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Interesting Facts About Mercury You Need to Know

Read Time: 5 minutes

Do you know how many planets are in our solar system? The answer seems to change every year as scientists and astronomers argue over what defines a planet, and whether poor Pluto deserves the moniker. Nevertheless, we’ve got eight fantastic heavenly bodies to moon over. Today, we’re going to take a closer look at the closest planet to the sun — Mercury.  Here are some interesting facts about Mercury that you need to know.

10 Interesting Facts About Mercury

Are you ready to become a Mercury expert? Then read the interesting facts below!

1. The Messenger

In Greek mythology, Mercury — the messenger of the Roman gods — was called Hermes. This figure was renowned for his swift movement and winged shoes. His speed is why Mercury got its name, as it is the fastest planet that orbits the sun.

2. The Core

NASA’s Messenger probe crash-landed on Mercury in 2015, but not before sending back information. Researchers learned that the planet’s inner core makes up around 85% of the globe’s entire mass. In fact, this core is more than 2,000 kilometers in diameter.

3. The Temperature

Despite its proximity to the sun, Mercury isn’t the hottest planet in the solar system. That honor belongs to Venus, which has a dense atmosphere that traps and concentrates solar heat.

4. The Sight

Mercury is one of five planets visible from Earth with the naked eye. The other four celestial bodies you can see without the aid of a telescope are Venus, Mars, Jupiter, and Saturn.

5. The Surface

If you were to blast off into space, you’d see that Mercury’s surface has wrinkles — just like your favorite shirt. These folds, which scientists named Lobate Scarps, formed as the planet first cooled and the core contracted. They can reach up to a mile high and stretch for hundreds of miles.

6. The Size

Even though you can spot Mercury with the naked eye, it’s the smallest planet in our solar system. It’s only 4,879 kilometers around its equator, roughly 1/3 of the size of Earth. In comparison to the planet Mars, Mercury is approximately 40% smaller.

7. The Days

Mercury’s rotation is very slow, likely due to its proximity to the intense gravitational forces of the sun. As a result, one day on the planet lasts around 59 Earth days.

8. The Years

Mercury orbits the sun extremely fast, with its year only taking 88 Earth days to complete. If you wanted to celebrate New Year on Mercury, you’d have to host a celebration every one and a half days.

9. The Position

Mercury’s long day is also because the planet is partially tidal-locked, meaning it almost doesn’t rotate on its axis. It experiences three days for every two orbits around the sun. The moon is another example of a tidal-locked celestial body. It orbits the Earth but doesn’t rotate on its axis, the reason we never see the dark side of the moon.

10. The Gravity

If you ever went to Mercury, you’d only weigh a fraction of what you do on our home planet. In fact, gravity on Mercury is around 38% of that on Earth. As a result, this planet can’t hold on to an atmosphere. Anything that does manage to wrap itself around the celestial body ends up getting blown away by solar winds.

core of mercury, mercury's core, composition of planet mercury
Image Credit: A loose necktie / CC BY-SA  via WikiMedia Commons

Mercury Properties & Information

Planning a trivia night with friends? Perhaps you just want some fun facts tucked up your sleeve. Either way, take a look at this interesting information about Mercury:

  • Location in solar system: First planet, closest to the sun.
  • Distance from sun: 57,909,227 km, or 35,983,125.4 miles.
  • Composition: Estimated 70% metals, 30% silicate materials.
  • Size: 4,879 km, or 3031.67 miles, at the equator.
  • Surface: 74.8 million square kilometers, or28.88 million square miles.
  • Structure: Rocky planet, solid crust and mantle, solid and liquid core layers.
  • Color: Gray, like the color of dust or ash.
  • Atmosphere: Thin, with traces of hydrogen, helium and oxygen.
  • Temperature: Ranges from -173° C to 427° C, or -280° F to 800° F.

galaxy-multi-color

What Will Scientists Discover Next?


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Who Discovered Mercury?

Who was the first to point out this fast-moving rocky planet as it sped across the night sky? The answer is that we don’t know. History books don’t credit one single astronomer with discovering the small planet that orbits closest to the heart of our solar system. Writings from as early as 3,000 BC mention it, though it wasn’t seen through a telescope until Galileo spotted it in the 1700s.

What Is Mercury Known For?

Experts recognize the planet named for the messenger of the gods as the smallest celestial body in the solar system. It’s also the one closest to the sun. They also point to it as having the shortest year in our solar system.

What Makes Mercury Unique?

It might not seem like Mercury has any defining features, but there are a couple of aspects that make it unique. For one, the planet is shrinking.

The scarps — geological wrinkles we mentioned earlier — suggest that the planet is shrinking as the core cools. In fact, it may have shrunk by as much as 4.4 miles — 7 kilometers — since it developed 4.5 billion years ago.

In spite of its proximity to the sun, NASA’s Messenger probe discovered water ice on the surface of the planet. Interestingly enough, it’s permanently frozen at the poles. The craters on the north and south poles are shaded from the heat of the sun, allowing the ice to remain frozen.

Mercury and the Future of the Milky Way

Mercury is the smallest planet in the solar system, and it’s possible to spot with the naked eye. However, the proximity doesn’t make it any less impressive. What is your favorite fact about this fast-moving celestial body? Let us know the comments below.

This knowledge is just the beginning of our journey. Stick around for more interesting facts about the rest of this interstellar neighborhood we call home.

Featured Image Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington. Edited version of Image: Mercury in color – Prockter07.jpg by Papa Lima Whiskey.
Interesting Facts About Mercury You Need to Know
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Article by: Megan Ray Nichols

Megan Ray Nichols is a freelance science writer and science enthusiast. Her favorite subjects include astronomy and the environment. Megan is also a regular contributor to The Naked Scientists, Thomas Insights, and Real Clear Science. When she isn't writing, Megan loves watching movies, hiking, and stargazing.