A meteorite found in the deserts of northwest Africa is telling a story 3.5 billion years old—one that rewrites our understanding of how catastrophic cosmic violence shaped the inner solar system during Earth's most formative epoch.
The meteorite, catalogued as NWA 12593, arrived on Earth as a lunar fragment, knocked loose from the moon by a more recent impact. But embedded within its structure are traces of three distinct impact events, the oldest of which occurred roughly 3.5 billion years ago, when the moon's surface was blasted so violently that rock melted into sheets resembling lava flows. That cataclysmic impact is the key to unlocking a cosmic mystery: understanding the rhythm of asteroid collisions during the period when life was just beginning to emerge 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," says Carolyn Crow, a planetary scientist at the University of Colorado Boulder who led the study published in Geology. "The question that we often have, even going back further, is what was the impact record when life was emerging?"
By studying NWA 12593, Crow and her team uncovered evidence that solves part of that puzzle. The oldest impact in the meteorite left behind traces of cubic zirconia—a mineral that forms only under the extreme temperatures and pressures generated by massive collisions. On modern Earth, cubic zirconia is synthesized for jewelry, but it cannot survive at the surface temperatures found on our planet or the moon unless conditions are perfectly controlled. Yet Crow's team detected its presence in the lunar sample, a fingerprint of that ancient violence.
The second impact recorded in the meteorite is visible in its very structure. NWA 12593 is a breccia, a type of rock composed of fragments from different sources fused together. "Breccias are similar to what you would see if you went and chipped out a chunk of concrete," Crow explains. "You would see all these little rocks, and then they're fused together by the cement. But the meteorite is fused together by the impact process." A smaller collision shattered the melt sheet left by the first impact, creating the jumbled assemblage of rock fragments preserved in the meteorite today.
What makes this discovery extraordinary is that the 3.5-billion-year-old impact recorded on the moon matches the timing of known impacts on Earth and on 4 Vesta, the fourth-largest asteroid in the asteroid belt. Finding evidence of the same impact event recorded simultaneously on three different celestial bodies is remarkably rare—so rare that Crow calls it "pretty rare to have all three records line up like this." This alignment suggests that the inner solar system experienced a synchronized bombardment roughly 3.5 billion years ago, a period when the solar system was transitioning from the constant collisions of planet formation to the more sporadic impacts that followed.
Understanding this impact record matters because it helps scientists connect catastrophic events to the emergence of life itself. The cadence of cosmic collisions shaped Earth's early environment—altering the atmosphere, oceans, and surface—at the very moment life was taking hold. By reading the story preserved in NWA 12593, researchers are beginning to understand not just where we came from, but how our world was forged in cosmic fire.