Life Everywhere: The Maverick Science of Astrobiology [Paperback]

Well, not in the center of the sun or on the surface of a neutron star--at least not life as we know it.

"Life as we know it." This is an important phrase that comes up again and again in discussions about astrobiology. "Life as we know it" means life with a carbon base and liquid water. David Darling considers silicone-based life and even life forms so bizarre that we wouldn't recognize them if we saw them, but basically he sticks with life as we know it in this very interesting answer to those who think that life in the universe is rare.

The two things:

(1) The discovery of extremophiles, bacteria that live in sulfurous hot springs, deep inside the earth, and at the bottom of deep oceans. Instead of deriving their energy from the sun, they are able to use heat coming from within the earth to metabolize.

(2) The discovery of scores of planets (albeit not earth-sized planets--yet) revolving around other stars.

What the first discovery means is that life doesn't have to exist or begin in conditions such as there are or have been on the surface of the earth, but can thrive in places previous thought hostile to life. That opens up a whole lot of the universe to life including parts of our solar system previously thought inimical to life, such as in an ocean under the icy crust of Europa or beneath the inhospitable surface of Mars. And the fact that planets are now clearly plentiful means that there are numerous places for life to develop.

Darling, who is an unusually lucid writer and a man who gets to the bottom of things, begins with the nitty-gritty problem of just how to define life. If you haven't been introduced to this strangely knotty problem, this book may open your eyes. Do we consider reproduction, metabolism, growth, etc. in our definition? And which of these elements are essential and which are not? The postmodern definition now preferred by most people I have read is "undergoes Darwinian evolution." Is that adequate? Is that the essence? Darling puts all the cards on the table and lets you decide.

Next Darling recapitulates ideas about how life began. The main new idea is that life may be an inevitable consequence of the nature of matter and energy. It appears that matter is self-organizing. Darling reviews the ideas of how lifeless matter might replicate and how cells might develop from various molecules and water. These "leaky membranes" could be the precursors of the first biological cells. (p. 40)

He goes on to make the case for a universe with abundant life. But along the way he presents a blistering critique of Rare Earth: Why Complex Life Is Uncommon in the Universe (2000) by Peter D. Ward and Donald Brownlee, in which it is argued that the circumstances that allow life are rare and that those circumstances as seen on earth are unlikely to be replicated anywhere else. Darling not only utterly destroys their argument, point by point, but even shows that part of the reason that it was advanced was because they were under the influence of one Guillermo Gonzalez, professor of astronomy at the University of Washington, who is also a creationist with the usual supernatural agenda.

This was bombshell to me. But Darling shows that nearly every argument that Gonzalez makes is designed (pun intended) to discredit the idea that there is life anywhere but on earth. On page 112, Darling refers to an article entitled "Live Here or Nowhere" co-authored by Gonzalez for a publication called "Connections" published by Reasons to Believe, Inc. of Pasadena, California, whose mission is "to communicate the uniquely factual basis for belief in the Bible." The article concludes, "The fact that the sun's location is fine-tuned to permit the possibility of life--and even more precisely fine-tuned to keep the location fixed in that unique spot where life is possible--powerfully suggests divine design."

A couple more points:

First, Darling argues that life forms on other worlds, however dissimilar their chemistry, are likely to be familiar to us in the sense that if there is an atmosphere, some will have wings, and if there is an ocean, some with have fins, if there is a solid ground to walk upon, some will walk and run, and if there is light to see, some with have eyes. This idea of "convergence" is dictated by the laws of physics which requires evolutionary adaptations to take forms that work efficiently within certain environments. Of course if the life forms we eventually discover exist in great dust clouds, their adaptations may be very dissimilar and surprising. Even on solid ground here on earth some run and some hop, some crawl and some slither.

Second, since it is now known that bacteria spores can exist more or less indefinitely (some have been revitalized after hundreds of millions of years of dormancy: see page 150), the once discredited idea of panspermia, namely that life originated elsewhere in the universe and arrived here as spores, has been rejuvenated. Personally, I've always liked this idea championed by Fred Hoyle and Chandra Wickramasinghe; however this book has convinced me that life could arrive from without or develop from within. Either way (or both) seem likely to me.