Magnitude     Path of
Date     Location/Event            /Size       Devastation 
_______  ____________________   _____________   ___________
??/05/96 283,000 Earth near     Unknown at      Missed earth by
	 miss			this writing	approx a quarter
						of a millon miles
						A "bullet graze"
						in astronomial terms.

6/30/08  Tunguska, Siberia      20 stories      Approx. the size 
                                                of  Washington DC
                                                but unpopulated.
                                                Meteor exploded OVER
                                                the site and didn't
                                                actually impact earth.
Last     Australia            over 24 craters 
5000 yrs

-50,0000 Winslow, AZ Iron       1.2K crater/
years    asteroid. First       size:30 meters 
         identified meteor     diameter 
         impact crater 1960.
         Estimated impact 
         speed: 43,0000 miles
         /hour.

          Canada 150 craters  largest is 20 miles
                              in diameter.
                             (Largest in US: 13 
                              1/2 miles).

First, some definitions:

• Asteroids Hunks of rock or metal that are leftover planetary building blocks from the formation of our solar system. Asteroids are predominantly located in the "Asteroid Belt" between Jupiter and Mars.
  
• Comets Fragments of ice that form at a distance from the sun. As they approach the sun, the ice begins to melt, forming the characteristic comet "tail".
  
  
• Meteors Any fragment of a comet or asteroid that enters earth's atmosphere.
  
• NASA scientists believe that our chances of dying from a maverick asteroid are statistically 6 times as greater than that of dying from a airplane accident and 10 times greater than tornado:
  

          Your chance of dying:
                  1 in 6000       Asteroid 
                  1 in 40,000     Airplane
                  1 in 50,000     Tornado
  

• The earth has many scars from already having been hit. One way to appreciate the amount of cosmic bombardment is to look at the moon's thousands of craters. The earth is equally subject to cosmic bombardment, but most of the craters from our early history have been erased or covered.
  
• Estimates are that about once a century about the size of the Siberian meteor (about 20 stories high) hits the earth. Since the Siberian impact occurred in the early 1900's, we're due for one this size soon!!
  
• Scientists further estimate that about every 100,000 years a large (Avg:1-6 miles) comet or asteroid will collide with a earth.
  
• We're probably about due for this one too, after the Winslow, Arizona, impact. It's estimated that the impact of a fragment this size would kill 1 billion people instantly.
  
• Finally, once every million years a fragment the size of the one that wiped out the dinosaurs is estimated to hit.
  
• Perturbations and collisions in the asteroid belt between Jupiter and Mars can knock asteroids out of their orbits and toward earth, giving us very little time to respond to the threat
  
• At current rate, it would take more than a century to map the over 1,000 asteroids that are larger than 1 kilometer.(9)
  
• During an average night, Space Watch may find as many as 600 asteroids! (9)
  
• Assuming no more funding cuts, it may take until 2008 to determine if an asteroid is out there with out name on it. (9)
  

• Amendez Father and son team also demonstrated that the earth, particularily the area around impact craters are high in irridium.
• Dinosaurs were around 1500 times longer than we humans!
• 1 mile = 1 billion Megatons
• EROS - 22 miles in diameter(?) - 2 times the size of Manhatten, NASA is sending a probe.
• Educators $ 19.95 (800) 255-9424 Doomsday Asteroid

• Six months to a year would not be enough time to do anything about a potential impact. Depending on the size of the fragment, it could take 5-10 years to develop an effective defense strategy.
  
• Some estimates are that even 10 years our chances would still be slim (9)
  
• Warning time is crucial.
  

• Robots called mass drivers have been conceived that could alter the trajectory of an asteroid.
  
• Focusing solar mirrors - see section on Dr. Jay Melosh at the Univ. of Arizona, Tucson.
  
• Deploying solar sails
  
• Microwave devices
  
• Laser
  

• The idea here is to send a nuclear bomb and detonate near the asteroid and send a shock wave to divert the path. However, to deflect a one mile diameter comet fragment would require a larger hydrogen bomb than exists today.
  
• Another option is direct targeting - i.e. Aim, Shoot, blow up. The problem with this approach is that irregular surfaces and unknown composition could create big rubble piles that would result in a large number of medium size objects coming down all over the place, which could be almost as destructive as a single larger impact depending on the fragments' sizes.
  
• Many scientists feel that shooting a nuclear weapon is NOT the solution: for a globe-threatening meteor approx. 1 mile to 6 miles in diameter a nuclear blast 10 times more powerful than the most powerful M.E.R.V.'s. existing today would be required. Building such a weapon would adversely impact global security and could cause another Cold War.
  

