About 66 million years ago, the true identity of the giant meteorite that wiped out the dinosaurs has been revealed by the latest nickel isotope analysis to be an extremely rare "CO chondrite".
This discovery goes beyond simply identifying the type of meteorite; it significantly overturns established theories regarding the mechanisms of the severe climate change that struck the Earth after the impact.
- Identity of the meteorite: An ultra-rare "CO chondrite" formed in the outer solar system, containing almost no water or sulfur.
- The true culprit of global cooling: Not the sulfur from the meteorite, but fine "silicate dust" kicked up from the Earth's crust by the impact.
On this page, we will explain in detail how they tracked down the traces of a meteorite that had vaporized, and what the latest research reveals about the true nature of the "impact winter".
Introduction: The Mystery of the Asteroid That Wiped Out the Dinosaurs and Latest Research
At the boundary between the Mesozoic Cretaceous and Cenozoic Paleogene periods about 66 million years ago, an event occurred in which about 75% of all life on Earth, including dinosaurs, pterosaurs, and ammonites, went extinct. Today, a giant asteroid with a diameter of 10 to 15 km that impacted the Yucatan Peninsula in Mexico (Chicxulub) is considered to be the primary cause of this mass extinction.
This massive meteorite impact caused not only direct destruction but also severe cooling known as an "Impact Winter," as enormous amounts of dust were kicked up, covering the atmosphere and blocking sunlight. This is considered the biggest reason why many organisms went extinct.
What is the K-Pg Boundary:
It is the boundary between the Cretaceous (Kreide) and Paleogene periods. In the strata of this period, elements like iridium, which hardly exist on Earth, are found in abnormally high concentrations, serving as evidence of a giant meteorite impact.
However, despite such clear evidence, the mystery of "what the asteroid was made of and where in the universe it came from" remained unsolved for a long time. This is because most of the impacting meteorite vaporized instantly due to its immense energy, leaving almost no fragments in their original form.
Meanwhile, in July 2026, an international research team led by Georgy V. Makhatadze published a groundbreaking answer to this long-standing mystery in the journal *Science Advances*.
Analytical Method: "Nickel Isotopes" for Tracing Cosmic Origins
Gemini Generated Image
It is extremely difficult to identify the original type of meteorite from a state where it has completely vaporized and mixed with Earth's rocks. Therefore, the research team focused on "isotopes" of the element "nickel (Ni)".
What is an isotope:
Even for the same element, the number of neutrons differs, resulting in slightly different weights. Depending on where in outer space it was formed, a unique difference like a "fingerprint" is created in the ratio of these isotopes.
Nickel is an element abundant in meteorites, and compared to rocks on the Earth's surface, it is found in extremely high amounts in extraterrestrial materials. The research team succeeded in reading the "chemical fingerprint" of the extraterrestrial material by cleanly separating and analyzing only nickel from the stratum samples using an ultra-high precision mass spectrometer (MC-ICP-MS).
Analysis Results: The Identity of the Chicxulub Impactor is an Ultra-Rare "CO Chondrite"
The research team collected K-Pg boundary stratum samples from five different locations in Europe to investigate the extent of meteorite mixing. They then compared them with data from various types of meteorites.
| Sample Location | Country | Estimated Meteorite Content |
|---|---|---|
| Stevns Klint | Denmark | Approx. 5% (Strongest meteorite characteristics) |
| Caravaca | Spain | Approx. 5% |
| Fornaci | Italy | Approx. 1% |
| Frontale | Italy | Approx. 1% |
| Furlo | Italy | Approx. 0.5% (Close to Earth's rock characteristics) |
As a result of comparing and analyzing the collected samples with various meteorites, it was found that the asteroid that impacted was a rare "CO chondrite (Ornans type)" even among carbonaceous chondrites.
What is a carbonaceous chondrite:
A primitive group of meteorites containing water and organic matter. The samples from the asteroid Ryugu brought back by the Japanese spacecraft "Hayabusa2" are also known to belong to this group (CI chondrite).
Among carbonaceous chondrites, CO chondrites are "very dry" meteorites with extremely small amounts of volatile components like water and sulfur. Carbonaceous chondrites themselves make up only about 5% of all meteorites found on Earth, and CO chondrites are just a tiny fraction of those, making them an astronomically ultra-rare meteorite.
