The term for the layer of gas surrounding a planet is called an atmosphere. An atmosphere consists of a mixture of gases, including nitrogen, oxygen, carbon dioxide, and others, which form a protective envelope around a planet. The composition and density of an atmosphere can significantly impact conditions on the planet's surface, influencing temperature, weather, and the potential for supporting life. For instance, Earth’s atmosphere provides essential oxygen for life, while also regulating temperatures through the greenhouse effect. Different planets have varying atmospheres; for example, Venus has a thick, toxic atmosphere primarily composed of carbon dioxide.