Windows Errors? Fix Them Before They Spread
Repair common Windows errors and clear accumulated junk for a smoother, more stable PC - no reinstall needed.Free scan · no reinstallOutdated Drivers Are Slowing You Down
One free scan finds every outdated or missing driver and matches the right update for your exact hardware.Free scan · exact hardware matchiTechGuides is reader-supported. When you buy through links on our site, we may earn an affiliate commission. As an Amazon Associate I earn from qualifying purchases. Learn more
Mercury is the smallest planet in the Solar System and the one with the smallest average distance from the Sun. Its days are unusually long, its daytime surface is extremely hot, and it is not the hottest planet: that title belongs to Venus. Mercury has no moons and no rings, and it may hold water ice, but only in a few permanently shadowed craters near its poles.
Mercury at a glance
The values below come from NASA Science’s Mercury facts page (reviewed in 2026; the page shows no publication date) and, where noted, from NASA Goddard’s NSSDCA planetary fact sheet. They are the reference figures used throughout this article.
| Measure | Value for Mercury | Source and qualification |
|---|---|---|
| Radius | 2,440 km (1,516 miles) | NASA Science, Mercury facts page |
| Average distance from the Sun | About 58 million km (36 million miles) | NASA Science, Mercury facts page |
| Distance range along its orbit | About 47 million km (29 million miles) to 70 million km (43 million miles) | NASA Science, Mercury facts page |
| One orbit (a Mercury year) | 88 Earth days | NASA Science, Mercury facts page |
| One rotation on its axis | About 59 Earth days | NASA Science, Mercury facts page |
| One solar day (sunrise to sunrise) | 176 Earth days | NASA Science, Mercury facts page |
| Daytime surface temperature | About 430°C (800°F) | NASA Science, Mercury facts page |
| Nighttime surface temperature | About −180°C (−290°F) | NASA Science, Mercury facts page |
| Moons and rings | None known and none reported | NASA Science, Mercury facts page |
| Age | About 4.5 billion years (rounded) | NASA Science educational page; a rounded educational figure, not a new dating measurement |
What Mercury is
Mercury is a rocky world, the innermost of the eight planets. Its radius of 2,440 km makes it slightly larger than Earth’s Moon, and NASA describes it as a little over one-third of Earth’s width. Its surface is heavily scarred by impact craters, much like the Moon’s, and it is the most crater-saturated large body we have studied closely. Because it is so small and so close to the Sun, it is also one of the hardest planets to observe from Earth; it never strays far from the Sun in the sky.
What’s actually slowing this PC down?
Pick the symptom - the matching free tool is one click away.
How far Mercury is from the Sun
Mercury is called the closest planet because its average distance from the Sun is the smallest, at about 58 million km (36 million miles). That average is about 0.4 astronomical units, where one astronomical unit is the average Earth–Sun distance.
#1 Best Overall
- Realistic View of the Swiftest Planet — A scientifically accurate depiction of Mercury, complete with cratered ridges and textured terrain—a tribute to the planet closest to the Sun.
- Solar-Powered Rotation – No Batteries or Wires — Utilizes ambient light and magnetic torque to rotate quietly and continuously. A seamless blend of movement and modern space education.
- Compact Size, Strong Presence – 4.5" in diameter — just larger than a softball — making it ideal for office desks, bookshelves, or gift displays. Measures ~7" tall when mounted.
- Premium Build with Seamless Movement — A fluid-suspended inner globe rotates within a clear acrylic outer shell, offering a smooth, almost magical visual experience.
- Gift for the Curious and the Cosmic — Great for astronomy lovers, educators, space fans, and collectors of planetary objects. A beautiful, kinetic sculpture that sparks curiosity.
Mercury’s orbit is not a circle. It is noticeably elliptical, so the distance changes over each orbit:
- Closest point (perihelion): about 47 million km (29 million miles) from the Sun.
- Farthest point (aphelion): about 70 million km (43 million miles) from the Sun.
The planet is closest to the Sun in average terms, but at certain points in its orbit it is closer than that average, and at others it is farther. The average figure is the one to quote when comparing planets.
How long is a day on Mercury?
