When Scientists Analyzed An Ancient Shell, They Uncovered A 70-Million-Year Old Secret About Earth

History’s greatest scientists have learned much about the ways in which Earth has changed over the years. However, there’s still plenty about our planet that we don’t know. So, when a team of researchers used lasers to analyze an ancient shell, their discovery sent shockwaves throughout the scientific community. That’s because this unassuming fossil provided not only the key to unlocking the secrets of our past, but potentially clues to our future, too.

Shocking findings

The experts behind the study were from Vrije Universiteit Brussel and Utrecht University and they published their results in February 2020 in the American Geophysical Union (AGU) journal. Their findings not only reveal a mind-blowing secret about our planet, they may also help to provide new information about the Moon. What’s more, these discoveries have all been made through close analysis of a long-extinct relative of the modern-day clam.

Going way, way back

The mollusk that the team studied dates back to around 70 million years ago, shortly before the dinosaurs were wiped out. It’s part of the Torreites sanchezi species, which belongs to a now-defunct group called rudist clams. These organisms are notable because they built up their shells in daily growth layers – a trait that proved particularly useful for the research team.

Ancient oceans

According to the AGU, T. sanchezi mollusks resembled “tall pint glasses with lids shaped like bear claw pastries.” They consisted of a pair of shells – or “valves.” And these were connected by a hinge which was akin to an asymmetrical clam. Apparently, they were most commonly found in water warmer than our oceans today and grew in thick reefs.

Long since dried up

The mollusk analyzed in this study originated from a shallow seabed, where it lived for more than nine years. The once-tropical area is now totally dry and sits within the mountains of modern-day Oman. But back then, it was home to clusters of the mollusks – until they disappeared in the same extinction event that’s thought to have eradicated the land-based dinosaurs.

Nothing like them today

The study’s lead author and analytical geochemist at Vrije Universiteit Brussel Niels de Winter told AGU in March 2020, “Rudists are quite special bivalves. There’s nothing like it living today. In the late Cretaceous especially, worldwide most of the reef builders are these bivalves. So, they really took on the ecosystem-building role that the corals have nowadays.” Seventy million years later, that same clam has become an ancient recording device – chronicling Earth’s secrets within its layers.

Expanding the findings

Through carefully conducted experiments, de Winter and his team were able to extract mind-blowing revelations from this unassuming shell. Their findings have helped to confirm long-held theories surrounding ancient Earth and beyond. Yes, the study has even helped experts understand more about our Moon and the role it has played in the evolution of our planet.

Dinos still roamed

While the shell has undoubtedly unlocked doors to new findings, scientists already know quite a lot about what life was like at the time. Dinosaurs still roamed the planet, for instance, as the end of the late Cretaceous period approached. Geologically speaking, the Earth was in the Maastrichtian stage of the Mesozoic era, which covers from 72.1 to 66 million years ago.

A new planet takes shape

Over the 79 million years that constituted the Cretaceous period, the planet underwent substantial changes. At its beginning, the planet’s landmasses were arranged in two supercontinents – Laurasia in the north and the huge southern island of Gondwana. But both had already begun rifting, and by the end of this monumental age, the continents as we know them today were starting to take shape.

Drifting continents

North America continued to drift away from what is now Europe in a shift that had begun during the earlier Jurassic period. And this, of course, further widened the span of the Atlantic Ocean. India was still planted next to Madagascar, but it was now adrift and beginning to move northward. Australia, on the other hand, was still connected to Antarctica – moving away from Africa and beyond the South Pole.

Considerable cooling

The climate cooled considerably over the Cretaceous period, but it was still much warmer than today. Instead of ice sheets, forests covered the poles and it allowed dinosaurs to wander Antarctica. However, as the planet cooled, these and other non-equatorial forests became more temperate. This effect was experienced across the Earth – bringing seasonal weather to the northern and southern hemispheres.

Thriving grass and plants

The aforementioned climatic changes ultimately gave way to the emergence of grass, deciduous forests and flowering plants. The latter proved particularly important, with their rapid growth providing a food source for many animals. The proliferation of plants was also aided by a rash of insects: including beetles, ants, wasps and bees. Nevertheless, the enormous grasslands that would come to cover swathes of the planet were still a few million years away.

Shifting the balance of power

The late Cretaceous period also saw many well-known dinosaurs come to the fore, as new species evolved and the power balance shifted. The Tyrannosaurus rex rose to the top of the food chain in the north, while the Spinosaurus did the same in the south. In addition, the northern continents were home to herds of herbivores such as the Triceratops.

