Jul 7, 2011
If life exists in space, rocks or comets could have brought it to Earth, seeding Earth with microorganisms.
Advanced civilizations in space could also spread life deliberately through directed panspermia, as proposed first by Carl Sagan and Iosif Shklovsky in 1966 in the book Intelligent Life in the Universe, and in 1973 by Francis Crick and Leslie Orgel in the journal Icarus. Suggested motivations could have been to secure their forms of life, and maybe to prepare Earth for colonization. Conversely, we could use directed panspermia to secure and advance our family of gene-protein life in space.
It is important to note that life in space is entirely speculative, without any evidence accepted by the general scientific community, although the search continues. Quite likely, there may be billions of habitable plants in our galaxy. However, even a single microorganism is extremely complex, requiring thousands of large, precisely shaped molecules to survive and replicate.
The chances of such complex life starting may be so small that it may have occurred only on Earth. Even if life exists in space, it would have had to start somewhere and then be transported to Earth from another solar system, another event of low probability. Assuming that an advanced civilization arose elsewhere and then seeded Earth deliberately, is even more speculative. The most simple theory is that life arose on Earth and advanced here to intelligent humans.
Whether life came from space, we know surely only that it exists on Earth. Science shows us that all life on Earth is related by its unique complexity, by common ancestors, and by the shared mechanisms of its survival and self-perpetuation. With our present knowledge, life may be unique to Earth, and we must base our ethical attitudes on this knowledge. If life is really unique to Earth, this places on us a great responsibility. We can then secure and expand life in space where it can achieve an immense future, giving our existence a cosmic purpose.
Michael Mautner is a research professor of chemistry at Virginia Commonwealth University.