Planetary scientists analyzing a lunar meteorite known as Northwest Africa (NWA) 12593 have uncovered evidence of an asteroid impact that occurred 3.5 billion years ago on the Moon, helping to reconstruct a period of intense bombardment that left lasting marks across the inner Solar System.
XRF map of 7.53 g slice of NWA 12593: calcium (Ca) and iron (Fe) illustrate the location and diversity of clasts; sulfur (S) highlights the location of cracks and terrestrial weathering. Image credit: Crow et al., doi: 10.1130/G54386.1.
The first few billion years of Earth’s history saw the rise of life, the atmosphere, and the oceans.
Still, that time is shrouded in mystery: not many rocks remain that preserve a record of those early iterations of our modern world.
Dynamic geologic processes like erosion, subduction, and burial mean the surface is constantly being reshaped, and older rocks aren’t very common.
But that time period is critical to understanding our own origins and how catastrophic events like asteroid impacts might have affected early life on the planet.
“On Earth, the first fossil evidence of life shows up around 3.5 billion years ago, meaning that life is emerging and evolving before then,” said Dr. Carolyn Crow, a planetary scientist at the University of Colorado, Boulder.
“The question that we often have, even going back further, is what was the impact record when life was emerging?”
“It is important for understanding how life is taking hold, how life is emerging. The cadence of these catastrophic events is an important part of the equation.”
In an analysis of the NWA 12593 meteorite, Dr. Crow and colleagues found evidence of three different impact events.
The first, which radiometric dating reveals occurred about 3.5 billion years ago, was massive — large enough to turn the surface of the Moon into a sheet of molten material resembling a lava flow and generate a mineral called cubic zirconia that only forms at super-high temperatures.
“Cubic zirconia is commonly manufactured for jewelry, but when the mineral’s cooling isn’t highly controlled in a lab, it doesn’t survive to low temperatures found on the surface of Earth or the Moon,” the researchers said.
“However, we were able to discern traces of the mineral, called cubic zirconia phase heritage, in the samples.”
The second impact event was recorded by the meteorite itself.
It’s a type of rock called a breccia, which formed after a smaller impact that broke up the melt sheet of the first impact.
“Breccias are similar to what you would see if you went and chipped out a chunk of concrete,” Dr. Crow said.
“You would see all these little rocks, and then it’s fused together by the cement.”
“But the meteorite is fused together by the impact process.”
“You get all these chunks of different kinds of rocks that the impact hit into.”
“These all get mixed up, and then it gets fused together like your concrete sidewalk.”
The evidence of the third impact is the meteorite’s presence on Earth.
A more recent collision must have knocked the chunk of breccia off the Moon and on a course toward our planet.
The timing of the first big impact recorded in NWA 12593 lines up with known impacts on Earth and Vesta, the fourth largest asteroid in the asteroid belt.
Finding similarly aged impact events recorded on three celestial bodies is uncommon and the new discovery provides a key link at a time when the Solar System was transitioning from constant collisions during planet formation to more sporadic impacts from the breakup of asteroids.
“It’s not very common, which is why we’re very excited about it,” Dr. Crow said.
“It’s pretty rare to have all three records line up like this.”
The results were published May 12, 2026 in the journal Geology.
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Carolyn A. Crow et al. Three-body evidence of ca. 3.7 Ga to 3.2 Ga bombardment across the inner Solar System. Geology, published online May 12, 2026; doi: 10.1130/G54386.1
