The Moon is 40 million years older than expected

A study published Oct. 23 in the Geochemical Outlook Newsletter found that the moon is 40 million years older than previously thought, meaning it was formed at least 4.46 billion years ago.

The “origin of the moon” is a very old question. Some scientists believe that in the early days of the evolution of the solar system, a planet the size of Mars collided with the Earth, and the sputtered material orbited the Earth in space, eventually forming the Moon.

When magma on the surface of the moon cools and solidifies, crystals called zircon may form. Because zircon crystals contain radioactive uranium, which decays into lead at a definite rate, scientists can determine its age by measuring the lead and uranium content in lunar rock samples.

The Moon was formed at least 4.46 billion years ago. Image source: NASA

One of the authors of the paper, Professor Philipp Heck of the University of Chicago, reanalyzed the zircon crystals brought back from the moon by the Apollo 17 mission in 1972 using a technique called atomic probe tomography and found that the zircon was 4.46 billion years old. 

“We have now established the history of Zircon, so we can know the fundamental time of the solidification of magma on the surface of the Moon.” “This basically anchors the lunar chronology,” Heck said. ”

In 2021, Heck’s team used a mass spectrometer to analyze a sample of moonrock and found that the sample was old, but the technique could not determine whether the lead in the sample came from radioactive decay or was accidental.

Today, atom probe tomography allows for detailed analysis of the composition and location of atoms, which can help prove that the lead in lunar rock samples is indeed from radioactive decay. The researchers used lasers to evaporate atoms from the surface of crystals that have been sharpened to very fine “nanoscale tips” to examine the ratio of uranium to lead atoms.

Mahesh Anand, a professor at the Open University in the United Kingdom, who was not involved in the study, commented: “The solar system was formed about 4.57 billion years ago, which means that we can determine the formation of the moon with reasonable precision. ”

Previous studies have shown that the particular impact that formed the moon occurred 50 million years after the formation of the solar system, so this study will give us a very narrow window of time, Anand said. The formation and solidification of the Moon is very rapid, both occurring within a time window of 50 million years. (Source: Meng Lingxiao, China Science News)

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