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An artist’s conception shows the Habitable Exoplanet Imaging Mission’s space telescope and its starshade. (NASA / JPL Illustration)

Global warming and nuclear blasts may be bad for humanity, but astrobiologists say they could be good indicators of the presence of intelligent life on distant worlds.

Such signatures of risky biological behavior should therefore be included in the list of things for future space telescopes to seek out, researchers say in a white paper prepared for the National Academy of Sciences.

The strategy would add a contemporary twist to the search for extraterrestrial intelligence, or SETI, reflecting the view that Earth is transitioning into a technology-driven geological era some call the Anthropocene.

“Examining the Anthropocene epoch through the lens of astrobiology can help to understand the future evolution of life on our planet and the possible evolution of technological, energy-intensive life elsewhere in the universe,” the researchers write.

Most of the researchers are affiliated with a Seattle-based organization known as the Blue Marble Space Institute of Science, although they may live elsewhere. Lead author Jacob Haqq-Misra, for example, is a meteorologist and astrobiologist who makes his home in Delaware.

The authors also include Woody Sullivan, a professor emeritus at the University of Washington.

Their perspective parallels a study published last year, in which three researchers proposed classifying planetary environments based on their energy potential and usage. Based on their classification scheme, Earth is on its way to becoming a Class V planet, dominated by the activity of a technologically advanced, energy-intensive species.

Adam Frank, a University of Rochester astrophysicist, is a co-author of last year’s study as well as the newly issued white paper.

The white paper basically suggests that telescope projects under consideration by NASA should look for the chemical signatures of other Class V planets.

NASA’s James Webb Space Telescope, currently due for launch in 2019, is expected to search for signs of life in alien atmospheres. But the researchers focus instead on concepts that are still early in their planning stages, such as NASA’s Origins Space Telescope, Large UV/Optical/IR Surveyor (a.k.a. LUVOIR) and Habitable Exoplanet Imaging Mission (HabEx).

The researchers also called on the NASA Astrobiology Institute to establish a focus group on Anthropocene-themed astrobiology. They said such a group could identify the potential “technosignatures” of alien civilizations.

“The terraforming of otherwise uninhabitable planets within a planetary system is one example of a possible technosignature, where powerful artificial greenhouse gases may be deployed to warm a planet outside the formal habitable zone,” they wrote. “Such planets may be identified from the spectral features of greenhouse gases such as perfluorocarbons (PFCs), which are not known to otherwise occur in high abundances.”

The identification of planetary-scale megastructures would be another example, they said. Just this month, a different team of researchers reported using telescopic observations to rule out the presence of an alien megastructure around a strangely dimming star known as KIC 8462852, or Boyajian’s Star.

Yet another long-lasting technosignature could be the presence of radioactive compounds associated with nuclear fallout. Here on Earth, the first atomic bomb test left just such a signature in 1945, which is seen as heralding the dawn of the Anthropocene Age.

Even if astrobiologists don’t detect the signs of energy-consuming civilizations beyond our solar system, the exercise could well yield payoffs closer to home. The authors point out that getting a better understanding of the theoretical constraints on alien civilizations — and the risks they may face — would improve policy decisions for the future of our own civilization as well.

In addition to Haqq-Misra, Frank and Sullivan, the authors of “The Astrobiology of the Anthropocene” include Sanjoy Som, Brendan Mullan, Rafael Loureiro, Edward Schwieterman, Lauren Seyler, Haritina Mogosanu, Eric Wolf, Duncan Forgan and Charles Cockell. Hat tip to Daniel Fischer.

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