Mercury is the smallest planet in our solar system. It is also the closest to the sun. Even though is is the closest planet to the sun, it is not the hottest planet. Instead, the hottest planet is Venus, because of its dense atmosphere.
Source:NASA Visualization Technology Applications and Development (VTAD)
Basic Knowledge
Mercury is known for being a very hot planet, since it is so close to the sun. If you think that is true, you are right. However, Mercury also gets really cold at night because it doesn't have an atmosphere to maintain the heat. When it is day time, Mercury's temperature can even get as hot as 800°F or 430°C. At night, Mercury can get as cold as -290°F or -180°C. Mercury is the fastest moving planet in our solar system, with the shortest year. A year on Mercury would only last 88 days on Earth!
Geographical Information
When it comes to size, Mercury is very small. It has a radius of only 1,516 miles or 2,440 kilometers, which is about 1/3 of Earth. Mercury is also 36 million miles or 58 million kilometers away from the sun. It's orbit is shaped like an egg when it goes around the sun. When it is its closest, it can be about 29 million miles or 47 million kilometers away from the sun. When it's at its farthest, it can be about 43 million miles or 70 million kilometers away from the sun.