To solve the problem of thirsty astronauts on Mars, NASA is considering a new proposal. The agency may develop a method to use synthetic biology to remove toxic perchlorate from Martian ice, making the water in those ices suitable for human consumption.
If you've read enough adventure novels set in the desert, sooner or later you'll come across the cliche plot: Our hero encounters a water hole, only to discover that it's filled with toxic minerals. Future astronauts will encounter similar situations on Mars. However, this will be a common problem rather than a rare one.
The culprit is a class of compounds called perchlorates. These molecules contain the ion CLO₄. They are not common on Earth because our planet's highly unstable environment, rich in water and oxygen, tends to destroy them. On Mars, things are different. Due to a lack of oxygen and water, coupled with hundreds of millions of years of relentless bombardment of the Martian surface by hard ultraviolet and cosmic rays, perchlorate has seeped into the soil and seeped into the ice beneath the surface.
This situation has caused a lot of trouble for NASA and other space agencies. Perchlorate is highly corrosive and its volatile nature caused notoriously inaccurate results in experiments to detect life on NASA's Viking landers. Initially, it was thought that Martian microorganisms were responsible for the sudden increase in gases being released. However, this is simply a chemical reaction that occurs when an aqueous nutrient solution comes into contact with perchlorate in a soil sample.
For astronauts, perchlorate is not a good thing. They would make any water in the Martian ice unsuitable for drinking, growing crops, or even making rocket propellant. It is possible to remove perchlorate using reverse osmosis membranes or anion exchange technology, but most methods tend to require extensive equipment, energy and water pretreatment.
The new approach proposed to NASA is to use a so-called regenerative perchlorate reduction system. This approach uses synthetic biology to create genetically engineered bacteria that can feed on perchlorate and convert it into oxygen and chloride.
Bacteria capable of doing this are not new. Therefore, the research team hopes to extract the key genes that catalyze the reaction and insert them into Bacillus subtilis strain 168 (which can be used for space flight), and then control the reaction with an active promoter.
According to the research team, this method is not only scalable but also eliminates perchlorate directly, rather than filtering it and then processing it.