The divergence between Earth and Venus is primarily driven by their different distances from the Sun and their internal compositions. Venus is located closer to the Sun, meaning it receives significantly more solar radiation. In the early stages of their formation, both planets likely possessed water. However, because Venus was closer to the heat, its oceans eventually began to evaporate into the atmosphere as water vapor.
Water vapor is a potent greenhouse gas. As it accumulated in the Venusian atmosphere, it trapped more solar heat, creating a feedback loop known as a runaway greenhouse effect. This intense heat eventually caused more evaporation, further heating the planet. Simultaneously, solar radiation began to break down these water molecules through a process called photodissociation. The hydrogen was light enough to escape into space, leaving the planet dry.
Earth remained stable because our distance from the Sun allowed us to maintain liquid water, which acts as a thermostat. Our carbon cycle helps regulate atmospheric carbon dioxide, preventing the extreme warming seen on Venus. For more detailed planetary data, you can visit https://science.nasa.gov.
