Get to know a planet: Mercury
Planets are awesome. Every one is completely unique and has a history of, like, billions of years. There are eight of them in the Solar System. Used to be nine but Pluto was demoted. Actually, some people are now looking at Pluto more like a huge comet than a dwarf planet... woe is Pluto.
But I digress. Planets. Really old, full of stories, stunningly beautiful etc. Just here on Earth are an un-told number of stories: Ice ages, dinosaurs, moving continents, us, asteroid collisions, asteroid near misses, also that time the Toronto Blue Jays won two World Series. Amazing.
As technology progresses we are able to reach out into space and discover the stories of other planets. That's the coolest part. Every dune, every crater, every ridge, valley, mountain or lake tells the story of the planet's past and future.
Of the eight planets here at home we've explored almost all of them remotely. Mercury, Venus, Earth, and Mars (the inner planets) have all been probed, photographed, radar'd, laser'd, and listened to by radio. Some of the outer planets have been explored by robots. One of Saturn's moons (Titan!) was even the target of a surface probe.
Outside of the Solar System astronomers have discovered hundreds of planets orbiting stars in the Milky Way Galaxy. Think of the huge number of stories which take place in those star systems. It's mind boggling.
So, why not get started! Every now and then I'll post a short planet biography starting with the seven nearest to ours. I'm going to ignore Earth since, well, go outside and see it for yourself.
So since today is Wednesday, or "The Day of Mercury" and it is the closest to the Sun, let's start there.
The earliest known observation of mercury was made in the 14 century BC by Assyrian astronomers. Babylonian records from the 1st millennium BC record the planet as 'Nabu', their messenger god.
Greek astronomers knew the planet by two names. Apollo when it could be observed in the morning sky. Hermes when it was seen in the evening sky. They eventually learned that these were the same object.
The Romans gave the planet its modern name; Mercury. Mercury was the name of the Roman messenger god. They chose this name because Mercury was the fastest planet.
The first modern observation of Mercury was made in the 17th century by Galileo.
In 1693 Giovanni Zupi observed orbital phases (like the ones seen on The Moon or Venus) for the first time. This confirmed that Mercury was a planet orbiting The Sun.
Radar observations done in 1962 helped establish the rotation period of Mercury. These observations disproved the long standing belief that Mercury was tidally locked to The Sun as The Moon is to The Earth.
Due to Mercury's position so close to the sun observation from The Earth is extremely difficult. Little was known about mercury besides size, rotation, location and temperature until the advent of interplanetary spacecraft.
Mariner 10 was the first spacecraft to visit Mercury. Not designed to enter orbit around Mercury Mariner made three flybys before running out of power.
Images of Mercury provided by Mariner were the first to show details on the surface. However, because of Mariner's trajectory the same part of the surface was seen on all three flybys. In total only 45% of the surface of Mercury was imaged.
During the first flyby Mariner 10 discovered that Mercury had a magnetic field similar to Earth's magnetic field. This discovery surprised scientists because early models had not predicted that Mercury would have a magnetic field.
Mariner 10 also discovered that Mercury possesses a very thin atmosphere of helium as well as an iron core.
After Mariner 10 no other spacecraft would visit mercury until the MESSENGER probe arrived in 2008.
Like Mariner 10, MESSENGER will make three flybys of Mercury. Unlike Mariner 10, MESSENGER will enter orbit around Mercury and collecting data for one Earth year.
During its three flybys MESSENGER has imaged most of the parts missed by Mariner 10. The map of Mercury is now 97.7% complete.
Once in orbit the probe will look for evidence that the planet has shrunk as the core solidified. It will also provide maps detailing what material Mercury is made of, a 3-D model of Mercury's magnetosphere, a 3-D map of the northern hemisphere, and a characterization of the volatiles in permanently shadowed craters at the poles.
Mercury is both the innermost and smallest planet in the Solar System.
Voted least memorable and least notable... by me.. after writing this article. Just kidding... kind of.
Travel Facts
When making travel plans to Mercury these figures may come in handy.
Mean Radius: 2,439.7 km +/- 1 km
Escape Velocity: 4.25 km/s
Average Orbital Speed: 47.87 km/s
Inclination to Sun's Equator: 3.38°
Semi-Major Axis: 57,909,100 km
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