- Jonathan Amos
- BBC science reporter
Scientists can’t pinpoint the exact year in which an asteroid fell from the sky to wipe out the dinosaurs, but they are now certain that a massive space rock hit Earth in the spring from the northern hemisphere.
They believe seasonal timing may have been a critical factor in influencing which animal populations survived the disaster.
This obviously didn’t make a difference for dinosaurs, but it could have done with some mammals, birds, and plants. It could have made all the difference.
This may be particularly the case for species living in the southern hemisphere, where autumn or early winter could have been observed at the time of impact.
“In the southern hemisphere, many organisms would have been hibernating or hibernating. This would have helped them,” says Melanie During, of Uppsala University in Sweden. Whether the animals are grazing their offspring, which are very fragile, or perhaps they are still caring for the eggs, waiting for them to hatch, or foraging for food in a vulnerable position.
The doctor has just published her analysis of paddlefish and fossil sturgeon from a site called Tanis in North Dakota, USA. This research strongly suggests that the fish died in the spring.
If you haven’t heard of Tanis yet, you’ll be hearing about him – a lot – over the next few years.
It is a site that records with extraordinary accuracy not only the day when an asteroid 12 kilometers wide collided with our planet 66 million years ago, but also in the minutes and hours that followed this catastrophic impact.
The giant space rock hit Earth in what is now the Gulf of Mexico, about 3,000 kilometers from Tanis, but the energy transferred during the event was such that its devastation was elusive.
The North Dakota fossil site contains the remains of fish that were dumped on dry land and buried in sediments by unimaginable earthquake water waves.
Fish have particles stuck in the gills. These are globules of molten rock that resulted from the impact and then spread across the planet.
“This deposit looks like a car crash frozen in place; it appears to be the wildest thing I have seen in a pristine condition,” said the lady during.
She and her colleagues examined the atomic structure of fish bones and subjected them to X-ray analysis.
Not only has this research revealed where paddlefish is located in their annual growth cycle, it has also revealed where they are in terms of seasonal food consumption (what you eat is reflected in your bone chemistry).
“There are two independent curves based on independent principles, but both converge in the spring, which means we can say with certainty that the meteorites fell in the spring,” said his colleague Denis Voitten, also from Uppsala.
The team’s study was published Wednesday in the journal Nature.
It echoes the work of another group whose findings were published in Scientific Reports in December. This gives us good confirmation that spring really was the season of influence.
Professor Phil Manning, from the University of Manchester (UK), was part of the team responsible for the December report.
He said the global climate was cold at the time of the impact, so ecosystems would have felt the pressure of the change anyway.
“Only when you put a wrench in the works in the form of an asteroid hitting Earth at 60,000 miles per hour does that tend to tip the scales and that’s definitely the last straw. The dinosaur bowl,” he told BBC News.
“But, yeah, it was at a sensitive time for the Northern Hemisphere. Spring is when everything literally comes to life, not the time to lay everything down.”
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