The document discusses the key factors that make Earth capable of sustaining life. It states that all planets in the solar system formed from dust particles through accretion. Two important characteristics for life are the presence of liquid water and an atmosphere. Water allowed the first photosynthetic organisms to emerge and produce oxygen. Heat from both the Earth's interior and Sun is also necessary, as it drives systems like plate tectonics and the greenhouse effect. The greenhouse effect helps regulate temperatures and enables photosynthesis, which controls gas levels. Together these factors have made the Earth uniquely suited for life.