A MEETING WITH THE UNIVERSE
Chapter 6-1
A Universe of Life
Planets seem to be reasonable
places for life. They are neither
as hot and deadly as the surfaces of
stars, nor as cold and empty as the
space between them. The only life
we know of in the universe has developed
on a planet, the Earth. Thus,
other planets have always been the
major focus of our search for other
forms of life. If planets are abundant
in the universe, life may be common.
If planets are rare, we and our fellow
Earthlings may be unique.
Only thirty years ago, most astronomers
believed that planetary systems
were extremely rare. It was even
thought that the solar system and the
habitat that Earth provides might well
be unique in the entire galaxy. At
the same time almost nothing was
known about the chemical basis for
the origin of life. Since then, our view
has changed drastically. Numerous
studies have eroded the reasons why
planetary systems and the development
of life on suitable planets should
be unlikely. Today, the leading theories
for star formation suggest that
planets may be the rule rather than
the exception and that the formation
of planets is expected to accompany
the formation of stars. At the same
time, new discoveries have shown
that the chemicals necessary for life
are abundant beyond the Earth. Inter
stellar gas clouds have been found to
contain biologically important organic
molecules made of carbon, hydrogen,
and other elements. Similar molecules
have been detected in comets and
meteorites. Therefore, today's theories
suggest that life could be wide
spread in the universe. Growing
numbers of scientists are now convinced
that extraterrestrial life must
exist, and more and more people feel
that contact with other civilizations is
no longer something beyond our
dreams but will be a natural event in
the history of mankind.
The existence of extraterrestrial
life and the origin of life are two questions
that are intimately related. The
major problem is the origin of life. This
topic is intrinsically fascinating. It is
surrounded by mystery, philosophy,
and religion, and it has been the subject
of contemplation and speculation
since the beginning of human history.
Only in the last century has the
question become recognized as a subject
suitable for direct scientific inquiry.
Individual researchers and
groups of scientists have considered
the problem for years, but NASA was
the first organization to provide a cohesive,
interdisciplinary approach,
combining the various scientific programs
that had investigated the question
since the early 1960s.
This integrated attack includes
disciplines as diverse as astronomy,
biology, chemistry, geology, and engineering.
Ground-based laboratory research,
astronomical observations,
and space missions have all been
brought to bear on the questions of
the uniqueness of life on Earth, the
origin of life in the universe, and the
place of life in the general cosmology.
We have come to the point that
scientists can now devise experiments
to answer such fundamental questions
as: "Where did life come from?",
"Why is life like it is?", "Are there other
forms of life in the solar system or in
the universe?", "Is there intelligent
life elsewhere?"
This new science of exobiology
has several goals. It seeks to understand
the origin, evolution, and distribution
of life and of the chemicals
necessary for life, both on Earth and
throughout the universe, and it seeks
to determine the relationship of life
to the evolution of planets. Through
research in chemistry, geology, and
biochemistry, and from our exploration
of the planets, we have begun to
pull together some parts of the origin-of-life
puzzle. Pieces of the puzzle are
being gathered from throughout the
universe, from interplanetary and interstellar
space, from other worlds,
and naturally, from the Earth.
