So far, scientists have not discovered any direct evidence of life at
any location beyond Earth, Morrison said. "Therefore, a great deal of
the research now being carried out in astrobiology is directed at a
better understanding of the origin and evolution of life on Earth,"
Morrison explained.
During its first three billion years, only microbes populated Earth,
according to Morrison. "This was not a stagnant time, however, as
these microbes evolved sophisticated and varied capacities to live in
a wide range of environments -- environments that we call extreme --
but that worked just fine for them," he explained. "As we explore
beyond Earth, we are looking primarily for microbial life. Thus,
scientists use the microbes on Earth as a model or analog for what we
may find beyond our own planet," Morrison concluded.
More information about astrobiology is on the World Wide Web at: