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September 7, 2017

Earth as hybrid planet: New classification scheme places Anthropocene era in astrobiological context

For decades, as astronomers have imagined advanced extraterrestrial civilizations, they categorized such worlds by the amount of energy their inhabitants might conceivably be able to harness and use.

Now, a team of researchers including Marina Alberti of the University of Washington has devised a new classification scheme for the evolutionary stages of worlds based on “non-equilibrium thermodynamics” — a planet’s energy flow being out of synch, as the presence of life could cause. The categories range from imagined planets with no atmosphere whatsoever to those with an “agency-dominated biosphere” or even a “technosphere,” reflecting the achievements of a vastly advanced, “energy-intensive technological species.”

Their paper, “Earth as a Hybrid Planet: The Anthropocene in an Evolutionary Astrobiological Context,” was published Sept. 6 in the journal Anthropocene. Lead author is Adam Frank, professor of physics and astronomy at the University of Rochester. Alberti is a professor of urban design and planning in the UW College of Built Environments, and director of the college’s Urban Ecology Research Lab.

“Our premise is that Earth’s entry into the Anthropocene represents what might, from an astrobiological perspective, be a predictable planetary transition,” they write. “We explore this problem from the perspective of our own solar system and exoplanet studies.

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