Zachary Adam, Ph.D.

Education: Montana State University, Ph.D., Geology
Institution: Harvard University

SCOL Project: Geologic Production of Polymer-Forming Solvents on the Prebiotic Earth

All living organisms require water to survive, but water also gradually degrades nearly all of the molecules that make us alive. As a result, all organisms spend a substantial amount of energy repairing and re-forming molecules like DNA, RNA and proteins, so they can remain alive. In light of the damaging effects of water, and the special steps life has to take to fight against them, it is difficult to imagine how life emerged on the prebiotic Earth. To get around this difficulty, some scientists have proposed that instead of exploring unlikely ways that prebiotic chemistry can be carried out in water, we should look for alternative liquids that follow different chemical rules than water. Specifically, it has been proposed that water-based life derives from even older chemical reactions that took place in a liquid called formamide. Formamide physically behaves like water in many ways, but chemically, it allows reactions to take place that lead to the production of molecules like RNA and proteins that are very unlikely to occur in water. However, it is not clear how formamide could have been formed in abundance on the early Earth.

I recently formed a team that found a way to produce abundant formamide and a sugar molecule called glycolaldehyde in a setting called a placer deposit, which is a location where dense minerals are concentrated due to waves or water currents. The dense minerals in placer deposits also include phosphate minerals. These are particularly promising discoveries because the three kinds of molecules that are found in RNA (nucleobases, sugars and phosphates) can theoretically all be produced in this one kind of geological setting. However, it is unknown if each of these three kinds of molecules can be produced at the same time and under realistic, naturally occurring conditions. If we can make all of the RNA compounds in a single setting from abundant starting materials, then we can create testable hypotheses to explore whether RNA can be formed from geochemically driven reactions and whether these reactions can lead to life forming on our planet. For these reasons, I propose to investigate placer deposits as one possible example of a setting that could have produced RNA on the early Earth by using experiments that mimic the physical and chemical conditions inside these sediments.