Bob the Alien's Tour of the Solar System
Bob the Alien's Tour of the Solar System

Ten Facts about Mercury

Mercury from Messenger Space Craft
Image Credit: NASA
Johns Hopkins University Applied Physics Laboratory
Carnegie Institution of Washington

Fact One

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.

Fact Two

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.

Fact Three

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!

Fact Four

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.

Fact Five

Mercury can only be seen just after the Sun has risen and just before the sun sets.

Fact Six

If you were to stand on Mercury, the Sun would appear two and a half times bigger than it appears on Earth.

Fact Seven

Mercury is about 100 times closer to the Sun than dwarf planet Pluto.

Fact Eight

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.

Fact Nine

Despite being the closest planet to the Sun, Mercury is not the warmest. Venus is warmer. In fact, Mercury can be one of the coldest planets in the Solar System

Fact Ten

By the time one year has passed on Pluto (after 248 years), 1028 years have happened on Mercury!

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Mercury Statistics Table

Meaning of NameRoman god of commerce, travel and industry. Its Greek equivalent is Hermes, the messenger of the gods. 
Name in Foreign LanguagesMercure (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 equator4,878 km / 3,031 miles
Comparison with Earth: 12,756 km / 7,926 miles
Diagram showing planet's size compared to the size of Earth Mercury and Earth size comparison
Circumference around equator 15,329.1 km / 9,525.1 miles
Comparison with Earth: 40,074 km / 24,901 miles
Mass330,220,000,000,000,000,000,000 kg
Comparison with Earth: 5,973,700,000,000,000,000,000,000 kg
Time to spin on Axis58 days, 15 hours and 30 minutes
Comparison with Earth: 23 hours, 56 minutes
Time to orbit the Sun88 days
Comparison with Earth: 365 days, 6 hours
Gravity (Earth = 1)0.38
Escape Velocity15,300 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 Temperature427 °c / 801 °F / 700 K
Comparison with Earth: 58 °c / 136 ° F / 331 K
Weather ConditionsThe 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 AtmosphereMercury'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 moonsThere are no known moons orbiting Mercury
Past Missions (including nationality and year of launch) Mariner 10 (USA, 1974), MESSENGER (USA, 2004)
Present MissionsNone
Future MissionsBepiColumbo (Europe, Japan, 2017)

Bob the Alien's Tour of the Solar System
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