Well, we did it. We have eight planets behind us, leaving us with only one more left to explore. Join us as we make our final landing on the 1st planet in the orbital order, as we explore ten amazing facts about the Sun’s closest neighbor - Mercury!
Being as vast as it is, it’s difficult to map out the entirety of the solar system, especially without the equipment astrologists have access to today. That’s partially why, during the 19th century, there was believed to be another planet tucked between Mercury and the Sun. French mathematician Urbain Le Verrier noted irregularities to Mercury’s orbit and dedicated the remainder of his life to studying the planet that had since been named “Vulcan.” Mercury’s orbit has a slight wobble to it, one that neither Earth nor Venus could be responsible for, leading to the hypothesis of planet Vulcan. Excitement over planet Vulcan eventually died down with Einstein’s General Theory of Relativity, which, in short, explains the wobble.
Mercury as an Element
The element of Mercury wasn’t named for an overabundance of it found on the planet, though it does have a small connection with the small body. Mercury, also known as quicksilver, is a fast-moving liquid element which was given its name due to its speedy property, much like the planet. Quicksilver remains the only metal still referenced by the alchemical planetary name and shares an alchemical symbol with the astrological symbol for the planet Mercury. The element is known to be very toxic and for years had been used in common household objects like thermometers, black lights, and had also been used - along with silver and tin - to create an amalgam used to fill decayed teeth.
Mercury’s proximity to the sun and large fluctuation in surface temperature may not seem like a problem to us here on Earth, but these two factors are direct reasons why there have only been two missions that have been able to perform flybys of the Swift Planet. On November 3rd, 1973, NASA launched Mariner 10 to fly past Mercury and Venus. On March 29th, 1974, the vessel came within 436 miles or 703 kilometers of the planet’s surface, flying by two more times over the next year and mapping approximately 45% of Mercury’s surface. In 2004, NASA sent MESSENGER to take higher resolution photos of the surface, succeeding with four flybys over the course of three years. In 2018, the ESA and JAXA will be launching BepiColombo to continue monitoring the tiniest planet.
Mercury’s Atmosphere, or lack thereof, is a unique feature to this tiny space-rock. Where most planets are surrounded by a steady atmosphere, Mercury’s small size and a weak gravitational pull makes it nearly impossible to keep a normal atmosphere. The thin layer that isn’t swept away by solar winds is made up of traces of hydrogen, helium, oxygen, sodium, potassium, magnesium and calcium. A lack of any sustainable atmosphere is responsible for Mercury’s strange fluctuation in temperature, which can range from -280° to 800° F or -173° to 427° C. In regards to temperature, the atmosphere acts as a sort of blockade that prevents heat from escaping easily, often causing higher temperatures on the surface. Without this barrier, heat is able to escape, leading to extremely low temperatures.
The Surface of Mercury
Besides the size, there is another major difference between Mercury’s crust and that of Earth’s. As we can feel with earthquakes, the crust of Earth is made up of several plate tectonics that float along the mantle. As these plates move over time, they can drastically alter the surface of the planet. Mercury is without these tectonic movements and, therefore, hasn’t experienced the same change in outward appearance as our home world. A visual of Mercury’s surface will show a speckling of impact craters all over, some of which are well preserved and believed to be billions of year’s old.
Mercury’s Crust, Mantle, and Core
Mercury’s most exterior layer is crust, falling somewhere within a thickness of 60 to 185 miles or 100 to 300 kilometers, making Earth’s puny 20 to 30 mile or 30 to 50-kilometer crust seem flimsy. Beneath that, though, the mantle of Mercury is considerably smaller than our home planet, coming in at 372 miles or 600 kilometers thick compared to Earth’s 1,802 mile or 2,900-kilometer thickness. It is believed that the Swift Planet’s mantle was once much thicker and a great portion of it was lost during the formation of the Solar System.
Your Life on Mercury
It’s always fun to muse what your life would be like on another planet, and even though we’ll never get to know what life on Mercury would be like, there are a few things we can figure out based on the orbital period and gravitational pull. For instance, if you were born in 1993, as of 2016, you would be quite the elder at just under 94 years old, though you would have only lived 141 Mercurian days. Compared to the 23 Earth years and 8,257 Earth days, that is quite a difference. If weight is your concern, you may fall in love with Mercury’s gravitational pull, as a person weighing 200 pounds or 90 kilograms is going to enjoy seeing 75 pounds or 34 kilograms pop up on the scale.
Mercury’s Orbital Pattern
We briefly touched on Mercury’s rapid orbit around the sun, but seeing as how it’s a rather stand-out trait, it deserves more than just a passing glance. Spending just under 88 days on Earth is the equivalent of one orbital period on Mercury, and though it was originally believed that Mercury had a 1:1 ratio of rotations per orbit, Einstein’s General Theory of Relativity showed a different light. Mercury is now known to have a spin-orbit resonance or direct correlation between orbital and rotational periods, and experiences 3 rotations per 2 orbits around the Sun. Mercury’s orbit also bears an eccentricity of .206, making it the 2nd most eccentric, or most elliptical planet, behind Pluto.
The Tiniest of Planets
We’ve covered 9 planets in the solar system and it was bound that one of them would wind up being the smallest. With a diameter of 3,032 miles or 4,879 kilometers, the swift planet is 38% the size of Earth and comes in at 83,850 miles or 134,943 kilometers smaller than the solar system’s largest planet, Jupiter. Since Mercury is so small and its mass is encased in such a tiny space, the planet is 98% the density of Earth, making it the second densest planet in the system.
The Naming of Mercury
If you’ve been following our journey through the solar system, you have likely picked up on a common trend when it comes to naming the planets. Most were derived from a Roman god, Mercury being among them. Observed long before the age of telescopes, it’s difficult to pinpoint who first saw this speeding planet, with mentions of it going as far back as the Late Archaic period, between 2000 and 1001 BCE. During that time, the Babylonians named the planet, Nabu. Due to Mercury’s rapid orbit around the sun, Ancient Greeks gave the planet two names – Apollo, when it was visible in the morning and Hermes, at night, but it was the Roman moniker for the Messenger God, Mercury, that wound up sticking.