Scientists Identify Origin of Dinosaur-Killing Asteroid: Jupiter

An intense debate over which cosmic rock killed the dinosaurs has roiled scientists for decades, but a new study has revealed important — and far-reaching — insights into the impactor’s origin story.

The researchers, whose results were published Thursday in the journal Scienceused an innovative technique to demonstrate that the apocalyptic culprit that crashed into the Earth’s surface 66 million years ago, causing the most recent mass extinction, formed beyond the orbit of Jupiter.

They also refute the idea that it was a comet.

New knowledge about the apparent asteroid that struck Chicxulub, in what is now Mexico’s Yucatan Peninsula, could improve our understanding of celestial objects that have struck our planet.

“We can now, with all this knowledge (…) say that this asteroid initially formed beyond Jupiter,” Mario Fischer-Godde, lead author of the study and a geochemist at the University of Cologne, told AFP.

These findings are particularly remarkable given how rare collisions of this type of asteroid with Earth are.

Such information could well prove useful in assessing future threats or determining how water got to this planet, Fischer-Godde said.

Samples

The new findings are based on the analysis of sediment samples formed between the Cretaceous and Paleogene periods, the time of the asteroid’s cataclysmic impact.

The researchers measured isotopes of the element ruthenium, an element that is quite common on asteroids but extremely rare on Earth. By inspecting the deposits in the multiple geological layers that mark the debris from the Chicxulub impact, they were able to be sure that the ruthenium studied came “100% from this asteroid.”

“Our laboratory in Cologne is one of the few laboratories capable of carrying out these measurements,” and it was the first time that such study techniques had been used on layers of impact debris, Fischer-Godde said.

Ruthenium isotopes can be used to distinguish between two main groups of asteroids: C-type, or carbonaceous, asteroids that formed in the outer Solar System, and S-type, silicate asteroids from the inner Solar System, closer to the Sun.

The study claims that the asteroid that triggered a mega-quake, precipitated a global winter and wiped out the dinosaurs and most other life forms was a C-type asteroid that formed beyond Jupiter.

Studies dating back twenty years had already put forward such a hypothesis, but with much less certainty.

The findings are striking because most meteorites – pieces of asteroids that fall to Earth – are S-type, Fischer-Godde pointed out.

Does this mean that the Chicxulub impactor formed beyond Jupiter and headed directly toward our planet? Not necessarily.

“We can’t be really sure where the asteroid was hiding just before it impacted Earth,” Fischer-Godde said, adding that after it formed it may have stopped off in the asteroid belt, which lies between Mars and Jupiter and is where most meteorites come from.

Not a comet

The study also rejects the idea that the destructive impactor was a comet, an amalgam of icy rocks from the outer reaches of the solar system. Such a hypothesis had been put forward in a highly publicized 2021 study based on statistical simulations.

Sample analyses now show that the composition of the celestial object was very different from that of a subset of meteorites once thought to be comets. It is therefore “unlikely” that the impactor in question was a comet, Fischer-Godde said.

As for the broader usefulness of his findings, the geochemist offered two suggestions.

He believes that a more precise definition of the nature of the asteroids that have struck Earth since its beginnings, about 4.5 billion years ago, could help solve the riddle of the origin of our planet’s water.

Scientists believe the water may have been brought to Earth by asteroids, probably C-type asteroids like the one that struck 66 million years ago, although they are less common.

Studying past asteroids also allows humanity to prepare for the future, Fischer-Godde said.

“If we find that previous mass extinction events could also be linked to C-type asteroid impacts, then… if there is ever going to be a C-type asteroid in an Earth-crossing orbit, we’ll have to be very careful,” he said, “because it could be the last one we ever witness.”

© 2024 AFP