Preventing Large Meteorite Impacts

The Threat of Rogue Comets and Asteroids

Introduction, Web Links, Film Reviews, & Bibliography

Compiled by John D. Furber.
Updated 30 December 2003.

[ John D. Furber home page ]

The following is general background information on the

ASTEROID and COMET Impact Threat

I have become very interested in asteroid and comet impacts because they can threaten the survival of our society and our species. In our Solar System, each of the planets is hit by large, high-velocity rocks at unpredictable times. A striking example occured in July 1994 when we observed Jupiter being struck by a series of large comet fragments.

<-- The photo at left is the Arizona Meteor Crater. It is more than a mile across. Between 20,000 and 50,000 years ago, a small metallic asteroid, about 25 meters (80 feet) in diameter impacted the Earth and formed this crater. (Smithsonian Scientific Series (1929), taken by the U.S. Army Air Service. Public domain.)

A meteorite which is 50 meters (150 feet) or more in diameter can wipe out a whole city. A larger meteorite hitting the ocean would cause tsunamis, huge waves which could wipe out all of the coastal cities on the shores of that ocean.
A meteorite several kilometers in diameter (more than a mile) would cause global firestorms, trigger massive earthquakes, volcanic eruptions, and tsunamis, and terminate human civilization and most "higher" species of life on Earth. For example, a 10 km (6 mile diameter) meteorite struck the Yucatan region of Mexico 65 million years ago, wiping out many species including the dinosaurs, who had successfully lived on the Earth far longer than have the humans. The Chicxulub crater which resulted is more than 180 km (100 miles) in diameter.
Ninety years ago, on June 30, 1908, a 60-meter (200 foot) meteor exploded in the atmosphere above Siberia near Tunguska, knocking down trees for hundreds of square kilometers.

Comet Hyakutake, pictured at right, was photographed by the Anglo-Australian Observatory as the comet raced by the Earth in March 1996. It was discovered only 7 weeks earlier! If it had been headed for a collision with Earth, 7 weeks would not have given us time to prepare and implement a successful diversion program.

On the other hand, if a comprehensive sky survey were in progress, Comet Hyakutake could have been discovered months or years earlier. And if diversion planning is begun in advance, then the longer lead time could be used to send up a rocket to divert an incoming comet before it strikes the Earth. The expense of such preparations could be justified as buying DISASTER INSURANCE or implementing safety programs.

"Earth's atmosphere protects us from the multitude of small debris, the size of grains of sand or pebbles, thousands of which pelt our planet every day. The meteors in our night sky are visible evidence of bodies of this type burning up high in the atmosphere. In fact, up to a diameter of about 10 meters (33 feet), most stony meteoroids are destroyed in the atmosphere in a terminal explosion. Obviously, some fragments do reach the ground, because we have stony meteorites in our museums. Such falls are known to cause property damage from time to time. On October 9, 1992, a fireball was seen streaking across the sky all the way from Kentucky to New York. A 12-kilogram (27-pound) stony meteorite (chondrite) from the fireball fell in Peekskill, New York, punching a hole in the rear end of an automobile parked in a driveway and coming to rest in a shallow depression beneath it. Falls into a Connecticut dining room and an Alabama bedroom are other well documented incursions in this century. A 10-meter (33-foot) body typically has the kinetic energy of about five Hiroshima fission bombs, however, and the shock wave it creates can do considerable damage even if nothing but comparatively small fragments survive to reach the ground.

"Many fragments of a 10-meter (33-foot) iron meteoroid will reach the ground. The only well studied example of such a fall in recent times took place in the Sikhote-Alin Mountains of eastern Siberia on February 12, 1947. About 136 metric tons (150 tons) of fragments reached the ground, the largest intact fragment weighing 1,741 kilograms (3,839 pounds). The fragments covered an area of about 1 to 2 square kilometers (0.4 to .8 square miles). within which there were 102 craters greater than 1 meter (39 inches) in diameter, the largest of them 26.5 meters (87 feet), and about 100 more smaller craters. If this small iron meteorite had landed in a city, it obviously would have created quite a stir. The effect of the larger pieces would be comparable to having a supersonic auto suddenly drop in! Such an event occurs about once per decade somewhere on Earth, but most of them are never recorded, occurring at sea or in some remote region such as Antarctica." (Calvin J. Hamilton, Los Alamos National Laboratory)

The importance of these rather small meteorites is that they remind us of the fact that rocks are bombarding us unannounced, and that one as large as the one that wiped out the dinosaurs could be on its way without our knowledge.

Taking Protective Action

Not only are these facts of fascinating scientific and historical interest, but we are able to take political and technological actions now to DETECT and DEFLECT the next one before it hits us. We can encourage our governments and universities to install the 25 automated, widefield CCD telescopes necessary for the early detection system.
Fear can be an appropriate first reaction, for it can spur people to examine the problem more closely and to take positive, constructive actions. As a society which hopes to endure, two kinds of action are necessary, and fortunately, they are possible with current technology.

