Abiotic Reduction of Carbon Dioxide as a Source of Early Earth’s Primitive Carbon

Credit: Hudson et al., 2020.

Life on Earth is composed primarily of organic matter made up of carbon, hydrogen, and oxygen with nitrogen, sulfur, and phosphorous also playing key roles. Synthesizing organic carbon through the reduction of carbon dioxide (CO2) by molecular hydrogen (H2) is a well-known biotic process that occurs in some bacteria and archaea such as acetogens and methanogens, respectively. However, for the analogous reaction to occur abiotically, an energy barrier exists during the first step of CO2 reduction to produce formate, a simple organic anion. Understanding the energetically favorable reactions that existed on the prebiotic Earth (i.e., before living organisms evolved) that could eventually drive metabolic pathways is crucial to gaining insight into the origins of life.

A recent study led by Reuben Hudson from the College of the Atlantic investigated the chemical reduction of carbon dioxide in a prebiotic context by conducting experiments in microfluidic chambers. Hudson and colleagues found that the first energy barrier in the reactions can be overcome under conditions of room temperature, moderate pressure (1.5 bar), and a pH gradient over mineral precipitates. These conditions are considered relatively mild and similar to those found at alkaline hydrothermal vent systems on Earth. Additionally, these results provide important constraints on energy-requiring reactions, particularly for assessment of habitability and the search for life on other worlds that may host these environments such as Europa and Enceladus. READ MORE