Astronomers Propose Radical New Way To Look For Signs Of Energy- Hungry Aliens

Why planetary scientists think advanced aliens will turn to nuclear fusion to meet their massive energy needs. Here’s how we might spot them.

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nuclear fusion power generator concept image, 3d rendering Nuclear fusion —- arguably the holy grail of all energy production here on earth —- could also meet the needs of the most ravenous energy-hungry alien civilizations in the cosmos. Or so says a new paper just accepted for publication in The Astrophysical Journal which advocates using a radical new way to look for the infrared spectroscopic technosignatures of such advanced civilizations. The crux of the idea is to use future space- and ground-based telescopes, hopefully as soon as next decade, to take high resolution spectra of water vapor in an extrasolar earth’s atmosphere. Astronomers could then determine the so-called deuterium to hydrogen ratio (or the abundance of deuterium relative to hydrogen) in the planet’s oceans. Measuring an exoplanet’s D to H ratio is where you stand a chance of identifying such a technosignature, David Catling, a planetary scientist at the University of Washington and the paper’s lead author, told me in his Seattle office. The difference in mass between deuterium and hydrogen is a factor of two and that would feed into the biggest difference in the observed spectroscopic signals, said Catling. The idea is that a telltale sign of a very advanced alien technology would fuse the hydrogen isotope of deuterium, which unlike normal hydrogen contains a neutron in its nucleus, into helium to produce massive amounts of energy. Here on Earth, our D to H ratio is some ten times higher than what’s measured in our Milky Way Galaxy’s interstellar medium. Thus, if a given exoearth’s atmospheric D to H ratio was found to be lower than the baseline minimum of what is found naturally in the interstellar medium that would be truly anomalous. Known D to H ratios of water on rocky worlds in the solar system are far higher than the interstellar medium D to H ratio, the authors note. This technosignature proposal would work because there would be no known natural means to explain such an anomalously low D to H ratio on a far flung exoearth. Why is deuterium fusion more attractive for energy production than the solar-type process of fusing hydrogen atoms into helium? Because the physics of it is such that deuterium is more reactive and you don’t need to have such exceptional temperatures, said Catling. You don’t need temperatures to be like the core of the Sun which does fuse hydrogen; you can do nuclear fusion in more moderate conditions, he said. If an advanced alien society were using deuterium fusion as a major source of their energy production, it would inherently cause an anomalously low D to H ratio. For a planet that has oceans and a D to H ratio similar to earth’s, deuterium fusion power would deplete the D to H ratio within a few hundred million years, Catling and colleagues noted. You’d shift the ratio of deuterium to hydrogen in your oceans to values that we don’t see in the galaxy, and it would become an anomaly, said Catling. Once a civilization pushes their ocean’s (or oceans’) D to H values to such anomalously low values, this technosignature —— remotely viewed via spectroscopy of the planet’s atmospheric water vapor —- should persist for eons, the authors note. That’s regardless of whether an extraterrestrial civilization has perished, relocated, or transitioned to another form of energy production, they write. Deuterium is about twice the mass of hydrogen because it has twice the mass in the nucleus, said Catling. There’s some 35 grams of deuterium per ton of sea water, which is still a lot when you consider the whole size of earth’s oceans, he said. Despite strides in making earth’s energy use more efficient, our actual energy use continues to increase almost exponentially. If you look at the last century, human civilization increased its energy demand by a factor of about nine, said Catling. And we continue to increase our energy use despite energy efficiencies in individual devices, he said. Energy use by an extraterrestrial society far more technologically-advanced than humankind will likely use AI, automation or robotics, and technologies that we cannot yet imagine, Catling and colleagues noted in their paper. Once you’ve got nuclear fusion, you have a very long-lived source of energy, and then energy use is no longer a problem, Catling told me. You just use what you want without worrying about it, he said. One Community. Many Voices. Create a free account to share your thoughts.  Our community is about connecting people through open and thoughtful conversations. 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