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Why Study Asteroids?


Why Study Asteroids? 
Don Yeomans
Jet Propulsion Lab
April 1998

The scientific interest in asteroids is due largely to their status
as the remnant debris from the inner solar system formation process.  
Because some of these objects can collide with the Earth, asteroids 
are also important for having significantly modified the Earth's 
biosphere in the past.  They will continue to do so in the future.  
In addition, asteroids offer a source of volatiles and an 
extraordinarily rich supply of minerals that can be exploited for 
the exploration and colonization of our solar system in the 
twenty-first century.

Asteroids represent the bits and pieces left over from the process 
that formed the inner planets, including Earth.   Asteroids are also 
the sources of most meteorites that have struck the Earth's surface 
and many of these meteorites have already been subjected to detailed 
chemical and physical analyses.  If certain asteroids can be 
identified as the sources for some of the well-studied meteorites, 
the detailed knowledge of the meteorite's composition and structure will
provide important information on the chemical mixture, and conditions 
from which the Earth formed 4.6 billion years ago.  During the early 
solar system, the carbon-based molecules and volatile materials that 
served as the building blocks of life may have been brought to the 
Earth via asteroid and comet impacts. Thus the study of asteroids is 
not only important for studying the primordial chemical mixture from 
which the Earth formed, these objects may hold the key as to how the 
building blocks of life were delivered to the early Earth.

On a daily basis, the Earth is bombarded with tons of interplanetary 
material.  Many of the incoming particles are so small that they are 
destroyed in the Earth's atmosphere before they reach the ground.   
These particles are often seen as meteors or shooting stars.  The vast 
majority of all interplanetary material that reaches the Earth's 
surface originates as the collision fragments of asteroids that have 
run into one another some eons ago.  With an average interval of about 
100 years, rocky or iron asteroids larger than about 50 meters would be 
expected to reach the Earth's surface and cause local disasters or 
produce the tidal waves that can inundate low lying coastal areas.  
On an average of every few hundred thousand years or so, asteroids 
larger than a mile could cause global disasters.  In this case, the 
impact debris would spread throughout the Earth's atmosphere so that 
plant life would suffer from acid rain, partial blocking of sunlight,
and from the firestorms resulting from heated impact debris raining 
back down upon the Earth's surface.  The probability of an asteroid 
striking the Earth and causing serious damage is very remote but the 
devastating consequences of such an impact suggests we should closely 
study different types of asteroids to understand their compositions, 
structures, sizes, and future trajectories.

The asteroids that are potentially the most hazardous because they 
can closely approach the Earth are also the objects that could be 
most easily exploited for raw materials.  These raw materials could be
used in developing the space structures and in generating the rocket 
fuel that will be required to explore and colonize our solar system 
in the twenty-first century.  By closely investigating the compositions
of asteroids, intelligent choices can be made as to which ones offer 
the richest supplies of raw materials.  It has been estimated that the 
mineral wealth resident in the belt of asteroids between the orbits of
Mars and Jupiter would be equivalent to about 100 billion dollars for 
every person on Earth today.