Reign of the reptiles

Meanwhile, the shifting continents created the necessary conditions for reptiles and amphibians to thrive. The expanded coastlines became home to all manner of beasts: including crocodiles, salamanders, turtles, frogs and snakes. The skies were dominated by enormous pterosaurs, but they found competition from the increasingly diverse array of birds.

Ancestors of birds

In fact, the ancestors of many present-day birds can be traced back to the Cretaceous period. While fossil records show modern birds can be traced back around 60 million years, a 2008 study which appeared in the journal BMC Biology revised that estimation by some 40 million years. As a result, it’s thought that the lineage of pelicans, sandpipers, cormorants and more all began in the Cretaceous period.

Flourishing ocean life

Life prospered on the shores, in the skies and in the oceans, too. The plesiosaurs were replaced in shallow waters by the snakelike mosasaurs during this time, while modern sea creatures including sharks and rays became commonplace. And coral reefs continued to blossom in warm waters – formed of rudist clams like the one analyzed in the 2020 study.

Cosmic conditions

While much of life on Earth in the Cretaceous period is well-documented, less is known about the cosmic conditions at the time. But thanks to the aforementioned shell, that may be about to change. Indeed, the positively ancient fossil has revealed an astonishing secret about the planet’s rotation. And in turn, it’s provided scientists with enough knowledge to estimate the length of a single day on Earth some 70 million years ago.

A geological lifetime

Prior to these recent revelations, scientists did have a general grasp on how the Earth’s rotation has changed over the years. We know, for instance, that it has been going on for almost the entirety of the planet’s existence. But because the change has been so slow in the grand scheme of things, it has been almost impossible to track year-on-year.

Small increments

The planet’s day/night cycle increases in length by roughly 1.7 milliseconds every century, according to Scientific American. That’s not a statistic you’d ever notice, of course, but over millions of years it can make an enormous difference. The phenomenon is driven by the way the Sun and our Moon interact with Earth on a cosmic scale. Effectively, it’s all caused by gravity and the tides.

Slowly spinning away

You see, the Moon is gradually spiraling away from the Earth at a rate of approximately 1.5 inches every year. NASA’s James Williams described the effects of this trend to the publication in 2010. The senior research scientist explained, “You’re putting energy into the Moon’s orbit and taking it out of the Earth’s spin.”

Affecting the tides

The Moon’s gravity controls the tides in our oceans, which outpace the former planet’s orbit due to the speed at which the Earth rotates. The resulting displaced mass pulls the planet forward, while the Earth’s rotation is simultaneously slowed by friction on the seabed. Together, these factors result in the imperceptible extension to the length of our days. Our years remain the same length, however, because our planet’s orbit around the Sun remains constant.

Determining amounts

To discover the rate at which the Moon is pulling away from Earth, Williams pointed lasers at reflectors left behind by Russian probes and U.S. astronauts in the 1960s and ‘70s. First, he calculated the time it took for the beam to return to Earth. Then, Williams compared changes between multiple results to reach the current figure of 1.5 inches per year.

Shorter days further back

Generally, the trend established by studying the Moon is that the further back you go, the shorter the days were. But the tricky part is figuring out their precise length. Australian National University geophysicist Kurt Lambeck told Scientific American, “As you start going further back in time, the records get difficult to interpret. But the records have tended to support a general pattern going back that the number of days in the year increases.”

But how did the moon form?

Analyses of the Earth’s tides can also tell us more about how the Moon was formed. Indeed, the data supports the dominant theory that the lunar body collided with our planet some 4.5 billion years ago. If it formed elsewhere and drifted into Earth’s gravity, Lambeck said, the tides wouldn’t have remained constant. Furthermore, Purdue University Earth and atmospheric scientist Jay Melosh added that our world had a speedy six-hour rotation immediately after the Moon impacted the Earth.

Lunar drift

Over billions of years, the Moon has drifted from its initial orbit of 16,000 miles to its current distance of 239,000 miles. As a result, the Earth’s rotation has apparently slowed four times over. And that’s what’s still happening now, as the Moon continues to pull further away from the planet. But to really trace the exact length of a day between those two epochs, you need to dig deep into scientific evidence.

