What happened to the asteroid that killed the dinosaurs?
Approximately 66 million years ago, an asteroid
the size of Mount Everest fell on earth, causing a cataclysm that devastated 75% of the living
beings.
But how do we know that happened?
If that meteorite was so giant, where is it?
Have we found it?
Let's find out!
"Introduction" In 1834 the English doctor Gideon Mantell
classified the first fossil of a dinosaur in history; from that moment on, around the
world, we were finding more fossils belonging to creatures that humanity had never seen,
dinosaurs.
These famous creatures that have caught the attention of young and old existed long before
the first humans walked on earth and had a great diversity of sizes and shapes.
The most enigmatic thing about dinosaurs is that despite their diversity and enormous
size, most of them are extinct today.
Why did such giant creatures that had populated the entire planet become extinct?
This was the question that scientists worldwide asked themselves for many years.
The Mysterious Cretaceous-Paleogene Mass Extinction During the 90s, paleontologists and geologists
worldwide made enormous efforts to solve the mystery of the extinction of dinosaurs.
During this time, several expeditions were carried out to the world's most critical fossil
extraction areas, and scientists found a pattern in all dinosaur samples.
When measuring the age of dinosaur fossils, scientists noticed that they stopped appearing
at a particular moment in history, meaning that most dinosaurs died simultaneously.
In other words, geological evidence showed that 66 million years ago, a sudden mass extinction
caused the end of the Cretaceous period and the Mesozoic Era, giving rise to the Paleogene,
the first period of the Cenozoic Era, which continues to this day.
This mysterious mass extinction was cataloged as the K–Pg event, which means Cretaceous-Paleogene.
In the geological record, the K–Pg event is marked by a thin layer of sediment called
the K–Pg boundary, which can be found worldwide in marine and terrestrial rocks.
Strangely, this clay that marks the K–Pg boundary shows unusually high levels of metallic
iridium, an element more common in asteroids than in the Earth's crust.
A METEORITE DIFFICULT TO FIND In 1980 a group of researchers led by physicist
Luis Álvarez, his son geologist Walter Álvarez and other collaborators discovered, in samples
taken around the world, the intermediate layers between the Cretaceous and Tertiary periods
of 65 million years ago, a concentration of iridium hundreds of times higher than usual.
Thanks to this finding, they raised the "Álvarez hypothesis", which explains that the extinction
of dinosaurs and many other life forms would have been caused by the impact of a large
meteorite against the surface of the Earth 65 million years ago, however, this proposal
ran into a problem.
That problem was that to cause a mass extinction, such a large meteorite would have left a crater
of at least 150 km in diameter on the Earth's crust, and until that date, no crater of such
dimensions was known.
Chicxulub Crater To corroborate the theory that dinosaurs had
become extinct due to the impact of an asteroid, it was necessary to find the crater where
it had fallen; for many years, geologists from all over the world tirelessly searched
for the famous crater without success.
This was a difficult task since the event took place 66 million years ago; at that time,
the continents did not have the configuration we know today, so it is most likely that the
crater was several kilometers deep below the ground.
How to find a crater that cannot be seen?
Fortunately for geologists, the crater had already been discovered by accident by a Mexican
company many years earlier.
In the seventies, geophysicists Antonio Camargo and Glen Penfield, engineers of the parastatal
company Petróleos Mexicanos (Pemex), detected a gravimetric anomaly in the Gulf of Mexico
while looking for oil deposits; this anomaly had a depth of several kilometers and extended
through the Gulf of Mexico and the state of Yucatan.
Initially, engineers did not know what it was, but the structure had the shape of a
crater generated by the impact of a meteorite.
The National Autonomous University of Mexico (UNAM), in collaboration with NASA, analyzed
the samples of the wells drilled by the Mexican company PEMEX to confirm this theory.
Thus, they determined the dimensions of a crater more than 2.5 km deep and a diameter
greater than 200 km, the biggest and best-preserved crater on the entire planet today.
The center of this crater is located a few kilometers east of Puerto Progreso, near the
town of Chicxulub, in the state of Yucatan.
Because of this, that was how the crater was called, Chixulub.
When the Álvarez researchers heard this news, they immediately went to where the crater
was located to study the concentrations of Iridium isotopes, which they found in abundance,
verifying that this was the crater that everyone was looking for.
That's where the meteorite that killed the dinosaurs fell.
WHERE WAS THE METEORITE?
Once the Chixulub crater was officially declared the site of the meteorite impact that killed
the dinosaurs, there was only one thing left: find the meteorite.
