Scientists used high-precision nickel-isotope analysis to identify the probable type of space rock behind the dinosaur-killing Chicxulub impact. The findings suggest the unusually rare object was a CO carbonaceous chondrite and that impact-generated dust may have played a greater role in the mass extinction than sulfur carried by the asteroid itself.
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The new research identifies the probable meteorite class of the Chicxulub impactor based on preserved chemical evidence. Scientists cannot recover and examine the original asteroid because it was largely vaporized during the collision. The conclusion is therefore strong scientific evidence rather than direct physical identification of an intact object.
Scientists May Have Identified the Dinosaur-Killing Space Rock
Scientists have narrowed the identity of the space rock that struck Earth approximately 66 million years ago and helped bring the age of the non-avian dinosaurs to an end.
The international research team concluded that the Chicxulub impactor was probably a rare CO chondrite, also known as a carbonaceous chondrite of the Ornans group. These primitive meteorites represent only a tiny portion of the space rocks collected on Earth.
Researchers reached the conclusion by studying nickel isotopes preserved in the thin geological layer left behind by the impact. The peer-reviewed study was published in Science Advances on July 17, 2026, while wider science coverage appeared on July 19.
The discovery does not change the central explanation for the extinction. A massive object struck near what is now Mexico’s Yucatán Peninsula, released extraordinary energy, and triggered rapid environmental disruption.
It does, however, give scientists a clearer picture of what that object was made of and how the collision may have transformed Earth’s atmosphere.
What Happened 66 Million Years Ago
Near the end of the Cretaceous Period, an object estimated to have been roughly 10 to 15 kilometers wide collided with Earth at approximately 64,000 kilometers per hour.
The impact created the enormous Chicxulub crater, most of which is now buried beneath the Yucatán Peninsula and the surrounding seafloor. The crater is approximately 200 kilometers across.
The collision released heat, shock waves, earthquakes, fires, debris, and atmospheric material on a planetary scale. Dust and other particles spread around the world, limiting sunlight and disrupting photosynthesis.
Plants and plankton declined. Food webs collapsed. Temperatures changed rapidly, and ecosystems that had developed over millions of years were placed under extreme pressure.
Approximately 75% of Earth’s species disappeared during the Cretaceous–Paleogene extinction event, including all non-avian dinosaurs. Birds survived because they are the living descendants of one dinosaur lineage.
The Asteroid Was Almost Completely Destroyed
Identifying the impactor has been difficult because very little of it survived.
The object struck Earth with enough force to vaporize most of its original material. Scientists cannot travel to the crater and recover a recognizable section of the asteroid in the way they might collect fragments from a smaller meteorite fall.
Instead, researchers must look for chemical traces preserved within the Cretaceous–Paleogene boundary layer.
This thin layer of clay appears at geological sites around the world. It marks the period when debris from the collision traveled through the atmosphere and eventually settled back onto Earth’s surface.
Only a minute portion of the original projectile remains mixed into that layer. Scientists therefore need extremely sensitive methods to separate the asteroid’s chemical signature from surrounding terrestrial material.
Nickel Isotopes Provided the Critical Evidence
The researchers used high-precision measurements of nickel isotopes to investigate samples from the global boundary layer.
Isotopes are different forms of the same chemical element. They contain the same number of protons but different numbers of neutrons.
Different meteorite groups can possess distinctive isotope patterns because they formed under different conditions during the early history of the solar system.
By comparing the nickel-isotope signature in the boundary material with known meteorite classes, the researchers were able to narrow the most likely identity of the Chicxulub object.
The results pointed toward a CO carbonaceous chondrite rather than a more common type of stony meteorite.
This is significant because the remaining asteroid material is extremely limited. Researchers effectively used a chemical fingerprint left in ancient clay to identify an object that disappeared during the collision.
What Is a CO Chondrite?
CO chondrites are part of the broader carbonaceous-chondrite family.
The letters “CO” refer to Ornans, a French location associated with the meteorite group’s classification. The name does not mean the object was made entirely of carbon monoxide.
Carbonaceous chondrites are some of the oldest and least altered materials remaining from the formation of the solar system. They contain minerals and chemical signatures that developed more than four billion years ago.
These meteorites are valuable because they preserve information from a time before planets had fully formed.
Carbonaceous chondrites account for only about 5% of meteorites sampled on Earth. CO chondrites represent only a small fraction of that already uncommon group.
The Chicxulub impact was therefore caused not simply by a large asteroid, but apparently by a particularly unusual member of the solar system’s surviving ancient material.
