On the Moon, We Can Look into the Past

On the Moon, We Can Look into the Past

Author: Kristin Leyerer, Ralf Jaumann

50 years ago, in July 1969, Man set foot on the Moon for the first time. Professor Ralf Jaumann, Head of the Department of Planetary Geology of the Institute of Planetary Research at the German Aerospace Center (DLR), reflects on the scientific outcome of the Moon missions and shares his perspectives on further research on and about the Moon.



The Apollo mission brought back nearly 400 kilos of samples from the Moon. What can Moon rock tell us?

The oldest Moon rocks are about 4.4 billion years old. This means that on the Moon, we can look into the past, back until the origin of the Moon. This is not possible on the Earth, because plate tectonics constantly changes the Earth’s crust. On the Moon, we can understand the thermodynamics around the origin of planets. This can be transferred not only to Earth, but to all planets of the solar system.

The Moon is like a record of the development of the whole solar system. It could be seen that the craters on the Moon are impact craters. In early solar systems, there were a lot of particles, and the older a surface or an area is, the more often it has been hit by them. Basically speaking, an area with many craters is very old and one without craters is very young.

And then there are the samples from the Moon. Every rock contains radioactive elements that decay over time. By looking at the elements and their decay, the age of a rock can be determined precisely. Comparing this with the crater density at the Apollo landing sites provides an absolute clock for the evolution of the Moon. This also works for other areas in the solar system, and the age of Mars, Venus, or other planets can be calculated like this.



What does it tell us about the origin of the Moon?

Moon rock is very much like rock on Earth, nearly identical. Most of the Moon rocks are basalt and look like the basalts found on Earth. But we can go further and look at isotope ratios. They are like a fingerprint of a particular rock, and vary throughout the solar system. But in case of the Moon, it could be seen that oxygen isotopes of Moon rock are identical to oxygen isotopes in Earth rock. This means that the Moon and Earth could have been one system, or that the Moon was formed together with or out of the Earth.



So, is it still unclear how the Moon was formed?

Yes, there still is a discussion about the origin of the Moon. Most scientists agree that it must have been a catastrophic event. But how it happened is still unclear. There are theories that one big body collided with Earth, or many small bodies collided. Moon rock from the inner Moon could help to answer this question.



What else remains unclear?

We do not know much about the interior of the Moon in general. What we know about the interior of Earth is based on seismic measurements. There are thousands of stations all over the Earth, and they record every shaking on the inside. We do not have that on the moon, but the only chance to look at the inside of a planet is seismic measurements. The Apollo missions did such measurements, but only on the near side of the Moon. To know more about the Moon’s inside, we need measurements on both sides simultaneously.

So, from a scientific point of view, these two are the remaining topics: seismics and geochemistry of the Moon’s interior.



Do you think that we will go back to the Moon to answer such questions?

I think that further crewed Moon missions will happen. Not necessarily to gain much more basic scientific knowledge about the Moon, but there are a lot of questions to be answered on the Moon. I think we will have manned stations on the Moon in the future, like those in the Antarctic.



What kind of research could be done on the Moon?

Conditions on the Moon are very different from those on Earth. Think about astronomy: from the far side of the Moon, it is possible to look into the depths of space via radio astronomy, which is not possible from the Earth in the future due to overloading Earth’s orbit with telecommunication smog.

The Moon is not influenced by the magnetic field, which means that the Moon is fully exposed to cosmic and solar radiation. Measurements on the Moon could provide us with a better understanding of the sun. I can imagine that we have a solar observatory on the Moon, which would be like a weather station for measuring the activity of the sun.



Which aspect of the Moon fascinates you most?

The whole Moon in itself. I started my scientific career investigating the Moon, I have observed it using a telescope for weeks. That gives you a special connection.

It still fascinates me that the Earth has such a big Moon. Venus, Mars, and Mercury do not, which supports the idea of a catastrophic event. To me, the Moon is like a sixth continent that belongs to the Earth.



Thank you very much for this interview.

Ralf JaumannRalf Jaumann studied geology at the Ludwig-Maximilian-University of Munich (LMU), Germany, and received his Ph.D. in 1989. His thesis dealt with the chemical and mineralogical composition of lunar surface materials. He joined the German Aerospace Research Center (DLR) in Oberpfaffenhofen, Germany, in 1988 as a scientist at the Institute of Optoelectronics. Since 1994, he is head of the Planetary Geology department of the DLR Institute of Planetary Research in Berlin-Adlershof, Germany. He received his habilitation from LMU in 2003. In 2006, he became professor for planetology at the Free University of Berlin (FUB).

Professor Jaumann’s research focuses on the origin and evolution of planetary surfaces in the solar system with respect to their geology, geomorphology, structure, composition, and stratigraphy as well as interactions with their endogenic and exogenic environment. Main research topics include, but are not limeted to the evolution of the terrestrial planets and the Moon, the role of water and ice with respect to geological surface processes, and the formation of possible habitable zones, e.g., on Mars. He is involved in several solar system exploring missions of the European Space Agency (ESA), the National Aeronautics and Space Administration (NASA), and the Japan Aerospace Exploration Agency (JAXA).

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