Planetary scientists are examining a lunar meteorite known as North West Africa (NWA) 12593, uncovering crucial evidence of an asteroid impact on the moon dating back 3.5 billion years. This discovery aids in reconstructing the era of catastrophic impacts that significantly shaped the inner solar system.
XRF map of a 7.53 g slice of NWA 12593: Calcium (Ca) and iron (Fe) depicting crust location and diversity. Sulfur (S) indicates cracks and surface weathering. Image credit: Crow et al., doi: 10.1130/G54386.1.
The early billions of years in Earth’s history were pivotal, giving rise to life, an atmosphere, and oceans. However, this period remains largely enigmatic, as few rocks survive that chronicle the early history of our planet.
Dynamic geological processes such as erosion, subduction, and burial continually reform surfaces, rendering older rocks increasingly rare.
This ancient era is essential for understanding our origins and the impact of catastrophic events, like asteroid collisions, on early life on Earth.
“The oldest fossil evidence of life on Earth is about 3.5 billion years old, implying that life must have appeared and evolved prior to that,” stated Dr. Carolyn Crowe, a planetary scientist from the University of Colorado Boulder.
“A critical question we explore is what kind of shock record existed when life began?”
“Understanding how life establishes itself and how it emerges is vital. The cycle of these catastrophic events is a key component of this equation.”
Through their analysis of the NWA 12593 meteorite, Dr. Crowe and colleagues identified three distinct impact events.
The first event, radiometrically dated to approximately 3.5 billion years ago, was large enough to transform the moon’s surface into a molten layer akin to a lava flow, leading to the formation of a mineral known as cubic zirconia, which forms only at extremely high temperatures.
“Cubic zirconia is typically synthesized for jewelry but cannot endure the low temperatures found on Earth and the Moon unless its cooling is meticulously controlled in a laboratory,” the researchers explained.
“Nevertheless, we managed to find traces of a cubic zirconia phase in our samples.”
The second impact event is recorded within the meteorite itself.
This event produced a type of rock called breccia, which formed after a smaller impact disrupted the molten layer from the initial event.
“Breccia resembles what you might see if you chipped away at a block of concrete,” Dr. Crowe explained.
“You can observe all these small stones fused together by cement — akin to how meteorites fusion occurs during impacts.”
“The impact led to a variety of rock fragments blending together like a concrete sidewalk.”
Evidence of the third impact is represented by meteorites found on Earth.
A more recent impact likely dislodged chunks of breccia from the Moon, setting them on a trajectory toward our planet.
The timing of the first major impact documented by NWA 12593 aligns with known impacts between Earth and Vesta, the fourth largest asteroid in the asteroid belt.
It is extraordinary for three events of similar age to be recorded, and this new discovery serves as a crucial link to a period when the solar system transitioned from frequent collisions during planet formation to sporadic impacts resulting from asteroid fragmentation.
“Such occurrences are rare, which is why we’re so enthusiastic,” Dr. Crowe remarked.
“It’s uncommon to find three records coinciding like this.”
The study was published in the journal Geology on May 12, 2026.
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Carolyn A. Crowe et al. Three pieces of evidence of approximately 3.7 Ga to 3.2 Ga impact events in the inner solar system. Geology published online on May 12, 2026. doi: 10.1130/G54386.1
Source: www.sci.news