• After the discovery of Shoemaker-Levy 9, NASA was commissioned by the congress to study the potential problem of a comet or asteroid collision with earth. However, there are currently less people working on this project than staff a typical McDonalds. As NASA's budget continues to be cut, this project gets lower and lower priority and currently less than 1/40th of the cost of a single space shuttle launch is spent on monitoring and researching asteroids and comets.
  

Many scientists believe that 65 million years ago a meteor hit the earth, probably in the area of the Yucatan peninsula, with a force equivalent to all the earth's nuclear arsenal. This meteor is thought to have been 6 miles in diameter, and is believed to have killed all the dinosaurs and 75% of all life on earth. Evidence that the earth was hit by at least one object in recent past include:

• The fossil evidence for dinosaurs lies within the Cretaceous and Tertiary periods, after which there is an abrupt lack of fossils. Additionally, in this fossil-free geologic layer, clay rich in iridium has been found. Iridium is a chemical element which is common to asteroids but found less commonly on earth.
  
• No dinosaurs traces have been found after this geological event.
  
• On a geologic scale the dinosaurs disappearance was geologically instantaneous.
  
• Most scientists will not dispute that a meteor of some magnitude hit the earth sometime in the distant past. Current estimates are about 65 million years ago.(2)
  
• It should be noted that the impact of this meteor was not all bad (provided you weren't a dinosaur!). If it weren't for this cataclysmic event altering the balance of life on earth, it's unlikely that mammals, let alone humans, would have risen to prominence. The event that caused the demise of the dinosaurs gave rise to more opportunistic life forms such as us to have a chance.
  
• Today, mammals may have a better or worse survivability if such a disaster were repeated because, unlike dinosaurs, we are warm-blooded. Regardless, it is likely that the majority of life on earth would be destroyed either by the impact of such a meteor or its aftermath.
  

On June 17, 1996, East Moriches, NY TWA flight 800 crashed and 230 people died. 1 year later, the examination of the crashed vessel, collected at West Hampton beach, and conducted at Long Island, at a cost of over 27 million dollars, involving 600 FBI agents, 25 YRI investigators, later, what exactly happened is still speculative at best.
Dr. Irving Itzkan, PhD in Boston, Mass. may have the unexpected answers. (br>
• 
  
• Every day 3 asteriods capable of bringing down an aircraft enter the earths atmosphere
  
• These asteroids are traveling at hypersonic velocity
  
• 20-100 observers saw a streak in the skies, of these 2 were helicopter pilots, trained observers.
  
• Abrupt ceasation of radio communication is typical of disturbance with asteriods not rockets
  
• Sonic booms were also heard, again typical of asteriods.
  

• Asteroids are hunks of rock or metal that are leftover planetary building blocks from the formation of our solar system. Asteroids are predominantly located in the "Asteroid Belt" between Jupiter and Mars.
  
• Asteroids tend to have very irregular, non-symmetrical and very unusual gravity's as demonstrated by computer modeling of gravity, orbit, etc.,(4)
  
• Castalia - 22 mile diameter. asteroid studied by Dr. Steve Ostro.
  
• On asteroids such as Castalia, if you threw an object in the air, it would have an irregular, intricate path landing many feet away from the origin.
  
• Asteroid Eros - the Near Earth Asteroid Rendezvous (N.E.A.R) project has sent a probe to scan this 22 mile diameter., potato shaped asteroid and determine its composition, etc. The probe will take 3 years to get there.
  
• Space Watch is a program in Tucson, AZ located over 100 asteroids Tom Gehrels Space Watch with recently upgraded CCD technology, funding is running out.
  

• Asteroids aren't the only thing to worry about, comets as well pose a threat. Comets are just defrosting "space icebergs". Comets form further from sun than asteroids and as they move toward the sun, they begin to defrost forming the characteristic "tail". Comets can come from two belts having short or long periods (orbits). Beyond Neptune, lies the short-period KUIPER belt. Halley's comet is an example of a comet from this belt.
  
• In the outer reaches of the solar system lies the Long-period belt, known as the Oort cloud. Comets that form here take millions of years to return. Comets are a major threat in that they move quicker than asteroids and harder to detect.
  
• COMET FACT: Comets are just water: when you are drinking water, in part you are drinking a comet!
  

• THE ORIGINS OF THE ASTEROIDS. Richard P. Binzel, M. Antonietta Barucci and Marcello Fulchignoni in Scientific American, Vol. 265, No 4, pp 88-94; Oct 91.
  
• HAZARDS DUE TO COMETS AND ASTEROIDS. Edited by T. Gehrels. University of Arizona Press 94.
  
• ROGUE ASTEROIDS AND DOOMSDAY COMETS. Duncan Steel, John Wiley & Sons, 95.
  

• ASTEROID Movie aired in Feb 97
  

• Call Cambridge Mass