Mercury is the closest planet to the Sun. It sits between the Sun and Venus.- Because Mercury is closer to the Sun than the Earth is, Mercury can appear in Earth's sky in the morning and the evening. For this reason the Greeks gave Mercury two names; Apollo and Hermes.
- Mercury is the fastest travelling planet in its orbit. For this reason when the Romans conquered the Greeks they renamed it Mercury, after their fast-flying messenger to the gods.
- Mercury is a terrestrial planet, like the Earth.
- Mercury is the smallest planet in the Solar System.
- Mercury is only a little bigger than the Moon.
- If the Sun were hollow you could fit roughly 21.3 million planets the size of Mercury inside.
- The Earth's gravity is measured as 1 unit of gravity. The gravity on all other planets is taken as a multiple of Earth's.
- Mercury's gravity is only 1/3rd as strong as Earth's gravity, which means that objects on Mercury don't weigh as much as they do on Earth.
- A 100 lb person on Earth would only weigh 38 lbs on Mercury.
- A day on Mercury is about 58 Earth days long.
- A year on Mercury is only 88 Earth days long.
- The distance from the Sun to the Earth is 1 AU and is used to measure distance in our Solar System. Mercury is roughly 0.4 AU from the Sun.
- The light from the Sun takes only 3.2 minutes to reach Mercury.
- If you were standing on Mercury the Sun would appear roughly 3 times larger than it does to us here on Earth.
- Mercury rotates in a counterclockwise motion or from West to East, the same as the Earth. So if you lived on Mercury you would see the Sun rise in the East and set in the West, the same as on Earth.
- Mercury has no moons.
- Mercury has no rings.
- Mercury has almost no atmosphere.
- Despite being the closest planet to the Sun, Mercury is not the hottest planet. Venus, because of the dense greenhouse gasses in its atmosphere, is hotter.
