There is not much known about Mercury or its surface, except that it is similar to the moon in appearance and its composition consists of primarily molecular oxygen, sodium and hydrogen. There are also small amounts of helium and potassium. The planet does not have an actual atmosphere, which causes the planet to have extreme temperature changes during its rotation.
Appearance is where the similarities to the moon end. Mercury's surface has a much different makeup with areas low in iron and high in sulfur. Its core is also thought to be the largest portion of the planet due to the magnetic field. One of the most interesting geological features is the scarps that indicate that the planet may shrunk or contracted at one point in its history.