We need to scan the entire sky every month to identify and catalog asteroids and comets which cross the orbit of the Earth. With computers, we can plot their future paths (orbits) to identify which ones are on a path to hit the Earth. This requires a modest program of about 25 automated widefield, 1-meter diameter telescopes with CCD detectors and computerized image analyzers, like the one borrowed from the US Air Force on Maui. And of course we need the astronomers to operate them. This would cost maybe $20 million per year, which is a small fraction of the NASA or NSF budget. By identifying the object months or years in advance, it is much easier to take effective action to either divert its path or break it into small enough pieces to safely burn up in the Earth's atmosphere.
Preparations need to be made to respond to an incoming asteroid or comet when it is identified by the astronomers. Some of the scientists and engineers who developed nuclear weapons and missiles are becoming interested in adapting these missiles and bombs to this healthy activity. With enough lead time, even a very small change in momentum will be enough to deflect its path and cause it to miss the Earth. Preliminary studies have been conducted by scientists from:
- US Air Force,
- Los Alamos National Lab,
- Lawrence Livermore National Lab,
- US DOE,
- US Naval Research Lab,
- AIAA,
- Russian Federal Nuclear Center,
- China (Beijing) Center of Advanced Science and Technology.
Proposals have so far included:
- Attaching large solar sails to divert the object with the force of the solar wind.
- Installing mass drivers powered by photovoltaics or nuclear power. The momentum of ejecting pieces of the object would change its course in the opposite direction.
- Detonating nuclear explosives near the surface of the object to change its course.
- Drilling and planting nuclear explosives inside the object to break it up and change its course.
- Firing powerful laser pulses at the object from a moon base to ablate spots on its surface and change its course. http://www.space.com/businesstechnology/technology/lunar_caps_011212-1.html

As individual citizens, we can encourage our government to increase current efforts to scan the skies. Interestingly, in the summer of 1994, the US House of Representatives asked NASA to take these actions, and several months later, NASA refused. We need to remind our government employees how important this is to all of us.

Private Sponsorship:

If the United States Government remains unresponsive, the telescopes are not too expensive to be built and operated by individual universities, corporations, or private foundations. Their observations could be coordinated via the Smithsonian Institution. The Maui telescope is one of a set of 6 or more that were built for the US Air Force to track satellites and missiles. They are lending it to the asteroid search for two weeks out of every month. Another, pictured at left, is operated in New Mexico by The LINEAR Project of the MIT Lincoln Laboratory. We could ask the Air Force and Lincoln Laboratories where they were built, and who built them, so that we could find out about making more. They cost about $100,000 each. A complete program will need 25 telescopes and would cost about $20 million, including salaries and buildings. This is a small budget, by government standards, and highly worthwhile insurance for society. Furthermore, we could be do this one-telescope-at-a-time, at different universities or observatories, in different countries, or with funding from different corporate or foundation sponsors.

Long lead times are essential
to successfully divert these objects
to safely miss us.

PARABOLIC COMETS (Long-period comets)
are a special threat because:

They come through the Solar System only in once in human history, so we have no historical records by which to predict them.
They can come in from any direction including the north or south pole.
They come at extremely high velocities (50,000 miles per hour).
They are rather large.
They could smash the Earth on their FIRST PASS through the inner Solar System.

Hence the NEED TO SCAN THE ENTIRE SKY EVERY MONTH.

(Photo at right) The ESA/NASA SOHO orbiting solar observatory shows the huge, long-period "Comet NEAT", not visible from Earth, as is approaches from behind the sun. http://sohowww.nascom.nasa.gov/hotshots/2003_02_12/

So, if you have any personal contacts in Government, corporations, academia, or a philanthropic foundation, we need you to talk to them about establishing more telescopes to open our eyes to the rocks and mountains whizzing by us in the Solar System.

Related Web sites:

