Mercury Facts

Sit back and get ready for a trip to Mercury!

Okay, we can’t really take you there, but here’s everything you need to know about this amazing planet.

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Mercury Facts for Kids

  • Mercury is 100 million km from Earth
  • It would take you 40 days to get to Mercury from Earth
  • The temperature can drop to minus 300 degrees Fahrenheit
  • It’s the closest planet to the Sun
  • It’s the smallest planet in the Solar System
  • One day on Mercury is almost 59 Earth days
  • It’s named after the Roman god Mercury

What Is Mercury’s Atmosphere Made Of?

The planet Mercury has a unique atmosphere because it is very thin. This is quite different from the protective atmosphere of the Earth. Mercury’s atmosphere also differs from Earth’s atmosphere in composition, what it is made of.

While Earth’s atmosphere is made mainly of oxygen, the atmosphere on Mercury is a combination of oxygen, sodium, hydrogen, helium, and potassium. Helium is the same type of gas you can find in a birthday balloon. Helium is lighter than oxygen, which is why a birthday balloon can float.

Can You Go To Mercury?

Right now, it is impossible for humans to visit Mercury. The main reason we cannot visit is that Mercury is over 60 million miles away. We do not currently have the technology to travel that far in space. Humans have only traveled in space as far as the moon.

That is about 239,000 miles. Another reason humans can’t visit Mercury is that the temperatures on Mercury can reach 800 degrees Fahrenheit. The hottest summer days on Earth are usually only about 90 degrees Fahrenheit. It would be very difficult for a human to enjoy a visit to Mercury.

How Did Mercury Get Its Name?

All of the planets are named after different Roman gods. The Roman gods were mythical characters which the ancient Roman people believed guided the world. Mercury was the Roman god of business and travel.

Mercury received this name because when ancient astronomers were observing Mercury in the sky, they could see that the planet traveled very quickly through space. Naming the planet after the Roman god of travel made good sense.

Each planet in our solar system was given a different name of a Roman god based on characteristics that ancient astronomers observed about the planet.

Can You See Mercury From Earth?

Mercury orbits the Sun within Earth’s own orbit, which means that it can be seen from Earth. The best time to view Mercury is by looking along the Western horizon after sunset or by looking at the Eastern horizon before sunrise.

Identifying planets can be a lot of fun. You can check out books from the library, which will teach you where in the sky to spot each planet during certain times of the year. You can also look for smartphone apps that can help you identify the planets in the night sky as well.

Has Anything Landed on Mercury?

As of today, no spacecraft has actually landed on Mercury. Spacecraft have been sent to Mercury, however. The spacecraft Mariner 10 and Messenger both made trips to Mercury for a fly-by and to spend a little time within its orbit.

Neither of these spacecraft landed on the planet, though. The extreme temperatures of Mercury make it impossible right now for our spacecraft to land.

How Does Mercury Compare to Earth

Mercury differs from Earth in many ways. The most important difference is in temperature. Although the Earth’s temperatures can vary depending on location and times of the year, those variations are still quite mild.

A human can survive at the North Pole in winter or at the hottest spot on the Equator. The temperature variations are not so severe. The temperature variations on Mercury, though, are very severe. Temperatures can move between -279 F to 801 F. These are extreme temperatures.

Another big difference between Mercury and Earth is that Mercury has a very little atmosphere. The Earth has a thick, healthy atmosphere that protects us from the sun’s radiation and debris flying through space. Mercury does not have this. This makes Mercury a very dangerous place to be.

Mercury is also much smaller than Earth. In fact, you could almost fit Mercury inside of Earth 3 times.

How Long Is A Day On Mercury?

Mercury has long days. A day on Mercury would last 58 Earth days. This is how long it takes Mercury to rotate once.

How Far From The Sun Is Mercury?

Mercury orbits in close proximity to the sun. Mercury is only 33 million miles away from the sun. That may sound like a long way, but it is actually rather close when you compare it to the other planets.

For instance, the Earth is 91 million miles from the sun. Mercury’s close location to the sun is one of the reasons why the temperatures are so severe.  

How Long Is A Year On Mercury?

A year on a planet is measured by how long it takes that planet to rotate around the sun. Although Mercury has very long days, they have a very short year compared to Earth. A year on Mercury lasts only 88 days.

The closer a planet is to the sun, the more quickly it will make a rotation. If you lived on Mercury, you could have a birthday party every 88 days!

Is Mercury The Oldest Planet?

Scientists theorize that there actually is no oldest or youngest planet. It is believed that our entire solar system came into existence around the same time, about 4.6 billion years ago.

Why Is Mercury Called The Fastest Planet?

Mercury is called the fastest planet because it makes its way across the night sky very quickly. This was first observed by ancient astronomers. Mercury appears to move quickly in our sky because it is moving quickly through its year rotation around the sun.

Mercury rotates around the sun once every 88 days. The reason Mercury moves so quickly is that it is so close to the sun.

How Cold Is Mercury At Night?

Although Mercury can have very high temperatures during the day, that is not the case at night. When night falls on Mercury, the temperatures plunge to -279 degrees F.

