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Mercury, Venus, Earth, and Mars are the planets closest to the Sun. They are called the inner planets. The inner planets are made up mostly of rock.
Of all the planets in our solar system, Venus is most similar to Earth in size and density. Venus is also our nearest neighbor. In addition, Venus’ interior structure is similar to Earth’s, with a large iron core and a silicate mantle. But the resemblance between the two inner planets ends there.
One way that Venus differs from Earth—and from all of the other planets in the solar system—is its direction of rotation. Venus rotates in a direction opposite to the direction that it orbits the sun, whereas the rest of the planets rotate in the same direction that they orbit the sun. Venus’ rotation is also extremely slow, with just one rotation every 243 days. This is longer than the 224 days it takes Venus to orbit the sun, so a day on Venus is longer than a year.
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