Length of a day

And the aforementioned fossil mollusk studied by de Winter helps us discover how the length of time in a day has changed. Owing to the way it progressively builds its layers, the researchers could use the rudist clam to accurately measure how long a day was 70 million years ago. The scientist added to Cosmos magazine in March 2020 that the shell is “a bit comparable to tree rings.”

30 minutes shorter

By carefully studying these lasers, the scientists determined that back then, the Earth rotated 372 times a year. That adds up to seven more days than our current year – making the average length of a day 23 and a half hours. Effectively, then, a day on Earth when dinosaurs roamed was actually half an hour shorter than it is now.

Laser precision

“We have about four to five data points per day, and this is something that you almost never get in geological history,” de Winter told AGU. “We can basically look at a day 70 million years ago. It’s pretty amazing.” To do so, though, the research team had to make very careful use of a laser on the ancient fossil.

Gaining an understanding

This technique allowed the scientists to examine the shell’s composition at a scale not visible through microscopes. First, they used the laser to fire tiny holes into the fossil, in order to gain a clearer understanding of its layers. They were then able to extract those layers in minuscule increments.

Extending the rate of growth

Each layer peeled back in this way was equivalent to approximately a quarter of the growth incurred over a single day in the clam’s life. The researchers then used that data to extend the fossil’s rate of growth over a nine-year span. From there, they could accurately determine the length of a day at the time the shell was in its prime.

Seasons come and go

“This allows us to measure how the composition of the shell changed over short time periods and learn about very rapid changes in the shell’s environment,” de Winter told Cosmos magazine. And from those findings, he continued, “[We could] count the number of days in a year, because we can also see seasonal cycles.”

All from one organism...

Most climate models of the ancient past examine changes taking place over tens of thousands of years. However, this mollusk has allowed researchers to drill down into changes occurring over the lifetime of a previously living organism. Indeed, as well as the length of a day, the shell has also been able to accurately reveal climate conditions 70 million years ago.

Top temperatures

For instance, analysis of the clam has shown that temperatures of the oceans in the late Cretaceous period were actually warmer than previous estimates. Winters were as hot as 86°C, while summers reached a blistering heat of 104°C. According to de Winter, those temperatures were likely reaching the maximum that mollusks were able to withstand.

Sharpening our understanding

Rudist expert Peter Skelton – who wasn’t involved in de Winter’s study – commented on the team’s findings to AGU. He said, “The high fidelity of this data-set has allowed the authors to draw two particularly interesting inferences that help to sharpen our understanding of both Cretaceous astrochronology and rudist paleobiology.”

Filling in the blanks

The research has essentially provided the most accurate reading yet of the length of a day in the late Cretaceous period. What’s more, it has also helped to fill in some of the blanks concerning the Moon’s rotation and influence on Earth. That’s because while the lunar planet recession rate currently stands at around 1.5 inches per year, the experts believe that it’s impossible for that to have always been the case.

Just 1.4 billion years or so

If the recession rate had never changed, it would mean the Moon would essentially have been inside the Earth just 1.4 billion years ago. But we know that the former planet is much older than that – having likely collided with our planet around 4.5 billion years ago. That suggests, then, that the rate at which the Moon is pulling away has changed over time.

Making sense of the changes

Astonishingly, tracing a nine-year span of this ancient clam’s life has helped scientists better understand those changes. Talking to Cosmos magazine, de Winter said, “The evolution of the Earth-Moon distance must have been more complex, but we don’t know exactly how. This type of measurement helps astronomers create better models about how the Earth-Moon system behaved from the moment of the [latter planet’s] formation.”

Laser focus

Seventy million years is really just a fraction of the Moon’s history, however. So, it’s no surprise that going forward, the study’s authors hope to apply their new laser-focused method to even older fossils. And in doing so, they hope to capture similarly precise snapshots of the differing lengths of days further back in time.

There's environmental changes, too

The scientific potential of these fossils doesn’t end with studying the Moon, though. Indeed, they also allow researchers to analyze environmental changes on a daily basis. Acknowledging that it’s a slow process, De Winter added, “Think of large storms or very hot days. It is hard to find fossils as well-preserved as the specimen we used, and [the work] takes a lot of time and effort.”

Big implications, indeed

Nevertheless, the ability to interpret weather patterns in such detail has “big implications” for studying ancient climates, according to de Winter. And in turn, it can help inform scientists about what’s to come. He concluded, “We climate scientists are very interested in such reconstructions. They may teach us how patterns in extreme weather and climate will evolve in the near future.”