A compelling new study suggests our Moon is significantly older than previously thought, with its youthful appearance masking an ancient origin. Research published in Nature reveals how intense volcanic activity about 4.35 billion years ago effectively reset the Moon’s geological clock, helping resolve a long-standing mystery about the age of Earth’s celestial companion.
Published in Nature | Estimated reading time: 6 minutes
The Moon’s age has long puzzled scientists, with estimates varying by hundreds of millions of years. While most lunar rocks suggest an age of 4.35 billion years, rare zircon crystals hint at a much older origin. Now, researchers have discovered why: a dramatic period of volcanic activity essentially gave our satellite a geological makeover.
According to Francis Nimmo, professor at the University of California Santa Cruz and the study’s lead author, the key lies in understanding the Moon’s early relationship with Earth. “We are particularly interested in the phase when the distance between the Earth and the Moon was about one third of today’s distance,” Nimmo explains. During this period, variations in the Moon’s orbit led to intense internal heating, similar to what we observe today on Jupiter’s moon Io.
The research team, including Professor Thorsten Kleine, Director at the Max Planck Institute for Solar System Research, discovered that this heating was sufficient to remelt most of the Moon’s crust. “The strong volcanism likely reset the Moon’s geological clock,” Kleine notes. “Lunar rocks samples therefore don’t reveal their original age, but only when they were last strongly heated.”
This finding elegantly resolves several puzzling observations about the Moon. For instance, the relatively smooth lunar surface, with fewer impact craters than expected for its presumed age, can now be explained. As Professor Alessandro Morbidelli from the Collège de France points out, “Lava from the Moon’s interior could have filled the early impact basins and thus made them unrecognizable.”
The research positions the Moon’s true age between 4.43 and 4.51 billion years old, with its apparent youthful features resulting from a massive remelting event around 4.35 billion years ago. This discovery aligns better with our understanding of the solar system’s early dynamics, when most planetary bodies were forming through collisions of cosmic debris.
Glossary
- Tidal Heating: A process where gravitational forces between celestial bodies create internal friction and heat, capable of causing significant geological changes.
- Zircons: Heat-resistant crystals of zirconium silicate that can preserve evidence of the Moon’s earliest history.
- Geological Clock: A dating method using radioactive isotopes in rocks to determine their age based on known decay rates.
Test Your Knowledge
What is the currently accepted age range for the Moon?
Between 4.43 and 4.51 billion years old.
How far was the Moon from Earth during its period of intense heating?
About one-third of today’s distance (which is now approximately 384,400 kilometers).
Why do most lunar rock samples show a younger age than the Moon’s true age?
The strong volcanic activity around 4.35 billion years ago reset their geological clock, only revealing when they were last heated rather than their original formation date.
How does tidal heating explain both the Moon’s apparent age and current surface features?
The tidal forces caused widespread remelting that both reset the rocks’ geological clocks and filled in ancient impact basins, creating a smoother surface that appears younger than its true age.
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