Size
- Diameter: about 3,030 miles (4,880 km)
- Mercury is the smallest planet in our solar system
Surface gravity
- 3.7 m/s²
- About 38% of Earth’s gravity
Density
- 5.43 g/cm³
- Similar to Earth, indicating a large metallic core.
Geology: Caloris Basin
- One of the largest impact basins in the solar system
- About 1,550 km (960 miles) wide
Large cliffs (scarps) formed as the planet cooled and shrank over billions of years.
Rotation
Sidereal rotation period
- 58.6 Earth days
Solar day (sunrise to sunrise)
- 176 Earth days
Mercury has a 3:2 spin–orbit resonance, meaning:
It rotates 3 times for every 2 orbits around the Sun.
Orbital speed: About 47.4 km/s (106,000 mph)
Atmosphere
Mercury does not have a thick atmosphere.
Instead, it has a very thin exosphere made of:
- Oxygen
- Sodium
- Hydrogen
- Helium
- Potassium
Particles come mostly from solar wind and surface vaporization.
Length of a Day: 176 Earth days
Temperature
Day: about 800°F (430°C)
Night: about -290°F (-180°C)
Gravity
Gravity is about 38% of Earth’s gravity
Moons
0 moons
Surface
Covered in craters (holes from space rocks).
Magnetic Field
Mercury has a weak global magnetic field.
- About 1% as strong as Earth’s magnetic field.
This suggests the planet still has a partially molten metallic core.