New Paper: Natural Nuclear Reactors & the Origin of Life

Zach Adam recently published a paper titled “Temperature oscillations near natural nuclear reactor cores and the potential for prebiotic oligomer synthesis” in the journal Origins of Life and Evolution of Biospheres. Below is a short summary of his idea.

This paper is about how complex geological energy transfer processes could have been on the early Earth. Most people don’t automatically think about nuclear fission reactors when they think about radioactive rocks. One reason is because we have this idea that rocks that contain elements like Uranium have to be highly processed and refined to create nuclear fuel. Another reason is because we think that reactors have to be designed, engineered and constructed by human thought.

But the young Earth was a very different place and time in our history. When Earth first formed, Uranium-bearing rocks at this time naturally contained so much fission fuel that processing the natural rock was not needed. And because this fission fuel was so abundant, you didn’t have to carefully design a reactor, you just needed to add water to sediments that happened to have some small amount of Uranium and a fission process would begin. We know this is true because we’ve found fossils of fission reactors that formed in geologic deposits about 2 billion years ago in Gabon, Africa.

In this paper, we take the reactor idea a step further to look at how a Uranium fission zone would have heated up and cooled down in cycles for hundreds of thousands of years. Like a pressure cooker, this would have heated and cooled prebiotic molecules in a very regular way, since the peak temperature would have been limited by the boiling temperature of water (once the water boils out of the system, the fission process stops and the zone cools down until the process repeats). This temperature profile resembles, in some ways, the temperature profile that we use today in polymerase chain reaction (PCR) devices to artificially amplify RNA and DNA sequences. The main conclusion of the paper is to emphasize that processes that seem very engineered, complex and artificial to us today may have had naturally-occurring geologic counterparts on the early Earth. These geologic processes could have helped to produce complex organic molecules that could have eventually become living systems.