How old is the Moon? Study finds it's 40 million years older than we thought

For centuries, the origin of Earth's closest celestial companion, the Moon, has been shrouded in mystery.

However, recent evidence suggests that the Moon may be significantly older than previously believed, shedding light on its enigmatic history.

The prevailing theory regarding the Moon's existence is the "giant-impact theory," which proposes that a Mars-sized planet collided with Earth in the distant past. This cataclysmic event resulted in the ejection of debris, which eventually coalesced to form the Moon.

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To determine the Moon's age more precisely, scientists turned to lunar crystals obtained from the Apollo 17 mission in 1972. These crystals, composed of zircon, are believed to have formed after the colossal impact event since the high-energy collision would have melted any pre-existing crystals.

Radiometric dating and a 40-million-year adjustment

Using radiometric dating, researchers assessed the rate of decay of the atoms within the zircon crystals to estimate their age. Their findings pushed the Moon's age back by a significant 40 million years, revealing it to be at least 4.46 billion years old.

Understanding the Moon's age is more than just a scientific curiosity. The Moon plays a crucial role in our planetary system. It stabilises Earth's rotational axis, resulting in a 24-hour day and governing the tides. Without the Moon, life on Earth would look drastically different. Therefore, uncovering the Moon's history contributes to our broader comprehension of our natural world.

The lunar dust sample

The pivotal lunar dust sample used for this study was collected during the Apollo 17 mission. This sample contained tiny crystals that had formed billions of years ago, serving as time capsules from the Moon's early history.

To fully understand the lunar crystals, scientists employed a cutting-edge technique called atom probe tomography. This process allowed for a meticulous examination of the crystals, revealing their internal composition and the extent of radioactive decay within.

By scrutinising the proportion of different uranium and lead isotopes within the zircon crystals, scientists determined their age. The results pointed to an age of approximately 4.46 billion years, providing a strong indication that the Moon is, at the very least, that ancient.

"I see this as a great example of what the nanoscale, or even atomic scale, can tell us about big-picture questions," study lead author Jennika Greer, a cosmochemist at the University of Glasgow in Scotland told Reuters.

(With inputs from agencies)

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