Mars
Mars is the fourth planet from the Sun and is about 142 miles from the Sun. Its diameter is about 2,960 km in diameter. Mars was named after the Roman god of war. This is because of its red color which is due to its soil which is composed of iron. Mars soil is also composed of basalt and its core consists of iron and some sulfur. Mars exemplifies the accretion theory because of its solid, rocky composition. The accretion theory says that Mars was composed of small pieces of rocks and other things found in the solar system known as planetesimals. The accretion theory's explanation for the relatively small size of Mars is that only a small planet was able to form before the rapidly growing Jupiter pulled all of the planetesimals away from Mars. This theory provides a sufficient explanation about the forming of the planets including Mars.
http://www.scribd.com/ioana_cn/d/55912234/26-The-Accretion-Theory#page=304
http://www.nasa.gov/audience/forstudents/5-8/features/what-is-mars-58.html