The topics of artificial intelligence (AI) and the search for extraterrestrial intelligence (SETI) have more in common than one might initially think.  For one thing, there is Seth Shostak's point to consider, that any extraterrestrial intelligence we eventually encounter will likely be 'artificial', in the sense that it will be the result of an intelligence that originated through biological evolution having improved on itself.  As I've noted in previous entries, I think this eventuality is less certain than Shostak does - a great deal depends on whether or not there are strict computational limitations on how far a common-sense intelligence like ours can go in 'improving on itself' along dimensions of speed, efficiency, scope of input, variegation of data channels and the like; and given the dynamicism and self-organization that is likely to be a necessary feature of any implementation of common-sense intelligence, there may be further questions about what we'd be willing to call 'artificial'.  Indeed, to the extent that one believes (as I do) that there is nothing supernatural about human-like intelligence, one can legitimately raise the question of whether the distinction between 'natural' and 'artificial' intelligence is even meaningful:  given that 'natural' intelligence is natural, 'artificial' intelligence must, per necessitans be a product of natural forces and processes of development, no less than the biological intelligences with which we're familiar.  But all that is beside my present point.  Thinking about extraterrestrial intelligence forces one to grapple with the very same set of issues that are at the heart of the artificial intelligence problem:  what is intelligence, how do we recognize it, what does it mean to recognize intelligence, and what are the conditions for the appearance of intelligence, among others.  It also forces one to try to come to grips with the relationship between intelligence and living systems -indeed, the problem of how we recognize intelligence may be isomorphic in many important respects to the problem of how we recognize life.  Because of these connections, I'll occasionally be using this venue to make postings about topics in SETI and exobiology - as, in fact, I'm doing now.

Not too long ago, I read David Grinspoon's Lonely Planets. I must say I find congenial its argument that life is something that happens to a planet in the course of its evolution, and also the point the author makes, that the search for extraterrestrial life ought therefore to look for the hallmarks of 'Gaia scale' re-entrant negative feedback loops underpinning far-from-equilibrium environments where ecologies can flourish.  The two principal markers Grinspoon indicates for such environments are structure coupled to extreme disequilibrium, and he observes that the two most underrated locales for life in the solar system by these criteria are Venus and Io.  Nothing to argue with, there - but if disequilibrium and structure are key, I wonder if we ought to also consider adding planet Saturn to the list.  Certainly the energy flows (hence the disequilibrium) are there:  possibly as extreme, or maybe even more so, than anything on Io or Venus in terms of scale.  And as for structure, well, what about those rings?  Granted, Jupiter, Uranus, and Neptune have rings, too; but in comparison they're rinky-dink affairs, so dull we didn't even discover them until the advent of sophisticated imaging enhancement in the late twentieth century.  Saturn's rings seem like an altogether different order of beast, standing out from their nondescript Jovian, Uranian, and Neptunian counterparts in more or less the same degree that the hydrologic situation on Earth compares with the one on Mars (a comparison that may in fact be telling).  Not only do the rings show complex structure; they have the singular characteristic of exhibiting increased organization and complexity as they are viewed at finer and finer scales of resolution (another feature which just may be discriminative of living systems).  Then, too, there's the peculiar fact that, as I understand it, nobody can come up with a model for the rings that doesn't imply they are a pretty recent phenomenon, destined to dissipation after just a few million years.  Except that leaves us with the familiar water-in-the-bathtub problem:  the chance that a transient phenomenon this spectacular should have occurred in the nick of time for humanity to have happened along to observe it beggars coincidence.  And in fact, we lately seem to be coming across evidence that the rings are a good deal older than we thought: mainly in the form of suggestions of replenishment (from places like Enceladus, outgassing in ways that nobody seems to have found a plausible explanation for, yet)- so, not only do we have disequilibrium, we have evidence that disequilibrium is being maintained for extended periods of time.  And if you want structure and disequilibrium beyond the rings, there's the incorrigible business of the Great North Polar Hexagon, which was troublesome enough even before the discovery of the aurorae that make it look like something out of a bad Star Trek episode.  In light of such considerations, I can't help but wonder:  what are the chances that Saturn is a 'living world' in Grinspoon's sense, with the hypertrophied ring system and Northern Hexagon independently evincing the presence of some kind of underlying biospheric organization and process?