Why the Meteorite’s Chemistry Matters
Knowing the asteroid’s composition helps researchers understand what happened after it struck Earth.
Different meteorite classes contain different amounts of carbon, sulfur, water, zinc, and other volatile substances. When an object strikes at extremely high speed, these materials can become part of the atmospheric plume generated by the collision.
CO chondrites contain less sulfur and other volatile substances than several other carbonaceous-meteorite groups.
This makes it less likely that sulfur carried inside the asteroid itself was the principal cause of the mass extinction.
Instead, the researchers argue that fine debris generated by the impact may have played the dominant role. The asteroid struck sulfur-containing and carbonate-rich rocks in the Yucatán region, while enormous amounts of pulverized material were launched into the atmosphere.
The distinction helps scientists determine whether the disaster was driven primarily by the incoming object’s composition or by what happened when that object struck a particular location on Earth.
Dust May Have Delivered the Deadliest Blow
A giant collision can launch enormous quantities of dust, soot, vaporized rock, and chemical aerosols into the atmosphere.
When these materials block sunlight, the effects spread far beyond the impact location.
Reduced sunlight limits photosynthesis. Plants become less productive, while phytoplankton in oceans struggle to survive. Herbivores lose food, and predators lose prey.
This can create a rapid collapse that moves upward through entire ecosystems.
The cooling period following the Chicxulub collision is often described as an impact winter. Temperatures dropped as sunlight was prevented from reaching Earth’s surface effectively.
The new meteorite classification strengthens the argument that fine impact-generated debris was central to this process.
It does not mean sulfur had no role. Sulfur released from rocks at the impact site may still have contributed to atmospheric cooling and environmental disruption.
The evidence instead suggests that sulfur contained within the incoming asteroid was probably not the main “smoking gun.”
The Location of the Impact Made the Disaster Worse
The consequences of an asteroid collision depend on more than size and speed.
Location matters.
An asteroid landing in a deep ocean, desert, forest, or region rich in sulfur-bearing rock could produce different atmospheric effects.
The Chicxulub object struck an area containing rocks capable of releasing additional gases and particles when heated and shattered.
That means the extinction was shaped by a dangerous combination: a very large, fast-moving object, an unfortunate impact location, and a chain of atmospheric and ecological consequences.
A similar-sized object striking another part of the planet might still have caused a global disaster, but the precise outcome could have been different.
This makes the Chicxulub event an example of how planetary history can turn on both astronomical forces and local geology.
Where Did the Asteroid Come From?
The study narrowed the object’s meteorite class but did not determine its exact original location.
Possible sources include the outer region of the asteroid belt near Jupiter or a more distant, debris-rich area of the solar system.
CO chondrites are considered primitive because their chemistry has changed relatively little since the earliest stages of planetary formation.
Their composition suggests connections with cold, distant regions where ancient materials could survive without being heavily altered by heat or geological activity.
The asteroid may have spent billions of years orbiting the Sun before gravitational interactions changed its path and eventually sent it toward Earth.
Jupiter can influence objects in the asteroid belt through its enormous gravitational pull. Over long periods, collisions or orbital disturbances can push asteroids onto trajectories that cross the inner solar system.
The researchers emphasize that the precise journey of the Chicxulub object remains uncertain.
The Finding Builds on Earlier Evidence
Scientists have spent decades investigating the Chicxulub impactor.
In 1980, researchers identified unusually high concentrations of iridium in geological material dating to the extinction boundary. Iridium is relatively rare in Earth’s crust but more common in certain meteorites.
That discovery helped establish the theory that a major extraterrestrial impact was connected to the extinction.
The later identification of the Chicxulub crater strengthened the case further.
More recent studies have examined other isotope systems to determine whether the object was an asteroid or comet and whether it originated in the inner or outer solar system.
Previous evidence had already supported the idea that the object was a carbonaceous asteroid. The new nickel analysis attempts to narrow that broad category to the much more specific CO group.
Science often advances this way. One study rarely replaces everything known before it. New methods progressively reduce uncertainty and refine the picture.
Why Scientists Say “Probably” Rather Than “Definitely”
The research provides strong evidence, but responsible scientific language remains cautious.
Researchers did not recover the intact Chicxulub object. They examined the extremely small amount of material preserved in clay layers after the impactor vaporized and mixed with Earth’s rocks.
Chemical signatures can provide powerful identification, but they may also be influenced by contamination, alteration, sampling limitations, and the similarity of some meteorite groups.
Scientists therefore describe the CO chondrite as the probable or most likely impactor type.
