Humans’ dream of living on Mars has been around for decades, and in recent years it has moved closer to serious scientific and engineering conversation than ever before. But a new study published in APS Open Science by Slava Turyshev of NASA’s Jet Propulsion Laboratory is a powerful reminder that dreaming about the Red Planet and making it habitable for humans are two very different things.
According to Turyshev’s calculations, transforming Mars into a world with breathable air, liquid water, and stable temperatures would require such enormous amounts of mass, heat, oxygen, and energy that the entire project would remain completely beyond humanity’s current industrial or technological reach, and may remain that way for centuries to come.
The five stages of terraforming Mars and what each stage requires
Before getting into what the numbers look like, it’s helpful to understand what it would actually take to actually terraform Mars in phases.
Turyshev’s study identifies five distinct milestones on the path from today’s Mars to something Earth-like.The starting point is Mars as we know it: an extremely cold planet with an atmosphere so thin that it cannot support liquid water on the surface and could kill a human in minutes without a pressurized suit. The first real milestone will be raising atmospheric pressure above 6.1 millibars at 0°C, which is water’s triple point – the specific combination of temperature and pressure at which water can exist as solid, liquid and gas simultaneously.
Next comes what scientists call a “short-sleeved greenhouse” environment, where large, pressurized domes can support agriculture in regional areas without the need for extreme engineering. Known as Paraterraforming, this approach involves building enclosed habitable areas rather than altering the entire planet at once.The fourth milestone will be reaching a global surface pressure of 62.7 millibars, at which point human blood will no longer boil at body temperature on Mars.
The ultimate goal will be a fully breathable atmosphere: approximately 210 millibars of oxygen at a total atmospheric pressure of about 500 millibars, at temperatures high enough for liquid water to exist on a large, constant scale.
Why does Mars need an atmosphere mass equivalent to the size of the entire Moon?
Each of these stages seems ambitious in its own right, but the study makes it difficult to address the physical scale involved. To raise Mars’ atmospheric pressure by just one millibar, about 3.89 x 10¹⁵ kg of gas would have to be added.
This is roughly equivalent to the total mass of Deimos, the smaller of Mars’ two moons. Raising that atmospheric pressure needed for a breathable environment would require something closer to 10¹⁸kg of material similar to Janus, an irregular moon of Saturn.To be fair to those who think terraforming is possible, there are expected to be hundreds of objects of this mass spread across the outer solar system.
Sacrificing one of them in order to build a habitable atmosphere on Mars is not physically impossible in principle. But the engineering required to move or redirect a large object dwarfs anything humanity has ever attempted.
The problem of temperature and size of mirrors would be solved
Atmospheric pressure is only one of two fundamental planetary variables that must be changed. Temperature is the other. The temperature of Mars today is about 60 degrees Celsius cooler on average than Earth needs to be for liquid water to exist stably across its surface.
To fill this gap, various methods have been proposed, starting with injecting nanoparticles that absorb shortwaves into the atmosphere, releasing huge amounts of carbon dioxide as a greenhouse gas.One idea that engineers frequently raise is to install massive orbital mirrors to focus additional sunlight on Mars. According to Turyshev’s calculations in the published paper, doing so effectively would require approximately 70 million square kilometers of mirror surface.
For context, this is larger than the surface area of the entire Asian continent. There is no industrial base, no manufacturing pipelines, and no launch capacity anywhere in the world today that could build something even remotely close to this scale.
Producing oxygen for a breathable Martian atmosphere would require the equivalent of ocean water
Even if the atmosphere and temperature could be addressed somehow, the oxygen problem adds another layer of scale that is difficult to comprehend. Producing enough oxygen for a fully breathable Martian atmosphere would require generating approximately 8.2 x 10¹⁷ kg of gas.
The most practical way to do this is to separate oxygen from water through electrolysis. Factoring in the hydrogen lost in the process, the water needed would amount to approximately six cubic meters per square meter of Mars’ surface.The surprisingly good news here, as mentioned in the study, is that Mars already has enough accessible surface ice to meet this requirement. All the water needed for oxygen alone would only use about 20% of the known surface ice.
This means that more extreme proposals, such as smashing several water-bearing comets onto Mars to build up its hydrosphere, may not be necessary. Mars has the raw material. What it doesn’t have is any way to process it at the desired rate.
Energy is the biggest obstacle to Mars’ habitability
Of all the constraints identified by Turyshev, it is energy that makes the timeline most realistic. The minimum energy needed to split enough water to produce the oxygen required by a breathable Martian atmosphere is about 1.2 x 10²⁵ joules.
Over a thousand years of continuous operation, meeting this requirement would require a sustainable energy production of about 380 terawatts. This number is equivalent to nearly 20 times the total annual energy consumption of every country on Earth combined today.There is no reasonable path in the short term to generate this kind of power. Current human civilization simply does not operate on this energy scale, and reaching this level will require progress in energy production, which is likely to take centuries even under optimistic assumptions.What the study leaves open is the longer view. Future civilizations, powered by energy sources and industrial capabilities that do not yet exist, may find some of these numbers more manageable. The solar system contains the raw materials that Mars needs. The physics of converting those materials into a livable atmosphere works in principle. The gap is largely one of capability, not concept, and this gap, while enormous by current standards, is at least something that technological progress could theoretically bridge over a sufficiently long period of time.
For now, however, Mars remains what it has always been: an attractive destination for exploration, and a very long way from being a second home.