Mercury is the Greek god that is the messenger of Zeus. The god Mercury is often shown with wings on his shoes so he can fly fast. If you saw the movie Percy Jackson & the Olympians: The Lightening Thief, Percy used a pair of Mercury’s hightops with wings to fly.
Venus is the Roman goddess of beauty. Venus is easy planet to see in the sky - it is very bright.
Mars is the Roman god of war.
Jupiter is the Roman name for the Greek god Zeus. Zeus was the king of all the Greek gods. The biggest planet in our solar system is named after the most powerful god.
Saturn is the Roman god of time.
Uranus is the grandfather of Zeus (Jupiter).
Neptune is a Roman god also know as Poseidon, the god of the sea. Neptune is blue, - it looks like the water on earth.
Pluto (which is no longer a planet, but a dwarf planet) is a god also known as Hades, the king of the underworld.
Space.com is a great website to learn generally about space. Another fun site specifically for kids is KidsCosmos.com.