Mercury's Interior

Density:

• Density is 5400 kg/m^3.
• This is similar to Earth's density.
• So need an iron core.
• Furthermore, since Mercury is smaller, it is not as compressed by its own gravity.
• So its core needs to be a bigger fraction of the planet than for the Earth.
• Why did this happen?
  • Mercury formed nearer the protosun, where it was hotter and more volatile substances didn't condense as readily.
  • Maybe a very powerful solar wind from the early sun blew away some mantle.
  • Maybe Mercury hit something that tore off a lot of its early mantle.

Magnetic field:

• Mercury has a small magnetic field.
• This suggests an iron core that is at least partly liquid.