A rare lunar meteorite that fell to Earth provides evidence of a previously unknown “impact event” that shook the Moon about 3.5 billion years ago, researchers say. Studying this ancient effect provides new information about how Solar system was behaving in those early days – around the same time that life began to appear on Earth.
In the new study, scientists looked at a lunar meteorite found in northwest Africa. The meteorite, called NWA 12593, contains information about three separate lunar impacts, but the researchers focused on the earliest of these crashes, the team reported in the journal Geology.
“On Earth, the first fossil evidence of life appears about 3.5 billion years ago, meaning life was emerging and evolving well before that.” Caroline CrowThe study’s first author and a planetary scientist at the University of Colorado Boulder said in a statement. “The question we often have, even going back further, is what was the impact record when life was emerging? This is important for understanding how life is taking off…the rhythm of these catastrophic events is an important part of the equation.”
In the study, scientists used radiometric dating on the meteorite. The method charts the decay rates of radioactive materials in the sample, allowing the team to estimate the first impact 3.5 billion years ago – about 1 billion years after the formation of the Solar System.
The meteorite contained cubic zirconia, which is known on Earth because of its resemblance to diamond. But in ancient meteorites, this material tells a different story: that the moon’s surface melted due to impact, because cubic zirconia forms only at extremely high temperatures. While the material is destroyed at the extremely cold temperatures found on the Moon, scientists found its presence through traces of its recrystallized products.
A large lunar impact crater was discovered by NASA’s Lunar Reconnaissance Orbiter.
(Image credit: NASA/GSFC/Arizona State University)
This impact occurred at approximately the same time as other large impacts, both on Earth and on a much larger asteroid. VestaWhich have been identified in independent research. It is rare to find three impacts on three different worlds so long ago, as erosion and other processes erase the evidence.
“It’s not very common, which is why we’re very excited about it,” Crowe said. “It’s very rare to have all three records together like this.” The team hopes that making deeper comparisons between impacts will reveal how the Solar System was changing 3.5 billion years ago, as impacts reduced the number of asteroids in the neighborhood.
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Scientists often say that the early Solar System was a collection of gas and dust that gradually evolved into smaller, comet-like and asteroid-like bodies. Over time, a subset of those bodies grew even larger (through collisions and accretion) to become today’s planets and moons.
The other two impacts on the meteorite were breccia (rock melt) that formed after a major collision 3.5 billion years ago and a third collision that sent the meteorite on a trajectory away from the Moon and toward Earth.
Crowe, C.A., Erickson, T.M., Economos, R., Lehman-Franco, K., Boyce, J.W., Richards, A.M., Diaz, C.A., Flowers, R.M., Browns, M., Schoen, B., and Benowitz, J.A. (2026). Three-body evidence of ca. The 3.7 Ga to 3.2 Ga bombardment in the inner Solar System. Geology. https://doi.org/10.1130/g54386.1
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