news

한어Русский языкEnglishFrançaisIndonesianSanskrit日本語DeutschPortuguêsΕλληνικάespañolItalianoSuomalainenLatina

In the early morning of August 16th, Beijing time, the world's top academic journal Science published a new paper, revealing the origin and nature of the Chicxulub meteorite, the suspected "culprit" of the mass extinction event.

In a newly published paper, researchers evaluated samples collected from the Cretaceous-Paleogene boundary (K-Pg) to determine the origin and composition of the asteroid that caused the mass extinction 66 million years ago, revealing that it was a rare carbonaceous asteroid from beyond Jupiter.

At the same time, their research results show that the meteorites in the other five asteroid impact events in the past 541 million years came from S-type asteroids formed inside the solar system, and they were all non-carbonaceous meteorites.

The findings help resolve a long-standing debate about the nature of the Chicxulub meteorite and reshape our understanding of Earth's history and the extraterrestrial rocks that have collided with our planet.

"Our future work will be to investigate the ruthenium isotope signatures of earlier asteroid impacts that could have been responsible for the mass extinction event that occurred before the K-Pg boundary," said Dr. Mario Fischer-Goede, corresponding author of the paper from the University of Cologne in Germany.

Mass extinction events

Throughout its long history, the Earth has experienced several large-scale biological extinction events.

The most recent mass extinction event occurred at the Cretaceous-Paleogene boundary 66 million years ago, resulting in the loss of approximately 60% of species on Earth, including non-avian dinosaurs.

The Chicxulub meteorite, a giant asteroid that collided with Earth in what is now the Gulf of Mexico, is thought to have played a key role in the extinction event.

The Chicxulub meteorite impact and the concurrent Deccan basalt flood eruption, which one was the "culprit" for the extinction? Or did both contribute to the extinction? This is a controversial question.

Mario Fischer-Gödde told The Paper: "Personally, I think it's probably not a coincidence that a huge asteroid hits the Earth when a mass extinction occurs."

The Cretaceous-Paleogene (K-Pg) boundary clay layers contain high concentrations of platinum group elements (PGEs), which are rare in crustal rocks but are found in high concentrations in certain types of asteroids.

In previous studies, PGE data indicated that the Chicxulub meteorite was an asteroid with a composition similar to that of chondrites. However, little was known about the nature of the Chicxulub meteorite—its composition and extraterrestrial origin.

Platinum group elements identify extraterrestrial meteorites

Mario Fischer-Goede and colleagues used the isotopic composition of ruthenium (Ru), a platinum group element, to investigate the nature of extraterrestrial impactors. For comparison, in addition to analyzing samples from the K-Pg boundary, they also analyzed samples from five other asteroid impacts in the past 541 million years, samples from impact-related chondrules from the Archean period (350-320 million years ago), and samples from two carbonaceous meteorites.

Ruthenium was chosen because it shows variation between different meteorite types, and the ruthenium isotope composition of these meteorite groups is also different from that of the Earth, so ruthenium can be used to determine the origin of the extraterrestrial component in the impact rock.

The ruthenium isotope signature of a meteorite varies with the heliocentric distance (distance from the Sun) of its parent asteroid when it formed in the early Solar System. Meteorites can be divided into two major categories based on the differences in the isotopic composition of various elements: carbonaceous chondrites (CC) and non-carbonaceous (NC) meteorites. In contrast, carbonaceous chondrites come from carbonaceous (C-type) asteroids, which formed at greater heliocentric distances, beyond the orbit of Jupiter. Many non-carbonaceous meteorites are fragments of siliceous (S-type) asteroids, which formed in the inner Solar System.

Mario Fischer-Goede and colleagues found that the Chicxulub meteorite, which produced the K-Pg boundary, and older Archean chondrite samples have ruthenium isotope compositions that are different from Earth's and overlap with those of carbonaceous chondrites. This means that the Chicxulub meteorite came from a body with a carbonaceous chondrite component, indicating an origin in the outer solar system. For the Archean chondrite, the carbonaceous chondrite component may have come from carbonaceous asteroid material that impacted the Earth during the final stages of Earth's accretion as a planet.

This excludes the possibility that the elevated platinum group elements in the Cretaceous-Paleogene boundary clay layer originated from the volcanic eruptions of the Deccan Large Igneous Province, as well as the possibility of a cometary origin for the Chicxulub meteorite proposed previously.