To give you an idea of just how cold this is, the coldest temperature ever recorded on Earth was -128 degrees F. That was in Antarctica in 1983.

Mercury’s nighttime temperatures drop quickly and severely because the planet does not have a strong atmosphere. An atmosphere is very important for keeping heat near the planet’s surface.

You can sort of think of it like a coat you would wear in winter. The coating help’s to keep your body heat near your body. An atmosphere does the same thing. Since Mercury does not have a strong atmosphere, when the planet turns away from the sun, the planet loses all of its heat.

What you need to know about Mercury

  • Mercury is the closest planet to the Sun; wow it must get hot there! It’s also the smallest of the planets in the solar system.
  • Mercury’s surface is barren with a full of craters, that looks a bit like our moon!
  • Are you ready for this? The daytime temperature on Mercury can reach up to 400⁰C. No way, we definitely wouldn’t be able to survive there!
  • But come night time, things change a little. The temperature nose-dives down to -180⁰C.
  • There is no atmosphere all the way up there, so that means no wind or even weather. How weird. There is also no water on the surface of Mercury, but no one knows if there could be water underneath! Maybe one day we’ll find out.
  • Besides having no atmosphere there’s also no air!

Fun Facts about Mercury

Wonder where the word Mercury comes from?

Well in astronomy mythology, Mercury was the Roman version of the Greek god Hermes. He was the messenger for all the other gods.

Wow, he had a tough job on his hands. This is why you often see pictures of Mercury with winged sandals! He was known to deliver messages in super speedy time, just like the speedy rotation of Mercury around the sun.

Do you think you would be heavier or lighter on Mercury?

Take a guess. Well, you’d actually be lighter, sorry it won’t be because you’ve lost weight, but there is hardly any gravity on Mercury. If you weighed 32kg on Earth, you would only weigh about 12kg on Mercury. That’s quite something!

Did you know that it’s called a ‘morning star’?

Well, that’s because it shines in all its brightness earlier in the morning before the sun decides to peek its head out! But it’s not just a morning star; it’s an ‘evening star’ too, as you can sometimes see it late in the evening. Cool huh?

  • Even though Mercury is rather small, it’s really heavy because it has its own special space near the sun. When the sun formed it pushed out all the lighter gas and dust out of the inner solar system, leaving behind only heavy things, which is why Mercury is heavy. It’s sucked up all that heavy stuff the sun didn’t want.
  • It’s mostly made of iron; in fact, it’s like a big iron ball. Don’t want to get in the way of that!
  • The core of Mercury makes up about 75% of the planet! It has a thin crust which is only about 500km to 600km thick.
  • Mercury seems to have aged a little. It has wrinkles! Awesome. Okay not the real kind, but as its iron core cooled it shrunk. This is what caused its wrinkles. How awesome. Scientists call these wrinkles Lobate Scarps. They can be hundreds of kilometers long, and up to 160km high.
  • Not only does Mercury have wrinkles, but it has scars too. Hope it hasn’t been fighting with the other planets! Well, no it hasn’t, it is just covered in heaps and heaps of craters. These have formed from years and years and years of being crashed into by asteroids and comets.

As we know, Mercury has no atmosphere, and any gases that escape, head on out into space. And, as it’s so close to the sun, that even if it had an atmosphere, the sun’s solar winds would just magically blow it away!


Now, this is seriously weird! A year in Mercury is 88 days, yet a day on Mercury is 176 Earth days. But those 88 days are similar to 3 months on Earth.

Over hundreds and even thousands of years, the tidal forces of the sun have slowed down the rotation of Mercury, almost to match its orbit around the sun.

This is cool! As Mercury orbits around the sun at such a speedy pace, early civilizations thought it was two different stars; one which they saw in the morning and another which they saw in the evening.

  • very small when you compare them to the other planets.
  • Mercury was only discovered as a planet it 1543, nobody realized it was a planet; they just thought it was a star.
  • Unlike other planets, Mercury has absolutely no moons, and that’s because of its low gravity and no atmosphere.

Okay, this might shock you…we know that Mercury is one seriously hot place, but there is another planet that is hotter! No way. Well, it’s actually Venus and unbelievably it gets even hotter than Mercury!

Mercury is the ONLY planet that doesn’t rotate exactly once a year.

When young genius Albert Einstein was creating his theory of General Relativity, Mercury gave him heaps of hints and clues to help him along the way!

The center of Mercury has a radius of about 1,800km to 1,900km and scientists think that deep down in there, molten has made its home.

Only 2 spacecraft have ever visited Mercury. Considering that heat, it’s hardly a surprise!

The Mariner 10 visited from 1974 to 1975 and flew past Mercury 3 times, which allowed them to map out its surface. This is unbelievable.

On March 24, 1975, it ran out of fuel and people still believe that’s it’s orbiting the sun. Whoa. The Messenger Probe was sent way up there in 2004 to study everything there is to know about Mercury. There are more trips planned, but who knows if they’ll happen. We’ll have to wait and see.

So keep a lookout for any exciting missions that might be visiting Mercury! Give yourself a pat on the back; you’re official ‘Mercury Smart.’