Inner Planets

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Inner Planets Noun

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[in-er plan-its]

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Inner Planets

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The four planets closest to the sun, Mercury, Venus, Earth, and Mars, which are characterized by their solid, rocky composition.

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Example: This diagram shows the four planets closest to the Sun—Mercury, Venus, Earth, and Mars—which are known as the Inner Planets.

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Terrestrial Planets Noun

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[tuh-res-tree-uhl plan-its]

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Terrestrial Planets

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A name for planets made of solid rock, derived from 'Terra' meaning 'Earth', and is another name for inner planets.

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Example: This image displays the four terrestrial (inner) planets of our solar system: Mercury, Venus, Earth, and Mars, all of which have solid, rocky surfaces.

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Composition Noun

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[kom-puh-zish-uhn]

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Composition

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The materials or substances that make up an object, such as the rocky and metallic elements of the inner planets.

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Example: This diagram shows the composition of Earth, an inner planet, by revealing its distinct layers: the crust, mantle, outer core, and inner core.

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Revolution Period Noun

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[rev-uh-loo-shuhn peer-ee-uhd]

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Revolution Period

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The time it takes for a planet to complete one full orbit around the sun, which is also known as its year.

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Example: This diagram shows a planet making one complete orbit around the Sun, which is its revolution period.

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Density Noun

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[den-si-tee]

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Density

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A measure of how much matter is packed into a given space, with inner planets having characteristically high densities.

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Example: This image shows that liquids with different densities, like honey, water, and oil, will separate into layers, with the densest liquid at the bottom.

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Crust Noun

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[kruhst]

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Crust

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The outermost solid layer of a terrestrial planet, which is composed of solid silicate rock and is chemically distinct.

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Example: This diagram shows a cutaway of the Earth, identifying the 'Crust' as the planet's thin, outermost solid layer, located above the mantle.

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Mantle Noun

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[man-tl]

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Mantle

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The layer of a terrestrial planet located between the crust and the core, primarily made of solid silicate rock.

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Example: This diagram shows the Earth's layers, with the mantle clearly labeled as the thickest layer located between the thin outer crust and the core.

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Core Noun

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[kor]

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Core

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The central part of a terrestrial planet, consisting of a liquid outer core and a solid inner core of metal.

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Example: This cutaway diagram shows the layers of the Earth, an inner planet. The core is the central part, made of a liquid outer core and a solid inner core.

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Silicate Rock Noun

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[sil-i-keyt rok]

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Silicate Rock

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Rock composed mainly of silicate minerals, which forms the crust and mantle of all the terrestrial planets in our solar system.

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Example: This image shows that silicate minerals, which contain silicon, are a major class of minerals. Silicate rocks are formed from these types of minerals.