Mercury is the smallest and innermost planet in the Solar System. Its orbit around the Sun is the shortest of all the planets in the Solar System.
1. Mercury is the closest planet to the Sun.
2. A day on the surface of Mercury lasts 176 Earth days.
3. Mercury has a very thin atmosphere made up of oxygen, sodium, hydrogen, and helium.
The first spacecraft to visit Mercury was Mariner 10, which flew by Mercury in 1974 and 1975.