The answer depends on what you mean by “day,” because Mercury has two different clocks.
Recommended Free Tools
Rotation: about 59 Earth days
Mercury turns once on its axis in about 59 Earth days. This is the time it takes for the planet to spin fully relative to the distant stars, which is what astronomers call its sidereal rotation period.
Rank #2
- Realistic View of the Swiftest Planet - A scientifically accurate depiction of Mercury, complete with cratered ridges and textured terrain — a tribute to the planet closest to the Sun.
- Solar-Powered Rotation – No Batteries or Wires - Utilizes ambient light and magnetic torque to rotate quietly and continuously. A seamless blend of movement and modern space education.
- Larger Display - Designed to draw focus in room settings like executive offices, museum shelves, or astronomy-themed decor.
- Premium Build with Seamless Movement - A fluid-suspended inner globe rotates within a clear acrylic outer shell, offering a smooth, almost magical visual experience.
- Gift for the Curious and the Cosmic - Great for astronomy lovers, educators, space fans, and collectors of planetary objects. A beautiful, kinetic sculpture that sparks curiosity.
Solar day: 176 Earth days
A solar day is the interval from one sunrise to the next, and it is what most people mean by “a day.” On Mercury that interval is 176 Earth days. The solar day is much longer than the rotation period because Mercury also moves along its orbit during each rotation. Its orbit is quick, at 88 Earth days per year, so by the time the planet has turned once, it has advanced part of the way around the Sun, and the Sun must “catch up” to the same position in the sky.
Why the Sun can seem to misbehave
Because of the orbit’s eccentricity, NASA notes that in some locations on the surface the morning Sun can rise, set briefly, and rise again. The effect is tied to how quickly Mercury moves when it is near the Sun in its orbit, and it occurs only in certain places.
The NSSDCA figures
NASA Goddard’s NSSDCA fact sheet gives the same ideas in hours: a sidereal rotation period of 1,407.6 hours (about 58.65 Earth days) and a length of day of 4,222.6 hours (about 175.94 Earth days). The rounded figures in the table above are the ones to use for general reading; the hour values are useful when a precise number is needed.
Quick wins for a faster PC:
Repair Windows errors before they cause bigger problemsFix Now →Scan for outdated or missing drivers - takes under a minuteDriver Scan →Clear out junk files and repair common Windows errorsFree Scan →Is Mercury the hottest planet?
No. Mercury is the closest planet to the Sun, but it is not the hottest. Venus is. NASA attributes Venus’s higher heat to its dense greenhouse atmosphere, which traps energy at the surface. Mercury has no substantial heat-retaining atmosphere, so its surface cools sharply once the Sun is below the horizon.
Rank #3
- BUILD & DISPLAY A MOVING, GLOWING SOLAR SYSTEM – With this kit, kids can customize all 8 planets and the sun, creating a stunning 3D solar system model that glows in the dark! It’s an awesome addition to any space-themed room.
- ALL-INCLUSIVE KIT – Everything needed to build a glowing solar system is included: 6 vibrant paint colors, glow-in-the-dark accent paint, brush, palette, fun decals, and a poster with solar system facts! Kid-friendly instructions make assembly easy!
- MOVABLE ARMS FOR EASY ADJUSTMENTS – Adjust the position of the planets with ease! The model’s movable arms allow kids to set up and rearrange their solar system display to match their imagination.
- LEARN HANDS-ON FUN FACTS ABOUT OUR SOLAR SYSTEM – Dive into the wonders of space with this engaging model kit! Kids will learn fascinating facts about each planet as they build and explore their own glow-in-the-dark solar system.
