The Planet Mercury

Out of all the planets in the solar system, the planet Mercury is the closest to the Sun. With a diameter of only 4879 km, it is also the smallest planet in the solar system.

Very little is known about Mercury. We know that the average surface temperature can range anywhere between -292 to 806 F (-180 to 430 C). It is estimated that 42% of Mercury's mass is made up of its core. According to estimates from the flight of the Mariner in 1973 and 1974, Mercury's core is most likely made up of about 60 to 70% iron. The same flight showed that Mercury's crust was very thin, not measuring much more than 100 km. between the core and the crust is about 600 km of mantle.

There are several theories as to how Mercury came to be. One of those theories is similar to how the Earth's moon was formed. According to this theory Mercury at one time had a mass about 2.25 times larger than it is at present. They believe that while our solar system was still young a planetesimal, with a mass around 1/6 Mercury's size, struck the planet. It is said that an impact of that nature would have striped the crust and mantle off of the planet, leaving the core. The planet would then have reformed a new crust and mantle.

Scaring on the surface of Mercury (which is similar to our moon) shows that it has been an "inactive" planet for billions of years. Scientists believe that shortly after Mercury formed itself; it was hit with comets and asteroids for a long period of time which may have ended 3.8 billion years ago.

The atmosphere of Mercury is extremely unstable and is constantly changing. The planets small size keeps its gravity from being able to form a more reliable atmosphere.

Mercury's distance from the Sun is also constantly changing. The distance can range anywhere from 46,000,000 to 70,000,000 km from the Sun. Studies have shown that it takes approximately 88 days for the small planet to orbit completely around the Sun.

Because of its strange orbiting patterns Mercury can be seen from Earth only at certain times of the night. The only two times that you are able to see Mercury from Earth is in the morning and right at evening twilight. More often, it is easier to see Mercury from the Earth's Southern Hemisphere.

The earliest recording of Mercury dates back to the Sumerians and Mesopotamians in 3000 B.C. The Babylonians over 1000 years later called the planet "Nabu" after a god in their religion. To the Greeks it was known as both "Apollo" and "Hermes." The Romans later gave the planet its final name "Mercury" after a swift footed god in their religion.

In the early 17th century a man named Galileo was the first to spy on the planet Mercury through a telescope. More observations were made by Pierre Gassendi in 1631, who was the first to see the transit of the planet across the Sun.

On May 28, 1737 John Bevis observed an occultation (overlapping of two planets as seen by Earth) of Venus and Mercury. This is a rare event and is only known to happen about every couple of centuries. It is estimated that the next occultation between Mercury and Venus will be the year 2133.

Because it is so difficult to observe Mercury, very little is known about the planet. Scientists learn more and more every year, but it's still the planet in our solar system that we know the least about. Maybe with future technologies, we will someday be able to change that.