Esoplanet

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Mercury

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.