Mercury

Smallest planet in the Solar System and closest to the Sun, with extreme surface temperature swings.

Core Principles & Analysis

• A 3:2 spin-orbit resonance makes one solar day on Mercury last 176 Earth days, two full Mercury years.
• Surface temperatures swing from about 430 °C in sunlight to -180 °C at night, the widest range of any planet.
• NASA's MESSENGER spacecraft confirmed water ice in permanently shadowed craters at Mercury's poles in 2012.

Specifications & Metrics

• DISTANCE FROM SUN: 0.39 AU
• DIAMETER: 4,879 km
• MOONS: 0
• ORBITAL PERIOD: 88 days