A new study suggests that the moon may be significantly older than previously believed. The research proposes that lunar rock samples from the Apollo missions, previously thought to date back to the moon's formation, actually correspond to an event that melted its surface, not its creation. The study's authors estimate that the moon formed around 4.51 billion years ago, over 100 million years earlier than the commonly accepted timeline of 4.35 billion years.
The study, published in Nature, challenges the long-held view that the moon formed after a Mars-sized object collided with Earth, creating the satellite. This timeline was based on analyses of lunar rocks from the Apollo missions. However, the new study suggests that the moon's formation occurred earlier and was followed by a dramatic "re-melting" event as it was moving away from Earth. This process, caused by Earth's gravitational forces, superheated the moon and altered its surface, effectively masking its true age.
Francis Nimmo, the lead author and a professor at the University of California, Santa Cruz, explained that the intense heating likely reset the clocks in the lunar rocks, meaning they reflect the timing of the later heating event, not the moon’s formation. The moon's precise age has been debated for decades, and this study adds to a growing consensus that there may be more to its history than what the Apollo samples reveal.
One of the key challenges in understanding the moon's age is explaining how such a massive collision could have occurred 200 million years after the solar system’s formation, when large objects were thought to have already coalesced into planets. The new findings also help explain the presence of zircon minerals in Apollo samples, which were previously estimated to be around 4.5 billion years old. The zircon's age had puzzled scientists, as they believed it crystallized from extreme temperatures at the time of the moon’s creation.
Nimmo and his team suggest that tidal heating, a process in which the moon is squeezed and stretched by Earth's gravity, could have caused this super-heating event. This process is similar to what is observed with Jupiter's moons, like Io, which experiences internal heating due to tidal forces.
The study’s conclusions could be further supported by upcoming lunar missions, such as China's Chang’e 6 and NASA's Artemis missions, which aim to gather more data on the moon’s evolution.
Carsten Münker, a scientist from the University of Cologne, who was not involved in the study, agreed that tidal heating offers a plausible explanation for the moon's formation timing. Although the difference between an age of 4.35 billion and 4.51 billion years may seem small, understanding these early events is crucial to understanding how the planets in our solar system formed.
As Münker noted, the rapid evolution of the solar system means that precise dating of its early events is essential to unraveling the history of the Earth-moon system.
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