Colonists on Mars could one day generate fuel and oxygen from saltwater on the Red Planet, a new study finds.
The novel technology behind this advance could also help submarines generate oxygen from seawater on Earth, researchers said.
In order to live on Mars, any potential colonists will need oxygen to breathe and fuels such as hydrogen gas to power their equipment. Any water they find on the Red Planet will therefore prove invaluable, as they can use electricity and other methods to break water down into both hydrogen and oxygen.
"Mars is a long way out there, and we are limited in the amount of stuff we can bring with us, so if we can utilize resources already present there, that's more economical and more viable than having to lug everything with us," study senior author Vijay Ramani, a chemical engineer at Washington University in St. Louis, told Space.com.
Previous research found Mars possesses large amounts of ice, and NASA's Phoenix lander also found signs the planet's arctic plains were covered with a film of liquid water in the last few million years. Phoenix also discovered compounds known as perchlorates in Martian soil, which can act like antifreeze, lowering the freezing point of water past its normal temperature.
Since brines containing water and perchlorates may remain liquid even at the chilly temperatures found on the Martian surface, Ramani and his colleagues wanted to see if they could use a technique known as electrolysis to split water molecules to form hydrogen and oxygen using electricity. (The average annual temperature on Mars is about minus 81.4 degrees Fahrenheit, or minus 63 degrees Celsius, although it can vary by more than 212 degrees F, or 100 degrees C, over the course of a day.)
"Electrolysis has been known for about 100 years or more, but mostly uses pure water as its feed," Ramani said.
In prior work, Ramani and his colleagues developed materials known as lead ruthenate pyrochlore electrocatalysts that could help them electrolyze seawater. In the new study, their experiments revealed such catalysts could help electrolyze perchlorate brines, generating ultra-pure hydrogen and oxygen at the kind of ultra-low temperatures found on the Martian surface.
"We can derive oxygen for breathing and hydrogen for fuel using materials on Mars itself, the briny water now known to be present there," Ramani said. "Future missions don't necessarily have to carry those components to Mars, but make them in situ with technology such as ours."
Some electricity is needed to drive these chemical reactions. On Mars, such electricity will likely come from solar power cells, Ramani noted.
Previously, the NASA Mars Perseverance rover's Mars Oxygen In-Situ Resource Utilization Experiment (MOXIE) showed it could use electricity to break down carbon dioxide into oxygen and carbon monoxide. For the same amount of power as MOXIE, the new study could generate 25 times as much oxygen or more, and not generate any toxic carbon monoxide to boot, the researchers said.
"When we're talking about exploring space or the surface of the moon or Mars, it's never just one technology that's used — it's never just one silver bullet that solves all issues," Ramani said. "A bunch of technologies will be needed to work in parallel with each other to make life easier on Mars, and our hope is that ours will be one of them."
The scientists noted this could help NASA fulfill its current mandate to land humans on Mars by the mid-2030s. "We hope we can interest NASA in trying to scale up this technology and further improve its performance, and in demonstrations in facilities simulating the Martian environment," Ramani said.
Such electrocatalysts may find use on Earth as well. "If you're in a submarine where there is limited oxygen and there is saltwater all around you, you could siphon in some saltwater and split it to get fresh oxygen," Ramani said. "In the U.S. Navy, most submarines are nuclear-powered, so there's no shortage of electricity. For applications on land, you could also split briny water to generate hydrogen fuel."
The scientists detailed their findings online Nov. 30 in the journal Proceedings of the National Academy of Sciences.
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