From Mars to the Earth

		             by

  		         Rob Perry


It happens once or twice every million years. A comet 
or asteroid tears through Earth's atmosphere and 
smashes into the ground or ocean with enough
 force to destroy civilization. 

About 2000 large bodies that cross the orbit of Earth 
could hit us. On March 23, 1989, an asteroid about 
a half-mile wide crossed the Earth's orbit about 
400,000 miles from Earth. The Earth had been in 
that same spot a mere six hours earlier.

On January 17, 1991, an asteroid estimated to be 
about 30 feet wide passed within 106,000 miles 
of Earth. 

Among the defensive maneuver under study and
debate is to Nuke It, a nuclear blast near the object 
could blow it off course. 

The consequences of such a collision are so 
catastrophic that it is prudent to assess the 
nature of the threat and prepare to deal with it.

Studies have shown that the risk from cosmic impacts
increases with the size of the projectile. The greatest 
risk is associated with objects large enough to disturb
the Earth's climate on a global scale by injecting large
quantities of dust into the stratosphere. 

Such an event could depress temperatures around the
globe, leading to massive loss of food crops and 
possible breakdown of society. 

Various studies have suggested that the minimum 
mass impacting body to produce such global
consequences is several tens of billions of tons,
resulting in a ground burst explosion with energy 
in the vicinity of a million megatons of TNT. 

The corresponding threshold diameter for Earth
crossing asteroids or comets is about a mile. 
Smaller objects can cause severe local damage
but pose no global threat. 

Cosmic impacts are the only known natural disaster
that could be avoided entirely by the appropriate 
application of space technology. 

Imaging of near-Earth asteroids is also possible using 
powerful planetary RADARS supported by NASA 
at Goldstone, California, and ARECIBO, Puerto Rico. 

The only technology we have today for defense against 
asteroids and comets is nuclear to deflect or disrupt an
asteroid or comet. 

This story is about an asteroid that's knocked off course 
when it hits Mars. It  deflects and is now on a path to earth.

The Asteroid is two miles across and it's lethal to Earth.

cnn/ap

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