Sustainable Living on Mars: Remediation of Martian Soil to Produce Oxygen

In 2008, the Phoenix Mars Lander detected perchlorate (ClO4⁻) in Martian regolith at a concentration of 0.5% - 1.0%, up to 10 000 times higher than that on Earth. Perchlorate is a chemical anion that has adverse health effects on humans, rendering Martian soil unfarmable and posing a challenge to any future pursuits at colonization. The main sources of exposure to perchlorate on Mars would be through the inhalation of dust and the ingestion of contaminated food/water. Once it enters the body, its primary target is the thyroid gland, which regulates the body’s metabolism. ClO4⁻ directly competes with the uptake of iodine ions by the thyroid, leading to decreased hormonal output, slowed metabolism, and the hindered function of many organ systems. If colonization on Mars is to be made possible, detoxifying the soil of perchlorate is a necessity.

When we dug deeper, we stumbled on the work of Davila et al [1] who proposed that the toxic concentration of ClO4⁻in Martian soil was actually a resource that could be exploited both as a source of rocket fuel and O2, while remediating the soil in the process. It can be broken down further into perchlorite (ClO2⁻), chlorine (Cl-), and oxygen (O2) using two already sequenced enzymes, perchlorate reductase and chlorite dismutase.

Our project has two main themes: 1) the extraction, purification and concentration of ClO4 from Martian soil, and 2) the bioconversion of ClO4 to oxygen using genetically engineered E. coli. These themes and others are covered more thoroughly under “Lab Notes”. ClO4 is highly soluble in water. We are testing the idea that ClO4 can be highly enriched and concentrated inexpensively using activated charcoal, as previously shown for a similar compound [4]. For O2 production, we plan to synthesize and express the genes from the soil bacterium that are responsible for ClO4 breakdown, Ideonella dechloratans, [3] into the bacterium E. coli. We have also developed a method for the recycling of Martian colony biowaste into a highly enriched media for bacterial growth.

We want to design an efficient metabolic pathway for the breakdown of perchlorate to produce oxygen by inserting the genes for these enzymes into E. coli, one of the fastest growing bacteria on Earth.