Author: Simon Rowendaal (Universitat Hamburg, Germany)

A personal reason for me to go into geology was my dream to become an astronaut. I was therefore very excited when in May 2019 the U.S. announced its plan to return to the Moon by 2024. When man will set foot on the lunar surface again, among them will almost certainly be geologists. I hear you think: isn’t it a waste of resources to hurl someone for billions of dollars 384.000 kilometers through the vacuum of space, just to have them look at rocks? Can’t they do that on Earth?

Back in the height of the Cold War, I write 1963, the Americans were working hard on the Apollo program to put mankind on the Moon. It was all about developing the technology to beat the Russians to it. In this haze of rocket- and missile-building, the science got overlooked. It was Max Faget, a director of engineering at NASA’s Manned Spacecraft Center, who uttered the famous words “It wouldn’t look very good if we went to the Moon and didn’t have something to do when we got there.” There is of course a lot you can do on the Moon, but the Moon is basically just a big pile of rocks. There is no mountain chains or oceans, no wind or rain, no atmosphere, no magnetic field, no life. Just lifeless rocks, cratered by meteorite impacts. But it is this lack of everything, which makes it so unique and interesting.

To understand why, I will explain some basic geology to you. Rocks are the natural record of an environment. Take for example a beach. It consists of a lot of sand. The tides of seawater, storms and the blowing wind move over it, laying down more sand on the beach. More and more sand accumulates through time. The previous beach gets buried underneath a new beach. The weight from the new beach above compacts the sand. When we wait long enough, this compaction causes a rock to form, in this case a sandstone. When we find such a sandstone, we can say “Eureka, there was a beach here in the past!” Looking at fossil shells from that beach, we can tell you, for example, how long ago there was a beach there or how warm it was. Thus, looking at rocks is like reading a planet’s history book, whether it is the Moon, Mars or Earth. However, on the surface of the Earth, everything is subjected to wind, water and flowing ice. Rocks break down under these forces. When they do not, they probably are mangled in a mountain building or seafloor subduction process. What this means is that we do not know a lot about our early Earth, because all the rocks from this time are destroyed. On the Moon, all the rocks are still the same since its formation roughly 4.5 billion years ago, cause these rock-destroying processes aren’t there (ignoring the occasional meteorite impact here and there). The Moon therefore represents an incredible archive of rocks that tell us about how the environment was during the formation of the Moon. The Moon itself formed during the very early days in Earth’s history, when an enormous meteorite slammed into our planet and the debris formed our lunar satellite. Therefore, it would also tell a lot about our early Earth and it could even shed light on the conditions that made life possible on Earth. It is this last question that intrigues space agencies and researchers worldwide especially.

Between 1969 and 1972, the astronauts that landed on the lunar surface hauled back with them a total of 380 kg of Moon rocks. In fact, from all the twelve astronauts that set foot on the Moon, eleven were former military test pilots and one was a scientist… you can guess: a geologist. Harrison H. Schmitt was part of the last mission to the Moon, Apollo 17, but was also instrumental in the geological training of the other astronauts. Geologists can’t just drive around and sample everywhere, otherwise it could turn out that the kilograms of rocks that have been dragged back to their lab are all the same. Geologists therefore have to learn how to recognize all different kinds of rocks in the field, but also structures, e.g. the pattern of sand dunes, and how the rocks layers are oriented and what all of this means, to understand what happened to the rocks in the area and what rocks can be found where. Geologists have to be adaptive, while our understanding of an area continually changes with the knowledge we obtain by looking at rocks. We categorize rocks, color maps accordingly and interpret structures while in the field. Often we joke that our field of study could also be called advanced coloring or high-risk puzzling. To acquire such a basic skill in geological mapping it requires extensive training. The best geological mappers on Earth spend years and years on perfecting their skills. Thus, field geology was the single most emphasized type of the astronauts’ scientific training, accounting to hundreds of hours and up to almost 25% of their time. Astronauts trained in all kinds of places that resembled the Moon, like volcanic fields in Iceland or the giant meteor crater in Arizona.

We learned from the past Apollo missions that a sustained program of scientific activities on the Moon brings unique and invaluable scientific results. We visited the Moon fifty years ago, but even now the science continues, as we re-analyze lunar rocks with new perspectives we gained from these very rocks. Through these rocks, we have started to understand our lunar neighbor, but the things we learned opened up deeper questions, even about our own planet. Such questions are only answered with new rocks from geologists that returned to the Moon.


Hodges, K.V., Schmitt, H.H. (2019) Imagining a new era of planetary field geology. Sci. Adv.5, eaaz2484.

Abbany, Z. (2019) Why NASA turned Apollo tough guy pilots to geologists. Retrieved from

Bartels, M. (2019) Before They Go to Space, Astronauts Go to Geology Camp. Retrieved from

Image insert:

Astronauts James A. Lovell Jr. (left) commander, and Fred W. Haise Jr., lunar module pilot, carry out a simulation of a lunar traverse at Kilauea, Hawaii, site.

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s