How Many Moons Does Mercury Have?

Mercury has no moons. This makes this planet special compared with most of the other planets in our solar system, considering it is the closest to the Sun. You may liken it to a lone traveler who zips around the Sun without any company, but basically, that’s what it does.

Mercury’s Size and Orbit

Well, Mercury is the smallest planet in our solar system. Actually, it’s something a bit less than twice the size of the Moon as it appears in the Earth’s skies. But if Earth were a basketball, Mercury would be about one centimeter in diameter made of clay.

Some Key Facts About Mercury’s Orbit:

• Orbital Period: 88 Earth Days (how long it takes to go around Sun)
• Distance From Sun: About 36 million miles 58 million kilometers
• Speed: Orbits the Sun almost 29 miles per second 47 kilometers per second

It is the closest to the sun; hence, it orbits faster than any of the remaining planets, and ancient astronomers thus named it after the Roman god of speed, Mercury. It is not easily viewable in the sky due to its nature, partly covered in the Sun’s glare, although closer observation directly after sunset or just before sunrise, you may be able to catch a sight of it.

Structure and Surface of Mercury

Mercury is a very large iron core rocky planet; it is part of the inside. Because it is hit by quite a number of space rocks, the surface of Mercury has many craters, much like the Moon. One of the most famous craters is named Caloris Basin, which is so large that if you were standing in the middle, you would not have been able to see the edges of it.

More Cool Surface Facts:

• Temperature Extremes: 800°F, –290°F at night
• Surface Features: Craters, cliffs—called scarps—and plains
• Caloris Basin: Over 800 miles in diameter—one of largest impact craters in the solar system

Surface temperatures on Mercury get very hot or very cold because it has almost no atmosphere to regulate its temperature. That means heat from the sun during the day is scorching, and the cold at night.

Time on Mercury

Time’s kinda weird on Mercury. It only takes about 59 days on Earth to complete one whole rotation, so essentially, that makes it only 1 Earth day on the planet. Because it is really fast circling the Sun, however, it used up its year—that’s its orbit around the Sun—in a little less than 88 Earth days.

Morsels of Time:

• Rotation period: 59 Earth days How long it takes to spin on its axis.
• Day length: 176 Earth days From one sunrise to the next.
• Length of year: 88 Earth days-one orbit around Sun That means one whole day on Mercury—from sunrise to sunrise—is about 176 Earth days long. So if you could stand on Mercury, you would see a very long day and a really long night.

Mercury’s Neighbors

Closest to Mercury would be Venus, being the second planet from the sun. Following that would be Earth as the next closest planet to Mercury. Although standing as the most near to the Sun, it is not the hottest — the title belonging to Venus with its thick, heat-trapping atmosphere.

Venus is the second planet from the Sun. The order of planets from the Sun would be as follows : Venus would come right after Mercury, and then there would be Earth.

Thick atmosphere—a great deal of heat: Venus would not be hottest.

Distance to Venus: Varies, can be as close as 31 million miles; 50 million kilometers

Quick History

People have known about Mercury for thousands of years. The Ancient Romans gave the planet its name based on their messenger god, Mercury, because it appears to whiz quickly across the sky. More recently we’ve sent spacecraft like Mariner 10 and MESSENGER to look very closely at Mercury. With these missions we have learned quite a bit about this small, fast, planet.

Historical Highlights:

• Ancient knowledge: Known since ancient times, named by Romans
• Space missions:

Mariner 10: First mission to visit Mercury in 1974-1975

MESSENGER: Orbited Mercury from 2011 to 2015 providing detailed images and data

BepiColombo: Launched in 2018 will arrive at Mercury in 2025 to continue exploration

When was Mercury Formed?

Compared with other planets, our planet Mercury formed some 4.5 billion years ago. It was really messy, that’s how much dust and gas swirled around within the solar system. That material gradually coalesced, over time, into the Sun and the planets. Near the Sun, Mercury formed from the remaining bits and is why it has so much metal in its makeup.

Formation FACTS:

• Age: ~4.5 billion years
• Early solar system: Dust and gas formed it
• Core Composition: Of Mercury’s core, the majority is composed of iron, and of the entire planet, much is iron

Scouting up clues for what Mercury’s formation looked like and evidence regarding the present state of the planet could help decipher how our solar system had formed. Among the eight planets of our Solar System, Mercury stands as a gatekeeper to unravel not only Earth’s past but the entire planetary system orbiting the Sun.

Fun Mercury Facts for Curious Minds

• Compact But Bulky: It has the smallest size but has the most massive core shaft to cover about 85% of the radius of the planet.
• Speed King: Mercury possesses the fastest orbit – able to zip around the Sun in just only 88 days.
• Day and Night: A Mercurian day, or basically the time taken from sunrise to warm up to the next sunrise is 176 Earth days that is longer than its year of 88 Earth days.
• Surface Temperatures: Mercury has got the most extreme temperature variations in the solar system.
• No Moons, No Rings: Mercury has no moons or even rings around it.
• Closest to the Sun: It is indeed the closest planet toward the Sun, but not the hottest.

Well, all the same—a very interesting planet, Mercury has no moons or fanciful rings like most of the other planets. Along with cool facts, there’s a lot of mystery yet left to discover. No matter whether you are that curious kid wanting more or an adult looking to learn more about the universe, this little speedster has much to offer.