Mercury is one of the smallest planets. Mercury is the sun's closest neighbor. It's average distance from the sun is 58 million kilometers. Unlike most other planets, Mercury has no moon.
Long Day, Short Year
Mercury is named after the speedy messenger of the Roman gods, which is very convenient because Mercury travels very fast through space at 23 to 35 miles per second. So, Mercury has the shortest year out of all the planets. It's year only lasts 88 Earth days. But, Mercury spins very slowly on it's axis, and it takes Mercury 59 Earth days to rotate once.
Mercury has a very thin atmosphere and it is very close to the sun which makes it very hot. Its temperature during the day is 662*F, it is so hot that lead would melt. But at night it is very cold, its temperature is -275*F. It's so cold at night because there is hardly any atmosphere to hold the heat received from the the sun during the day.
No one knew and could know what Mercury was like until the American space probe, Mariner 10, flew past the planet 3 times in the 1970's. This gave the world its first view of Mercury. Scientists were surprised to see that Mercury looked like our moon. Its face is heavily scarred with big and small craters. Scientists have calculated that Mercury's core is very big. It reaches out three-quarters of the way from the center of the planet. Mercury has so less gravity that you would weigh one-third as much on Mercury as you do on Earth.
Mercury looks like a badly lit, fuzzy ball through a telescope. Sometimes you can see Mercury as a pinkish star in the east before sunrise or in the west after sunset. On occasions, Mercury can be seen across the sun disc, an event called a transit. Those occasions occurred in 1973, 1986, 1993, and 1999.
Mercury is an airless, silent, cratered planet, baking under a huge sun in a jet black sky. There is still much to be learned about Mercury.
Mercury's Core, Face and, Atmosphere
Mercury in the Sky
