Couldn't find element LayerAd

Error finding content

Lunar Geology - Windows to the Universe

Shop Windows to the Universe

The Universe at Your Fingertips 2.0 DVD from the Astronomical Society of the Pacific is in our online store, filled with Earth and space science resources.
The two basic types of regions on the Moon: a smooth, dark mare on the left and a heavily-cratered, light-colored highland region on the upper right.

Lunar Geology

Looking up at the Moon, you can distinguish dark regions and light regions. With binoculars, you can even see that the dark regions are smooth compared to the light regions which have many craters.

Dark regions on the Moon are called maria, which is Latin for "seas". Thus, Mare Tranquilatis is the "Sea of Tranquility". Apollo astronauts discovered that these regions are smooth, low-lying plains with relatively few craters. Maria are covered with a type of rock (called basalts) similar to the dark colored rocks formed by lava from volcanoes here on Earth. Basalts are composed of relativley heavy elements such as iron, manganese, and titanium. Radioactive age-dating of these rocks showed them to be between 3.1 and 3.8 billion years old.

Light-colored regions turned out to be heavily-cratered highlands covered with a type of light-colored rock called anorthosite. Anorthosite contains relatively lightweight elements such as calcium and aluminum. This type of rock is found only in the oldest mountain ranges on the Earth, and radioactive age-dating proved the lunar anorthositic rocks were over 4 billion years old.

Once it was known that the light highlands were old and the dark maria younger, scientists could piece together the Moon's history.

Shop Windows to the Universe Science Store!

Our online store includes issues of NESTA's quarterly journal, The Earth Scientist, full of classroom activities on different topics in Earth and space science, as well as books on science education!

Windows to the Universe Community



You might also be interested in:

Traveling Nitrogen Classroom Activity Kit

Check out our online store - minerals, fossils, books, activities, jewelry, and household items!...more

Element (Chemical Element)

An element (also called a "chemical element") is a substance made up entirely of atoms having the same atomic number; that is, all of the atoms have the same number of protons. Hydrogen, helium, oxygen,...more

What are the flat surfaces on the Moon called? What is maria? What are lunar highlands?

What phase was the Moon in on December, 22 1962? How long does it take the Moon to travel from one phase to the next? Suppose that the Moon spun twice on its axis during each orbit around the Earth. How...more


This picture shows a part of the Earth surface as seen from the International Space Station high above the Earth. A perspective like this reminds us that there are lots of different things that cover the...more

Desert Birds

Like the other inhabitants of the desert, birds come up with interesting ways to survive in the harsh climate. The sandgrouse has special feathers that soak up water. It can then carry the water to its...more

The Desert Biome

Deserts are full of interesting questions. How can anything survive in a place with hardly any water? Why is it so dry to begin with? You can find at least one desert on every continent except Europe....more

Desert Insects and Arachnids

You can find insects almost anywhere in the world. So it should be of no surprise that there are plenty of insects in the desert. One of the most common and destructive pests is the locust. A locust is...more

Desert Mammals

There are several species of mammals in the desert. They range in size from a few inches to several feet in length. Like other desert wildlife, mammals have to find ways to stay cool and drink plenty...more

Windows to the Universe, a project of the National Earth Science Teachers Association, is sponsored in part by the National Science Foundation and NASA, our Founding Partners (the American Geophysical Union and American Geosciences Institute) as well as through Institutional, Contributing, and Affiliate Partners, individual memberships and generous donors. Thank you for your support! NASA AGU AGI NSF