What If? Lab
What if people built homes on Mars?
Mars is cold and dusty, and you cannot breathe its air. What would people need to build a home there? Plan a Mars base with Olly!
Mars has air you cannot breathe, temperatures far below freezing and no magnetic shield like Earth's. A home there would need sealed rooms, a way to make oxygen and water, and gardens for fresh food. NASA is already testing pieces of the puzzle, from an oxygen maker on Mars to a 3D-printed practice habitat in Texas.
A Mars settlement must supply what Earth gives for free: pressure, oxygen, water, food and protection from cold and radiation. NASA's MOXIE made 122 g of oxygen from Martian carbon dioxide, Veggie grows lettuce on the space station, and CHAPEA crews live for 378 days in a 3D-printed analog. How a full settlement would work remains an engineering question.
The big question
People live in houses on Earth. The air, water and food are all around us.
What if people wanted to live on Mars? What would they need to bring or make?
On Earth, we never have to think about making air to breathe. It is simply there, along with water to drink, soil to grow food and a thick blanket of atmosphere that keeps us warm and safe.
Mars has none of that ready to use. So what would it take to build homes there, not just for a visit but to live? In this thought experiment you plan a Mars base, step by step, using what scientists and NASA engineers have actually tested.
Human life support needs a breathable, pressurized atmosphere, potable water, food, thermal control and shielding. On Earth the environment supplies these; on Mars each must be shipped, recycled or made from local resources, an approach NASA calls in-situ resource utilization (ISRU).
This lab works through a settlement's needs in turn: shelter, air and water, and food, and ends with how NASA rehearses Mars living on Earth. Where the sources describe a test or a measurement, the card says fact; where it describes a possible design, it says idea.
Explore the idea
Make a prediction
Could people breathe the air on Mars?
If you stepped outside on Mars without a spacesuit, could you breathe the air?
Could unprotected humans breathe Mars's ambient atmosphere?
- No: it is mostly carbon dioxide
- Yes, just like on Earth
- Yes, but only at night
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Established fact
People cannot breathe the air on Mars.
Mars's air is mostly carbon dioxide with much less than 1 percent oxygen, so people could not breathe it (NASA).
Mars's atmosphere is 95.1 percent CO₂ and 0.16 percent O₂ at 6.36 mb mean surface pressure (NASA Mars Fact Sheet).
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Established fact
A machine made oxygen from Mars air.
NASA's MOXIE made 122 grams of oxygen from Mars's carbon dioxide (NASA).
MOXIE showed oxygen extraction from Martian CO₂ is feasible: 122 g over 16 runs (NASA).
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An idea scientists discuss
One day, people might build homes on Mars.
People might one day live on Mars in sealed homes that make their own air, water and food, but no one has built one yet.
A self-supporting settlement remains a design idea that combines systems tested only separately so far.
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Established fact
People cannot breathe the air on Mars.
Mars's air is more than 95 percent carbon dioxide and much less than 1 percent oxygen, so people could not breathe it.
Mars's atmosphere is 95.1 percent CO₂ and 0.16 percent O₂ at a mean surface pressure of 6.36 mb (NASA).
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Established fact
Mars is very, very cold.
Mars's average temperature is about −80 °F, way below freezing.
Mars averages about −80 °F (NASA); temperatures range from about 20 °C to −153 °C.
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Established fact
Mars has no big magnetic shield like Earth.
Mars once had a magnetic field that shielded it from harmful cosmic rays, but it has no global magnetic field today.
Mars lacks a global magnetic field; only southern crustal regions are strongly magnetized, traces of a field about 4 billion years old (NASA).
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Established fact
Space travelers get extra radiation, so they need protection.
Measurements from NASA's Curiosity rover suggest a round trip with 500 days on Mars would expose astronauts to about 1 sievert of radiation, split about evenly between the trip out, the stay and the trip home.
RAD data imply about 1 Sv for a 180-day transit, 500-day stay and 180-day return, with roughly equal contributions from each stage (NASA).
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An idea scientists discuss
Mars homes might have thick walls or domes.
A Mars home might be a dome, or have very thick walls, to hold in air and warmth and block some radiation.
