Scientists have long been baffled by carbon-rich meteorites that show little evidence of violent space collisions. But new experiments reveal the truth: impacts on these meteorites trigger explosive chemical reactions that create intense gases, blasting away the very signs of the collision.
It’s not that these space rocks weren’t hit hard, it’s that the evidence didn’t stick around. This breakthrough not only solves a 30-year mystery but could guide future missions to places like Ceres, where some of that ejected material might still be found.
Unusual Impact Clues in Carbon Meteorites
Understanding what happens when meteorites collide is crucial for piecing together the history of the solar system. These collisions offer valuable clues about the violent events that shaped planets and other celestial bodies. However, scientists have long been puzzled by a curious observation: meteorites that contain carbon show far less evidence of high-speed impacts compared to those without carbon. It’s as if the carbon-rich meteorites somehow experienced gentler collisions, but the reason for this remained unclear.
Astrophysicist Kosuke Kurosawa of Kobe University says, “I specialize in impact physics and am interested in how the meteorite material changes in response to impacts, something called ‘shock metamorphism.’ And so I was very interested in this question.”
A Brilliant but Incomplete Theory
Kurosawa revisited an old theory proposed two decades earlier by another Kobe University researcher. The theory suggested that, during an impact, water-bearing minerals inside meteorites release vapor that blasts away the shock evidence into space.
“I thought the idea was brilliant, but it had problems. For one, they did not perform calculations whether this process would produce enough water vapor. Also, there are carbon-containing meteorites without such water-containing minerals that also seem to be less shocked,” explains the astrophysicist.
Kurosawa hypothesized that carbon itself could be responsible. To test this, he turned to a specialized instrument he developed: a two-stage light gas gun attached to a sealed sample chamber. This setup allowed him and his team to fire high-speed pellets into meteorite-like samples — some containing carbon, some not — and analyze the resulting gases. Crucially, the system prevented contamination from the gases generated by the gun itself, allowing for clean measurements of what the impact released.
Shocking Findings From Impact Experiments
The Kobe University team published their results today (April 24) in the journal Nature Communications. Their experiments revealed that impacts on carbon-containing meteorites cause chemical reactions that produce extremely hot carbon monoxide and carbon dioxide gases.
Kurosawa says: “We found that the momentum of the ensuing explosion is enough to eject the surrounding highly-shocked rock material into space. Such explosions occur on carbon-rich meteorites, but not on carbon-poor ones.” The team thus concluded that carbon-containing meteorites are no less shocked, but that, in fact, the evidence is quite literally blown away.
What Happens on Ceres Stays on Ceres
All may not be lost, however. On larger space rocks such as the dwarf planet Ceres, the team calculated that gravity may be strong enough to pull the ejected material back to the body’s surface. “Our results predict that Ceres should have accumulated highly-shocked material produced by these impacts, and so we believe that this provides a guideline for planning the next generation of planetary exploration missions,” Kurosawa explains.
Reference: “Impact-driven oxidation of organics explains chondrite shock metamorphism dichotomy” by Kosuke Kurosawa, Gareth S. Collins, Thomas M. Davison, Takaya Okamoto, Ko Ishibashi and Takafumi Matsui, 24 April 2025, Nature Communications.
DOI: 10.1038/s41467-025-58474-2
This research was funded by the Japan Society for the Promotion of Science (grant JP19H00726), the Hyogo Science and Technology Association (grant #6077), and the Science and Technology Facilities Council (grant ST/S000615/1). It was conducted in collaboration with researchers from the Chiba Institute of Technology and Imperial College London. This work was supported by ISAS/JAXA as a collaborative program with the Hypervelocity Impact Facility. Numerical computations and analyses were in part carried out on the general-purpose PC cluster and the analysis servers at the Center for Computational Astrophysics, National Astronomical Observatory of Japan.
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