Civilizations of Planetary Endemism: Part IV
18 February 2016
In earlier posts of this series on Civilizations of Planetary Endemism we saw that planets not only constitute a “Goldilocks” zone for liquid water, but also for energy flows consistent with life as we know it. I would like to go into this in a little more detail, as there is much to be said on this. It is entirely possible that energy flows on a planet or moon outside the circumstellar habitable zone (CHZ) could produce sufficient heat to allow for the presence of liquid water in the outer reaches of a planetary system. Indeed, it may be misleading to think of habitable zones (for life as we know it) primarily in terms of the availability of liquid water; it might be preferable to conceive a habitable zone primarily in terms of regions of optimal energy flow (i.e., optimal for life as we know it), and to understand the availability of liquid water as a consequence of optimal energy flow.
Our conception of habitability, despite what we already know, and what we can derive from plausible projections of scientific knowledge, is being boxed in by the common conceptions (and misconceptions) of biospheres and CHZs. We can posit the possibility of “oasis” civilizations on worlds where only a limited portion of the surface is inhabitable and no “biosphere” develops, although enough of a fragment of a biosphere develops in order for complex life, intelligence, and civilization to emerge. We do not yet have an accurate term for the living envelope that can emerge on a planetary surface, but which does not necessary cover the entire planetary surface. I have experimented with a variety of terms to describe this previously. For example, I used “biospace” in my 2011 presentation “The Moral Imperative of Human Spaceflight,” but this is still dissatisfying.
As is so often the case, we run into problems when we attempt to extrapolate Earth sciences formulated for the explicit purpose of accounting for contingent terrestrial facts, and never conceived as a purely general scientific exercise applicable to any comparable phenomena anywhere in the universe. This is especially true of ecology, and since I find myself employing ecological concepts so frequently, I often feel the want of such formulations. Ecology as a science is theoretically weak (it is much stronger on its observational side, which goes back to traditional nature studies that predate ecology), and its chaos of criss-crossing classification systems reflects this.
There are a great many terms for subdivisions of the biosphere — ecozone, bioregion, ecoregion, life zone, biome, ecotope — which are sometimes organized serially from more comprehensive to less comprehensive. None of these subdivisions of a biosphere, however, would accurately describe the inhabited portion of a world on which biology does not culminate in a biosphere. Perhaps we will require recourse to the language and concepts of topology, since a biosphere, as a sphere, is simply connected. The bioring of a tidally locked M dwarf planet would not be simply connected in this topological sense.
If we conceptualize habitable zones not in terms of a celestial body being the right temperature to have liquid water on its surface, or perhaps in a subsurface ocean, but rather view this availability of liquid water as a consequence of habitable zones defined in terms of the presence of energy flows consistent with life as we know it, then we will need to investigate alternative sources of energy flow, i.e., distinct from the patterns of energy flow that we understand from our homeworld. Energy flows consistent with life as we know it are consistent with conditions that allow for the presence of liquid water on a celestial body, but this also means energy flows that would not overwhelm biochemistry and energy flows that are not insufficient for biochemistry and the origins and maintenance of metabolism.
Energy flows might be derived from stellar output (thus a consequence of gravitational confinement fusion), from radioactivity, which could take the form of radioactive decay or even a naturally-occurring nuclear reactor, as as Oklo in Gabon (thus a consequence of fission), from gravitational tidal forces, or from the kinetic energy of impacts. All of these sources of energy flows have been considered in another connection: suggested ways to resolve the faint young sun paradox (the problem that the sun was significantly dimmer earlier in its life cycle, while there still seems to have been liquid water on Earth) are the contributions of other energy sources to maintaining a temperature on Earth similar to that of today, including greater tidal heating from a closer moon, more heating from radioactive decay, and naturally occurring nuclear fission.
It would be possible in a series of thought experiments to consider counterfactual worlds in which each of these sources of energy flow are the primary source of energy for a biosphere (or a subspherical biological region of a planetary surface). The Jovian moon Io, for example, is the most volcanically active body in our solar system; while Io seems to barren, one could imagine an Io of more clement conditions for biology in which the tidal heating of a moon with an atmosphere was the basis of the energy flow for an ecosystem. A world with more fissionables in its crust than Earth (the kind of worlds likely to be found during the late Stelliferous Era under conditions of high metallicity) might be heated by radioactive decay or natural fission reactors (or some combination of the two) sufficient to generate energy flows for a biosphere, even at a great distance from its parent star. It seems unlikely that kinetic impacts from collisions could provide a sufficiently consistent flow of energy without a biosphere suffering mass extinctions from the same impacts, but this could merely be a failure of imagination. Perhaps a steady rain of smaller impacts without major impacts could contribute to energy flows without passing over the threshold of triggering an extinction event.
Each of these exotic counterfactual biospheres suggests the possibility of a living world very different from our own. The source of an energy flow might be inconsistent, that is to say, consistent up to the point of making life possible, but not sufficiently consistent for civilization, or the development of civilization. That is to say, it is possible that a planetary biosphere or subspheric biological region might possess sufficient energy flows for the emergence of life, but insufficient energy flows (or excessive energy flows) for the emergence of complex life or civilization. Once can easily imagine this being the case with extremophile life. And it is possible that a bioregion might possess sufficient energy flows for the emergence of a rudimentary civilization, but insufficient for the development of industrial-technological civilization that can make the transition to spacefaring civilization and thus ensure its longevity.
Civlizations of planetary endemism on these exotic worlds would be radically different from our own civilization due to differences in the structure and distribution of energy flow. Civilizations of planetary endemism are continuous with the biosphere upon which they supervene, so that a distinct biosphere supervening upon a distinct energy flow would produce a distinct civilization. Ultimately and ideally, these distinct forms of energy flow could be given an exhaustive taxonomy, which would, at the same time, be a taxonomy of civilizations supervening upon these energy flows.
However, the supervenience of civilization upon biosheres and biospheres upon energy flows is not exhaustive. Civilizations consciously harness energy flows to the benefit of the intelligent agent engaged in the civilizing process. The first stage of terrestrial civilization, that of agricuturalism and pastoralism, was a natural extension of energy flows already present in the bioshere, but once the breakthrough to industrialization occurred, energy sources became more distant from terrestrial energy flows. Fossil fuels are, in a sense, stored solar energy, and derive from the past biology of our planet, but this is the use of biological resources at one or more remove. As technologies became more sophisticated, in became possible to harness energy sources of a more elemental nature that were not contingent upon extant energy flows on a planet.
It may be, then, that biocentric civilizations are rightly said to supervene upon biospheres. However, with the breakthrough to industrialization, and the beginning of the transition to a technocentric civilization, this supervenience begins to fail and a discontinuity is interpolated between a civilization and its homeworld. According to this account, the transition from biocentric to technocentric civilization is the end point of civilizations of planetary endemism, and the emergence of a spacefaring civilization as the consequence of technologies enabled by technocentric civilization is a mere contingent epiphenomenon of a deeper civilizational process. This in itself provides a deeper and more fundamental perspective on civilization.
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● Civilizations of Planetary Endemism: Introduction (forthcoming)
● Civilizations of Planetary Endemism: Part IV
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