Why is Venus hotter than Mercury, when Mercury is closer to the Sun?

Venus' scorching temperatures, despite Mercury's closer proximity to the Sun, hinge on Venus' thick, carbon dioxide-rich atmosphere that traps heat, creating a runaway greenhouse effect. Unlike Earth, Venus has no significant water vapor to moderate temperatures, resulting in surface heat exceeding 400 degrees Celsius. This phenomenon underscores the critical role of atmospheric composition in planetary climate, providing a stark contrast to Earth's more temperate environment. Understanding these differences is key to comprehending planetary evolution and the potential habitability of other worlds.