9.5 Mercury

Orbit

• Closest to the sun

• Shortest period of revolution 

• HIghest average orbital speed 

• Highest eccentricity

Composition of Mercury

• Greater density than the moon 

  • Made of heavier materials such as metals 

• SMall diameter of 4878km

• Lack of atmosphere

  • Extremely hot and cold

• Weak magnetic field 

  • Large metal core, part of it being liquid 

Planet rotates

•  but very slowly → once every 59 days

  • Determined through: If a planet rotates, one side of the surface is moving toward Earth (reflecting radar waves at slightly higher frequency) while the other side moves away (reflecting at slightly lower frequency).

    • This creates a Doppler shift, spreading the radar signal into a range of frequencies instead of just one.

Orbit Resonanc

• Ratio of number of times the planet orbits about itself vs the sun

Surface of Mercury: 

• Extremely cratered

• Water as ice found at the poles

• Scarps: The cliffs on a planet 

  • Formed after craters → since some craters have the line through them

    • Due to the planet shrinking with the cooling temperature causing wrinkles

Origins of Mercury

1. Must have had impacts that stripped away most of its mantle and crust leaving a dominating iron core

2. Heat from the early sun must have evaporated the lighter and volatile materials