>>JACKIE FAHERTY (astrophysicist, AMNH): How
do we know an asteroid hit Earth 66 million years ago?
[MUSIC] [BOOM]
>>FAHERTY: Here at the American Museum of
Natural History, we’re pretty well known
for two things, and that’s space and dinosaurs.
And there’s one unifying tie between the
two.
66 million years ago there’s very strong
evidence that a giant asteroid hit the Earth
and caused a mass amount of change on this
planet which led to the extinction of the dinosaurs.
How do we know that happened?
Well in the 1980s, a geologist named Walter
Alvarez uncovered, with the help, actually
of his physicist, Nobel Prize-winning father,
that right at the K-Pg boundary which was
the point of dinosaurs’ extinction, you
had a particularly strong amount of whats
called iridium.
And iridium, which is atomic number 77 on
your periodic table, is mostly found in high
quantities in asteroids.
In the Earth we can find it but it’s locked
further down in the Earth.
When you find a lot of iridium, that’s a
bit of a smoking gun that you’ve got the
signature of an asteroid impact.
So the theory was put out there that an asteroid
impact was the reason that the dinosaurs were extinct.
So if something hits you would expect there
to be a crater.
Now around the same time that the theory was
put out there, there were oil exploration
surveys that were ongoing in the Yucatan Peninsula.
By chance, they uncovered what’s now called
the Chicxulub Impact Basin which is the right
size and had the right chemical composition
around it that we think that that is the site
of the giant impact that led to the extinction
of the dinosaurs.
The thing is that asteroids or parts of asteroids,
dust of an asteroid, we actually get hit by
it all the time.
Anytime you see a shooting star, you’re
seeing a bit of a piece of rock that’s burning
up in your atmosphere.
The ones that we worry about are the big ones.
The one that knocked out the dinosaurs was
six miles in diameter.
That kind of impact – it happens, but it’s
far more rare.
And unlike the dinosaurs, astronomers are
ready and watching for one that might be hazardous.
If you want to hear more about what exactly
the asteroid did to the dinosaurs, then click
here and hear from Team Dinos on the asteroid
and dinosaurs themselves.
Thanks everybody for watching, tune in for
more videos where Team Space will yet again
take out Team Dinosaur.
