Mercury
“The Smallest Planet”
Basic facts
- Distance from the Sun: 57.9 million km (36 million miles)
- Diameter: 4,879 km (3,032 miles)
- Mass: 3.30 × 10²³ kg
- Gravity: 3.7 m/s²
- Orbital period: 88 Earth days
- Rotation period: 59 Earth days
Atmosphere
- Composition: Very thin, mostly oxygen, sodium, hydrogen, helium, potassium
- Function: Almost none — too thin to protect from the Sun
- Temperature extremes: Day up to 430°C (800°F), night down to -180°C (-290°F)
Surface Features
- Covered with craters, like the Moon
- Huge cliffs (scarps) formed as the planet cooled
- Rocky and barren, no oceans or water
