Evidence garnered from the analysis of a Martian meteorite has cast new light on the timeline of habitability on the Red Planet, indicating that conditions suitable for life may have emerged millions of years later than prior estimates suggested. This revelation comes from detailed examination of a mineral grain exhibiting the scars of ancient cosmic impacts.
Billions of years ago, our inner solar system experienced a cataclysmic period known as the Late Heavy Bombardment. It was a time marked by intense asteroid activity, pummeling young planets and moons with a fierce barrage of collisions. The timeline of these events is crucial for understanding when planets like Mars might have cooled and settled enough to potentially harbor life.
Aaron Cavosie, from Curtin University in Perth, Australia, along with his team, painstakingly analyzed 66 grains of zircon from the famed Martian meteorite known as Northwest Africa 7034, or “Black Beauty.” “To give you a sense of scale, you could set several of the grains side by side across the width of a human hair,” Cavosie elucidates. These microscopic grains, ranging from 40 to 50 micrometres across, hold within them a record of the planet’s tumultuous past.
Their findings were striking: among the grains studied, one in particular bore the distinctive marks of a violent cosmic event. Researchers described the evidence: “We saw these little planes or lines that we call twins, where the shock pressures were so high that atoms in zircon literally were rearranged into a different direction in the grain.” The level of deformation observed in this zircon grain is remarkably akin to that seen in the three largest impact sites in the world, including Chicxulub crater responsible for the extinction of the dinosaurs.
The research team traced the samples back to approximately 4.45 billion years ago, indicating that the duration of large asteroid impacts lasted 30 million years later than proposed at the end of the asteroid impacts
As a result of these new findings, scientists are now considering the possibility that the emergence of habitable conditions on Mars may have been delayed beyond the previously theorized point of 4.2 billion years ago. The implications of such a shift in the habitability window are profound, suggesting that Mars could have taken longer to cool and stabilize following the bombardment than previously understood.
Cavosie underlines the significance of the discovery, stating, “The process that made this zircon is unique to meteorite impact.” He contends that while additional evidence would be beneficial, even a single grain exhibiting such features is sufficient to suggest a later end to bombardment.
Relevant articles:
– Mars may have been habitable millions of years later than …, New Scientist, Feb 2, 2022
– Infamous Mars meteorite contains organic molecules, but they aren’t proof of life, space.com, Jan 14, 2022
– The Habitable Zone, pbs.org