The runaway greenhouse effect on Venus was caused by high levels of carbon dioxide in the planet's atmosphere, which led to extreme temperatures reaching around 900 degrees Fahrenheit. The thick atmosphere of Venus traps heat from the Sun, creating a vicious cycle that only intensifies the greenhouse effect. This extreme heating caused the oceans to evaporate, releasing even more water vapor - another potent greenhouse gas - into the atmosphere. As a result, Venus became a hellish, uninhabitable planet with a dense, toxic atmosphere.
