Dinosaur-killing asteroid came from beyond Jupiter

• A massive asteroid impact wiped out the dinosaurs about 66 million years ago. It happened in what is now the Gulf of Mexico and left behind a huge crater.
• Where did the asteroid come from? According to a new study, it formed in the outer solar system behind Jupiter and contained a large amount of carbon.
• It was not a comet This led to the extinction of the dinosaurs, says the study, which refutes previous theories.

Dinosaur-killing asteroid from beyond Jupiter

About 66 million years ago, an asteroid hit Earth and caused the extinction of the dinosaurs. It appears to have created the Chicxulub crater beneath Mexico's Yucatán Peninsula. Since at least 1990, when scientists found the Chicxulub crater and identified it as an asteroid impact site, there has been much debate about what type of asteroid it was. And now an international team of scientists says they have pinpointed the origin and composition of the Chicxulub impactor. The researchers reported on August 16, 2024, that it was a carbonaceous, or C-type, asteroid (which contains rock, metals, and lots of carbon). They said the asteroid got there this way from beyond Jupiter.

The research team led by Mario Fischer-Gödde of the University of Cologne published its peer-reviewed study in the journal Science on August 15, 2024.

Chicxulub, the asteroid that wiped out the dinosaurs

The asteroid Chicxulub was estimated to be about 10 kilometers in diameter. It hit the Earth 66 million years ago in what is now the Gulf of Mexico. Scientists have said it was one of the main causes, although not The Cause of the extinction of the dinosaurs. Scientists call the collapse a Cretaceous-Paleogene extinction event. As the paper states:

The geological boundary between the Cretaceous and Paleogene periods, 66 million years ago, is marked by global deposits from an impact event at what is now Chicxulub, Mexico. The impact coincided with a mass extinction that wiped out the dinosaurs and many other species.

The impact is believed to have left behind a huge crater, now known as the Chicxulub crater. It has a diameter of about 195 km and a depth of 20 km.

Why do scientists think an asteroid created this crater? First of all, they found high concentrations of platinum group elements (PGEs) such as iridium, ruthenium, osmium, rhodium, platinum and palladium in the K-Pg interfaces. This is a geological feature, usually a thin band of rock, that contains much more iridium than other bands. These elements are rare on Earth but are often found in meteorites or rocks from space. In addition, similarly high PGE concentrations have also been found worldwide. This finding suggests that the impact scattered debris all over the world.

Before this discovery, some scientists had interpreted these rare elements at the K-Pg boundary as evidence of volcanic activity. However, many scientists believe that the specific PGE ratios are more consistent with those of meteorite impacts.

But even with this data, scientists were still not sure what type of asteroid Chicxulub was and where it came from.

A carbonaceous asteroid from beyond Jupiter

Most asteroids are located in the asteroid belt between Mars and Jupiter. Was the asteroid belt the origin of the asteroid that wiped out the dinosaurs? Fischer-Gödde said:

We wanted to identify the origin of this impact body.

Fischer-Gödde and his colleagues examined the ruthenium (Ru) isotopes in samples taken from the K-Pg boundary. They then compared these with samples from five other asteroid impacts within the last 541 million years, samples from ancient Archean (3.5 – 3.2 billion years old) impact sphere layers and samples from two carbonaceous meteorites.

The results showed that the ruthenium isotope signatures were uniform and very close to those of carbonaceous chondrite meteorites, not those of other types of meteorites or the Earth itself. In addition, the asteroid was most likely a C-type, or carbonaceous, the most common type of asteroid. As the name suggests, they are rich in carbon. In addition, the asteroid probably came from the outer solar system, beyond Jupiter.

Fischer-Gödde said:

The composition of the asteroid is consistent with that of carbonaceous asteroids that formed outside the orbit of Jupiter during the formation of the solar system.

The ancient Archean samples also supported these conclusions. However, the samples from the other five asteroid impacts came from S-type (hydrochloric acid) asteroids that originated in the inner solar system.

No comet

The results also rule out the possibility that the impactor was a comet rather than an asteroid, as some scientists had also postulated. William Bottke, a planetary scientist at the Southwest Research Institute in Boulder, Colorado, noted:

The assumption that it was a comet is widespread in the literature. The probability of large carbonaceous asteroids hitting the Earth is much higher than that of comets.

Fischer-Gödde also said that the ruthenium isotope data did not match a comet.

The Chicxulub impact was a rare event, but it changed the course of evolution on Earth. Co-author Carsten Münker of the University of Cologne added:

We found that the impact of an asteroid like the one at Chicxulub is a very rare and unique event in Earth's history. The fate of the dinosaurs and many other species was sealed by this projectile from the outer regions of the solar system.

Conclusion: An international team of scientists has determined that the dinosaur-killing asteroid Chicxulub was carbonaceous and came from the depths of the outer solar system.

Source: Ruthenium isotopes show that the Chicxulub impactor was a carbonaceous asteroid

Above:

University of Cologne

Nature

American Association for the Advancement of Science (EurekAlert!)

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