MIT’s MOXIE has finished its mission with the Perseverance Rover
Around 2–3 years ago, the Massachusetts Institute of Technology (MIT) created MOXIE, which stands for Mars Oxygen In-Situ Resource Utilization Experiment, to convert Mars's atmosphere into breathable oxygen. Currently, after more than 2 years, MOXIE has generated 122 grams of oxygen, which is equal to what a small dog breathes in 10 hours. But is this technology the best way to breathe on Mars?
Levels
Dr. Ben Miles on his YouTube channel explains three different levels of survival in extreme locations without oxygen.
The first level is taking an atmosphere with a person. This is a terrible method because there is no way to clean up the carbon dioxide (CO2). For example, Alexander the Great used a giant glass dome to explore the ocean. However, as oxygen levels decreased, he had to eventually go back up.
The second level is taking an atmosphere with a person and cleaning it. Instead of using level one, he uses level two, where he takes with him a cockerel, a cat, and a dog. The cockerel keeps time, the dog is to be inflated to quickly rise to the surface in case of emergency, and the cat is to act as a rebreather to purify the vessel’s atmosphere. However, the person will need backup as, in this example, the cat might die. Also, resources such as food and water may be in need. Therefore, even if you periodically receive resources, they will run out over time.
The third and final level is to make it when a person gets there. This is exactly what the MOXIE does by creating oxygen from the Martian atmosphere. But what does the exact process look like?
Process
According to Miles, MOXIE splits CO2 to produce oxygen through solid oxide electrolysis. Miles describes the process: “A scroll compressor pulls Martian atmosphere from outside the Rover through a filter and pressurizes it to about half an atmosphere. The pressurized CO2 gas is then fed into the solid oxide electrolyzer, the socks, where it is electrochemically split to produce pure oxygen. The socks operate at 800 degrees Celsius, requiring a sophisticated thermal isolation system including input gas preheating and exhaust gas cooling. The reason MOXIE is gold is to help limit the heat produced during operation from affecting the other instruments of perseverance."
According to NASA, MOXIE generates about 12 grams of oxygen per hour when it is most efficient. However, since the process needs a lot of energy, it has only been used 16 times. Though this process is twice as good as scientists thought, it still has some disadvantages.
Disadvantages
According to Miles, the disadvantages of MOXIE are that it is highly inefficient, uses limited rare earth metals and works best with a lot of pressure and heat, which is the opposite of Mars’s atmosphere. For example, the Earth’s atmosphere is 101,325 pascal, while Mars’s atmosphere is only 600 pascal. This is why MOXIE needs the compressor at the pre-stage and the 800-degree oven to operate. Due to these drawbacks, some experts are looking for better strategies.
Better Plans
According to Science, Vasco Guerra, a physicist at the University of Lisbon, claimed a plasma reactor could provide better results. More specifically, a beam of electrons, elevated to a certain energy level, can split CO2 into its component ions, or plasma, just like MOXIE. In addition, a plasma reactor would be appropriate for the Martian atmosphere, which is a lot thinner than Earth’s.
“It is much easier to create and accelerate a beam of electrons in thin air,” Guerra said. “There is an ideal pressure for plasma operation. Mars has precisely this correct pressure.”
Going back to Miles’s ideas, he also believes in a better way to create oxygen on Mars – an approach called “low temperature plasmas.” This technology requires enough energy to remove oxygen from CO2 by striking it hard with an electron, heating it up or shaking the molecule apart.
“Where two molecules with slightly different energies couple with each other, the energy of the interaction is preferentially added to the higher energy molecule, making its amplitude of vibration increase even more,” Miles said. “This causes the less energetic molecule to reduce its amplitude. As this process continues, the up-pumped molecules, the excited molecules, amplitude gets so big they spontaneously dissociate, producing carbon monoxide and atomic oxygen.”
This approach has been tried on Earth, but Mars's atmosphere, temperature and pressure are great for low temperature plasmas. If this approach is much better on Mars, will scientists apply this method?
The Next Step
According to Space.com, a group of scientists says that they wouldn’t create a MOXIE 2.0 but rather a larger system containing a MOXIE box while storing and liquifying all the oxygen produced. In reality, though low temperature plasmas are a great approach, they will not be confirmed for use until maybe the far or near future, when we need to.