A Class M planet is a 'Terrestrial' planet. They have an age that ranges from 3-10 billion years and a diameter between 10,000 and 15,000 km. They are located within the Ecosphere of a solar system. A Terrestrial planet is categorized by an abundance of surface water (however, if this amount goes above 80%, then the planet is considered a Class O or P) and an atmosphere high in nitrogen with oxygen and trace elements. Life is often abundant on Class M planets; they contain extensive vegetation, animal life and often have native humanoids.