Recent analysis of lunar crystals brought back by Apollo 17 astronauts has unveiled a surprising revelation: the Moon is significantly older than previously believed. Formerly estimated to be around 4 billion years old, these lunar crystals indicate that the Moon is, in fact, at least 40 million years older, making it approximately 4.46 billion years old. This study, published in Geochemical Perspective Letters, offers a more precise timeline for the Moon’s formation, contributing to our understanding of Earth’s celestial partner.
The Moon’s Formation and Previous Assumptions
The traditional explanation for the Moon’s creation posited that a massive object, roughly the size of Mars, collided with Earth around four billion years ago. This impact led to the Moon’s formation from a fragment of our planet. However, the exact timeline of this event has remained uncertain.
Apollo 17’s Pioneering Role
Apollo 17, launched in 1972, marked the last time humans set foot on the Moon. During this mission, lunar dust was brought back to Earth, containing tiny crystals formed billions of years ago. These crystals provide vital clues about the Moon’s history.
Oldest Known Solids and Anchors for Lunar Chronology
Philipp Heck, a senior author of the study, highlighted the significance of these lunar crystals. They are among the oldest known solids formed post the massive impact and serve as anchors for lunar chronology. By determining their age, scientists can pinpoint when the Moon was formed more precisely.
The Role of Zircon Crystals
Zircon crystals, found within these lunar samples, are essential to determining the Moon’s age. The colossal energy released during the Earth’s collision with the Mars-sized object melted the rock, forming the Moon’s surface. During this molten state, zircon crystals could not form, and any existing crystals would have been melted, erasing their chemical signatures.
Determining the Minimum Age of the Moon
The study explains that the age of zircon crystals establishes the minimum possible age of the Moon. This is because these crystals must have formed after the lunar magma ocean cooled.
Analytical Technique: Atom Probe Tomography
To unlock the age of the lunar crystals, scientists employed atom probe tomography, a powerful microscopy technique revealing three-dimensional atomic arrangements within nanoscale matter. Greer explained that this technique involves sharpening a lunar sample into a fine tip and using UV lasers to evaporate atoms from the tip’s surface. The mass spectrometer then measures the mass-to-charge ratio of these molecules, enabling researchers to discern their composition.
Radiometric Dating for Lunar Age Determination
The researchers found that several atoms inside the zircon crystals had undergone radioactive decay. Radiometric dating relies on understanding the time it takes for atoms to transform due to an unstable configuration of protons and neutrons in their nuclei. For instance, uranium decays into lead, and the duration of these processes is known. By evaluating the proportion of different uranium and lead atoms in a sample, its age can be determined.
Conclusive Age of the Moon
After calculating the proportion of lead isotopes, the researchers concluded that the lunar sample is approximately 4.46 billion years old, unveiling the Moon’s true age. This revelation holds significant importance in understanding Earth’s celestial partner, which influences our planet in various ways.
Significance of Moon’s Age
Knowing the Moon’s age is pivotal, as it plays an essential role in our planetary system. It stabilizes Earth’s rotational axis, determines the length of our day, and influences tides. Understanding the Moon’s age contributes to unraveling the intricate dynamics of Earth’s natural systems, making this study a vital piece in the celestial puzzle.