Mercury is the smallest and innermost planet in the Solar System. It is about one-third the size of Earth but has extreme surface temperatures that range from -173°C to 427°C. Mercury has no moons, is the closest planet to the Sun with an orbit of just 88 days, and is heavily cratered, having been visited by only two spacecraft.

1. Mercury

2. Profile
 Mass: 330,104,000,000,000 billion kg (.0055 x Earth)
 Equatorial Diameter: 4,879
 Polar Diameter: 4,879
 Known moons: none
 Surface temperature: -173 to 427°C

3. Size compared to the Earth

4. Fun Facts
 Closest planet to the sun
 One year in Mercury is just 88 days
 Most cratered planet in the Solar System
 Two spacecraft have visited Mercury