External Shape and Internal Structure or What is the Moon Made of?

Within the next two years, NASA, along with other space agencies, is planning to send a manned mission to the Moon for the first time since 1972. However, even though no one has stepped foot on the Moon’s surface for the last fifty years, robotic missions to the Moon have never stopped. Thanks to all those missions, we now know a lot about the external and internal structure of the Moon, which allows us to make tangible plans for the new manned missions. So, what is a moon made of, and what else do we know about the  Moon? Read on to find out.

What is the external part of the Moon made out of?

Before we dig any deeper into the external part of the Moon, let’s recall — what is the physical shape of the Moon? Our satellite is a spherical rocky body with visible dark spots. Initially, many scientists believed that those spots were seas, and even today, they are still officially referred to as ‘seas.’ In practice, they are craters that were presumably formed when meteorites bombarded our natural satellite. Their impact was so strong that many meteorites pierced the Moon’s crust, causing lava eruptions. In freezing conditions, magma quickly solidified, forming a landscape with craters and mountains. But what is this external landscape made of 

Manned missions to the Moon collected many rock samples, which now give us a good idea not only of the Moon’s external shape but also of its mineral composition. Mostly, the external shape is made of basalt, very similar to the basalt we have on Earth. The lunar external shape also has traces of other silicate minerals, such as plagioclases and olivines. External Moon rocks are mostly composed of phosphorus and potassium — rather rare elements back on Earth.

However, the external Moon surface is not exactly bare — it is covered in a layer of dust called regolith. Regolith covers the entire shape of the Moon, sometimes reaching 66 feet in depth. Similar to terrestrial dust, regolith is the remains of external rocks, so abundant on the lunar surface. This external dust is rich in iron and titanium oxide, which is why we can sometimes see the Moon shape casting a reddish or blueish hue. But Orbital Today reports, with reference to Neil Armstrong, that up there, this dust shape always looks coal grey.

That all sound great, but do we know anything about Moon’s internal structure? Thanks to seismic, rotational and gravity studies, we now have a pretty good idea of what’s inside of the Moon.

Internal Structure: Moon’s Mantle & Core

Similar to most celestial bodies, Moon has a mantle and core below its external shape. Based on measurements, scientists believe that there are actually two cores — a liquid outer core and a solid inner one. The solid core mostly consists of iron and should be approximately 240 km in radius. Like most cores, it is also very hot — up to 1400 degrees. This temperature is the reason why there are two cores instead of one — the external iron core melted into liquid iron of an estimated 330 km radius.

Behind lunar cores, there is a mantle, which scientists believe consists of three layers and was formed as a result of magma crystallization. According to this lunar shape theory, dense crystals sank deeper into the ocean of magma, while lighter minerals floated to the external lunar surface, forming its rocky shape as we know it. 

What Do We Know About Moon’s Atmosphere?

Now that you understand lunar external and internal shape, the next logical question is — what about the lunar atmosphere? Many believe it is non-existent, and if we compare the lunar atmosphere to the terrestrial one, such an assumption is not too far off. But technically, our satellite has some sort of thin atmosphere above its external shape. This atmosphere consists of hydrogen, argon, helium, and neon and is incredibly thin — way thinner than a terrestrial one. That is why our natural satellite is so prone to temperature fluctuations — there is simply not enough ‘air coating’ to retain any heat coming from the Sun. And, yes, the Moon gets heated by sunlight — in fact, temperatures on the external sunny side may reach +134 Celsius. In contrast to that, the dark side gets no heat at all and is very cold — minus 150 degrees.

From what you’ve read above, it certainly seems that our natural satellite is in no shape for space tourism right now. Still, as we build bases on the Moon, things may well change. Of course, no one can say now if lunar colonization will ever be viable. But, getting a better understanding of the lunar shape, along with its external and internal resources, may soon answer that question.

Martin Woolridge

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