Mercury Planet

Mercury is the second smallest planet in the solar system. It is 4,879 kilometers across. Compare that with our moon, which is 3456 km across, and you can see that mercury is not very big. In fact, Jupiter's moons Ganymede and Callisto and Saturn's moon Titan are bigger! Even though those moons are bigger, Mercury weighs a lot more than they do because it is made of mostly metal and rock. In fact, Mercury has the most metals for its size of any planet in the solar system. Mercury is also the closest planet to the sun. Here you can see Mercury pass in front of the sun. This is called a "transit". It goes around the sun in 88 days. Mercury rotates on its axis (like a top) two times for every three times it goes around the sun. This means that days on Mercury are really weird! Since it rotates so slow and goes around the sun so fast, if you were standing on the surface of Mercury (I wouldn't suggest it!) you would see the sun rise in the east for a while, then dip back down towards the horizon, then zip over to the west to set! The sun would be above the horizon for about 60 days.

Mercury has an unusual orbit. It is more elliptical than most planets, which means it is more of an oval. For a long time, nobody could quite explain the way that Mercury orbited. Many astronomers thought there might be a smaller planet even closer to the sun that was tugging on Mercury and making its orbit disagree with their calculations. It turned out that they weren't using the right physics! When Einstein
Mercury is one of the rocky inner planets. It has a crust a lot like the earth, except mercury is not geologically active. This means that the crust you're seeing has not been "recycled" by erosion, volcanism, or plate tectonics. Below that is probably a mantle made of partially melted rocks. Because mercury is so heavy for its size, scientists think that it has a very large, metal