Mercury: Swift Survivor

Mercury orbits just 58 million km from the Sun yet is not the hottest planet. With no atmosphere, heat escapes instantly at night: the day side hits 430°C while the night side plunges to -180°C. Its cratered surface resembles our Moon.

The largest crater, Caloris Basin, spans 1,550 km — formed by an impact so violent it sent shockwaves through the entire planet. Despite extreme heat, permanently shadowed polar craters contain water ice.