Future studies may test more boundary samples, use additional isotope systems, or compare the evidence with material collected directly from known asteroids.
A later study could refine the classification further or challenge parts of the interpretation.
That uncertainty is not a weakness. It is part of how scientific conclusions are strengthened.
The Discovery Does Not Change the Basic Extinction Story
Some headlines may make the finding sound as though scientists have only now discovered what killed the dinosaurs.
That is not accurate.
Strong evidence has linked the Chicxulub collision to the mass extinction for decades. Scientists have also studied the possible contribution of extensive volcanic activity in India’s Deccan Traps.
The new study does not replace the impact theory.
It answers a more specific question: What kind of object caused the collision?
The answer may help researchers better model the amount and type of material released into the atmosphere, the duration of environmental disruption, and the relationship between the asteroid’s composition and the rocks it struck.
The discovery therefore refines the mechanism rather than rewriting the entire event.
Dinosaurs Were Already Living in a Changing World
The Late Cretaceous was not a completely stable period before the asteroid arrived.
Earth experienced volcanic activity, climate changes, shifting sea levels, and ecological pressures. Scientists continue debating whether some dinosaur groups were already declining.
However, the fossil record shows that dinosaurs remained widespread and diverse shortly before the impact.
The Chicxulub event appears to have produced a sudden environmental crisis too rapid and extensive for many large species to survive.
Smaller animals, species capable of sheltering, organisms with flexible diets, and creatures that could survive on decaying material may have had advantages.
The disappearance of dominant dinosaur groups created ecological opportunities for surviving mammals and birds.
The impact was therefore not only an ending. It redirected the evolutionary history of life on Earth.
Human Evolution Was Indirectly Shaped by the Collision
Humans did not exist when the asteroid struck.
Our distant mammalian ancestors did.
Mammals had lived alongside dinosaurs for millions of years, but most remained relatively small and occupied limited ecological roles.
When non-avian dinosaurs disappeared, mammals gained access to habitats and food sources that had previously been dominated by much larger animals.
Over millions of years, mammals diversified into a wide range of forms, eventually including primates and the evolutionary lineage that produced humans.
This does not mean the asteroid “created” humans in a direct or intentional sense.
It means that one rare collision changed the environmental conditions under which evolution continued. Without the Chicxulub event, Earth’s later biological history might have looked very different.
The Research Also Teaches Us About Planetary Defense
Understanding ancient impacts has modern value.
Scientists monitor near-Earth objects to determine whether any could pose a future collision risk. The threat from an object as large as Chicxulub is extremely rare, but the consequences would be global.
The meteorite’s unusual classification illustrates that dangerous objects can originate from distant or uncommon populations.
Planetary-defense programs therefore need to study objects with different compositions, structures, and orbital histories.
A dense metallic asteroid may respond differently to a deflection mission than a fragile carbonaceous object. Some asteroids may be loosely assembled collections of rock rather than solid bodies.
NASA’s successful DART mission demonstrated that humanity can intentionally alter an asteroid’s orbit under test conditions. Much more research is needed before every possible threat could be addressed.
Ancient impact studies help scientists understand not only what happened in the past, but what characteristics could matter during a future planetary-defense emergency.
The Finding Connects Geology With Astronomy
The Chicxulub research sits at the intersection of several scientific fields.
Astronomy helps explain where the object may have formed and how it traveled through the solar system.
Geochemistry allows researchers to compare isotope signatures and identify meteorite classes.
Geology preserves the global clay layer and the buried crater.
Paleontology records which organisms disappeared and which survived.
Climate science helps reconstruct the atmospheric and temperature changes that followed the collision.
No single field can fully explain the event.
This makes the discovery particularly useful in education. It shows students that major scientific questions often require evidence from several disciplines rather than one isolated experiment.
What Researchers Still Need to Learn
The exact origin of the impactor remains unresolved.
Researchers still need to determine whether the object came from a known asteroid family, how it left its original orbit, and how long it traveled before reaching Earth.
Questions also remain about the exact mixture of dust, soot, sulfur compounds, and other particles released into the atmosphere.
Scientists continue investigating how long the impact winter lasted, how quickly temperatures changed, and why some species survived while closely related species disappeared.
Researchers are also examining how rapidly ecosystems recovered.
The Chicxulub event is one of the most studied catastrophes in Earth’s history, but it involved a complicated chain of physical, chemical, climatic, and biological processes.
Identifying the likely meteorite class provides another important piece rather than completing the entire puzzle.
