in the Solar System.

Bibliography and Additional Sources of Information

Astronomy Sight. www.astronomysight.com/as/welcome.html

WebStars. heasarc. gsfc.nasa.gov/docs/www_info/webstars.html



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