The dream of humans living on Mars has existed 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 firm reminder that dreaming about the Red Planet and actually making it liveable for human beings 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 amounts of mass, heat, oxygen, and energy so enormous that the entire project remains completely beyond humanity’s current industrial or technological reach and may stay that way for centuries to come.
The five stages of Mars terraforming and what each one demands
Before getting into what the numbers look like, it helps to understand what terraforming Mars would actually require in stages. Turyshev’s study lays out five distinct milestones on the path from the Mars that exists today to something resembling Earth.The starting point is Mars as we know it: a bitterly cold planet with an atmosphere so thin it cannot support liquid water on the surface and would kill a human being in minutes without a pressurised suit. The first real milestone would be raising atmospheric pressure above 6.1 millibars at 0°C, which is the triple point of water the specific combination of temperature and pressure at which water can exist as a solid, liquid, and gas simultaneously. After that comes what scientists call a “shirtsleeve greenhouse” environment, where large pressurised domes could support agriculture across regional areas without extreme engineering. This approach known as paraterraforming involves building enclosed habitable zones rather than changing the whole planet at once.The fourth milestone would be reaching a global surface pressure of 62.7 millibars, at which point human blood would no longer boil at body temperature on the Martian surface. The final goal would be a fully breathable atmosphere: roughly 210 millibars of oxygen within a total atmospheric pressure of around 500 millibars, at temperatures high enough for liquid water to exist widely and stably.
Why Mars needs an entire moon’s worth of atmospheric mass
Each of these stages sounds ambitious on its own, but the study makes the physical scale involved almost difficult to process. To raise Mars’s atmospheric pressure by just one millibar, about 3.89 × 10¹⁵ kg of gas would need to be added. That is roughly equivalent to the total mass of Deimos, the smaller of Mars’s two moons. Scaling that up to the atmospheric pressure needed for a breathable environment requires something closer to 10¹⁸ kg of material comparable to Janus, an irregular moon of Saturn.To be fair to those who believe terraforming is achievable, there are expected to be hundreds of bodies of that mass scattered across the outer solar system. Sacrificing one of them to build a livable atmosphere on Mars is not physically impossible in principle. But the engineering required to move or redirect an object that large dwarfs anything humanity has ever attempted.
The temperature problem and the scale of mirrors that would solve it
Atmospheric pressure is only one of the two core planetary variables that would need to change. Temperature is the other. Mars today is an average of about 60°C colder than Earth needs to be for liquid water to exist stably across its surface. To close that gap, various approaches have been proposed from injecting shortwave-absorbing nanoparticles into the atmosphere to releasing massive quantities of carbon dioxide as a greenhouse gas.One idea frequently raised by engineers is installing enormous orbital mirrors to concentrate additional sunlight onto Mars. According to Turyshev’s calculations in the published paper, doing this effectively would require approximately 70 million square kilometres of mirror surface. For context, that is larger than the entire surface area of the Asian continent. There is no industrial base, no manufacturing pipeline, and no launch capacity anywhere in the world today that could build something remotely close to that scale.
Oxygen production for a breathable Mars atmosphere would require an ocean’s worth of water
Even if atmosphere and temperature could somehow be addressed, the oxygen problem adds another layer of scale that is hard to absorb. Producing enough oxygen for a fully breathable Martian atmosphere would require generating roughly 8.2 × 10¹⁷ kg of the gas. The most practical way to do that would be to split oxygen from water through electrolysis. Accounting for the hydrogen lost in that process, the water needed would amount to approximately six cubic metres for every single square metre of Mars’s surface.The surprising piece of good news here, as noted in the study, is that Mars actually has enough accessible surface ice to meet this requirement. All the water needed for the oxygen alone would use only around 20% of the known surface ice. This means the more extreme proposals such as crashing multiple water-bearing comets into Mars to build up its hydrosphere may not be necessary. Mars has the raw material. What it does not have is any way of processing it at the required rate.
Energy is the biggest barrier to Mars habitability
Of all the constraints Turyshev identifies, energy is the one that makes the timeline most sobering. The minimum energy required to split enough water to produce the oxygen a breathable Martian atmosphere demands is approximately 1.2 × 10²⁵ joules. Spread across a thousand years of continuous operation, meeting that requirement would call for a sustained power output of around 380 terawatts. That figure is nearly 20 times the total annual energy consumption of every country on Earth combined today.There is no plausible near-term path to generating that kind of power. Humanity’s current civilisation simply does not operate at that energy scale, and getting there would require advances in energy production that are likely centuries away even under optimistic assumptions.What the study leaves open is the longer view. Future civilisations, operating with energy sources and industrial capacities that do not yet exist, may find some of these numbers more manageable. The solar system does contain the raw materials Mars would need. The physics of converting those materials into a liveable atmosphere does work in principle. The gap is entirely one of capability, not concept and that gap, while enormous by current standards, is at least something that technological progress can theoretically close over a long enough timescale. For now, though, Mars remains exactly what it has always been: a compelling destination for exploration, and a very long way from being a second home. Go to Source
