Kids' illustration of Mercury.
Mercury looks a lot like our Moon.

The Swiftest Planet

Mercury is the closest planet to our sun. It is named for the ancient Roman god of trade and profit. Legend says Mercury's winged sandals gave him super speed. Mercury the planet is super fast, too. It zips around the sun every 88 days -- faster than any other planet. No wonder it got its name from the quickest of the ancient gods.

Mercury is the smallest planet in our solar system, but there are dwarf planets that are smaller. If Earth were the size of a baseball, Mercury would be a golf ball.

Full disk image of Mercury.
Why does Mercury travel around
our sun faster than any of the other
planets? Ask your teacher
if you need help.

Imagine looking up at a sun that is three times larger than what you see on Earth. That is how our sun would look on Mercury. Because of Mercury's wild elliptical (egg-shaped) orbit and weird rotation, the morning sun appears to rise briefly, set and rise again. The same thing happens in reverse at sunset.

Mercury is not as hot as you might think it would be since it is so close to the sun. Venus is actually hotter.

The temperature on Mercury can change more than 1,000 degrees Fahrenheit (530 degrees Celsius) between night and day. This happens because here is very little air -- atmosphere -- to hold in the heat when the sun is not shining. The thin atmosphere also means meteors don't burn up before they hit Mercury's surface, so Mercury is covered with craters. It looks a lot like our Moon.

There is no water on Mercury. But there might be a little ice in deep craters. Mercury has cliffs and valleys just like Earth. Some cliffs are a mile high.

You would need very special spacesuit to visit Mercury. It would have to protect you from the extreme heat and cold and the dangerous radiation from the sun. Even NASA's MESSENGER spacecraft needs a special shade to protect it from the sun's blistering heat and radiation.