Designs might add shielding mass to the habitat; how much protection is needed and which materials to use are open engineering questions.
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Established fact
A machine made real oxygen on Mars.
NASA's MOXIE made 122 grams of oxygen from Mars's air on the Perseverance rover, about what a small dog breathes in 10 hours.
MOXIE produced 122 g of O₂ over 16 runs, up to 12 g/h (twice its goal) at ≥98 percent purity, through a full Mars year (NASA).
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Established fact
There is ice under the ground on Mars.
Water on Mars today is mostly ice just under the surface in the polar regions, plus salty water that flows down some slopes in certain seasons.
Present-day water on Mars is near-surface polar ice and seasonal briny flows; liquid water cannot last long in the thin atmosphere (NASA).
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An idea scientists discuss
People on Mars might melt ice to get water.
Settlers might dig up ice and melt it for water, and use bigger MOXIE-like machines for oxygen to breathe and for rocket fuel.
A settlement might pair scaled-up oxygen production with ice mining; NASA notes the next step after MOXIE would be a full-scale generator with liquefaction and storage.
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Established fact
Astronauts grow and eat lettuce in space.
The Veggie garden on the space station has grown lettuce, Chinese cabbage, kale and zinnia flowers, and crews have eaten some of the harvest.
Veggie has grown three lettuce varieties, Chinese cabbage, mizuna mustard, red Russian kale and zinnias; some were eaten and others returned for analysis (NASA).
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Established fact
Space food in packets slowly loses its vitamins.
Vitamins in packaged space food break down over time, which is a problem on long trips with no deliveries.
Prepackaged vitamins break down over time, a problem for missions lasting months or years without resupply (NASA).
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An idea scientists discuss
A Mars home might have a big glowing garden.
A Mars base might grow much of its fresh food in sealed greenhouses with lights, though growing enough for a whole crew is still being studied.
Scaling from a six-plant chamber to a crew's diet might require large controlled-environment farms; NASA notes that growing plants in a closed environment without sunlight or Earth's gravity is still a challenge.
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Established fact
Four people live in a pretend Mars home for over a year.
NASA's CHAPEA missions have four crew members live for 378 days in a 3D-printed habitat at the Johnson Space Center.
CHAPEA: four-person crews, 378-day missions, a 1,700 ft² 3D-printed habitat; Mission 1 ran 25 June 2023 to 6 July 2024 (NASA).
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An idea scientists discuss
One day, people might really live on Mars.
Tests like these might one day help people build real homes on Mars, but many problems still have to be solved first.
Analog missions, ISRU demonstrations and space crops each address part of the problem; whether and when a settlement is built is not something these tests can predict.
In our world
Mars is a cold, dusty desert. Its air is very thin.
The air on Mars is mostly a gas called carbon dioxide. People could not breathe it.
NASA describes Mars as a dusty, cold desert with a very thin atmosphere. Its average temperature is about −80 °F (around −60 °C). The air is more than 95 percent carbon dioxide and much less than 1 percent oxygen, so people could not breathe it, and it presses down with less than 1 percent of the force of Earth's air.
There is water, but not as lakes or rivers. Today it is mostly ice just under the surface near the poles, plus salty water that seasonally trickles down some slopes.
NASA's Mars fact sheet gives a mean surface pressure of 6.36 mb (Earth: 1,014 mb), an atmosphere of 95.1 percent CO₂ and 0.16 percent O₂, and an average temperature near 214 K (−59 °C). Temperatures range from about 20 °C to −153 °C, and the thin air lets the Sun's heat escape easily.
Mars has no global magnetic field today, only magnetized crust in the south. Water exists as near-surface ice in the polar regions and as seasonal brines (NASA).
Planning a Mars home
A Mars home would need sealed rooms full of air. It would need a way to make air and water.
It would need a garden too. Follow the story to plan each part!
A Mars home would have to be sealed and filled with air at a pressure people can live in, and kept warm. It would need oxygen, and NASA has shown oxygen can be made from Mars's own carbon dioxide. It would need water, perhaps from ice in the ground. And it would need fresh food, because packaged food slowly loses its vitamins.
