Editor’s Note: Katie Mack is an assistant professor of physics at North Carolina State University, researching dark matter, the early universe and other topics in theoretical cosmology. She is the author of The New York Times Notable Book “The End of Everything (Astrophysically Speaking).” The views expressed in this commentary belong to the author. View more opinion at CNN.
On April 20, after two months on Mars, NASA’s Perseverance rover performed a magic trick: it produced breathable oxygen out of thin air. An instrument called MOXIE (the Mars Oxygen In-Situ Resource Utilization Experiment) used electricity to split a small amount of the carbon dioxide of Mars’ tenuous atmosphere into pure oxygen and carbon monoxide.
The total quantity of oxygen produced in this proof-of-concept test was small – only about five grams, enough to sustain a breathing human for about 10 minutes – but it serves as an essential prototype of a system that may someday be vital for human explorers of the Red Planet.
Engineers hope that a larger-scale version of MOXIE could run autonomously for years, carefully teasing out and storing oxygen in tanks on the surface for future access. Some of that oxygen can be set aside for replenishing the breathable air in human habitats, but, most likely, most of it will be used for another purpose entirely: allowing the astronauts to someday come home. Because in addition to being essential for human life, oxygen can be rocket fuel.
Oxygen’s purpose in our bodies is to enable cellular respiration – the process by which we derive energy from food – which is, essentially, a combustion reaction. We use the oxygen to “burn” the sugars in food and that powers our cells and keeps us alive.
A faster and more violent version of this energy production process happens when you add oxygen to a rocket propellant, such as hydrogen. The Space Shuttle’s giant orange external fuel tank did just that, working with the two solid rocket boosters to fire the vehicle into orbit.
SpaceX’s Starship rocket uses supercooled methane as the fuel it combines with oxygen. Now that oxygen has successfully been produced on Mars, it raises hopes that with larger-scale instruments, one component of the rocket fuel for a future return trip could be ready and waiting before astronauts even arrive on the Martian surface.
Other scientists have performed promising laboratory experiments to show that methane could theoretically be produced on Mars as well by combining the carbon dioxide in the air with water found under the surface in the form of ice.
Given the difficulty and expense involved in launching every kilogram of material off the Earth’s surface and the added complication of landing a heavy rocket carrying supplies, the idea that we could create these fuels ahead of time on Mars, via automated facilities, could bring a human return trip much closer to reality.
As exciting as this development is for future exploration, the transportation of air and rocket fuel are not the only massively difficult challenges to overcome when we contemplate actually putting humans on the Red Planet.
While the technology side of physically getting humans to Mars is more or less understood – in principle it could be done with more powerful adaptations of what we first used to send people to the Moon in the 60s – everything beyond that point will be uncharted territory.
Any trip to Mars is a long one. A trip optimized to use as little fuel as possible will take six to nine months, making use of a launch window that only occurs every two years or so. We don’t really know what it will do to humans to be isolated in a small space like that for so long and simulation missions on Earth, in which a crew is isolated on a mountaintop in a small space for hundreds of days at a time, have had mixed results in terms of the mental and physical health of the participants.
Maybe being in actual space would be more motivating, but it will also come with extra stresses such as the damaging effects of weightlessness on the body and a dangerous radiation environment that might be hard to mitigate.
Landing on Mars isn’t easy, either: historically, about half of Mars lander missions have ended with sudden uncontrolled surface impacts and none have tried to land a vehicle large enough to carry humans and all their stuff.
The problem with Mars is that it has enough atmosphere to burn up in, but not enough to slow a parachute for a soft landing. Vertical-landing rockets such as SpaceX’s Starship (which was recently chosen by NASA for its next Moon lander) might be the only practical solution, but for now, those are still in the explode-y early days of their development.
Once on the surface, the astronauts will need to find a way to survive and stay healthy until their return voyage. One of the biggest challenges at that point will be creating a habitat to shield them from radiation.
The fact that Mars has a very thin atmosphere and no global magnetic field means that the radiation environment on the surface isn’t much safer for humans than it is en route to the planet. Most likely, Mars explorers will need to spend most of their time living underground to reduce the chance of radiation sickness or cancer.
It’s possible that the water ice present under the surface of Mars can provide drinking water, once the toxic chemicals are filtered out, and there’s even a chance that the local dirt can be used to grow food, as in the film “The Martian.” And energy shouldn’t be a problem, assuming we are able to get solar panels or nuclear generators to Mars, either ahead of time or along with the travelers.
But something less obvious might end up causing even more trouble. For instance, the Martian soil includes incredibly fine dust that could prove difficult to filter and toxic if breathed in. Once you have boots on the surface, it becomes impossible to leave all that dust outside.
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As much as Mars might look like a familiar Earth desert in NASA photographs, it’s hard to overstate the extent to which it is hostile to human life. And the logistical and even ethical considerations aren’t trivial either. Who gets to go? What rules should govern exploration, or exploitation of resources? If it turns out that there’s some kind of indigenous life, even if it’s only microscopic, what are we obligated to do to safeguard it and protect it from contamination?
All these questions, too, need answers – preferably, before anyone goes out there and tries to plant a flag.
Still, whether or not humans ever create a permanent habitat on Mars, it seems inevitable that someone will eventually go, set up camp and take a look around. Technological innovations like MOXIE bring that just a little bit closer and might make those future astronauts breathe a little easier as they step out into the inhospitable unknown.