When it comes to our modern society and the many crises we face, there is little doubt that fusion power is the way of the future. The technology not only offers abundant power that could solve the energy crisis, it does so in a clean and sustainable way. At least as long as our supplies of deuterium (H2<\/sub>) and helium-3 hold up. In a recent study, a team of researchers considered how evidence of deuterium-deuterium (DD) fusion could be used as a potential technosignature in the Search for Extraterrestrial Intelligence (SETI).<\/p>\n <\/p>\n The study was conducted by David C. Catling and Joshua Krissansen-Totton of the Department of Earth & Space Sciences and the Virtual Planetary Laboratory (VPL) at the University of Washington (respectively) and Tyler D. Robinson of the VPL and the Lunar & Planetary Laboratory (LPL) at the University of Arizona. In their paper, which is set to appear in the Astrophysical Journal<\/em>, the team considered how long-lived extraterrestrial civilizations may deplete their supplies of deuterium \u2013 something that would be detectable by space telescopes.<\/p>\n At the heart of SETI lies the foregone conclusion that advanced civilizations have existed in our galaxy long before humanity. Another conclusion extends from this: if humanity can conceive of something (and the physics are sound), a more advanced civilization is likely to have already built it. In fact, it has been suggested by many SETI researchers and scientists that advanced civilizations will adopt fusion power to meet their growing energy needs as they continue to grow and ascend the Kardashev Scale.<\/p>\n This is understandable, considering how other forms of energy (fossil fuels, solar, wind, nuclear, hydroelectric, etc.) are either finite or inefficient. Space-based solar power is a viable option since it can provide a steady supply of energy that is not subject to intermittency or weather patterns. Nevertheless, nuclear fusion is considered a major contender for future energy needs because of its efficiency and energy density. It is estimated that one gram of hydrogen fuel could generate as much as 90,000 kilowatt-hours of energy \u2013 the equivalent of 11 metric tons (12 U.S. tons) of coal.<\/p>\n In addition, deuterium has a natural abundance in Earth\u2019s oceans of about one atom of deuterium in every 6,420 atoms of hydrogen. This deuterium interacts with water molecules and will replace one or both hydrogen atoms to create \u201csemi-heavy water\u201d (HOD or DOH) and sometimes \u201cheavy water\u201d (D2<\/sub>O). This works out to 4.85\u00d71013<\/sup> or 48.5 billion metric tons (5.346\u00d71013<\/sup> U.S. tons) of deuterium. As they argue in their paper, extracting deuterium from an ocean would decrease its ratio of deuterium-to-hydrogen (D\/H), which would be detectable in atmospheric water vapor. Meanwhile, the helium produced in the nuclear reactions would escape to space.<\/p>\n In recent years, it has been suggested that excess carbon dioxide and radioactive isotopes in an exoplanet\u2019s atmosphere could be used to infer the presence of an industrial civilization. In the same vein, low values of D\/H in an exoplanet\u2019s atmosphere (along with helium) could be used to detect a highly advanced and long-lived civilization. As Catling explained in a recent interview with phys.org, this possibility is one he began pondering years ago. <\/p>\n \u201cI didn\u2019t do much with this germ of idea until I was co-organizing an astrobiology meeting last year at Green Bank Observatory in West Virginia,\u201d he said. \u201cMeasuring the D\/H ratio in water vapor on exoplanets is certainly not a piece of cake. But it\u2019s not a pipe dream either.\u201d <\/p>\n To model what an advanced civilization dependent on DD fusion would look like, Catling and his colleagues considered projections for what Earth will look like by 2100. At this point, the global population is expected to reach 10.4 billion, and fusion power is projected to provide 100 Terawatts (TW). They then multiplied that by a factor of ten (1,000 TW) for a more advanced civilization and found that they would reduce the D\/H value of an Earth-like ocean to that of the interstellar medium (ISM) in about 170 million years.<\/p>\n The beauty of this approach is that the low D\/H values in an exoplanet\u2019s atmosphere would persist long after a civilization went extinct, migrated off-world, or became even more advanced and \u201ctranscended.\u201d In terms of search strategies, the team used the Spectral Mapping Atmospheric Radiative Transfer (SMART) model to identify the specific wavelengths and emission lines for HDO and H2<\/sub>O. These findings will be useful for future surveys involving the James Webb Space Telescope (JWST), NASA\u2019s proposed Habitable Worlds Observatory (HWO), and the Large Interferometer For Exoplanets (LIFE).<\/p>\n \u201cIt\u2019s up to the engineers and scientists designing [HWO] and [LIFE] to see if measuring D\/H on exoplanets might be an achievable goal. What we can say, so far, is that looking for D\/H from LIFE appears to be feasible for exoplanets with plenty of atmospheric water vapor in a region of the spectrum around 8 microns wavelength.\u201d<\/p>\n<\/blockquote>\n Further Reading: phys.org, arXiv<\/em><\/p>\n![\"\"](\"https:\/\/www.universetoday.com\/wp-content\/uploads\/2024\/08\/STScI-01FN6ZE72TTVG311966205YWQW-1-1024x457.jpg\")
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