I wonder… What is the smallest planet in the Solar System? That’s one of the questions that might come to the minds of all those kids out there and one which they usually ask their parents about to try and get an answer for. The smallest planet in our Solar System is Mercury. The surface of Mercury is very similar to our moon. It has a very barren, rocky surface covered with many craters. Being so close to the Sun, the daytime temperature on Mercury is scorching – reaching over 400 Degrees Celsius. At night however, without an atmosphere to hold the heat in, the temperature’s plummet, dropping to -180 Degrees Celsius. Since Earth is where we tend to live, it will always be measured among the other planets found in the solar system. When it comes to the smallest planet which is Mercury, it is important to mention that Mercury is actually 20 times less massive than Earth and its diameter is about two and a half times smaller. Mercury is closer in its size to the moon that it is to Earth.