The detection of this radioactive relic of nuclear weapons tests in a remote environment shows humanity’s far-reaching environmental impact
The Mariana Trench, in the western Pacific Ocean between Japan and Papua New Guinea, plunges nearly seven miles below the surface at its deepest point. It is one of the most inaccessible environments on Earth, but it has not escaped the impact of humanity’s violence.
A group of scientists have now found radioactive carbon-14—at levels high enough to indicate it originated from the detonation of nuclear bombs—in the flesh of shrimplike crustaceans living in the trench. “Typically, we say the trenches are far away from us; they’re very deep and they’re pristine. But actually, they’re not,” says earth scientist Jiasong Fang of Shanghai Ocean University, who worked on the new study. “Everything can get into the trenches.”
Scientists can trace the reach of aboveground nuclear detonations, the first of which was conducted in 1945, by measuring levels of carbon-14—a radioactive isotope of carbon produced when neutrons from nuclear reactions collide with nitrogen atoms in the atmosphere. (It is also produced naturally, at lower levels, by cosmic rays bombarding the atmosphere.) Atmospheric carbon-14 levels doubled in the 1950s and 1960s as scores of hydrogen bombs were tested. A very small amount of the “bomb carbon” from these gigantic explosions has decayed, but the rest has spread around the world and been taken up via carbon dioxide by plants, which are then eaten by animals—including humans.