In a revelation that could rewrite the early history of the Moon, a team of scientists have determined that the Moon is about 40 million years older than previously known by studying ancient crystals brought back to Earth by the crew of Apollo 17 half a century ago, according to a new study.
The team determined that a grain of lunar zircon crystals from the Apollo 17 landing site is 4. 46 billion years old. This timeline fits well with earlier predictions about the formation of the Moon, but the study offers new empirical proof that the Moon has been at Earth’s side–and indeed, was likely once a part of it–for almost all of the solar system’s history.
For many years, scientists have believed that the Moon was formed by the debris of an early solar system collision involving Earth and Mars. The crash was so energetic that the infant Moon was covered in a liquid magma ocean for millions of years before it eventually cooled into a solid surface.
While the Moon was likely forged by an ancient dustup, there has been some debate about the timeline of both the collision and the subsequent crystallization of the lunar surface into a solid material. The Moon has a huge influence on Earth. It can affect the weather, produce tides and even stabilize the climate. This suggests that the Moon played an important role in the evolution of life.
Now, a team led by Jennika Greer, a research associate in Earth sciences at the University of Glasgow, has pinned down a new minimum age for the Moon by examining lunar zircon crystals with advanced techniques. The results suggest that these crystals first solidified from a liquid magma ocean about 4. 46 billion years ago, making this zircon “the oldest evidence found to date for lunar zircon crystallization,” according to a study published on Monday in Geochemical Perspective Letters.
“These results require that the time of solidification of lunar crust be pushed back to the very first 100million years after the formation of solar system. They also provide an age minimum for the Giant Impact Event which formed the Earth and Moon system.
“The researchers said that this interval serves as a reference age for the beginning of intense gravitational forces exerted by the Moon’s early closeness on Earth and when it began to record a history bombardments.
Many previous studies have tried to pinpoint the earliest age of the Moon, but Greer and her colleagues were able to build on this work with a sophisticated technique called atom probe tomography.
The process involved whittling down nanoscale samples of lunar dust retrieved from a valley called Taurus-Littrow, where Apollo 17 landed in December 1972, in what was the last mission by humans to the lunar surface. The researchers then fed evaporated particles of dust crystals through a device that could read fine details about their composition. This allowed the team to figure out how much uranium in the sample had decayed into lead over geological timescales, providing a new estimate for the age of the Moon at 4. 46 billion years.
The results push the age of the first preserved lunar crust back by about 40 million years, which implies that the Moon solidified within 110 million years after the birth of the solar system. These ancient zircon-based crystals would have formed several million years prior to the collision which created the Moon.
While scientists are one step closer to understanding the origin of our closest neighbor, the Moon is still full of secrets. In the future, researchers hope to constrain the timeline and nature of the giant Moon-forming collision, and to assess how the fallout of that ancient event contributed to the emergence of life as we know it on Earth today.
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