Although the moon’s interior structure is difficult to study, scientists believe that it has a small iron core. Surrounding this is a partially molten zone called the lower mantle. Above this lies the mantle, which is made up of dense rock, and the crust, which is also made of rock. Together, the mantle and the crust form the lithosphere, which can be up to 800km (500 miles) thick. There are only two basic regions on the Moon’s surface — dark plains called mania and lighter highlands. These heavily cratered highlands are the oldest parts of the Moon’s crust, dating back over four billion years. The darker plains are craters that were filled with lava.
The composition of the Moon is a bit of a mystery. Although we know a lot about what the surface of the Moon is made of, scientists can only guess at what the internal composition of the Moon is. Here’s what we think the Moon is made of.
Like the Earth, the Moon has layers. The innermost layer is the lunar core. It only accounts for about 20% of the diameter of the Moon. Scientists think that the lunar core is made of metallic iron, with small amounts of sulfur and nickel. Astronomers know that the core of the Moon is probably at least partly molten.
Outside the core is the largest region of the Moon, called the mantle. The lunar mantle extends up to a distance of only 50 km below the surface of the Moon. Scientists believe that the mantle of the Moon is largely composed of the minerals olivine, orthopyroxene and clinopyroxene. It’s also believed to be more iron-rich than the Earth’s mantle.
The outermost layer of the Moon is called the crust, which extends down to a depth of 50 km. This is the layer of the Moon that scientists have gathered the most information about. The crust of the Moon is composed mostly of oxygen, silicon, magnesium, iron, calcium, and aluminum. There are also trace elements like titanium, uranium, thorium, potassium and hydrogen.