The moon may have formed tens of millions of years earlier than previously thought –

Analysis of lunar dust collected by Apollo 17 astronauts in 1972 shows that Earth’s natural satellite formed at least 4.46 billion years ago. This is 40 million years earlier than previously thought.

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Apollo 17 astronaut Harrison Schmitt collects samples from the lunar surface.

Photo: NASA/Johnson Space Center

In a new study published by Geochemical Perspectives Letters (New Window), University of Chicago cosmochemist Philipp Heck and his colleagues used an atomic tomography probe, a high-resolution three-dimensional microscopy instrument, to determine the age of zircon crystals present in moon dust .

A lunar zircon grain under the microscope.

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A lunar zircon grain under the microscope.

Photo: Northwestern University/Jennika Greer

These crystals were among the first materials to solidify during the formation of the moon, which is believed to have been formed by the giant impact of the early Earth and a celestial object likely as massive as the planet Mars.

Artist's impression of the collision between a protoplanet and Earth.

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Artist’s impression of the collision between a protoplanet and Earth.

Photo: Rice University

Zircon is a mineral of choice for dating work because it contains uranium. Using atom-by-atom analysis, scientists were able to count the number of atoms in zircon crystals that were subjected to radioactive decay.

When an atom decays, it releases protons and neutrons to transform into different elements. In the case of uranium, it turns into lead, explains Professor Heck.

Since the duration of this transformation process is known, the researchers were able to estimate the age of the sample based on the proportion of uranium and lead atoms. This made it possible to estimate the age of Earth’s natural satellite with unprecedented precision.

Additional samples collected on the Moon will be analyzed in the coming months and may even be older than those examined in the current work.

Sightseeing features

  • The Big Bang, that great formative upsurge of the universe, would have occurred 13.78 billion years ago.
  • The oldest star in our galaxy, the Milky Way, appeared 13.2 billion years ago.
  • The sun and the solar system formed about 4.5 billion years ago from the collapse of a huge cloud of gas and dust in the Milky Way.
The surface of the Moon as observed by the Galileo probe in 1992.

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The surface of the Moon as observed by the Galileo probe in 1992.


An important partner

Knowing when the Moon formed is an important element in our understanding of the evolution of the planetary system because the Moon stabilizes the Earth’s rotation axis. It is also thanks to him that a day lasts 24 hours and that the oceans are determined by the tides.

Without the moon, life on Earth would be completely different. It is a central element of our natural system that we want to better understand. “Our study contributes a small part to the overall picture,” says Professor Heck.

In addition, the Artemis III mission, which is scheduled to return humans to the lunar surface by 2025, offers the opportunity to collect more than 25 kg of lunar rocks.