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18 Amazing Facts about the Planet Mercury

Named after the Roman god with winged sandals, Mercury is the fastest planet in the solar system, gliding swiftly around the sun. But there’s more to Mercury than speed. Here are 18 fun facts about Mercury that will make you adore the solar system’s smallest planet.

Planetary Facts about Mercury

1. Mercury Is Closest to the Sun

Mercury is closest to the sun, which is why it has the shortest year. It completes its trip around the sun in only 88 Earth days. It’s so near that if you stand on its surface, the sun would appear three times larger, and sunlight would be seven times brighter.

2. Mercury Is the Smallest Planet in the Solar System

It’s only slightly larger than Earth’s moon, making Mercury the smallest planet in the solar system. In fact, it has a radius of 2,440 km (1,516 miles), making Mercury about one-third of the width of the Earth.

3. It’s Also the Fastest

Because it is closest to the sun, it revolves around the sun faster than other planets. In fact, Mercury flies through space at about 180,000 km/h (112,000mph). However, it spins slowly on its axis; one day on Mercury is equivalent to 59 days on Earth.

an image of mercury

4. It Can Be Seen with the Naked Eye

Mercury is one of five planets (alongside Venus, Mars, Jupiter and Saturn) that can be seen without a telescope. Since it’s close to the sun, Mercury can be spotted in the same section of the sky as the sun.

5. Mercury Is the Densest Planet

Although Mercury is small, it has a density that rivals the Earth’s. It’s the second densest planet, right behind Earth. Its large, metallic, partly molten core takes up about 85% of its radius, while its outer shell is solid and rocky, just like the Earth’s.

6. Mercury’s Surface Has Wrinkles

Mercury has long, wrinkle-like ridges on its surface called Lobate scarps. These lines of cliffs indicate that the crust shrunk some time ago. As the planet’s interior cooled, it contracted, causing the crust to adjust to a smaller interior and create the wrinkles.

7. Mercury Is Only the Second Hottest Planet

Although Mercury is the closest to the sun, it’s only the second hottest planet. Its neighbor, Venus, has the highest planetary temperatures in the solar system, thanks to a dense atmosphere that keeps the entire planet warm. Mercury reaches 430°C (800°F), but Venus easily surpasses it at 471°C (880°F).

8. Mercury Has a Weak Atmosphere

The consensus is that Mercury has an atmosphere, albeit a thin and weak one. NASA calls it an exosphere, which is made up of atoms blown off the surface by solar winds and meteoroids. This exosphere is made up of sodium, hydrogen, helium, oxygen and potassium.

9. Mercury’s Temperatures Drop Significantly at Night

Mercury may be the second hottest planet, but it’s a different story when nighttime falls. Because it has a thin atmosphere, it can’t trap any heat from the sun, and temperatures drop to -180°C (-290°F). This is the biggest temperature variance in the solar system.

10. Mercury Has the Most Craters

Because Mercury has a thin atmosphere, nothing stops meteoroids and comets from crashing into its surface. As such, craters are found across the surface of Mercury, which in fact, are named after amazing artists, authors and musicians. Some craters even have crater rays, or bright streaks formed when the vast amounts of energy blast rocks far from the point of impact.

Mercury Facts

11. Mercury Has No Ring or Moons

Because of its relatively weaker gravity and smaller orbit, Mercury doesn’t have moons or rings.

12. Mercury’s Magnetic Field Is Also Weak

Compared to other planets, Mercury’s magnetic field is offset to the planet’s equator. Also, its magnetic field at the surface is just 1% of the Earth’s.

Historical Facts about Mercury

13. No One Knows When Mercury Was Discovered

It seems that Mercury has always been in astronomical charts, as no one knows for sure when it was discovered. The ancient Sumerians acknowledged Mercury as early as 5,000 years ago and associated it with Nabu, the Sumerian god of water and writing.

14. Most People Thought that They Were Observing Two Different Stars

Many ancient peoples across the world believed that they saw two different celestial bodies when they saw Mercury in different positions and times of the day. The celestial body they saw on the east at dawn was different from the star that appeared in the west at dusk. Eventually, it was established as a fact that these two are one and the same planet, Mercury.

Satellite image of Mercury

15. The Greeks Had Two Different Names for Mercury

Unlike other civilizations, the Greeks knew that the two stars they see are just one celestial body. However, they still called Mercury by two names. At dawn, the celestial body is the morning star called Apollo, named after the Greek god of music and prophecy. Then at night, it becomes an evening star called Hermes, named after the Greek god of messengers.

16. Mercury Was Named after the Roman God of Messengers

Because it is the fastest planet, Mercury was officially named after the Roman god of messengers, commerce and communication. According to myth, Mercury wore winged sandals and a winged hat as he sped across the earth and heavens.

17. It Was Recognised as a Planet in 1543

For many centuries, Mercury was thought to be a star or any celestial body other than a planet. When Copernicus published his heliocentric (sun-centred) model of the solar system in 1543, people realized that Mercury was a planet.

18. Some Believed that Mercury Was But the Second Planet from the Sun

In the 19th century, people believed that Mercury wasn’t the closest planet to the sun. Instead, they thought there was another planet in front of Mercury called Vulcan, which allegedly exerted a gravitational influence on Mercury. As the years went on, however, astronomers discovered that such a planet never existed.

Do you know any more amazing facts about Mercury? Share them in the comments below.

And if you’re interested in the space rocks that gave Mercury its famous craters, check out these mesmerizing facts about meteorites.

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This page was last modified on October 21, 2021. Suggest an edit

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