Probably because it is a solid surrounded by liquid molten rock and iron and has its own chemistry and physics.
Pulsar planet.
The dwarf planet Pluto is believed by astronomers might be the core of a much larger planet
core
The core of Uranus is in the center of the planet.
Mercury is slightly smaller then the Earths Core. Mercury is believed to have been struck by a planet sized object billions of years ago which blew away everything but the core of the planet.(If Pluto was still a planet, Pluto would also be smaller than the Earth's core, but it was demoted to the status of a dwarf planet.)
Pluto used to be the smallest planet, but it was deemed to not be a planet. The smallest planet now is Mercury within our Solar System
No. Jupiter is a gas planet. It has no definite surface. The only solid portion is its core, deep within the planet under enormous heat and pressure.
No known planet has a core of metallic hydrogen, but Jupiter and Saturn have layers of liquid metallic hydrogen surrounding their cores.
Thebeon VIII (the eigth planet located in the Thebeon system within the Daupherm States in the Core Worlds).
No. The only part of Saturn that is solid is the core, which is thousands of miles deep within the planet under enormous pressure, and heated to thousands of degrees.
Pulsar planet.
The dwarf planet Pluto is believed by astronomers might be the core of a much larger planet
Jupiter is a gas planet so the surface is a gas which cannot have crevices. It's not known if it has a solid core.
core
The core of Uranus is in the center of the planet.
The center of the planet is called the "core."
Mercury is slightly smaller then the Earths Core. Mercury is believed to have been struck by a planet sized object billions of years ago which blew away everything but the core of the planet.(If Pluto was still a planet, Pluto would also be smaller than the Earth's core, but it was demoted to the status of a dwarf planet.)