The findings suggest that the Moon formed between 4.43 and 4.51 billion years ago, though its crust appears to be 80 to 160 million years younger.
The Moon, our closest celestial neighbor, holds secrets that are gradually being unraveled. A groundbreaking study has revealed that the Moon is significantly older than previously estimated, and its turbulent volcanic history has left profound imprints on its surface and crust.
After its formation, the Moon experienced extreme volcanic activity so intense that its entire crust melted multiple times. This violent period was fueled by the tidal forces exerted when the Moon orbited much closer to Earth than it does today. These forces caused the Moon’s interior to heat up, driving relentless volcanic activity comparable to what we see on Jupiter’s moon Io, the most volcanically active body in the solar system.
A study published in Nature by researchers from institutions including the University of California Santa Cruz and the Max Planck Institute has helped resolve long-standing debates about the Moon’s age. The findings suggest that the Moon formed between 4.43 and 4.51 billion years ago, though its crust appears to be 80 to 160 million years younger.
Decoding the Age Mystery
Determining the Moon’s age has been a persistent challenge. Estimates have ranged from 4.35 billion to 4.51 billion years. Much of the confusion stems from lunar rock samples, which often point to a younger age, while rare zircon crystals—minerals resistant to extreme heat—indicate much older origins.
The new study resolves this discrepancy. Researchers propose that intense volcanic activity after the Moon’s formation reset the “geological clock” of most lunar rocks. When rock is molten, it exchanges isotopes with its surroundings, preventing accurate age measurements. Only when it cools does it lock in its composition, allowing scientists to measure its age based on radioactive isotope decay.
Heat-resistant zircon crystals, however, survived these fiery episodes, preserving evidence of the Moon’s older history. The study reveals that while most of the crust was remelted, some zircons remained insulated beneath the surface, untouched by the lava flows.
The Moon’s Violent Birth and Evolution
The Moon’s story (allegedly) begins with a colossal collision: a Mars-sized body slammed into the young Earth, melting both and ejecting debris into space. Over time, this material coalesced into the Moon, initially covered by a vast ocean of molten rock.
As the Moon cooled, it moved further from Earth, eventually settling into its current orbit of about 384,400 kilometers. During this time, tidal forces from Earth caused the Moon’s orbit to become elliptical, generating immense internal heat that reignited volcanic activity.
This heat melted the Moon’s mantle, churning its crust and creating conditions where molten rock surged to the surface in some areas while remaining trapped below in others. These processes shaped the Moon’s surface and reset the geological record.
Solving Long-Standing Mysteries
The study also addresses other puzzles about the Moon’s history. For instance, the relatively few visible craters on its surface seemed inconsistent with an ancient origin. The researchers suggest that lava flows from its volcanic interior may have filled early impact basins, erasing evidence of these collisions.
Another enigma was the composition of the Moon’s mantle, which differs significantly from Earth’s. The study posits that the secondary melting allowed certain elements to migrate deeper into the Moon’s iron core, altering its composition.
These findings present a cohesive narrative of the Moon’s formation and evolution. “The Moon’s rocks tell a story of formation, destruction, and renewal,” says Thorsten Kleine, one of the study’s co-authors. “What seemed like contradictions now fit into a single, coherent model.”
The Moon’s violent volcanic past not only shaped its crust but also serves as a window into the dynamic processes that govern planetary formation. As researchers continue to analyze lunar samples and data, our understanding of the Moon—and its influence on Earth—will only deepen.
