Mercury

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Mercury is the nearest planet to the sun. It is around 36 million miles (58 million km) from the sun. It takes 88 days for Mercury to orbit the Sun. It is usually only visible before sunrise or after sunset for a little while.

Mercury is the second smallest planet in the solar system with a diameter of about 3,000 miles or 4,800 kilometers. Its density or thickness of the materials that make it up is similar to that of the earth. Because it is very small it has less of a gravitational pull on other space objects - one would weigh less on Mercury. Mercury does not have much of an atmosphere. Small amounts of carbon dioxide have been detected.

The surface of Mercury is like that of the moon. Most of its craters were formed during a time it was hit by millions of small asteroids early in the solar system's history. Mercury's rotation on its axis is equal to 59 earth days. This results in periods of daylight and night of 90 earth days.

Temperatures during the day get as high as 800 degrees Fahrenheit or 450 degrees Celsius. Night temperatures are thought to get as low as -300 degrees Fahrenheit or -180 degrees Celsius.