The True Culprit of Cooling is Not the Meteorite But "Silicate Dust"
This discovery of an "extremely dry meteorite" overturned conventional wisdom about the climate change mechanisms that triggered the dinosaur extinction.
Where did the massive amount of sulfur come from?
Previously, it was thought that the severe cooling caused by the "impact winter" was because the meteorite itself brought a massive amount of "sulfur" to Earth, which became sulfate aerosols in the atmosphere and blocked sunlight for a long time.
However, if the impactor was a CO chondrite containing almost no sulfur, the amount of sulfur released from the meteorite itself would be far less than expected. In other words, the massive amount of sulfur that caused the climate change did not come from the meteorite, but from the rocks (evaporites like gypsum) in Mexico's Yucatan Peninsula where the meteorite struck, which vaporized due to the immense energy and were released into the atmosphere.
Fine dust (silicate dust) that stopped photosynthesis
So, was sulfur aerosol the only cause of cooling? According to the latest simulation research, it was not the only one.
It has become clear that "silicate dust" kicked up from the Earth's crust by the impact played a crucial role. Because this dust was extremely fine in size, it remained in the stratosphere for up to 15 years. This giant veil of dust completely blocked sunlight, causing the Earth's average temperature to plummet by a maximum of 15°C.
The recent discovery of the "sulfur-poor CO chondrite" provided strong chemical backing for the latest theory that the main culprit behind the cooling and the halt of photosynthesis (collapse of the food chain) was not the meteorite itself, but "fine silicate dust kicked up from the Earth".
Cosmic Romance: Why Did a Rare Outer Solar System Meteorite Strike Earth?
The results of this study also teach us interesting facts about the formation of the solar system and the movement of celestial bodies.
Carbonaceous asteroids like CO chondrites are thought to have formed in a distant, cold place beyond Jupiter's orbit during the early days of the solar system. In fact, other large meteorites that have impacted Earth in the past 500 million years (those that created giant craters) were all rocky asteroids (S-type) born much closer to Earth (in the inner solar system), such as between Mars and Jupiter. About 80% of meteorites falling to Earth today are also this S-type.
Despite this, the fact that an ultra-rare celestial body born beyond Jupiter pinpoint-struck the Earth in a relatively "recent" era of 66 million years ago can be described as an "extremely unlucky coincidence" even from an astronomical perspective.
It is speculated that this asteroid had stayed in a safe orbit for a long time, but for some reason, such as the gravitational influence of Jupiter or a collision with another asteroid, it fell out of orbit and flew toward Earth with a one-in-a-million probability.
Conclusion and Future Prospects
By analyzing microscopic nickel isotopes, this study pinpointed that the true identity of the asteroid that wiped out the dinosaurs was an ultra-rare "CO chondrite".
This strongly supported that the main driver of the climate change that triggered the extinction was not sulfur from the meteorite, but "silicate dust" kicked up from Earth's rocks. They succeeded in connecting an event from over 100 million years ago to cosmic-scale movements from a slight trace at the atomic level.
This new analytical method is expected to be highly useful in the future for investigating the causes of meteorite impacts and mass extinctions that occurred in other eras.
References & Bibliography
- Dinosaurs May Have Been Wiped Out by 'Oddball' Space Rock | Sci.News, https://www.sci.news/space/chicxulub-c0-chondrite-14927.html
- The origin of Cretaceous - Semantic Scholar, https://pdfs.semanticscholar.org/aa18/9299366726d6d8da73cb5b36a905933a6ecb.pdf
- Researchers Identify Class Of Oddball Meteorite That Killed Earth's Dinosaurs - Astrobiology, https://astrobiology.com/2026/07/20/researchers-identify-class-of-oddball-meteorite-that-killed-earths-dinosaurs/
- The origin of Cretaceous-Palaeogene impactor revealed by nickel isotopes - PMC - NIH, https://pmc.ncbi.nlm.nih.gov/articles/PMC13378546/
- Chicxulub impact winter sustained by fine silicate dust | Request PDF - ResearchGate, https://www.researchgate.net/publication/375088454_Chicxulub_impact_winter_sustained_by_fine_silicate_dust
- Ruthenium isotopes show the Chicxulub impactor was a carbonaceous-type asteroid, https://gardenia-buffalo-679m.squarespace.com/s/62_FischerGoddeetal_2024_Science.pdf