is the third planet from the Sun and the only known celestial object capable of harboring and supporting life.

Land, which consists of continents and islands, covers 29.2 percent of the ’s surface.

The remaining 70.8 percent is covered by , largely in the form of oceans, seas, gulfs, and other salt- bodies, but also in the form of lakes, rivers, and other freshwater bodies, which comprise the hydrosphere.

The polar areas of the are mostly covered with ice.

The ’s outer layer is divided into several rigid tectonic plates that migrate across the surface over many millions of years, while its interior remains active, with a solid iron inner core, a liquid outer core that generates the magnetic field, and a convective mantle that drives plate tectonics.