Mars colonization demands technological advances to enable the return of humans to Earth. Shipping the propellant and oxygen for a return journey is not viable.
Now, a team of researchers at the Georgia Institute of Technology has developed a concept that would make Martian rocket fuel on Mars that could be used to launch astronauts back to Earth. The bioproduction process would use three resources native to the red planet: carbon dioxide, sunlight, and frozen water.
It would also include transporting a microbe called cyanobacteria (algae), along with a strain of E. coli bacteria, to create rocket biofuel. The cyanobacteria (algae) would take CO2 from the Martian atmosphere and use sunlight to create sugars, while an engineered E. coli would be shipped from Earth, which would convert those sugars into a Mars-specific propellant called 2,3-butanediol, for rockets and other propulsion devices.
Current rocket engines departing Mars in the near future are planned to be fueled by methane and liquid oxygen (LOX), but neither exists in abundance on the Red Planet. This means that astronauts would need to be transported from Earth to power a return spacecraft into Martian orbit, but its transportation is very expensive. NASA and other studies have suggested some alternatives to derive the two elements on the spot, but these technologies are still immature to work on a large scale.
The Georgia Institute of Technology’s proposal involves biotechnology-based in-situ resource utilization (bio-ISRU) that can produce both propellant and LOX from CO2. In addition to reducing the mission costs, the process would also generate 44 tons of excess clean oxygen that could be set aside to use for other purposes, such as supporting human colonization.
The process of producing enough propellant for the trip back to Earth begins by ferrying plastic materials to Mars that would be assembled into photobioreactors occupying the size of four football fields. In these reactors, sunlight and carbon dioxide from the atmosphere would be provided to the cyanobacteria. Enzymes in a separate reactor would break down the cyanobacteria into sugars, which could be fed to the E. coli to produce the 2,3-butanediol and oxygen, which would be separated out by further steps in the process.
The team’s research found that the process uses 32% less power – but weighs three times more – than the proposed chemically enabled strategy of shipping methane from Earth and producing oxygen via chemical catalysis.
“You need a lot less energy for lift-off on Mars, which gave us the flexibility to consider different chemicals that aren’t designed for a rocket launch on Earth,” said Pamela Peralta-Yahya, a corresponding author of the study and an associate professor in the School of Chemistry & Biochemistry and ChBE who engineers microbes for the production of chemicals. “We started to consider ways to take advantage of the planet’s lower gravity and lack of oxygen to create solutions that aren’t relevant for Earth launches.”
The team is now looking to perform the biological and materials optimization identified to reduce the weight of the bio-ISRU process and make it lighter, faster, and more efficient than the proposed chemical process.
“We also need to perform experiments to demonstrate that cyanobacteria can be grown in Martian conditions,” said Realff, who works on algae-based process analysis. “We need to consider the difference in the solar spectrum on Mars both due to the distance from the Sun and lack of atmospheric filtering of the sunlight. High ultraviolet levels could damage the cyanobacteria.”