Video transcript
The video is 7 minutes and 28 seconds long.
Produced by the American Museum of Natural History, May 2005.
Visual: Montage of city scenes with traffic, planes, crowds, trains.
Speaker: Grant Stokes, MIT Lincoln Laboratory
Title Graphic: Impact
Visuals: Exteriors and interiors of telescope in southwestern desert setting.
The LINEAR program is the near-Earth asteroid research program. We operate at Lincoln Laboratory, and the idea is to take technology that we've developed for the air force—tracking objects in space—and applying that to hunting for near-Earth asteroids.
Visuals: Visualization of the solar system. Zoom into asteroid belt. Zoom into close up asteroid passing by Earth.
An asteroid is kind of the leftovers from the formation of the Solar System. If you look at the Solar System, there's a big gap between Jupiter and Mars where there's material that never really formed into a planet. And so there are millions of objects out there in what's called the main asteroid belt. Near-Earth asteroids are a special subclass of asteroids that get disturbed out, probably due to gravitational interactions with the planet Jupiter, and they get pushed into orbits that could bring them fairly close to the Earth. That doesn't mean impact, but that means within, say, five lunar distances to the Earth, which is in the immediate neighborhood in the scale of the Solar System. And we're interested in those because over some time there are some number of those that will collide with the Earth.
Speaker: David Kring, Lunar and Planetary Lab, University of Arizona
Visuals: David Kring hiking around very large crater rim.
Meteor Crater was produced 50,000 years ago when an iron asteroid plummeted to Earth, hitting with an explosive force several hundred to perhaps a couple of thousand times more energetic than the bombs that destroyed Hiroshima and Nagasaki.
Visuals: Aerials of Meteor Crator, David Kring holding up black metal fragment.
This asteroid was approximately half the size of a football field in diameter, and only a few percent of that object actually survived to litter the landscape with these metal fragments like I have here.
Visuals: Earth from space, active volcano, waves hitting shore.
We only know of about 170 impact craters on the surface of the Earth, but the impact cratering record on Earth is actually very deceiving. The Earth is a very dynamic planet in terms of geology. There's plate tectonics, there's volcanism, there's erosion. All of these processes have the tendency to erase the signatures of impact events.
Visuals: Crater-scarred moon, Earth.
But if we look at the Moon where these processes don't occur, we can actually count 300,000 impact craters the size of Meteor Crater or larger. That implies the Earth, which is in the same part of the Solar System, but a larger body, has been hit by over four million asteroids and comets.
Visuals: Rotating telescope.
The key, in terms of evaluating the future threat of these objects, is to locate all of them in space. Map out where they are, map out their orbits, so that we can predict when, in the future, they are going to hit the Earth.
Speaker: Grant Stokes
Visuals: Woman at computer. Screens filled with numbers and star field.
The data that LINEAR collects is actually intended to distinguish an asteroid, which is a object that is relatively close by, from something that's in the far starfield. And the way we do that is over a period of time we go and we track the stars. We leave them apparently not moving and take a picture.
Visuals: Shots of telescope exterior as day turns to night, followed by snapshots of star field with a single point moving through images series.
We then come back a half an hour later, and we take another picture. And we do that five times in a row. And spread over a couple of hours the asteroid has apparent motion. Once an asteroid is discovered, there's still a need for follow-up observations. Having us find it once is not sufficient. Somebody has to provide the observations that allow the Minor Planet Center to calculate an orbit.
Visuals: Exterior sign: Center for Astrophysics, Harvard College Observatory, Smithsonian Astrophysics Observatory. Interior office with man at computor displaying star field, and a web site titled “NEO Confirmation Page”.
Speaker: Brian Marsden, Minor Planet Center, Harvard-Smithsonian Center for Astrophysics
Every day we receive a lot of observations of asteroids, possibly as many as 15,000 from the LINEAR project alone. And 99.9 percent of those asteroids are absolutely no danger to the Earth at all. So we pick out those that seem most promising, put them on a Web site called the Near-Earth Object Confirmation Page in the hope of inspiring more observations, because that is what is needed in order, really, to calculate the orbits of these objects.
Speaker: Bert Stevens, Desert Moon Observatory
Visuals: Bert rolling telescope out of garage and making adjustments to instrument.
This is Desert Moon Observatory, Minor Planet Center number 448.
Speaker: Brian Marsden
Visuals: Bert observing through telescope. And second man manipulating large telescope in his backyard.
The people who are making the follow-up observations, some of them are professionals, most of them are amateur astronomers. There are a lot of very sophisticated amateur astronomers around the world nowadays with the latest equipment that will allow them immediately to get onto these objects and measure their positions and report them to us.
Speaker: David Dixon, Jornada Observatory
Visuals: David Dixon inside, observing star fields on computer screen.
We're going currently to 2005CL, which is a potentially hazardous asteroid.
Speaker: Brian Marsden
If something is going to hit us for sure, then that has a probability of one. If the probability is zero, it's not going to hit us.
Visuals: Visualizations of asteroid moving through space, asteroid belt, and asteroid passing by Earth.
We know the laws of motion, we know that asteroids are going around the Sun basically according to Newton's principles, but we cannot predict exactly based on limited amount of information that there is or is not going to be an impact. It will show up with a small probability, like one in a million, one in a thousand sometimes, and we recently had a case of one in thirty-seven. Now what almost invariably happens as you get more observations, those impact possibilities go away, because ultimately the probability of impact is either zero or one. Usually it's zero, but we could always be unlucky.
Visuals: Men observing through telescopes and computers, and posting information to the Web.
So the whole idea is to try and find these things before they find us. NASA's aim being to find 90 percent of the ones larger than one kilometer by the end of the year 2008. We think there are 1,200, 1,500 such objects. We've found 700, so we're actually doing quite well on that.
Speaker: Grant Stokes
Visuals: Montage of telescopes and crater images from show, ending with large asteroid passing through screen.
Well, I think we're making the effort to track the objects for a couple of reasons. Number one, it's very interesting. It's interesting to understand what the makeup of the Solar System is and it's kind of a cosmic Easter egg hunt, if you will. In addition, if you look at the average statistical danger to the Earth in any particular year, it's nonnegligible. It just happens to come in big chunks. It's kind of an all or nothing game. Well, our job at LINEAR is in fact to search the sky and report all of the objects. It's not really our job to decide what you do if you find one.