The Moon Is Older Than We Thought, And It Could Have Formed As Early As 4.53 Billion Years Ago
The moon is much older than we thought, according to a new analysis conducted by researchers from the United States, France, and Germany.
It is possible that Earth’s companion formed as early as 4.53 billion years ago, which is hundreds of millions of years earlier than scientists have estimated in the past.
This could answer other questions about the moon, such as why it has less metal than Earth and why there aren’t as many large impact basins as expected.
In a new study, the research team shows how a massive event may have reset the ages of nearly all lunar rocks, misleading scientists into believing that Earth’s moon is younger than it actually is. The moon’s exact date of birth is still unclear and will probably stay that way for a while.
The moon is said to have formed during the early days of the solar system. The sun formed around 4.6 billion years ago.
Back then, it was surrounded by a disk of gas and dust that developed into rocks that crashed into each other. Scientists think the moon formed when a large object named Thea collided with a baby Earth.
A huge portion of Earth’s mass would have been ejected into space and become trapped in orbit around Earth. Then, it cooled and condensed, coming together to create the moon we all know and love today.
After its formation, the moon was thought to have been home to a magma ocean that quickly cooled and hardened into the lunar surface.
Based on lunar samples that were collected during NASA’s Apollo missions, this is estimated to have happened around 4.35 billion years ago.
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But a recent reanalysis of the lunar samples has revealed tiny structures called zircon crystals. They are significantly older than the rest of the sample material.
During their formation, zircon crystals incorporate uranium but reject lead. Over time, the radioactive uranium decays into lead.
Scientists can examine the ratios of uranium to lead in zircon crystals and accurately determine how long ago the zircon formed.
Interestingly enough, the zircon crystals from the moon were dated at ages much higher than 4.35 billion years. One was estimated to be 4.46 billion years and another at 4.51 billion years.
The researchers created computer models to explain why the crystals are older than the lunar rocks. The moon likely experienced a remelting event, which caused the lunar surface to turn into molten rock before cooling again. Thus, the crystals were formed in the rocks.
“When these materials were heated, their internal clocks were reset to that time,” said Francis Nimmo, the lead author of the study and a planetary scientist at the University of California Santa Cruz. “But some near-surface zircons never got heated up and reset and so retained the older ages.”
The moon could be anywhere between 4.43 billion and 4.53 billion years old. In the future, a true age for the moon could be determined by analyzing more lunar samples. But for now, its age is shrouded in uncertainty.
The study was published in Nature.
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