The Solar System

How are Mercury's rotation and orbit speeds unusual?
Answered by Science Channel
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    Science Channel

  1. Mercury rotates slowly; spinning around on its axis just once takes Mercury the equivalent of 59 Earth days. However, Mercury has a super-fast orbit speed. The planet travels nearly 30 miles (50 kilometers) per second, making it the fastest of all the planets, thus earning its name "Mercury" after the Roman god of speed. One year (the time the planet takes to orbit the sun) is equal to 88 days on Earth. One complete day on Mercury (the time it takes for the sun to return to the same point in the sky) is almost 176 Earth days. Thus Mercury only orbits the sun twice within the time it takes to rotate on its axis three times. This means that a day on Mercury is twice as long as its year!

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