Thursday, August 1, 2019

The Moon Is Older Than Previously Thought

A research team from the University of Cologne has redefined the age of the moon with the aid of new geochemical information from rock samples 

Apollo Sample 12054: This sample is an ilmenite basalt collected during the Apollo 12 mission. The stone contains on its surface glass, which has come there by the collision of another basalt stone with a meteor there. Samples like 12054 enable us to reconstruct the history of the moon.

 Credit: Maxwell Thiemens 2019

A new study led by geoscientists at the University of Cologne has narrowed the age of the moon to approximately 50 million years after the birth of the solar system. Our solar system is 4.56 billion years old. The new study thus dates the age of the moon to approximately 4.51 billion years. This means that the moon is much older than previously thought. So far, his age in research has been estimated to be significantly less than 4.5 billion years. To achieve these results, scientists analyzed the chemical composition of a variety of rock samples collected on different Apollo missions. The study "Early Moon formation inferred from hafnium-tungsten systemics" was published in the journal "Nature Geoscience".

On July 21, 1969, humans first landed on another celestial body. The crew of the Apollo 11 mission collected 21.55 kilograms of rock samples in their few hours on the lunar surface and returned them to Earth. 50 years later, researchers will be able to gain new insights into key events in the early solar system and about the evolution of the Earth-Moon system from these samples. The creation of the moon was the last major planetary event after the creation of the earth. An exact determination of the age of the moon therefore also allows conclusions about how and when the earth originated and how it developed at the beginning of the solar system.

In their study, geoscientists studied the chemical signatures of different types of lunar rocks collected during the various Apollo missions. "A comparison of the relative abundance of individual rare elements in the rock shows how the individual samples are related to the Moon's interior and the solidification of the once liquid magma ocean on its surface," says Dr. Raúl Fonseca from the University of Cologne. Together with his colleague In laboratory experiments Felipe Leitzke simulates processes that take place inside the moon.

The moon probably originated as a result of a gigantic collision between a celestial body the size of Mars and the early Earth. Over time, the moon grew out of the material that was thrown into orbit after the collision. The early moon was covered by a liquid magma ocean that formed various types of rocks when cooled. "In these rocks, which can still be found on the lunar surface today, information about the formation of the moon is archived," says dr. Maxwell Thiemens, first author of the study, who until recently did research at the University of Cologne. Co-author dr. Peter Sprung adds, "Such observations are no longer possible on Earth because our planet has been geologically active over time. The moon thus offers a unique opportunity

Based on the relationship between the rare elements hafnium, uranium and tungsten, the Cologne scientists showed how the basalt rock of the mare (black plains on the lunar surface) was formed by melting processes. Thanks to unprecedented measuring accuracy, the Cologne geoscientists discovered that these elements occur in different proportions in the different rock units. They can thus more accurately characterize the behavior of these rare elements in the formation of the moon.

By studying hafnium and tungsten on the moon, geologists can apply a radioactive clock that decays the radioactive isotope hafnium-182 to tungsten-182. This radioactive decay was completely completed after the first 70 million years of the solar system. A combination of this data with the information from laboratory experiments now shows that the moon has already begun to solidify 50 million years after the formation of the solar system. "This age determination shows that the great collision event must have taken place before this time and answers the highly controversial question in science about the exact timing of the formation of the moon," says Professor. Carsten Münker from the Institute of Geology and Mineralogy of the University of Cologne, senior author of the study.

Maxwell Thiemens concludes: "Humanity's first steps on another planet fifty years ago provided samples to help us understand the timing and evolution of the Moon and the origin of the Earth. Since the formation of the moon was the last planetary event after the formation of the earth, we can also use the age of the moon to determine the minimum age of the earth. "

Contacts and sources:
Dr. med. Raúl Fonseca
Institute of Geology and Mineralogy
University of Cologne

Professor Carsten Münker
Institute of Geology and Mineralogy
University of Cologne
Citation: Early Moon formation inferred from hafnium–tungsten systematics.
Maxwell M. Thiemens, Peter Sprung, Raúl O. C. Fonseca, Felipe P. Leitzke, Carsten Münker. Nature Geoscience, 2019; DOI: 10.1038/s41561-019-0398-3

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