The Surface & Atmosphere on Mercury

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  • 0:01 Mercury: God & Planet
  • 0:48 Mercury's Surface
  • 2:38 Mercury's Interior
  • 4:04 Mercury's Atmosphere
  • 4:56 Lesson Summary
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Lesson Transcript
Instructor: Artem Cheprasov

Artem has a doctor of veterinary medicine degree.

This lesson will describe the planet Mercury's surface components and how they came to be as the planet formed. It will also go into the planet's interior and atmosphere.

Mercury: God and Planet

The ancient Roman god Mercury was the fleet-footed messenger of the gods. The planet Mercury was appropriately named after him since it is the closest planet to the sun and is the planet that revolves fastest around the sun. How fast? About 107,000 miles per hour! At that speed, you can travel from New York to LA in about 1.5 minutes. No need for the Concord either!

Because of that speed, Mercury makes a full revolution around the sun every 88 days. That would make you four times older on Mercury than on Earth. Mercury looks a lot like our moon, but there are some differences, notably the fact that Mercury is bigger than our moon.

Mercury's Surface

Back in 1974-1975, a U.S. robot called Mariner 10 photographed half of the planet. Analysis of data collected by Mariner 10 showed that the surface of Mercury had large areas that were extensively flooded by lava and heavily cratered thereafter during an ancient bombardment of the planet by meteorites. The largest such crater, Caloris Basin, is 800 miles across!

While large craters do exist on our moon as well, Mercury has something the moon doesn't. A recent visit by the MESSENGER spacecraft revealed interesting-looking raised ridges extending from a crater. The formation was initially given the nickname 'The Spider,' and geologists aren't fully sure of what process caused the spider-like formation to appear.

Images from both the MESSENGER and Mariner 10 also showed that the surface of Mercury has something called lobate scarps, which are long curving ridges upwards of two miles high and 300 miles long. Because these scarps run right through craters, scientists believe they must have formed after the majority of the heavy bombardment of the planet was over, about 3.9 billion years ago.

What happened was, as Mercury's interior cooled and shrank, the crust compressed and formed these types of faults. You can think of this process as 'puckering' of the crust. Take, for example, dried apricots. The drying of the apricot is like the cooling of Mercury. As the apricot dries up, it has all these wrinkles appear that form something analogous to lobate scarps on Mercury.

Mercury's Interior

Now, as for Mercury's interior, it is quite dense and consists of a metallic core. Models show that this metallic core accounts for about 70 percent of the planet's radius, the distance from the center to the outer edge of the planet. Here is why we believe this is so. Mercury initially underwent differentiation, the separation and layering of planetary material according to their chemical and physical properties.

You know those jawbreakers that are multi-layered in color and flavor? Well, as a planet forms and settles, it also separates out into different layers, but not so much based on color and flavor, and more so based on things like density. This process helps explain why some celestial objects, like Mercury, are layered into things like a mantle and a core.

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