Ten Facts about Mercury
Johns Hopkins University Applied Physics Laboratory
Carnegie Institution of Washington
Before the first space-crafts flew to Mercury to take pictures of its surface, some astronomers believed that the planet would have a smooth surface. When Mariner 10 took pictures of Mercury during its flyby of Venus and Mercury in November 1973, scientists discovered that Mercury is the most cratered planet in the Solar System with a surface similar to Earth's Moon.
Mercury has no atmosphere at all. Sunlight reflects off its surface, similar to how light is reflected directly off the Moon's surface. The lack of atmosphere means that sunlight cannot be spread through the atmosphere. The planet's sky is dark, just like the Moon's and, if you were able to stand on the side of the planet not facing the Sun, you would be able to see billions of stars in the sky.
A year on Mercury is only 88 days long, but a full day (from sunset to sunrise) takes 176 days, even though the planet takes 58 days to rotate on its axis. This causes the Sun to rise above the horizon at the beginning of a Mercurian day in the East (as on Earth), then move higher into the sky, move back down towards the horizon at the East, and then quickly move over to the Western horizon to set, after about 60 days!
Mercury (4,878km wide) is slightly bigger than Earth's Moon (3475.6km wide) and is smaller than Ganymede (5,270km) and Callisto (4,890km), two of Jupiter's moons, and Titan (5,150km wide), a moon of Saturn.
Mercury can only be seen just after the Sun has risen and just before the sun sets.
Mercury's speed is caused by the Sun strong gravitational pull. Hold a short piece of string with something tied to the end of it and spin it around. Try it again with a longer piece of string. Notice how much longer it takes for the object tied to the end of it to spin round. Your finger acts like the Sun, and the object acts like a planet orbiting the Sun.
By the time one year has passed on Pluto (after 248 years), 1028 years have happened on Mercury!
View facts about other destinations
Mercury Statistics Table
|Meaning of Name||Roman god of commerce, travel and industry. Its Greek equivalent is Hermes, the messenger of the gods.|
|Name in Foreign Languages||Mercure (French), Mercurio (Spanish), Merkur (German), Merkurij (Russian), Mercurio (Italian), Mercúrio (Portuguese), Mercurius (Latin), Hermes (Greek)|
|Average Distance from the Sun||
57,909,175 km / 35,983,095 miles / 0.387 A.U.
Comparison with Earth: 149,597,890 km / 92,955,820 miles / 1.000 A.U.
|Closest Distance to the Sun (Perihelion)||46,000,000 km / 25,580,000 miles / 0.308 A.U.
Comparison with Earth: 147,100,000 km / 91,400,000 miles / 0.983 A.U.
|Farthest Distance from the Sun (Aphelion)||
69,820,000 km / 43,380,000 miles / 0.467 A.U.
Comparison with Earth: 152,100,000 km / 94,500,000 miles / 1.017 A.U.
|Diameter across equator||4,878 km / 3,031 miles
Comparison with Earth: 12,756 km / 7,926 miles
|Diagram showing planet's size compared to the size of Earth|
|Circumference around equator||
15,329.1 km / 9,525.1 miles
Comparison with Earth: 40,074 km / 24,901 miles
Comparison with Earth: 5,973,700,000,000,000,000,000,000 kg
|Time to spin on Axis||58 days, 15 hours
and 30 minutes
Comparison with Earth: 23 hours, 56 minutes
|Time to orbit the Sun||88 days
Comparison with Earth: 365 days, 6 hours
|Gravity (Earth = 1)||0.38
|Escape Velocity||15,300 km/h / 9,500 mph
Comparison with Earth: 40,248 km/h / 25,009 mph
|Minimum Surface Temperature||-173 °c / -279 °F / 100 K
Comparison with Earth: -88 °c / -126 °F / 185 K
|Maximum Surface Temperature||427 °c / 801 °F / 700 K
Comparison with Earth: 58 °c / 136 ° F / 331 K
|Weather Conditions||The atmosphere on Mercury is almost non-existent, so there is no weather on Mercury. Mercury is prone to meteor impacts as the lack of atmosphere means it isn't protected. The planet's temperature range from the minimum temperature to the maximum is the greatest of all planets in the Solar System, but despite being the closest planet to the Sun, it is not the hottest.|
|Contents of Atmosphere||Mercury's atmosphere is very thin, and is actually created by atoms blasted from the surface from solar wind. These atoms, containing nitrogen and hydrogen, quickly escape into space so a proper atmosphere cannot be formed.|
|Known moons||There are no known moons orbiting Mercury|
|Past Missions (including nationality and year of launch)||Mariner 10 (USA, 1974), MESSENGER (USA, 2004)|
|Future Missions||BepiColumbo (Europe, Japan, 2017)|