Venus is the hottest planet in the solar system because it has an extremely thick atmosphere made mostly of carbon dioxide, which creates a massive greenhouse effect. This dense atmosphere traps heat very effectively, preventing it from escaping back into space and causing surface temperatures to soar to around 864 degrees Fahrenheit (462 degrees Celsius), hotter than even Mercury, which is closer to the Sun.
Thick Carbon Dioxide Atmosphere
Venus's atmosphere is about 100 times more massive than Earth's and is composed of about 96.5% carbon dioxide, a greenhouse gas that absorbs and traps heat. The pressure at the surface is about 93 times that of Earth's, equivalent to the pressure nearly 1 km under Earth's ocean. This thick CO2 atmosphere generates the strongest greenhouse effect in the solar system, insulating the planet and raising its temperature dramatically.
Greenhouse Effect and Heat Trapping
The greenhouse effect on Venus is a runaway process: sunlight heats the surface, but the thick atmosphere traps the infrared radiation emitted by the heated surface. This trapped heat builds up, causing extreme surface temperatures. This is similar to how glass traps heat in a greenhouse, but on a much more intense scale due to the atmospheric composition and density on Venus.
Comparison with Mercury
Although Mercury is closer to the Sun and has hotter temperatures during the day, it lacks a substantial atmosphere to retain that heat. Without an atmosphere, Mercury's surface temperature drops drastically at night. Venus, with its thick heat-trapping atmosphere, maintains uniformly high temperatures both day and night, making it the hottest planet overall.
In summary, Venus's extreme heat is due to its thick carbon dioxide atmosphere causing a runaway greenhouse effect that traps heat and results in surface temperatures higher than any other planet in the solar system.
