60 minutes rewind
for a long time astronomers saw the asteroids and comets that come close to earth as useless debris
space rocks that blocked our view of distant galaxies not anymore they're now viewed as
scientifically important and potentially very dangerous if they were to collide with our planet
the odds of that happening on any given day are remote but over millions of years
scientists believe there have been lots of impacts and few doubt there are more
to come a former astronaut told us it's like a game of cosmic roulette and one mankind cannot
afford to lose concern over our ability to detect these objects that come near the earth
grew after an incident in russia this february when an asteroid crashed into the atmosphere
with many times the energy of the bomb dropped on hiroshima narrowly missing a city of one million
this is video of that asteroid in russia barreling toward earth at 40 000 miles an
hour it exploded into pieces 19 miles above and 25 miles south of the city of chelyabinsk
people thought it had missed them entirely until minutes later when the shock wave arrived
shattering glass crushing doors knocking some people right off their feet more than a thousand
were injured how much warning did people in chelyabinsk have none paul chodes is a
scientist at nasa's jet propulsion laboratory in pasadena california he and his boss don
yeomans have been trying to track near-earth objects for decades we didn't see it coming
it was coming from the general direction of the sun so it was in the daytime sky as it approached
so how did you find out about it twitter and youtube when we first saw the images so the first
people at nasa heard about it was twitter exactly says an object this size hits earth once
every hundred years on average yet the same day purely by chance another asteroid twice as large
came within 17 000 miles of earth passing between us and the satellites that are bringing you this
broadcast the only reason there was any advance warning was because an amateur astronomer in spain
an oral surgeon by day noticed it just before it moved out of view we know about some of the
most distant galaxies in the known universe and yet we don't really know everything that's right
in our own backyard wow amy mainzer is a nasa scientist who focuses on detecting asteroids
so we've got to move the dome out of the way and then we're going to start to follow the asteroid
as it tracks across the sky this telescope at the table mountain observatory in california
is one of dozens all over the world that are used to track and study near-earth objects mainzer told
us they're often very hard to find some of these asteroids are really really dark darker even than
coal in some cases kind of like the soot at the bottom of a barbecue grill so you're looking for
something that's darker than coal against a black sky exactly and now you see the problem
another problem is that ground-based telescopes can't see objects coming from the direction of
the sun because they're in the daytime sky like the asteroid that hit russia
astronomers find asteroids by taking repeated pictures of the night sky
and looking for things that change position professionals and amateurs all over the world
work together sharing information once paul chotis and his nasa colleagues have multiple
sightings they can predict an object's location as far as a hundred years into the future
this particular object has a very well known orbit because the asteroid amy mainzer was
observing the night we visited didn't look like much on her screen that little thing yep that's it
but it's nearly half a mile wide and capable of destroying an entire continent so that's actually
that's a huge asteroid yeah it's a huge asteroid something this size hit the earth it would be
devastating it would be very bad asteroids are composed mostly of rock comets ice and dust they
come in all shapes and sizes some look like small planets others giant dog bones for a long time
nobody thought they were worth tracking at all it wasn't thought that they really did hit the earth
astronomers debated for a long time about the nature of the craters on the moon they thought
the craters on the moon were volcanic possibly yeah and it's only been fairly recently within
the last 50 years or so that the field has really recognized that yeah impacts actually do happen
and not only do they happen on geological time scales you know millions and billions of years but
on human time scales in some cases the last major asteroid to collide with earth hit in 1908 in the
tunguska region of siberia it's believed to have been 40 yards wide and to have exploded in the air
like a nuclear bomb leveling 80 million trees in an area the size of metropolitan washington
this crater in northern arizona was created 50 000 years ago it's one of more than 180 impact
craters geologists have found so far they think there are many more hidden by water
and vegetation more even than on the moon because the earth's gravity is greater the most famous
impact of all is the one that may have wiped out the dinosaurs more than 65 million years ago
the theory is that an enormous asteroid or comet collided so violently with earth
it created a cloud of debris that blocked out the sun killing off 75 percent of all species
leaving behind a crater in mexico more than a hundred miles wide
these are objects that were once in space pieces of asteroids yeomans and chodas showed us some of
the remarkable things that have fallen from the sky this is a piece of mars you have it in your
hand it wandered around the inner solar system for a few million years and a 40-pound stone came down
in africa about 10 feet from a farmer in uh really october of 1962. let's see there's anything from
mars yeah i know they played a trick on me as well would you hand that one to me that big one yeah
this one was iron nickel and heavy as an anvil not all asteroids are made of such dense stuff