However, this would be a futile task since such a meteorite no longer existed.
A meteorite is a smaller astronomical object that impacts the planet's surface.
However, before impacting, this meteorite can be classified in two ways, as an asteroid
or as a comet.
Asteroids are enormous rocks containing large concentrations of metals and minerals, while
comets contain rocks, metals, and ice.
Initially, the Chixulub meteorite may have come from a vast metallic asteroid, but more
recent evidence suggests that it was most likely a comet.
Thanks to the measurements carried out in the crater of Chixulub, it is known that at
the time of impact, the meteorite must have had a diameter of between 9km and 11km.
However, if it were a comet and not an asteroid, this would have caused that, at the entrance
to the atmosphere, much of the comet's outer layers were ejected by reducing their size,
leaving its inner layers exposed.
When the comet hit the Earth's surface, the heat generated was so high that the rock and
metals that made it up passed directly from the solid state to the gaseous state; that
is, the meteorite evaporated instantly due to the very high temperatures of the impact.
In addition, the impact soil turned the rocks into liquid, causing massive tsunamis several
kilometers high.
In other words, the meteorite disintegrated in the same place where it fell.
THE EFFECTS OF IMPACT The meteorite's impact devastated the global
environment, raising the entire planet's temperatures and causing earthquakes that activated all
the volcanoes in the world; this caused a series of eruptions that flooded the sky with
dust, ash, and steam, darkening the planet for thousands of years.
Although at first, the entire planet was warmed by the impact, a short time later, it cooled
due to the smoke that covered the sky.
The event quickly acidified the oceans, producing an ecological collapse that ended the plants,
breaking the food chain and initiating the extinction of 75% of the species that inhabited
the planet.
With the sky darkened, the plants could not do photosynthesis, which caused them to become
extinct.
Then the herbivorous animals that fed on those plants began to die, and the predatory animals
that fed on the herbivores also died.
The only animals that managed to survive were those that could feed on things other than
plants, such as roots or seeds.
In this way, the small rodents resembling modern marsupials could take refuge from the
ashes that fell from the sky in burrows and feed on the roots of the dead plants.
Other more intelligent animals, such as birds, managed to survive by eating the seeds and
nuts left over from the dead trees and searching for water in underground mantles that had
not been affected by the ashes that fell due to the impact of the meteorite.
A wide range of species perished in the K–Pg extinction, the best known being non-avian
dinosaurs.
Although other terrestrial organisms also died, including some mammals, birds, lizards,
insects, plants, and all pterosaurs.
In the oceans, the meteorite impact wiped out plesiosaurs and mosasaurs and devastated
teleost fish, sharks, mollusks, and many plankton species.
However, the extinction also provided evolutionary opportunities: as a result, many groups of
animals and plants underwent a remarkable adaptation, caused mainly by the sudden disappearance
of those who, until then, had ruled the planet, the dinosaurs.
Without the presence of dinosaurs, small mammals began to adopt new shapes and sizes within
the disorganized and emptied ecological niches Developing new forms such as horses, whales,
bats, and primates.
The surviving dinosaurs were birds, land and water birds that evolved into all modern bird
species, so when asked what happened to dinosaurs, remember that birds are dinosaurs.
IT WASN'T JUST A METEORITE Contrary to what is known in popular culture
today, there is a theory called "Multiple Impact Theory," which indicates that the extinction
of the dinosaurs was not due to a single meteorite but that there were many meteorites that fell
all over the Earth.
This theory points out that perhaps the comet that caused the Cretaceous extinction broke
into several pieces, and these pieces fell at different points on Earth.
One of them would be "The Silverpit crater" this is an underwater impact crater in the
North Sea, off the coast of the island of Great Britain.
It was discovered in 2002 by analyzing seismic data collected during routine oil exploration.
When dating the crater's age, everything indicates that it impacted the Earth approximately 65
million years ago, so its formation coincides with the impact that created the Chicxulub
crater in the Yucatan Peninsula, Mexico.
If Silverpit is an impact crater, this could imply that the Earth received collisions from
several objects and not just one at that time.
Be that as it may, today we know that extinction and meteorite impacts did occur and were the
cause of the extinction of the dinosaurs.
We know that this event occurred and is likely to happen again, but if so, when will another
meteorite like the one that killed the dinosaurs fall back on Earth?
Do you think we could defend ourselves if a comet like the one that killed the dinosaurs
were heading toward Earth just now?
If you want us to make a video about that, let us know your opinion in the comments.