Seems a bit misleading.
Either national geographic does not understand basic astronomy or they are misleading people in an attempt to get page views.
IAU definition of a planet.
A "planet" is a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and (c) has cleared the neighbourhood around its orbit. If its just like earth then wouldn't all that^ be true of this moon as well? If its just like earth then wouldn't all that^ be true of this moon as well? SMH!