How is it that Earth is the only known planet with active plate tectonics?
Erik McKenna
Stamford, Connecticut
Earth is special in that it has two things that other terrestrial planets don’t: an abundance of internal heat, from when our planet was molten rock, and liquid water. To understand why our planet is unique in this regard, let’s first look at Earth versus Mars.
Earth is relatively large for a rocky planet. Its sheer amount of mass has allowed it to hold onto its intern