Reply #19: I admire Kauffman's work very much, and I think he's on to something, but [View All]

[NNadir]

I think the evidence is pretty solid that a minimal condition for the existence of life is liquid water. The extraterrestrial planet that we know best is of course Mars, and while the question of whether there was once life there is still open, the preponderance of evidence is that there is not any there now. Neither does there seem to be much liquid water, if any at all.

The existence of extremophiles such as those found at deep sea vents or in hot pools does nothing to disprove the assertion that liquid water is not required. Although a lot of great work has been published in recent times about self-organizing systems, I am not familiar with any work that suggests that these types of events happen in the absence of a liquid solvent, of which water, with its polarity and hydrogen bonding capacity is the best. I can imagine circumstances under which liquid ammonia might fill a similar role, but symmetry considerations suggest that absenting either water or ammonia, any other solvent system could be so versatile.

Kauffman, if I recall, and it's been some time since I've read him, refers to life as a "thermodynamic eddy." I like this very much. If we extend that analogy somewhat we can see that "eddies" don't really exist under all conditions. There are no eddies in ice. There may be some in steam, but they are transitory at best and do not last long.

There is evidence for complex organic molecules distributed throughout the universe, and my own bias is for a kind of panspermia. But just as seeds need an appropriate place to germinate, I believe that for these molecules to develop, through some mechanism, a metabolism, certain minimal conditions must prevail, including a pressure and temperature suitable for multiphasic water (or less likely, ammonia). Earth clearly has those conditions, and has been particularly blessed with remarkable stability. But I think it would be a mistake to believe that the earth cannot be driven away from the conditions under which life can exist.

As for Kauffman's hypothesis, it will be interesting to see if liquid water is discovered elsewhere in the solar system, say in the core of Europa, what exactly the molecules there are doing with one another. But the existence of life engaging in metabolism is a very different deal than life with consciousness. I would suspect that this is far more rare in the universe than people generally seem to believe.