Mercury is the closest planet to the Sun, so you’d assume it’s also the hottest. Surprisingly, it’s not - Venus is much hotter. But Mercury has something more dramatic: the most extreme temperature swing of any place in the solar system.
During its long day, the side of Mercury facing the Sun heats up to about 430°C - hot enough to melt lead. During its equally long night, the same surface cools to around -180°C, far colder than anywhere on Earth. Day to night, the temperature swings by about 600°C.
The reason for the extremes is what Mercury lacks: a real atmosphere. Earth’s air helps spread heat around the planet, smoothing out hot and cold. Mercury has practically none, so the daytime side bakes uninterrupted, and the nighttime side has nothing to keep its heat in. Each spot on the planet alternates between oven and deep freezer.
