13 facts about the swift planet Mercury

| Mercury Facts Table |

Mass (1024 kg ): 


Volume (10km^3): 


Equatorial Diameter (km):


Polar Diameter (km):


Age of the Planet: 

4.5 billion years

Number of Moons: 


Temperature Range (min~ max): 

(- 184 °C ~ 427 °C)

Average Surface Temperature: 

167 °C

Gravity (m/s2):


Oxygen Level (O2)


Carbon Dioxide Level (CO2):


Day Length (hrs):


Average Distance from Sun (106 km):


Closest Distance to Sun (Perihelion) (106 km):


Furthest Distance from Sun (Aphelion) (106 km):


Orbit Distance: 

360.4 million km

Orbiting velocity (km/h):


Time to Orbit the Sun (Orbital Period): 

0.24 Earth year

Actual Color: 

Dark Gray

Atmosphere Thickness:

Very thin

Axial Tilt Angle (degrees):


Magnetic field:


Ring system: 

Not exist

Mercury is a planet that loves to break records. It is only slightly larger than the Moon that orbits Earth – making it the smallest planet in our solar system. Mercury is not only the smallest, but also the fastest planet orbiting the Sun. Noticing the swift pace at which Mercury revolved around the Sun, ancient Romans named the planet after Mercury: the “swift-footed messenger of the gods”.

Mercury is a terrestrial planet that has three main layers: the core, the mantle, and the crust, which has no tectonic plates. Its enormous core makes up around 85% of its total volume and is becoming cooler over time. As a result, Mercury is progressively shrinking in size.

Read on to discover the most interesting facts about the swiftest planet in the solar system: Mercury.

1. Mercury is visible to the naked eye.

Mercury is one of the five bright planets in our solar system that can be seen in the night sky (the full list includes Mercury, Venus, Saturn, Mars, and Jupiter).

The best upcoming dates to view Mercury from Earth are as follows: 

  1.    February 10, 2020 (Mercury Greatest Eastern Elongation): On these dates, Mercury can be best viewed in the western sky just after sunset.
  2.   March 24, 2020 (Mercury Greatest Western Elongation): On these dates, catch a glimpse of Mercury in the eastern sky just before sunrise.

2. If you weigh 100 kg on Earth, you would weigh 38 kg on Mercury.

Weight essentially measures the amount of gravity that acts upon an object. While gravity determines the weight of an object, the weight of an object differs depending upon which planet it is on, as different planets exert different amounts of gravity. Mercury has a gravity of 12.1 ft/s(3.7 m/s2), which is 62% less than the gravity on Earth, which equals 32 ft/s(9.8 m/s2). Thus, the weight of an object would be 0.38 what it would weigh on Earth.

3. Even though Mercury is the closest planet to the Sun, it is not the hottest planet in the solar system.

Mercury is 36 million miles (57.9 million km) from the Sun, which means out of all the planets in our solar system, it is the closest planet to the Sun. The temperature on Mercury can reach 800 °F (427 °C). No doubt, such an exceedingly hot temperature is largely attributable to Mercury’s close proximity to the Sun. Even so, Mercury is not the hottest planet in the solar system. That title belongs to Venus. Even though Venus is 67.3 million miles (108.2 million km) from the Sun, a distance that is almost twice as great than that which occupies the space between Mercury and the Sun, Venus is hotter than Mercury as well as the hottest planet in the solar system.

While Mercury is not the hottest planet in the solar system, this small planet still experiences extreme temperatures and temperature fluctuations. As Mercury has almost no atmosphere, which is necessary for retaining heat and keeping a planet’s surface warm, the temperature of Mercury’s dark side can drop to a bitter minus 300 °F (minus 184 °C). [1]

4. NASA's MESSENGER spacecraft discovered ice in the craters around Mercury’s north pole.

MESSENGER, a NASA spacecraft which was sent into space to investigate the planet of Mercury, made the remarkable discovery of the presence of ice on Mercury’s surface. NASA postulates that this ice could have been delivered to the planet by way of comets and meteorites, or potentially water vapor that traveled outward from the planet’s interior and became frozen upon reaching the planet’s poles.

5. The strength of Mercury’s magnetic field is 1% that of Earth’s magnetic field.

Curious about learning more about how important the magnetic field is to a planet’s existence? Check out “How does the magnetic field protect Earth from dangerous space radiation?

6. Mercury’s surface is full of craters.

Craters and geological features are named after famous deceased authors, artists, or musicians. Mercury’s bountiful supply of craters is the result of numerous collisions with asteroids and comets. Some other planets, like Venus, Earth, and Mars, are able to heal surface damage caused by collisions through the process of erosion, which is accomplished with wind, volcanic activity, and rain. On the contrary, the story is very different for Mercury. With the absence of an atmosphere, the erosion process cannot be initiated and thus, all craters that form on Mercury are permanent.   

7. Mercury doesn’t have moons or rings.

Other than Venus, Mercury is the only planet in the solar system to not have a moon. Moreover, Mercury is also one of the four planets to be lacking a ring system, the other planets being Mercury, Venus, Earth, and Mars.

8. Mercury is the smallest planet in the solar system.

The equatorial diameter of Mercury is 3,032 miles (4,879 km), which makes it only slightly bigger than the Moon, which has an Equatorial diameter of 2,159 miles (3,475 km).

9. Mercury is the fastest planet in the solar system.

Mercury orbits the Sun at a velocity of 29.5 miles/s (47.4 km/s), which is almost 1.6 times faster than Earth. Mercury was named after the Roman god Mercury, who was also referred to as the “swift-footed messenger of the gods”; thus making it the perfect name for the planet which moves across the sky faster than any other planet in our solar system.

10. Mercury is the second densest planet, after Earth, in the solar system.

Though Mercury is the smallest planet in our solar system, it is also one of the densest. Mercury has a density of 339 lbs/ft3 (5,427 kg /m3), which is 98.4% of Earth’s density, making it the second densest planet in the solar system only after Earth. Mercury has a huge metallic core with a diameter that equals 2,577 miles (4,148 km). This enormous core takes up around 85% of the planet’s entire diameter 3,032 miles (4,879 km), and is one of the main reasons why Mercury manages to be so dense even though it is so small.

11. Mercury has a molten core.

Mercury planet layers
Credit: NASA

NASA is able to determine the composition of a planet’s interior layers through studies of both the planet as well as spacecraft behaviors when near to the planet. NASA is quoted as saying, “Start by watching the way the planet spins, then measure how your spacecraft orbits it — very, very carefully.”

Though Mercury’s outer core is a molten core that is composed of liquid metal, NASA theorizes that Mercury’s inner core is solid.

12. Mercury planet is gradually shrinking over time.

13. Recent studies found that Mercury’s surface has dark hue due to the carbon settled from the planet's primordial crust.

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