The most devastating asteroid to hit Earth - Sean P. S. Gulick
66 million years ago,
near what’s now the Yucatán Peninsula,
a juvenile sauropod feasted
on horsetail plants on a riverbank.
Earth was a tropical planet.
Behemoth and tiny dinosaurs alike
roamed its lands,
while reptiles and tentacled ammonites
swept its seas.
But, in an instant,
everything would change.
A roughly 12-kilometer-wide asteroid
was careening toward Earth
at around 20 kilometers per second.
From where the sauropod stood,
there would have been
no early warning signs.
The asteroid barreled through Earth's
atmosphere in a matter of seconds
and struck the Yucatán’s
submerged continental shelf.
It exploded upon impact,
instantaneously creating
a 100-kilometer-wide hole
and ejecting sedimentary
and crystalline rocks.
Within minutes, the impact crater,
known today as Chicxulub,
began collapsing inwards.
Meanwhile, the base rebounded some
20 kilometers above the Earth’s surface,
then fell back down and moved outwards,
creating a ring of mountains.
The energy released from the asteroid’s
impact is estimated to have been
several billion times that
of a nuclear bomb.
The force sent seismic energy
across the planet
at a much greater magnitude
than any earthquake
a tectonic fault could ever produce.
Massive landslides ensued.
And a tsunami sped
from the newly formed crater,
potentially reaching 1,500 meters high.
Countless lives were extinguished.
Some instantly: all life
within 1,500 kilometers of the impact site
was incinerated;
others right after: by colossal waves,
landslides, and hurricane force winds.
But many organisms
across the planet survived.
It was what came next that would bring
about the end for many species,
including almost all dinosaurs.
This was just the beginning of one
of the most devastating periods
in the history of life on Earth.
When the asteroid struck,
it sent hundreds of gigatons
of carbon-dioxide-rich limestone
and sulfur-saturated-sediments
into the atmosphere.
The sulfur combined with water vapor
to create sulfate aerosols.
This plume of limestone dust,
soot, and sulfate aerosols
spread from the impact site
at several kilometers per second,
blanketing the globe in a matter of hours.
It’s thought to have blocked the Sun,
plunging Earth into an extended period
of darkness
and dropping the temperature
in many places by at least 25°C.
The asteroid’s immediate
impact was devastating,
but it seems to have been
the rapid climate change it triggered
that ended the roughly 165-million-year
reign of the dinosaurs.
Plants and plankton rapidly died,
causing the collapse
of food webs worldwide.
An estimated 75% of life on Earth
went extinct,
including almost all dinosaurs.
Small birds were the only
kinds that remained,
perhaps because they relied on hardy seeds
that weathered the catastrophe.
It's unclear why exactly the lifeforms
that survived the extinction did.
Many smaller organisms,
like insects, persisted.
So did early mammals— perhaps because
of their ability to burrow and hibernate.
And photosynthetic lifeforms like algae,
that had ways of withstanding
low-light conditions,
also survived.
Traces of the asteroid scattered worldwide
and the scar of the Chicxulub crater
attest to this period
of monumental destruction.
So, what are the chances of another
Chicxulub happening?
Space programs are continuously
identifying and tracking
near-Earth asteroids.
Fortunately, the likelihood of one
as large and cataclysmic
striking in the next thousand or so years
seems to be small—
something like a 7 in a million chance.
However, we are facing the consequences
of another kind of rapid climate change,
this time because of humanity's
own emissions.
Animals are going extinct faster
than ever in our history,
and people are being displaced
from their homes.
But, unlike the dinosaurs,
we have the opportunity to avoid the
large-scale devastation that will come
if governments continue
with the status quo.
