Mars is not habitable for humans in its current state. The planet has no breathable air, almost no atmospheric pressure, extreme cold, toxic soil, and radiation levels hundreds of times higher than Earth’s. But “habitable” and “survivable with technology” are different questions, and the second one is where things get interesting. With enough engineering, humans could potentially live on Mars inside artificial habitats, though the challenges are severe and unlike anything we’ve solved before.
Why You Can’t Breathe the Air
Mars’s atmosphere is almost entirely carbon dioxide, with only trace amounts of nitrogen, argon, and oxygen. The oxygen concentration is so low it’s essentially zero for breathing purposes. But the bigger problem is pressure: the Martian surface sits at roughly 7.3 millibars, less than 1% of Earth’s sea-level pressure. At that pressure, your blood would effectively boil at body temperature. Stepping outside without a pressurized suit would be fatal within seconds, long before the lack of oxygen became relevant.
NASA’s Perseverance rover carried a small experiment called MOXIE that demonstrated one possible workaround. The device pulled carbon dioxide from the Martian atmosphere and split it to produce oxygen at a rate of about 6 grams per hour, with a design capacity of up to 10 grams per hour. That’s a tiny amount (a person needs roughly 840 grams of oxygen per day), but it proved the chemistry works. A scaled-up version could theoretically produce breathable air from local resources rather than hauling all of it from Earth.
Temperature Swings and Radiation
Surface temperatures on Mars range from about 20°C (70°F) on a good day near the equator down to a brutal -153°C (-225°F). Even at the warmest spots, the temperature gradient is strange: standing at the equator at noon, your feet might feel a pleasant 24°C while the air at head height hovers around 0°C. The thin atmosphere holds almost no heat, so temperatures crash as soon as the sun dips.
Radiation is an equally serious problem. Earth’s magnetic field and thick atmosphere block most cosmic radiation, giving us a background dose of about 2.4 millisieverts per year. On Mars, which has no global magnetic field and barely any atmosphere, astronauts would absorb roughly 1 millisievert per day or more. That’s over 150 times the annual dose on Earth, and it adds up fast. Extended exposure at that level significantly raises the risk of cancer and can damage the central nervous system.
One promising natural solution exists: lava tubes. Mars has vast underground tunnels carved by ancient volcanic activity, and with multiple meters of solid rock overhead, the interior of a lava tube offers excellent shielding from both solar particle events and background cosmic rays. Building habitats inside these structures, or burying surface habitats under several meters of Martian soil, could bring radiation exposure down to manageable levels.
Toxic Soil
Martian regolith (the loose, rocky material covering the surface) contains perchlorates at concentrations of 0.4 to 0.6% by weight, as detected by the Phoenix lander near the north pole. For comparison, the highest perchlorate concentrations found on Earth occur in Chile’s Atacama Desert at similar levels, but only in specific ore deposits. Typical Atacama soil runs about 0.03%.
Perchlorates are strong oxidizers that interfere with thyroid function in humans. Chronic exposure can disrupt hormone production even at low levels. This means Martian dust isn’t just inert grit. It’s chemically hostile. Any habitat would need rigorous dust control, and any attempt to grow food in Martian soil would require washing or chemically treating the regolith first.
Growing Food on Mars
Even setting perchlorates aside, Martian soil lacks the basic ingredients plants need. It contains no organic matter and is deficient in nitrogen and phosphorus, two nutrients essential for plant growth. Its water-holding capacity is only about 30% of typical Earth soil, meaning it drains too quickly to keep roots hydrated.
The soil does contain some useful minerals. Feldspar in Martian regolith can release potassium, calcium, and sodium, all of which support plant development. Potassium drives photosynthesis and enzyme function. Calcium builds cell walls. Recent experiments with Martian soil simulants have shown that mineral-supplemented irrigation can promote leaf growth, preserve chlorophyll, and increase overall plant mass. But nitrogen and phosphorus would still need to come from somewhere, likely recycled from human waste, brought from Earth, or synthesized on-site. Farming on Mars is possible in principle but would require closed greenhouse systems with heavily amended soil or hydroponic setups.
Water Is There, but Hard to Reach
Mars has significant water ice, but it’s not conveniently located. Surface ice is stable only at high latitudes where conditions are too cold for humans or equipment to operate long-term. NASA’s Subsurface Water Ice Mapping (SWIM) project has mapped ice deposits buried underground at mid-latitudes, roughly between the equator and 60 degrees north, where landing and working would be more feasible. Accessing this ice would mean drilling or excavating, then melting and purifying it. The water is there in meaningful quantities, but extracting it adds another layer of infrastructure that any Mars settlement would need before it could function.
What Low Gravity Does to Your Body
Mars has about 38% of Earth’s gravity. That’s better than the zero-gravity environment of the International Space Station, but no one knows whether it’s enough to prevent long-term health decline. In microgravity, astronauts lose 1 to 1.5% of their bone mineral density per month in weight-bearing bones like the femoral neck. The maximum total bone loss is estimated to plateau around 69% of pre-flight density, with a half-life of about 1,088 days, meaning the most rapid losses happen in the first few years.
Whether Mars’s partial gravity slows this process significantly or just delays it is still unknown. There is no human data from partial gravity environments lasting more than a few days (the Apollo lunar stays were short). Muscle atrophy follows a similar pattern. Settlers would almost certainly need daily resistance exercise programs, and even then, long-term residents might develop bones too fragile to ever safely return to Earth’s gravity.
Getting There
The trip itself is a major obstacle. Using current chemical propulsion, a one-way transit to Mars takes roughly 90 days under optimal orbital alignment. A 2025 analysis of SpaceX’s Starship architecture published in Nature identified feasible 90-day transfer windows in 2033 and 2035, with a 104-day option in 2037. These windows open only every 26 months when Earth and Mars align favorably.
During the three-month journey, crew members would be exposed to deep-space radiation without Earth’s magnetic protection, accumulating roughly 90 millisieverts before even arriving. The transit also means that if something goes wrong on Mars, rescue is not an option. The earliest a return or resupply mission could launch would be over two years away.
What Habitability Would Actually Look Like
No one is talking about walking around on Mars like you would on Earth. Habitability, in the context of a human settlement, means sealed pressurized structures with manufactured atmospheres, radiation shielding (either underground or under meters of regolith), closed-loop water recycling, greenhouse food production, and oxygen generated from Martian CO₂. Every system would need redundancy because a single failure in pressure, air, or water could be fatal within hours or days.
The individual technologies for each of these challenges exist in some form. MOXIE proved oxygen extraction works. Water ice mapping shows where to find it. Lava tubes offer natural radiation shelters. Soil amendment experiments show plants can grow in regolith simulants. But none of these have been tested together, at scale, on Mars, with human lives depending on them. The gap between a proof-of-concept experiment and a functioning life-support ecosystem is enormous, and that gap is what separates Mars from being truly habitable for humans today.