When a massive space rock slammed into Earth 66m years ago, it wiped out large swathes of life and ended the reign of the dinosaurs. Now scientists say they have new insights into what it’s made of.
Experts studying material deposited at the time of the event say they have found telltale signs to support the idea that the Chicxulub impact crater was produced by a carbon-rich, “C-type” asteroid originally outside the orbit of Jupiter formed. .
Mario Fischer-Gödde, co-author of the research from the University of Cologne, said the team was now keen to look at deposits related to an impact that some thought was behind. a major extinction about 215m years ago.
“Perhaps this way we can find out whether C-type asteroid impacts will have a higher probability of causing mass extinction events on Earth,” he said.
Write in the journal Sciencereport the researchers how they studied different types, or isotopes, of ruthenium within a layer of material that settled over the globe after the impact 66m years ago.
“This layer contains traces of the remains of the asteroid,” said Fischer-Gödde.
The team chose to look at ruthenium because the metal is very rare in the Earth’s crust.
“So the ruthenium that we find in this layer is almost 100% derived from the asteroid,” said Fischer-Gödde, adding that it gives scientists a way to determine the composition, and thus the type, of the impactor itself. determine
The team found that samples of the coating from Denmark, Italy and Spain all showed the same ruthenium isotope composition.
It is important, says Fischer-Gödde, that the result is different from the composition commonly found on Earth, ruling out a theory that the presence of ruthenium and other metals such as osmium and platinum is due to previous eruptions of the Deccan Traps – volcanoes.
The team also doubts the possibility that the impactor was a comet, saying the ruthenium isotope composition of the samples differs from that of meteorites, which are thought to be fragments of comets that have lost their ice.
Instead, the ruthenium isotope findings are consistent with the average composition of meteorites from carbonaceous (C-type) asteroids – carbon-rich space rocks that would have formed at the beginning of the solar system, beyond the orbit of Jupiter.
But questions remain about where exactly the asteroid came from before heading to Earth.
Fischer-Gödde said C-type asteroids can be found today in the asteroid belt that sits between Mars and Jupiter because not long after the formation of the solar system, Jupiter migrated, scattering asteroids in the process.
Because of this, he suggests that the fateful space rock probably came from there.
“Maybe there was a collision of two asteroid bodies in the belt, and then this piece kind of went into an Earth-crossing orbit. That could be one scenario,” he said, although he noted that there are other possibilities, including that it originates from the Oort cloud which is thought to surround the solar system.
Dr Craig Walton of the University of Cambridge, who was not involved in the work, said the research was exciting, although he said it remained unclear whether the impactor was an asteroid or comet.
“Even so, this kind of work gives us ever more detailed insights into the nature of the objects that have shaped Earth’s history so dramatically,” he said.
