Why has Earth's metallic core not cooled as much as Mercury's? Did the atmospheres of both planets have a role in this?

Why has Earth's metallic core not cooled as much as Mercury's? Did the atmospheres of both planets have a role in this?

Mercury: Its extremely cratered surface implies little if any geological activity since the end of the heavy bombardment of the Solar System around 4 billion years ago. In addition, the small size...