Wikijunior:Solar System/Mercury
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Mercury Facts:
- Mercury orbits around the Sun faster than any other planet.
- Mercury's surface temperature can vary from -180°C (-300°F) to 430°C (800°F). On Earth, the hottest temperature was recorded at 58°C (136°F).
- There may be ice on the top and bottom of Mercury.
Mercury is the closest planet to the Sun. It is a terrestrial planet. That means a planet made from rock like Earth.
For a long time, only one spacecraft, Mariner 10, had visited Mercury. In January 2008, the MESSENGER spacecraft went by Mercury. It will go by Mercury two more times before starting to go around the planet in 2011.
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[edit] How big is Mercury?
Mercury is 4879 km across. Mercury's diameter is just less than half the diameter of the Earth. It is the smallest planet in the Solar System. Only dwarf planets like Pluto are smaller. Mercury's small size and its closeness to the Sun sometimes make it difficult to see without a telescope or binoculars. The best time to spot Mercury in the sky is just after the sun goes down at night or shortly before it rises in the morning.
[edit] What is Mercury's surface like?
Mercury has craters like those on the Earth's moon. The largest crater on Mercury is the Caloris Basin. It is about 1300 km wide. It was created by a huge asteroid hitting Mercury. The asteroid was probably 100 km wide, but it hit Mercury's surface so hard that it made a much bigger hole.
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The surface also has big cliffs called scarps. They were made long ago when Mercury cooled down. It shrank, causing the surface to get wrinkled in some places. This wrinkling created the scarps.
There may also be ice on the top and bottom of Mercury. Like the Earth, these areas (called poles) don't get much warmth from the Sun. Any ice there won't melt.
It is very hot during the day (over 400°C) because Mercury is so close to the Sun. At night it is very cold because Mercury loses almost all its heat since there is almost no atmosphere to keep the warmth there. The temperature can fall to almost -175°C.
[edit] How long is a day on this planet?
Mercury rotates (spins around) much more slowly than the Earth. It takes Mercury 58 days to spin once. Because Mercury orbits the sun very quickly, a day on Mercury lasts longer than 58 days. If you were standing on Mercury, at the equator and timed how long it took the sun to go from directly overhead to sunset to sunrise and then rise directly overhead again, it would take 176 Earth days. These long days and nights allow for the temperatures to rise as high, and fall as low, as they do.
[edit] How long is a year on Mercury?
Mercury has the shortest year in the Solar System. It is about 88 Earth days long.
It used to be believed that the same side of Mercury always faced the Sun. In order for this to be true, Mercury would have to take the same amount of time to rotate (spin around) as it does to circle the sun. Through careful observation we now know that Mercury's rotation is somewhat faster than its orbit. Because of the way the orbit and rotation work together, on Mercury, a day is actually almost twice as long as a year.
[edit] What is Mercury made of?
The center of Mercury is made of iron in partly-molten (liquid) form. We know that it is iron at the center because the planet generates a magnetic field. It contains more iron for its size than any other planet in the Solar System. The rest of Mercury, its thick crust, is made of a special type of rock called silicate rocks. There are craters near the poles that are constantly in shadow. Some of these craters contain ice. There is a huge crater on Mercury called Caloris Basin. It was formed when a comet hit the planet and lava or molten rock filled the impact crater. The round wall of this crater is over 2km tall.
[edit] How much would Mercury's gravity pull on me?
If you were on Mercury, it would pull you down less than half (38%)as much as the Earth. An item that weighs 100 Newton on Earth, would only weigh 38 Newton on Mercury.
[edit] Who is this planet named after?
In Roman mythology, Mercury was the messenger of the gods. He wore a hat and sandals with wings on them, allowing him to travel around the world very quickly. The planet Mercury was named after him because it moves around the Sun faster than any other planet in the Solar System. It moves nearly 48 km every second!
[edit] How long would it take people to get there?
Could someone answer this please?
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[edit] References
NASA's Solar System Exploration[1]
Arnett, Bill. The Nine Planets[2]
Worldbook Online [3]
Worldbook@NASA, "Mercury"[4]
NASA Planetary Fact Sheet [5]
Hamilton, Calvin J. . Solarviews.com, "Mercury" [6]
Encyclopedia Mythica, "Mercury" [7]
Col, Jeananda. Enchanted Learning/Zoom Astronomy [8] 1998-2005
Usborne Internet-Linked Science Encylopedia, Usborne Publishing Ltd. ISBN 0794503314[9]
Dickinson, Terrence. The Universe and Beyond . Firefly Books ISBN 1552093611
