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- [Narrator] The Chicxulub impactor
was tens of miles wide and forever changed history
when it crashed into earth about 66 million years ago.
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The devastation brought the reign of the dinosaurs
to an abrupt and calamitous end.
Where did this Armageddon-causing object come from,
and how did it come to hit our planet?
A pair of Harvard researchers, Avi Loeb
and Amir Siraj believe they have the answer.
- So in the early 1980s, Luis Alvarez,
a Nobel Laureate in physics, and his son,
the geologist Walter Alvarez,
made the breakthrough discovery that the Chicxulub impactor
and the global extinction that occurred around the same time
were causally connected.
- The Chicxulub impactor was an asteroid
of 10 to 80 kilometers in diameter,
roughly the size of Boston,
with a mass of about a 1,000,000,000,000 kilograms,
up to 100,000,000,000,000 kilograms.
- [Narrator] Their theory on where the Chicxulub came from
goes like this.
A type of long-distance comet coming from the edge
of the solar system known as the Oort cloud,
got bumped off its course by gravitational fields
coming from Jupiter.
The planet acted as a kind of pinball machine,
catapulting the incoming comet into an orbit
that brought the comet so close to the sun,
but the part that's closer to it
felt a stronger gravitational pull, causing a tidal force.
The tidal forces broke pieces of this massive comet apart,
sending some of those pieces into the orbit
of the planet earth.
One of those hit off the coast of Mexico, leaving behind
a crater spanning 93 miles wide and 12 miles deep.
- The impact caused tsunamis, wildfires,
and a massive cloud of debris and aerosols
that enshrouded the planet,
darkening the skies and cooling the atmosphere.
- [Narrator] The theory also looks to explain
what type of space rock many of these impactors are made of.
The scientists say Chicxulub-sized craters on earth
are more likely to be made of carbonaceous chondrite.
This is important because a popular theory
on the origin of the Chicxulub says that the impactor
is a fragment of a large asteroid, came from the Main Belt,
a space between the orbit of Jupiter and Mars.
Only about a tenth of all Main Belt asteroids
are made of carbonaceous chondrite,
while it's assumed most long-period comets
that come from the Oort cloud are made of this material.
- We know that very few asteroids match this composition,
but both observational data
and planetary system formation theories
point to the possibility that this composition
might be widespread amongst long-period comets.
This would be consistent with the fact that
not only the Chicxulub crater matched such a composition,
but so did the largest confirmed crater on earth,
as well as the largest in the past million years,
both of which fall in the size range
that our model predicts an enhanced impact rate for.
- [Narrator] That new rate of impact is consistent
with the age of the Chicxulub,
providing a reasonable explanation for its origin
and other impactors like it.
These smaller comets, if produced in the same way,
would strike earth once every 250,000 to 730,000 years.
- Asteroids are the biggest risk in the short-term
and therefore we should monitor the sky
and make sure that there is no big enough object
approaching earth in our life.
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