Adventures of an asteroid hunter

I am holding something remarkably old.

It is older than any human artifact,

older than life on earth,

older than the continents
and the oceans between them.

This was formed over 4 billion years ago
in the earliest days of the solar system

while the planets were still forming.

This rusty lump of nickel and iron
may not appear special.

But when it is cut open,

you can see that is differently
from earth lymetals.

This pattern reveals metallic crystals
that can only form out in space

where molten metal can cool
extremely slowly,

a few degrees every million years.

This was once part of a
much larger object,

one of millions left over
after the planets formed.

We call these objects asteroids.

Asteroids are our oldest
and most numerous cosmic neighbors.

This graphic shows near-earth asteroids
orbiting around the sun,

shown in yellow,

and swinging close to the earth's orbit,
shown in blue.

The sizes of the earth, sun and asteroids
have been greatly exagerrate

so you can see them clearly.

Teams of scientists across the globe
are searching for these objects,

discovering new ones everyday,

steadily mapping near-earth space.

Much of this work is funded by NASA.

I think of the search for these asteroids
as a giant public works project.

But instead of building a highway,
we're charting outer space,

building an archive that will last
for generations.

These are the 1,556 near-earth asteroids
discovered just last year.

And these are all of the known
near-earth asteroids,

which at last count was 13,733.

Each one has been imaged, catalogued,

and had its path around
the sun determined.

Although it varies from asteroid
to asteroid,

the paths of most asteroids
can be predicted

for dozens of years.

And the paths of some asteroids
can be predicted with incredible precision.

For example, scientists at the
jet Propulsion Laboratory

predicted where the asteroid Toutatis
was going to be

four years in advance within
30 kilometers.

In those four years, Toutatis
travelled 8.5 billion kilomters.

That's a fractional precision
of 0.000000004.

(Laughter)

Now the reason I have this
beautiful asteroid fragment

is because, like all neighbors,
asteroids sometimes

drop by unexpectedly.

Three years ago today,

a small asteroid exploded
over the city of Chelyabinsk, Russia.

That object was about 19 meters across,

or about as big as a convenient store.

Objects of this size hit the earth
every 50 years or so.

66 million years ago,

a much larger object hit the earth,
causing a massive extinction.

75 percent of plant and animal species
were lost,

including, sadly, the dinosaurs.

That object was about
10 kilometers across,

and 10 kilometers is roughly
the cruising altitude

of a 747 jet.

So the next time you're in an
airplane,

snag a window seat, look out

and imagine a rock so enormous that
resting on the ground,

it just grazes your wingtip.

It's so wide, that it takes your
plane 6 full minutes

to fly past it.

That's the size of the asteroid
that hit the earth.

It has only been within my lifetime

that asteroids have been considered
a credible threat to the planet.

And since then, there's been
a focused effort underway

to discover and catalogue
these objects.

I am lucky enough to be part
of this effort.

I'm part of a team of scientists
that use NASA's