66 million years ago, a asteroid It hit Chicxulub, in the current Yucatan Peninsula (Mexico), and ended with the dinosaurs non-avian, pterosaurs, ammonites and most marine reptiles, that is, about 60% of the species on Earth.
Now, a new international study led by Mario Fischer-Gödde of the University of Cologne (Germany) and published this Thursday in the journal Science, has determined that That huge rock came from the orbit of Jupiter and it was a carbonaceous type asteroid.
The multidisciplinary research, carried out by researchers from Italy, Brazil, Sweden, the United States, Austria, the United Kingdom, Denmark and Belgium, has revealed the composition of this asteroid, which only mammals, birds, crocodiles and turtles survived.
The discovery has also resolved a long-standing debate about the nature of the Chicxulub asteroid, and has reshaped our understanding of the history of Earth and the extraterrestrial rocks that have collided with it.
The last mass extinction
The Earth has suffered several mass extinctions, the most recent of which occurred 66 million years ago, at the boundary between the Cretaceous and Paleogene eras, what scientists call the ‘K-Pg boundary’.
The object that impacted Chicxulub, a huge asteroid with a diameter of approximately 6 to 12 kilometers that collided with Earth in what is now the Gulf of Mexico, is believed to have played a key role in this extinction.
This gigantic rock collided with the force of 10 billion atomic bombs like those of Hiroshima and Nagasaki, generating a huge explosion and a gigantic tsunami that spread thousands of kilometers from the point of impact, even over continental masses.
Stratigraphic sediments in the K-Pg boundary layers collected by scientists in the area so far contain high levels of platinum group elements (PGEs) such as iridium, ruthenium, osmium, rhodium, platinum and palladium, which are rare on Earth but common in meteorites.
These elevated levels of PGE have been found all over the world, suggesting that the impact scattered debris across the planet.
But some scientists have been arguing for years that the extinction was caused by eruptions recorded some 66 million years ago in the so-called ‘Decan Traps’ region in western India, which were so large that they could have caused the disaster.
So far, the specific PGE ratios at the K-Pg boundary are more consistent with asteroid impact than volcanic activity, however, the nature of the asteroid, its composition and extraterrestrial origin are still poorly understood.
Comparing meteorite samples
To try to clarify these unknowns, the study led by Fischer-Gödde analyzed the ruthenium (Ru) isotopes in samples taken from the K-Pg boundary and compared them with samples from five asteroid impacts from the last 541 million years, with samples of ancient small spheres (spherules) related to impacts from the Archean era (3.5 to 3.2 billion years old) and with samples from two carbonaceous meteorites.
The team found that the Ru isotopic signatures in the K-Pg boundary samples were uniform and closely matched those of carbonaceous chondrites (CC), suggesting that the Chicxulub rock was likely a C-type asteroid that formed in the outer Solar System.
The analysis also ruled out the asteroid being a comet.
As for the other samples, those from the Archean era suggest that the asteroids that impacted in the area had a composition similar to that of CC, indicating that they also emerged from the outer Solar System and could be part of the material that impacted in the final stages of accretion of the Earth.
Finally, the analyses also showed that other impact sites from different times displayed Ru isotopic compositions derived from S-type asteroids (Salicaceans) from the inner Solar System.