Mercury Facts for Kids

Closest to the Sun!

Mercury is the closest planet to the Sun, orbiting at only about 36 million miles away! That sounds far, but compared to Earth's 93 million miles, Mercury is practically next door to our star!

The Tiniest Planet!

Mercury is the smallest planet in our solar system! It is only about 3,032 miles across - that is smaller than some moons! Jupiter's moon Ganymede and Saturn's moon Titan are both bigger than Mercury!

Hot AND Cold!

Mercury has the wildest temperature swings of any planet! The sunny side can reach 800 degrees Fahrenheit (hot enough to melt lead!), but the dark side drops to minus 290 degrees! That is a difference of over 1,000 degrees!

No Air at All!

Mercury has almost no atmosphere! Without a blanket of air to trap heat, the planet cannot keep warm on its dark side. That is why one side is boiling hot and the other is freezing cold at the same time!

Super Slow Spinner!

Mercury spins incredibly slowly on its axis! One full spin takes about 59 Earth days. Imagine if one day on your planet lasted almost two whole months - you would have the longest school day ever!

A Weird Year!

A year on Mercury is only 88 Earth days long, but a single Mercury day-night cycle takes 176 Earth days! That means a Mercury day is actually LONGER than a Mercury year! How wild is that!

Craters Everywhere!

Mercury is covered in thousands of impact craters, just like our Moon! Without weather or wind to erase them, craters from billions of years ago are still perfectly visible on the surface today!

The Giant Caloris Basin!

The Caloris Basin is one of the biggest impact craters in the entire solar system! It is about 960 miles wide - big enough to fit the entire state of Texas inside it! A massive asteroid smashed into Mercury to create it!

A Giant Iron Heart!

Mercury has a HUGE iron core that takes up about 85 percent of the planet! If Mercury were an egg, the yolk would be enormous and the shell would be super thin. Scientists think this giant core is why Mercury has a magnetic field!

A Tiny Magnetic Shield!

Mercury has a magnetic field, just like Earth! But it is much weaker - only about 1 percent as strong as Earth's. It is still strong enough to deflect some of the Sun's powerful solar wind away from the planet!

Ice on a Hot Planet!

Believe it or not, there is ICE on Mercury! Deep inside craters at Mercury's north and south poles, the Sun's rays never reach the bottom. These permanently shadowed spots are cold enough to keep water ice frozen forever!

Mercury is Shrinking!

Mercury is actually getting smaller over time! As its giant iron core slowly cools down, the whole planet contracts and shrinks. Scientists have found huge wrinkle-like cliffs on the surface caused by this shrinking!

Giant Wrinkle Cliffs!

Mercury has enormous cliff-like ridges called scarps that stretch for hundreds of miles! These formed as the planet shrank, crinkling its surface like a raisin. Some of these cliffs are over a mile tall!

Named After a Speedy God!

Mercury is named after the Roman messenger god who had winged sandals and flew super fast! The planet got this name because it zips around the Sun faster than any other planet - finishing a lap in just 88 days!

The MESSENGER Spacecraft!

NASA's MESSENGER spacecraft orbited Mercury from 2011 to 2015 and took over 250,000 photos! It discovered ice in craters, mapped the entire surface, and taught us tons about this tiny planet before it crashed into Mercury's surface!

BepiColombo is On Its Way!

A spacecraft called BepiColombo launched in 2018 and is heading to Mercury right now! It is a joint mission between Europe and Japan. It will arrive and start orbiting Mercury to study it up close with brand new instruments!

Double Sunrise!

If you stood on Mercury, you might see the Sun rise, stop, go BACK DOWN, and then rise again! This bizarre double sunrise happens because Mercury's orbit speed changes compared to its slow rotation. It is the weirdest sunrise in the solar system!

The Sun Looks Enormous!

From Mercury's surface, the Sun would look about three times bigger than it does from Earth! It would be blindingly bright and incredibly powerful. You would definitely need the strongest sunglasses in the universe!

No Moons At All!

Mercury has zero moons! It is one of only two planets in our solar system with no moons (Venus is the other). Mercury is so small and so close to the Sun that the Sun's gravity would steal any moon it tried to keep!

Known for Thousands of Years!

People have known about Mercury since ancient times! The Sumerians recorded it over 5,000 years ago. Because it is so close to the Sun, you can only spot Mercury near the horizon right after sunset or just before sunrise!