- AWARD-WINNING PRODUCTS - Blue Marble, winner of the Toy Association's prestigious Toy of the Year Award, proudly develops products that foster education, imagination, and creativity, with a U.S. support team to ensure a stellar experience!
| Location | Temperature | Source and qualification |
|---|---|---|
| Mercury, daytime surface | About 430°C (800°F) | NASA Science, Mercury facts page |
| Mercury, nighttime surface | About −180°C (−290°F) | NASA Science, Mercury facts page; “may fall” to this range |
| Venus, mean surface | 464°C (867°F) | NASA Science temperature explainer |
The gap between Mercury’s day and night is the most striking thing about its temperature. Venus’s surface, by contrast, stays hot across its whole surface, which is why it holds the record for surface heat even though its average is measured in a different way than Mercury’s day and night extremes.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Surface, interior, atmosphere, and magnetic field
Surface
Mercury’s surface looks like the Moon’s in its dense cratering. The largest impact feature is the Caloris Basin, about 1,550 km (960 miles) across. Mercury also has long cliffs, called scarps, which formed as the interior cooled and the planet contracted.
Core and interior
Mercury has a large metallic core with a radius of about 2,074 km (1,289 miles), roughly 85% of the planet’s radius. NASA says evidence indicates the core is partly molten or liquid. The outer shell, made of mantle and crust, is about 400 km (250 miles) thick.
Free tools Windows power users keep installed
One-click scans. No signup required.
Exosphere
Mercury has a thin exosphere rather than a true atmosphere. Its main constituents, according to NASA, are oxygen, sodium, hydrogen, helium, and potassium. Because there is so little gas, the surface is exposed to the full force of sunlight and solar particles.
Rank #4
- More Than Just A Fidget Toy - The solar system stress balls are fun to play around with. They aren't just squeeze balls for kids. They could also be used to set up as a 3D solar system model to provide an interesting & easy way for children to learn & understand our Universe & space science
- Fun Space Toys For Kids 3-5 - The Sun, Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, Pluto & Moon balls. A set of 11 solar system balls, wall stickers & 12 educational flashcards that comes in a gift box for easy storage
- Stress Relief Ball & Many More - These planet toys for children could also be used as stress balls for adults for stress relief, solar system kit for school science projects, teaching material & space party favors
- STEM Flashcards For Kids Learning Planets - The flash cards provide realistic images & fun facts for kids to learn about each planet & how different they are from each other. It guides your kids to have their first understanding of our solar system & planets in a fun way
- Perfect For Playrooms or Outer Space Theme Parties - Our kids wall decals / stickers beautifully decorate and captivate young space enthusiasts. They could also enhance the charm of themed party decorations
Magnetic field
Mercury has a magnetic field, but it is weak. At the surface it is about 1% as strong as Earth’s, and it interacts with the solar wind, the stream of charged particles flowing from the Sun.
Is there ice on Mercury?
NASA says Mercury may have water ice in deep craters near both poles, but only where the craters are permanently shadowed from sunlight. These spots stay cold enough to keep ice from evaporating. The claim is about these cold, shadowed crater floors. It does not mean the planet’s surface is widely covered in ice, and the word “may” reflects that the evidence is not a confirmed inventory of ice deposits.
Does Mercury have moons or rings?
Mercury has no known moons and no rings, according to NASA’s Mercury facts page. Its gravity and orbit are not associated with any satellites, and no ring system has been reported.
Seasons and the possibility of life
Mercury’s axis is tilted only about 2 degrees relative to the plane of its orbit, so it is nearly upright. It does not experience the seasons most planets have, because no hemisphere is tipped strongly toward or away from the Sun for long periods.
NASA says Mercury’s environment is not conducive to life as we know it, mainly because temperatures and solar radiation are likely too extreme. That is a judgment about conditions across the planet, not a finding that has ruled out every possible niche.
How Mercury has been explored
- Mariner 10 was the first spacecraft to visit Mercury.
- MESSENGER made three flybys, then orbited Mercury for four years. NASA’s feature article on Mercury’s surface dates the mission’s end, an impact with the planet, to April 2015.
- BepiColombo, a joint European and Japanese mission, made its first Mercury flyby in October 2021, according to the same NASA article.
Older NASA coverage anticipated BepiColombo arriving at Mercury in 2025. That date is outdated. The current operational status and arrival schedule should be checked with the European Space Agency’s BepiColombo mission pages rather than taken from older articles.
Quick Recap
Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon at the time of purchase will apply.
Do these 3 things before closing this tab:
1Clear out junk files and repair common Windows errors2Fix the driver behind crashes, sound loss and screen glitches3Repair Windows errors before they cause bigger problems
