Planet Mercury Facts: Lesson for Kids

Instructor: Jeremy Cook

Jeremy has been teaching in elementary education for 13 years and holds a master's degree in Education

It's small, it's hot and it's the closest planet to the sun. In this lesson, we will learn about Mercury. We'll find out what it might be made of and how it moves through our solar system.

What Is Mercury?

Mercury is the smallest planet in our solar system. The distance from one side to the other, or the planet's diameter, is about 3100 miles. This is much smaller than our home Earth, which is about 7900 miles across.

Mercury is small compared to Earth.
Mercury Compared

The surface of Mercury is dry, rocky and full of craters, much like our moon. Some parts of the surface appear to be wrinkled. Scientists think this is because of iron within the planet shrinking over time. Iron is an element classified as a metal. There's a lot of iron in the earth too.

Mercury has craters just like our moon.
Planet Mercury

Temperature and Gravity

Mercury has extreme temperatures because it has no atmosphere. Atmosphere can help trap heat to even out temperatures on a planet when the sun goes down. The sunny part of Mercury can get boiling hot - over 800 degrees Fahrenheit! A kitchen stove can only get about half as hot as that! However, when a part of the planet is darker because it is facing away from the sun, it can get freezing cold - more than -270 degrees Fahrenheit!

Because Mercury is small and has no moons orbiting around it, it has much less gravity than we have here on Earth. If you weighed 72 pounds on Earth, you would only weigh 27 pounds on Mercury's surface!

Crater on the surface of Mercury
Mercury Crater

Mercury's Orbit and Rotation

Even though Mercury is the closest planet to the sun, it's still more than 30 million miles away from it. Mercury takes about 87 Earth days to complete its egg-shaped orbit around the sun. Talk about a quick year! But while Mercury speeds rather quickly around the sun, it spins slowly on its axis, or the imaginary line that runs through the planet. It takes Mercury about 59 Earth days to make one rotation. That means that one day on Mercury takes nearly two Earth months!

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