The strange lack of shock damage in carbon-containing meteorites has intrigued scientists – until now. New research shows that explosive gases from impacts erase the evidence, not the violence
Unusual clues to carbonaceous meteorite impacts
Understanding what happens when meteorites collide is essential to understanding the history of the solar system. These collisions provide important information about the violent events that shaped planets and other celestial bodies. But a strange observation has long intrigued scientists: Carbon-containing meteorites show much less evidence of high-velocity impacts than carbon-free meteorites. It seems that the collisions of carbon-rich meteorites are somehow more gentle, but the reason for this is still unclear.
Astrophysicist Kosuke Kurosawa says: "I specialize in impact physics and am interested in how the material of meteorites changes in response to impact. So this question really interested me."
|A brilliant but incomplete theory"
Kurosawa revisited an old theory proposed two decades ago by another Japanese researcher. According to the theory, at the time of impact, water-bearing minerals inside meteorites release vapors that blast the evidence of shock waves into space.
"I thought the idea was brilliant, but there are problems with it. For example, they didn't calculate whether this process would produce enough water vapor. And yes, there are meteorites that contain carbon that don't have such water-bearing minerals, so it seems that the shock waves are less strong in them too," he explains.
Kurosawa suspected that the carbon itself might be responsible. To test this, he turned to a special device he had developed: a two-stage light gas gun attached to a sealed sample chamber. This setup allowed him and his team to fire high-velocity pellets into meteorite-like samples—some containing carbon, some not—and analyze the resulting gases. The system prevented contamination from the gases produced by the gun itself—a critical aspect that allowed for clean measurements of what the impact released.
In carbonaceous meteorites, the impacts produce very hot carbon monoxide and carbon dioxide gases (in yellow). Says Kurosawa: "We found that the momentum of the resulting explosion was enough to eject the rocky material that had been subjected to strong shock waves (in red) into space. Such explosions occur in carbonaceous meteorites (left), but not in carbonaceous meteorites (right)." The team therefore concluded that carbonaceous meteorites undergo equally strong shock waves, but the evidence is simply dismissed. Credit: Kosuke Kurosawa
What happens in the hook stays in the hook
But all may not be lost. For larger space rocks like the dwarf planet Ceres, the team calculated that gravity might be strong enough to pull the ejected material back to the surface of the body. “Our results predict that Ceres accumulated material that was subjected to strong shock waves, which created these impacts, so we think this provides guidance for designing the next generation of planetary exploration missions,” Kurosawa explains.
More of the topic in Hayadan:
