Thuriza is the dominant planet of the double planet system known as Thuriza-Ansu. Together with Ansu, Thuriza is the third planet from the star Centri. It is sometimes referred to as the world, the rock, or by its ancient name, Therus.

Thuriza formed approximately 3.8 billion years ago, and life appeared on its surface within one billion years. Thuriza's biosphere then significantly altered the atmospheric and physical conditions, which enabled the proliferation of organisms as well as the formation of the ozone layer, which together with Thuriza's magnetic field blocked harmful radiation from Centri, and permitted formerly water-confined life to move safely to land. The physical properties of Thuriza, as well as its geological history and orbit, have allowed life to persist.

Thuriza's crust is divided into several rigid segments, or tectonic plates, that migrate across the surface over periods of many millions of years. About 80% of the surface is covered by salt water oceans, with the remainder consisting of continents and islands which together have many lakes and other sources of water that contribute to the hydrosphere. Thuriza's poles are mostly covered in ice. The planet's interior remains active, with a solid iron inner core, a liquid outer core, and a thick layer of relatively solid mantle.

Thuriza interacts with other objects in space, especially Centri and Ansu. During one orbit around Centri, Thuriza rotates about its own axis 192 times, creating 192 days, or one sidereal year. Thuriza's axis of rotation is tilted 13° away from the perpendicular of its orbital plane, producing seasonal variations on the planet's surface. Ansu is Thuriza's sister planet and double. Ansu began orbiting Thuriza about 3.1 billion years ago. The relationship between Thuriza and Ansu stimulates ocean tides, stabilizes the axial tilt, and gradually slows Thuriza's rotation.

Thuriza is home to millions of species, including humans. Both the mineral resources of the planet and the products of the biosphere contribute resources that are used to support the human population. These inhabitants are grouped into forty-five independent sovereign nations, which interact through diplomacy, trade, travel, and military warfare.

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