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Abstract:
We develop a classification scheme for the evolutionary state of planets based on the non-equilibrium thermodynamics
of their coupled systems, including the presence of a biosphere and the possibility of what we call
an “agency-dominated biosphere” (i.e. an energy-intensive technological species). The premise is that Earth’s
entry into the “Anthropocene” represents what might be, from an astrobiological perspective, a predictable
planetary transition. We explore this problem from the perspective of the solar system and exoplanet studies. Our
classification discriminates planets by the forms of free energy generation driven from stellar forcing. We then
explore how timescales for global evolutionary processes on Earth might be synchronized with ecological
transformations driven by increases in energy harvesting and its consequences (which might have reached a
turning point with global urbanization). Finally, we describe quantitatively the classification scheme based on
the maintenance of chemical disequilibrium in the past and current Earth systems and on other worlds in the
solar system. In this perspective, the beginning of the Anthropocene can be seen as the onset of the hybridization
of the planet – a transitional stage from one class of planetary systems interaction to another. For Earth, this stage
occurs as the effects of human civilization yield not just new evolutionary pressures, but new selected directions
for novel planetary ecosystem functions and their capacity to generate disequilibrium and enhance planetary dissipation.
