Why Study Asteroids?
Donald K. Yeomans (April 1998)
Jet Propulsion Laboratory/California Institute of Technology
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
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.