The Asteroid and Comet Impact Hazards web site is maintained by David Morrison at the NASA Ames Research Center
The NASA Near Earth Object Program site at JPL has news as well as excellent images of EROS from the NEAR spacecraft.
The Near Earth Asteroid Rendezvous - NEAR site at Johns Hopkins Applied Physics Lab has news, mission history, spacecraft description, images, and movies of EROS from the NEAR spacecraft.
The NASA NEO Program also maintains an updated list of currently known Potentially Hazardous Asteroids.
The NEODyS Near Earth Object Dynamic Site provides information on all Near Earth Asteroids. Each NEA has its own dynamically generated home page providing information and services. The site is maintained by an Italian group started by Andrea Milani.
The NASA/JPL Comet Observation Home Page maintained by Charles S. Morris.
The LINEAR Project of the MIT Lincoln Laboratory is funded by the US Air Force. The goal of the LINEAR project is to demonstrate the application of technology originally developed for the surveillance of earth orbiting satellites, to the problem of detecting and cataloging Near Earth Asteroids (also referred to as Near Earth Objects, or NEOs) that threaten the Earth.
The Spacewatch Project of the University of Arizona Lunar and Planetary Observatory.
The JPL Picture Archive has radar images of asteroid Kleopatra.
Views of the Solar System
Proceedings of the Planetary Defense Workshop, May 22-26, 1995,
Lawrence Livermore National Laboratory at Livermore, California.
US Space Command -- Their primary mission is to watch for missiles, but they also monitor space junk in Earth orbit.
The Minor Planet Center operates at the Smithsonian Astrophysical Observatory under the auspices of the International Astronomical Union. It is responsible for the efficient collection, computation, checking, and dissemination of astrometric observations and orbits for minor planets and comets.
"Moon Base Would Scan The Sky, And Deflect Threats To Earth," by Leonard David, discusses the Comet/Asteroid Protection System (CAPS) study, based at NASA Langley. Try the animated video which illustrates the system. http://www.space.com/businesstechnology/technology/lunar_caps_011212-1.html
James A. Marusek has printed instructions for building and operating an impact shelter at http://personals.galaxyinternet.net/tunga/
SpaceWeather.com has Science news and information about the Sun-Earth environment including Near Earth Objects.
Links to other Astronomy and Physics sites, compiled by John D. Furber.

MAGAZINE Articles:

Dana Desonie. "The Threat from Space," (cover story) Earth. August 1996 pp. 24-31.
Tom Gehrels. "Collisions with Comets and Asteroids," Scientific American. March 1996. pp. 54-59.
David Morrison. "Target: Earth," (cover story) Astronomy. October 1995 pp. 34-41.
Peter Tyson. "Cometbusters," (cover story) Technology Review, Feb/Mar 1995 pp. 22-30.
Newsweek. March 23, 1998, pp. 38-42.
Greg Bryant The Dark Ages : Were They Darker Than We Imagined? Universe. Sept 1999.

Three good BOOKS on the subject are:

The Hammer of God. Arthur C. Clarke. (1993. Fact-based science fiction novel, with positive suggestions for detection and deflection.)
Rogue Asteroids and Doomsday Comets. Duncan Steel (John Wiley & Sons, 1995. Nonfiction by Australian professional astronomer. Foreword by Arthur C. Clarke)
Lucifer's Hammer. Larry Niven and Jerry Pournelle. (Playboy Press, 1977. Fact-based science fiction novel, vividly describing a plausible disaster scenario.)

VIDEOS and MOVIES:

"Deep Impact" (Stephen Spielberg, Exec. Producer) May 9, 1998. Starring Robert Duvall. Directed by Mimi Leder, Dreamworks LLC and Paramount Pictures. This movie is well researched, scientifically valid, and a plausible political intrigue as well.
"The Doomsday Asteroid," (NOVA, PBS, 31 Oct 1995, 55 minutes). This science documentary discusses evidence of past impacts, and liklihood of a future serious impact. (It's not a matter of if. It's a matter of when.) It includes a detailed examination of how scientists during the 20th century gradually accumulated evidence for large impact craters on Earth and the Moon.
"Fire From the Sky," (Turner Original Productions, March 1998, 58 minutes). Documentary with plausible enactment of news coverage which might take place if an impactor were heading toward Earth.
"Cosmic Travelers: Asteroids and Comets," (1997) looks at how comets and asteroids have affected the earth and the plans NASA is developing to protect Earth from future impacts.
The sci fi movie, "Meteor," (Orion, 1979, 103 minutes, PG) is worth renting. It stars Sean Connery, Natalie Wood, Karl Malden, Henry Fonda, Brian Keith, Martin Landau, Trevor Howard. (It's main scientific flaw is that the distances traveled by the spaceship and the asteroid between the asteroid belt and the Earth would take months, rather than a few days.)
"Armageddon" (Touchstone Pictures, July 1, 1998, 151 minutes, PG-13.) Although the plot and the science become unrealistic in the second half, this movie begins with an excellent computer simulation of the impact which wiped out the dinosaurs. Also good are the meteor storm impacts and the dialog between the head of NASA and the President of the United States.

Additional Reading List:

John C. Brandt, Robert C. Chapman. Rendezvous in Space: The Science of Comets. (W.H. Freeman & Co., 1992) (Nonfiction)
Carl Sagan. Pale Blue Dot. (Random House, 1994) 420pp. (Reviewed by Arthur C. Clarke in "Sky and Telescope," June 1995.) Chapters 17-18. (Science essay emphasizing the importance of forethought, planning, and vigilance.)