An Ancient Space Crystal May Have Just Rewritten the History of the Moon

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. 

The scientific community has long thought the Moon formed from the rocky detritus of a catastrophic collision between Earth and a Mars-sized planet in the early solar system. 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. Solving these mysteries is important in part because the Moon exerts enormous influence over Earth, from stabilizing the climate to producing tides, suggesting that it played a key role in the emergence of life on our world. 

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 findings require pushing the timing of the solidification of the lunar crust to within at least the first 100 million years of the formation of the solar system and provide a minimum age for the Giant Impact event that formed the Earth-Moon system,” Greer and her colleagues wrote in the study. 

“This serves as an anchoring age interval for the onset of the intense gravitational effects that the early, much closer Moon had on the young Earth, as well as when the Moon began recording a history of bombardments,” the researchers added. 

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. The ancient collision that created the Moon would have, in turn, occurred several millions years before the formation of these ancient zircon crystals.

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.