The Moon, spinning quietly through space, looks completely different from the world we live in. With the Earth so full of life and color, people have wondered for years what rocks the Moon is made of. It was a mystery for years until man finally landed on the Moon in 1969.
Scientists were blown away by what rocks brought back from Lunar missions told them about our closest neighbor.
Layers of the Moon
Our Moon consists of different layers, each composed of different types of rock.
What Is the Surface of the Moon Made From?
Rocks, Rocks, and More Rocks
Gazing up at our neighbor in the sky, the Moon appears to be a beautiful, white, glowing ball. Pictures from events like the Moon landing give it a much more bland, gray appearance.
A fairy tale from the height of the Middle Ages had children (and maybe some adults) believing that the Moon was made out of cheese.
Truth be told, when the lunar module “Eagle” touched down on the surface of the Moon during the climax of the Apollo 11 mission, they were met with a resounding, rocky thud.
Lunar samples collected from these missions revealed that the rocks of the Moon’s crust are made mostly of oxygen, silicon, iron, calcium, aluminum, and magnesium. These elements are all common on Earth, leading scientists to believe that perhaps once upon a time, the Moon and the Earth were one and the same.
The Moon’s crust is also covered in mare, which is the Latin word for seas. These large dark areas of the Moon (which can even be seen from Earth) were once thought to be water.
Apollo 15 landed at one such sea and revealed that these areas are large expanses of hardened lava that flowed when the Moon was hotter. These solid lava lakes are primarily basalt material.
The Soil on the Moon
Upon landing on the Moon, astronauts also noticed a layer of rocky soil covering the entire surface. This soil, known as regolith, is simply a layer of loose dust and rock covering the surface of a rocky celestial body.
With such a thin atmosphere, the Moon has been subject to countless meteor impacts over its life. Each impact smashed through the Moon’s crust and threw Lunar regolith out from ground zero.
This dust caused a literal stink for astronauts. Lunar regolith was sticky, got everywhere, and astronauts said it smelled of gunpowder.
Astronaut Gene Cernan of Apollo 17 shared his thoughts about it: “I think dust is probably one of our greatest inhibitors to a nominal operation on the Moon. I think we can overcome other physiological or physical or mechanical problems except for dust.”
What Is the Core of the Moon Made From?
Rocky celestial objects were incredibly hot as they took shape during formation many years ago. As gravity pulled them into a spherical (or at least near-spherical) shape, the densest materials are drawn down into the object’s core.
The Moon doesn’t have an abundance of dense materials and is left with quite a small core, at least on the cosmic scale.
No one is one-hundred percent certain what the Moon’s core consists of. Density calculations and orbital patterns lead scientists to believe that the Moon’s core is almost entirely metallic iron with bits of sulfur and nickel thrown in.
Minerals of the Lunar Crust
Through six Apollo missions collecting Lunar samples and countless hours studying the Moon from Earth, scientists have yet to locate anything on the Moon that does not already exist on Earth.
That being said, some minerals are found more commonly on the Moon than on Earth. This probably had something to do with how the Moon formed and cooled over the years.
Only four minerals make up 98% of all the crystalline material located within the Moon’s crust. These minerals are rarely found on the Moon’s surface and instead are typically buried a little deeper.
Interestingly, many of the most common minerals on Earth, such as quartz, calcite, and hematite, have never been discovered on the Moon.
When scientists and meteorite hunters need to determine if a rock found on Earth originated on the Moon, they look for these minerals. Without at least one of these, they are confident the rock did not come from the Moon.
The four most common minerals on the Moon are as follows:
| Mineral | Composition |
| Pyroxene | Magnesium, iron, calcium, and silicon |
| Ilmenite | Iron and titanium |
| Olivine | Magnesium, iron, silicon |
| Plagioclase feldspar | Calcium, sodium, aluminum, silicon |
Of these four minerals, ilmenite with its titanium has the potential to be quite valuable.
The other 2% of known Lunar minerals are made up of the following:
| Mineral | Composition |
| Clinopyroxene | Magnesium, iron, calcium, oxygen, and silicon |
| Orthopyroxene | Magnesium, iron, silicon, oxygen |
| Feldspar | Calcium, sodium, aluminum, silicon, oxygen |
| Anorthite | Calcium, sodium, aluminum, silicon, oxygen |
As you can see, these are all variants of the more common minerals listed above.
What Is the Most Common Rock on the Moon?
Almost all rocks on the Moon are igneous rocks. Igneous rocks, just like on Earth, are formed by the cooling of lava.
The large solid lava seas consist of igneous basaltic lava that now sits silently with their dark complexion. Almost all of the Lunar basalt is on the side of the Moon that we always see. These dark spots help make up the “man on the Moon” that we see.
Anorthosite is an igneous rock that makes up a majority of the Moon’s surface and the Lunar highlands. It is a light material that made its way to the surface as the Moon cooled and has a light color.
Breccia is a Lunar rock that has experienced the full force of a meteor impact. It is known as “shocked rock” and exists primarily in craters.
Differences Between Moon Rocks and Earth Rocks
As mentioned above, the Moon is made up of igneous rock. On Earth, the majority of our rocks are sedimentary in nature.
Sedimentary rocks are formed through the layering of materials that are compressed together over time. Water and wind often play a part in shaping these rocks over considerable periods.
The Earth does have igneous rock, especially in volcanic zones. However, without wind or water on the Moon, there was no chance of sedimentary rock-forming there.
What Have We Learned From Lunar Samples?
The Apollo astronauts brought back over 2,200 separate Lunar samples from each landing site over the six different missions. These rocks weighed in at 842 pounds (382 kilograms).
All those samples ultimately told us a lot about what the Moon is made of. Interestingly, scientists discovered that the oxygen isotopes trapped in lunar rocks match those on Earth.
These findings led to some amazing hypotheses about the origin story of our heavenly neighbor.
With characteristics so close to our own, scientists developed the “Great Impact Hypothesis”. This theory states that a Mars-sized object slammed into Earth during its formation, causing a ring of debris that eventually came together to be our Moon.
To date, this is still the most promising theory about how the Moon formed so long ago.
Scientists are also able to learn about the Moon’s age and how it formed by determining how old those lunar samples are.
How Are Moon Rocks Dated?
The age of Lunar samples are measured by how radioactive materials that occur naturally in Moon rocks have decayed over time. Since some of these materials decay over 100 billion years, scientists are able to trace the decay in these rocks back to the date they would have formed.
This has led to the conclusion that the Moon is older than initially thought, at over 4.5 billion years old.
Final Thoughts
Understanding what the Moon is made of helps us understand more about the origins of our own world. While nothing is yet certain, scientists have come a long way in developing solid theories about how both the Moon and the Earth must have formed.
While the Moon formed much differently than Earth, there are many striking similarities between the two. As scientists continue to study the Moon, time will tell what future discoveries will reveal about our only satellite.