Washington:

An intense debate surrounding the cosmic rock that killed the dinosaurs has stirred scientists for decades, but a new study has revealed some important — and far-out — data about the impactor’s origin story.

Researchers, whose findings were published Thursday in the journal Science, used an innovative technique to demonstrate that the apocalyptic culprit which slammed into the Earth’s surface 66 million years ago, causing the most recent mass extinction, had formed beyond Jupiter’s orbit.

They also refute the idea that it was a comet.

The new insights into the apparent asteroid that cratered into Chicxulub, in what is present-day Mexico’s Yucatan Peninsula, could improve the understanding of celestial objects that have struck our planet.

“Now we can, 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.

The conclusions are particularly notable, given how rarely this type of asteroid collides with Earth.

Such information may well prove useful in assessing future threats, or determining how water arrived on this planet, Fischer-Godde said.

Samples 

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

Researchers measured the isotopes of the element ruthenium, which is not uncommon on asteroids but extremely rare on Earth. So by inspecting the deposits in multiple geological layers that mark the debris from the impact at Chicxulub, they could be sure that the ruthenium studied came “100 per cent from this asteroid.”

“Our lab in Cologne is one of the rare labs that can do these measurements,” and it was the first time such study techniques were used on impact debris layers, Fischer-Godde said.

Ruthenium isotopes can be used to distinguish between the 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, nearer the sun.

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

Studies from two decades ago had already made such an assumption but with far less certainty.

The conclusions are striking, because most meteorites — pieces of asteroids that fall to Earth — are S-types, Fischer-Godde pointed out.

Does that mean the Chicxulub impactor formed beyond Jupiter and made a beeline for our planet? Not necessarily.

“We cannot be really sure where the asteroid was kind of hiding just before it impacted on Earth,” Fischer-Godde said, adding that after its formation, it may have made a stopover in the asteroid belt, located between Mars and Jupiter and where most meteorites originate.

Not a comet 

The study also dismisses the idea that the destructive impactor was a comet, an amalgam of icy rock from the very edge of the solar system. Such a hypothesis was put forward in a much-publicized study in 2021, based on statistical simulations.

Sample analyses now show that the celestial object was far different in composition from a subset of meteorites which are believed to have been comets in the past. It is therefore “unlikely” the impactor in question was a comet, Fischer-Godde said.

As to the wider usefulness of his findings, the geochemist offered two suggestions. 

He believes that more accurately defining the nature of asteroids that have struck Earth since its beginnings some 4.5 billion years ago could help solve the enigma of the origin of our planet’s water.

Scientists believe water may have been brought to Earth by asteroids, likely of the C-type like the one that struck 66 million years ago, even though they are less frequent.

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

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

(Except for the headline, this story has not been edited by NDTV staff and is published from a syndicated feed.)

Around 2,500 years ago, at the western end of the island of Kadavu in the southern part of Fiji, the ground shook, the ocean became agitated, and clouds of billowing smoke and ash poured into the sky. When the clouds cleared, the people saw a new mountain had formed, its shape resembling a mound of earth in which yams are grown. This gave the mountain its name – Nabukelevu, the giant yam mound. Image for Representation.
| Photo Credit: The Hindu

Can you imagine a scientist who could neither read nor write, who spoke their wisdom in riddles, in tales of fantastic beings flying through the sky, fighting each another furiously and noisily, drinking the ocean dry, and throwing giant spears with force enough to leave massive holes in rocky headlands?

Our newly published research in the journal Oral Tradition shows memories of a volcanic eruption in Fiji some 2,500 years ago were encoded in oral traditions in precisely these ways.

They were never intended as fanciful stories, but rather as the pragmatic foundations of a system of local risk management.

Life-changing events

Around 2,500 years ago, at the western end of the island of Kadavu in the southern part of Fiji, the ground shook, the ocean became agitated, and clouds of billowing smoke and ash poured into the sky.

When the clouds cleared, the people saw a new mountain had formed, its shape resembling a mound of earth in which yams are grown. This gave the mountain its name – Nabukelevu, the giant yam mound. (It was renamed Mount Washington during Fiji’s colonial history.)

So dramatic, so life-changing were the events associated with this eruption, the people who witnessed it told stories about it. These stories have endured more than two millennia, faithfully passed on across roughly 100 generations to reach us today.

Also Read | Kilauea, one of the world’s most active volcanoes, begins erupting after three-month pause

Scientists used to dismiss such stories as fictions, devalue them with labels like “myth” or “legend”. But the situation is changing.

Today, we are starting to recognise that many such “stories” are authentic memories of human pasts, encoded in oral traditions in ways that represent the worldviews of people from long ago.

In other words, these stories served the same purpose as scientific accounts, and the people who told them were trying to understand the natural world, much like scientists do today.

Battle of the vu

The most common story about the 2,500-year-old eruption of Nabukelevu is one involving a “god” (vu in Fijian) named Tanovo from the island of Ono, about 56km from the volcano.

Tanovo’s view of the sunset became blocked one day by this huge mountain. Our research identifies this as a volcanic dome that was created during the eruption, raising the height of the mountain several hundred feet.

Enraged, Tanovo flew to Nabukelevu and started to tear down the mountain, a process described by local residents as driva qele (stealing earth). This explains why even today the summit of Nabukelevu has a crater.

Also Read | One year after volcanic blast, many of Tonga’s reefs lay silent

But Tanovo was interrupted by the “god” of Nabukelevu, named Tautaumolau. The pair started fighting. A chase ensued through the sky and, as the two twisted and turned, the earth being carried by Tanovo started falling to the ground, where it is said to have “created” islands.

We conclude that the sequence in which these islands are said to have been created is likely to represent the movement of the ash plume from the eruption, as shown on the map below.

‘Myths’ based in fact

Geologists would today find it exceedingly difficult to deduce such details of an ancient eruption. But here, in the oral traditions of Kadavu people, this information is readily available.

Another detail we would never know if we did not have the oral traditions is about the tsunami the eruption caused.

In some versions of the story, one of the “gods” is so frightened, he hides beneath the sea. But his rival comes along and drinks up all the water at that place, a detail our research interprets as a memory of the ocean withdrawing prior to tsunami impact.

Other details in the oral traditions recall how one god threw a massive spear at his rival but missed, leaving behind a huge hole in a rock. This is a good example of how landforms likely predating the eruption can be retrofitted to a narrative.

Our study adds to the growing body of scientific research into “myths” and “legends”, showing that many have a basis in fact, and the details they contain add depth and breadth to our understanding of human pasts.

The Kadavu volcano stories discussed here also show ancient societies were no less risk aware and risk averse than ours are today. The imperative was to survive, greatly aided by keeping alive memories of all the hazards that existed in a particular place.

Australian First Peoples’ cultures are replete with similar stories.

Literate people, those who read and write, tend to be impressed by the extraordinary time depth of oral traditions, like those about the 2,500-year old eruption of Nabukelevu. But not everyone is.

In early 2019, I was sitting and chatting to Ratu Petero Uluinaceva in Waisomo Village, after he had finished relating the Ono people’s story of the eruption. I told him this particular story recalled events which occurred more than two millennia ago – and thought he might be impressed. But he wasn’t.

“We know our stories are that old, that they recall our ancient history,” he told me with a grin. “But we are glad you have now learned this too!”