but many contain high concentrations of valuable minerals like platinum
that might someday be mined in space we'll start by sending astronauts to an asteroid
for the first time in history president obama's proposed budget for next year
includes a plan to capture a tiny asteroid so that astronauts could rendezvous with it by 2025. the
idea is to perfect techniques needed to explore deep space and perhaps find a way to exploit the
water resources that many comets and asteroids have you could extract water from them you can
break the water down into hydrogen and oxygen which is the most efficient form of rocket fuel so
asteroids may serve as the fueling stations and watering holes for future planetary exploration
but as the scriptwriters of the hollywood blockbuster armageddon vividly imagined
asteroids have the potential to harm mankind as well for better or worse this is what many of us
know about near-earth objects that if bruce willis hadn't nuked one it would have destroyed the world
you see these movies with bruce willis where an asteroid is coming and is going to destroy the
world is that likely no no we found 95 percent of the large ones and none of them represent
a threat in the next hundred years or so what about the other five percent we're still looking
he's talking about objects over half a mile wide that are big enough to cause global destruction
the problem is there are lots of smaller objects over 40 yards in diameter that are unaccounted for
and potentially very dangerous the story will continue after this
if you look at the light green dot that's the orbit of the earth ed lew is a former astronaut
who spent six months on the international space station he showed us a computer generated
representation of our solar system that's the sun in the center and those green dots are ten
thousand near-earth objects astronomers have found so far so these green dots are the asteroids that
could hit the earth this is of the about the ten thousand known asteroids yes these are the 10 000
known asteroids here's the problem there's about a factor of 100 more the real solar system looks
like this and we know this because we've only been able to observe a small fraction of the sky and we
know that there's about 100 times more asteroids this is all the asteroids that are there are
about a million asteroids large enough to destroy acidity out there and right now we only know of of
what percent of those asteroids about one half of one percent does it worry you that you only know
one percent of these asteroids that are big enough to destroy a city well most of those are really
small and the odds are that many of these would hit in a remote area or or could hit in an ocean
so that is why the larger ones are those that we were paying attention to first now the next
size range is the one to concentrate on those that could cause you know continent wide extinction or
destruction yeah that would be pretty good to prevent that continent-wide destruction those
are the next ones we'll continue to find those and when we work our way down to the small ones
but right now an object that could wipe out the eastern seaboard or new york city
could be a day away and there's a very good chance we wouldn't know about it
well we're working to make sure that we will know about it but right now we wouldn't know about it
it's possible yes the committee on science space and technology will come to order
nasa administrator charles bolden faced similar questions from congress after the near miss in
russia earlier this year what would we do if you detected even a small one like the one that
detonated in russia headed for new york city in three weeks what would we do if
it's coming in three weeks uh pray is there anything you can do to deflect an asteroid
that's gonna hit besides evacuating a city if you find it 10 or 20 or 30 years in advance
then yes you could actually send a spacecraft up run into it slow it down a millimeter or two
per second so that in 10 or 20 years when it was predicted to hit the earth it wouldn't just slam
a spacecraft into it slam into it in 2005 nasa did just that as an experiment firing a small unmanned
spacecraft into a comet called temple one but you can't deflect what you don't detect which is why
former astronaut ed lew has taken on a new mission here's the telescope that we're building he's now
chairman of the b612 foundation which has designed a space-based telescope to speed up the discovery
of near-earth objects nasa's amy mainzer has been developing one too both telescopes would be able
to find asteroids by using infrared sensors that detect heat rather than light but a telescope like
this would cost roughly half a billion dollars and so far neither the united states nor any
other government has committed significant funds so the b612 foundation is trying to raise the
money privately by reaching out to individual donors i don't think there's any other global
uh catastrophe global scale catastrophe that we can prevent this is the only one that i know of
we can solve this particular issue for the cost of building a freeway overpass i mean
that's literally what it is but nobody has been killed by an asteroid yeah and what i'm saying is
that you can't wait to that point afterwards when you say we should have done it you have to think
of this as cosmic roulette right the phrase that they have in vegas is that the house always wins
and you know the sort of secret to all this is that we're not the house at some point
you know the solar system's going to get you they're very
low probability events but very high consequence events the problem it seems like is you're asking
people to care about something which may not affect their lives may not even affect
their children's lives that's true it's a tough concept to get across because as you say it's
something that may not happen for another 100 years 200 years it may happen tomorrow morning