Key Takeaways
A study published in Science Advances concluded that the Chicxulub impactor was probably a rare CO carbonaceous chondrite.
The international research team used high-precision nickel-isotope measurements from the global Cretaceous–Paleogene boundary layer.
CO chondrites represent a tiny portion of meteorites collected on Earth and contain primitive material dating to the early solar system.
Because this meteorite class contains relatively little sulfur, the findings suggest that fine debris generated by the impact may have contributed more to the extinction than sulfur carried inside the asteroid itself.
The impactor was approximately 10 to 15 kilometers wide and struck near Mexico’s Yucatán Peninsula around 66 million years ago.
The collision triggered environmental changes associated with the extinction of approximately 75% of Earth’s species, including all non-avian dinosaurs.
The study was published and announced on July 17, 2026. It received broader science-news coverage on July 19.
Frequently Asked Questions
Was the Dinosaur-Killing Object an Asteroid or a Meteorite?
The object was an asteroid while it traveled through space. Meteorite classifications are used to describe its composition based on material associated with rocks that reach Earth. Researchers concluded that it likely had the composition of a CO carbonaceous chondrite.
What Does CO Chondrite Mean?
CO refers to the Ornans group of carbonaceous chondrites. They are rare, primitive meteorites preserving material from the early formation of the solar system.
Did Scientists Recover the Original Asteroid?
No. Most of the object vaporized during the impact. Scientists identified its likely composition from chemical traces preserved in the global boundary layer.
How Did Nickel Reveal the Asteroid’s Identity?
Different meteorite groups have characteristic nickel-isotope patterns. Researchers compared the ancient impact material with known meteorite signatures.
How Large Was the Chicxulub Asteroid?
The object is estimated to have been approximately 10 to 15 kilometers wide.
Did the Asteroid Kill Every Dinosaur?
It killed all non-avian dinosaur lineages. Birds survived and are recognized as living dinosaurs.
Did Sulfur Cause the Extinction?
Sulfur released from rocks at the impact location may have contributed to climate disruption. The new findings suggest that sulfur carried by the asteroid itself was less important than previously possible and that fine atmospheric debris may have played a leading role.
Where Did the Asteroid Come From?
Its precise origin remains unknown. Researchers suggest it may have come from the outer asteroid belt near Jupiter or another distant region of the solar system.
Was the Study Published on July 19, 2026?
The peer-reviewed paper and UBC announcement were published on July 17. ScienceDaily highlighted the research on July 19.
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Final Thoughts
The asteroid that ended the age of the non-avian dinosaurs was already extraordinary because of its size and destructive power.
The new research suggests it was extraordinary in another way.
It may have belonged to one of the rarest groups of meteorites found on Earth a primitive CO carbonaceous chondrite carrying chemical information from the earliest history of the solar system.
Scientists identified it not from a surviving boulder but from traces hidden inside a thin layer of ancient clay.
That achievement demonstrates how much information can remain after almost everything visible has disappeared.
The finding also makes the Chicxulub story more complicated. The asteroid’s own sulfur content may not have been the main cause of the prolonged environmental disaster. The enormous quantities of dust and debris produced when it struck Earth may have delivered the more decisive blow.
That changes how scientists reconstruct the months and years after the collision.
It also shows that the outcome of an impact depends on more than the object itself. Size, speed, composition, angle, and location can combine to determine whether a collision creates a regional disaster or reshapes life across the planet.
The dinosaurs were struck by a rare object at an exceptionally destructive location.
Life survived, but it followed a new path.
Sixty-six million years later, scientists are still finding pieces of that story sometimes in a crater, sometimes in fossils, and sometimes in the isotope pattern of a nearly invisible amount of nickel.
Sources
University of British Columbia — Researchers Identify Class of “Oddball” Meteorite That Killed the Dinosaurs
https://science.ubc.ca/news/2026-07/researchers-identify-class-oddball-meteorite-killed-dinosaurs
Science Advances — The Origin of the Cretaceous–Palaeogene Impactor Revealed by Nickel Isotopes
https://www.science.org/doi/10.1126/sciadv.aef4858
ScienceDaily — Scientists Identify the Rare Meteorite That Killed the Dinosaurs 66 Million Years Ago
https://www.sciencedaily.com/releases/2026/07/260718010142.htm
Phys.org — Researchers Identify Class of “Oddball” Meteorite That Killed the Dinosaurs
https://phys.org/news/2026-07-class-oddball-meteorite-dinosaurs.html
Nature Reviews Earth & Environment — The Chicxulub Impact and Its Environmental Consequences
