The discovery of a lunar meteorite in northwest Africa has shed new light on the early history of the Solar System and the emergence of life on Earth. This meteorite, NWA 12593, contains evidence of three separate impact events on the Moon, each of which has left distinguishable mineralogical signatures in the same small fragment of rock. The oldest and most significant event occurred approximately 3.486 billion years ago, melting the surface of the surrounding lunar region into a flowing sheet of liquid rock and producing cubic zirconia, a mineral form of zirconium dioxide that is also synthesised commercially for use in jewellery.
What makes this discovery particularly fascinating is the fact that it matches independently dated impacts on Earth and on the asteroid 4 Vesta from the same period. This convergence of impact ages on three separate bodies in different parts of the inner Solar System points to a common cause rather than a series of independent coincidences. The most parsimonious common cause, on the available evidence, is the catastrophic breakup of a large asteroid somewhere in the inner Solar System at approximately that time.
This raises a deeper question: what was the relationship between these impacts and the emergence of life on Earth? One view is that large impact events would have been catastrophically destructive to any nascent biosphere, sterilising the surface and forcing life either to retreat into deep subsurface refugia or to begin again after the bombardment subsided. However, another view is that the impacts may have been crucial to the emergence of life rather than hostile to it. Major impacts can produce sustained hydrothermal systems, deliver organic molecules and water from the impactors themselves, and create chemically diverse environments of the kind that prebiotic chemistry models have suggested as plausible sites for the assembly of the first biological molecules.
In my opinion, the discovery of NWA 12593 is a significant step forward in our understanding of the early history of the Solar System and the emergence of life on Earth. It demonstrates the power of reconstructing Earth's earliest history through lunar and meteoritic samples, and it raises important questions about the relationship between impacts and the emergence of life. Personally, I think that this discovery is a reminder of the fragility of life and the importance of understanding the early history of our planet. It also highlights the need for further peer-reviewed work to establish a definitive causal relationship between impacts and the emergence of life.
