* Inner core is a solid sphere made of iron and nickel metals about 1,518 miles in diameter

* Temperature around 5,400 degrees Celsius

* Outer core is about 1,400 miles thick

* In between the outer core and crust is the mantle, the thickest layer. This hot, viscous mixture of molten rock is about 1,800 miles (2,900 kilometers) thick and has the consistency of caramel.

Atmosphere / Weather

* 78 percent nitrogen, 21 percent oxygen, and 1 percent other gases such as argon, carbon dioxide and neon.

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* Atmosphere affects Earth's climate and shields us from much of the harmful radiation coming from the Sun and also protects us from meteoroids, most of which burn up in the atmosphere.