* The right temperature: The planet must be warm enough to allow liquid water to exist on its surface, but not so hot that water boils away.
* The right amount of water: The planet must have enough water to support life, but not so much that it covers the entire planet.
* The right atmospheric composition: The planet must have an atmosphere that contains the right gases, including oxygen, carbon dioxide, and nitrogen.
* The right amount of sunlight: The planet must receive enough sunlight to support photosynthesis, but not so much that it burns the planet's surface.
The term "Goldilocks conditions" comes from the children's story "Goldilocks and the Three Bears." In the story, Goldilocks finds three bowls of porridge, one that is too hot, one that is too cold, and one that is just right. The Goldilocks conditions refer to the "just right" conditions that are necessary for life to exist on a planet.