2023-10-27 08:04:48
Analysis of lunar dust collected by Apollo 17 astronauts in 1972 shows that Earth’s natural satellite was formed at least 4.46 billion years ago. This is 40 million years earlier than previously estimated.
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Astronaut Harrison Schmitt, from the Apollo 17 mission, collects samples from the surface of the Moon.
Photo : NASA/ Johnson Space Center
In a new study published by the Geochemical Perspectives Letters (New window) (in English), cosmochemist Philipp Heck of the University of Chicago and his colleagues used an atom tomographic probe, a high-resolution three-dimensional microscopy instrument, to determine the age of zircon crystals present in the lunar dust.
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A grain of lunar zircon under the microscope.
Photo : Université Northwestern/Jennika Greer
These crystals are among the first materials to solidify during the formation of the Moon, which is believed to have originated from the giant impact of the early Earth and a celestial object probably as massive as the planet Mars.
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Artistic representation of the collision between a protoplanet and Earth.
Photo: Rice University
Zircon is a mineral of choice for dating work since it contains uranium. Atom-by-atom analysis allowed scientists to count the number of atoms in zircon crystals that underwent radioactive decay.
When an atom decays, it sheds protons and neutrons to transform into different elements. In the case of uranium, it turns into lead, explains Professor Heck.
As the duration of this transformation process is well known, the researchers were able to assess the age of the sample by examining the proportion of uranium and lead atoms. This made it possible to estimate the age of the Earth’s natural satellite with a precision never before achieved.
Other samples collected on the Moon will be analyzed in the coming months and could even be older than those studied during the current work.
Landmarks
The big bang, this great formative boom of the Universe, would have occurred 13.78 billion years ago. The oldest star in our galaxy, the Milky Way, would have appeared 13.2 billion years ago. years.The Sun and the Solar System emerged from the collapse of a giant cloud of gas and dust in the Milky Way about 4.5 billion years ago.
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The surface of the Moon as observed by the Galileo probe in 1992.
Photo : NASA/JPL/USGS
A vital partner
Knowing when the Moon formed is an important element in our understanding of the evolution of the planetary system, since the Moon stabilizes the Earth’s axis of rotation. It is also thanks to it that a day lasts 24 hours and that the oceans are governed by the tides.
Life on Earth would be very different without the Moon. It is a central element of our natural system that we want to better understand. Our study adds a tiny piece to the bigger picture, says Professor Heck.
In addition, the Artemis III mission, which is to bring human beings back to the lunar surface by 2025, will be an opportunity to collect more than 25 kg of lunar rock.
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