Mars is the fourth planet from the Sun, often called the "Red Planet" due to its iron oxide-rich surface, and is known for its cold, dry conditions and exploration interest for potential past or present life. Articles are a unique way for readers to learn about the world around them. In addition to building reading comprehension skills and increasing vocabulary, articles can be used for writing and research. Each Planet is broken into 6 single-page sections: Introduction, What is it Made of?, By the Numbers, Neighbors, Amazing Facts, and Words to Know.