One of the biggest remaining questions about life on our planet is how it all started. At this point, we know that when you combine heat and common chemicals, amino acids can form. For this reason, scientists have long pointed to deep-sea hydrothermal vents as the most probable crucible for DNA. Now, a new study is challenging this popular hypothesis, suggesting that a nuclear reactor kick-started life on Earth. Before you dismiss the idea, you should know that it’s one of the most credible ideas to date.
Shortly after the Earth formed 4.5 billion years ago, it began to cool. Still, it was inhabitable by most standards. The oceans had not yet taken shape, water was mostly a superheated gaseous vapor, and asteroids regularly pummeled the surface. For what it was lacking in water, Earth had in abundance in uranium-235—which releases radiation and heat as it decays.
The heat has a huge influence on worlds like Pluto and Saturn’s Enceladus, both of which have cryovolcanic features. On Earth, approximately half the heat that goes into generating volcanism and the movement of tectonic plates comes from radioactive decay.
During the Hadean, this extra supply meant that it was “cooking” basic carbon, potassium, and nitrogen-based constituents of Earth’s volcanic atmosphere. The radiation given off by these isotopes was could have promoted the type of chemical reactions that form amino acids, RNA, and DNA. This heat would have also fueled geysers with the same type of organic chemistry you see in deep-sea hydrothermal vents. The advantage of these geysers is that the temperature of the water would never reach boiling point.
To back their claims, researchers referred to the Miller-Urey experiments, which added several gases to those found in the earth Earth’s atmosphere—water, methane, ammonia, and hydrogen. When they added a spark to simulate lightning strikes, amino acids spontaneously appeared. This new study notes that the energy in these “lightning strikes” is identical to that of the U-235 nuclear reactor.