Describes the atmosphere and surface of Mars, including recent findings from NASA space probes, and surveys the history of our attempts to discover more about this planet.
Discusses several threats to the environment, laws that have been enacted to protect it, and the branch of the Environmental Protection Agency and other local groups that enforce such laws.
Discusses the functions of the body's systems, including skeletal, muscular, and nervous; and examines the relationship between nutrition and breakdowns in body systems and diseases.