Each of these is a branch in this thought experiment. The facts come from real tests; the designs are ideas, because no one has built a Mars home yet.
Each branch maps a need to evidence: shelter (temperature, pressure and radiation measurements), air (MOXIE's electrochemical oxygen production), water (subsurface polar ice) and food (Veggie's crops in orbit). The settlement designs themselves are ideas.
NASA's radiation detector on the Curiosity rover gives a sense of scale: a reference mission of 180 days to Mars, 500 days there and 180 days back would mean a radiation exposure of about 1 sievert, split roughly equally across the three stages.
Why it is hard
On Earth, there is oxygen in the air all around us.
On Mars, the air is thin and cold, with almost no oxygen. So people would have to make their own safe little world inside.
On Earth, about 21 percent of the air is oxygen, and the air presses down more than 150 times as hard as Mars's thin air. Mars's air is so thin that the Sun's heat easily escapes. Long ago Mars had a magnetic field that shielded it from harmful cosmic rays, but it does not have one now.
So a Mars home has to do all of those jobs itself, all the time. Bringing everything from Earth would be hard, which is why NASA tests ways to make supplies on Mars, an idea called 'living off the land'.
Each Earth service becomes an engineered system: pressure vessels and seals, oxygen generation or recycling, water extraction and recycling, crop production, heating, and shielding. Mars Global Surveyor found that Mars once had a magnetic field shielding it from cosmic rays, but today it has no global magnetic field (NASA).
NASA frames ISRU as the alternative to shipping consumables: MOXIE's main purpose was to show a way to make rocket propellant oxygen for the trip home, in industrial quantities, with breathable air a further use.
Practicing for Mars
NASA has a pretend Mars home in Texas. It was made by a giant 3D printer!
Crews of four people have lived inside for more than a year to practice.
NASA practices Mars living here on Earth. Its CHAPEA missions put four volunteers inside a 1,700-square-foot habitat, made with a 3D printer at the Johnson Space Center in Houston, for 378 days. They take pretend spacewalks while NASA studies how people cope with isolation and limited supplies.
The first mission ran from June 2023 to July 2024. NASA scheduled the second crew to stay inside until October 31, 2026.
NASA's Crew Health and Performance Exploration Analog (CHAPEA) runs 378-day simulated Mars surface missions with four-person crews in a 1,700 ft² 3D-printed habitat at Johnson Space Center. Mission 1 ran from 25 June 2023 to 6 July 2024; NASA scheduled Mission 2's crew to stay in the habitat until 31 October 2026.
Crews conduct simulated spacewalks and provide data on physical and behavioral health and performance under isolation, confinement and resource limits. Along with MOXIE on Mars and Veggie in orbit, these analogs test parts of a settlement; none yet demonstrates a full one.
Amazing facts
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A day on Mars is a bit longer than a day on Earth.
A day on Mars lasts about 24 hours and 40 minutes, so a Mars home's clocks would need a little extra time.
Mars's length of day is 24.66 hours (NASA Mars Fact Sheet).
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On Mars, your feet could be warm while your head is cold.
At noon on Mars's equator, it could feel like spring at your feet (about 24 °C) but freezing at your head (about 0 °C), because the thin air holds so little heat.
NASA notes a person at the equator at noon would feel about 24 °C at the feet and 0 °C at the head, since heat escapes the thin atmosphere easily.
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The space garden glows pink!
The Veggie garden glows magenta pink, because plants mainly use red and blue light and reflect green.
Plants reflect much green light and use more red and blue, so Veggie's LED-lit chamber typically glows magenta pink (NASA).
Words to know
- habitat
- a place built or found for living things to live in
- atmosphere
- the layer of gases around a planet
- carbon dioxide
- a gas made of carbon and oxygen; most of Mars's air
- radiation
- energy from space that can harm living things in large doses
- in-situ resource utilization
- using materials found where you are, instead of bringing them
- analog mission
- a practice mission on Earth that copies conditions of a real one
Discovery challenge
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What is most of the air on Mars?
What gas makes up most of Mars's air?
The dominant component of Mars's atmosphere is…
- Carbon dioxide
- Oxygen
- Water vapor
Show the answer
Carbon dioxide
Carbon dioxide, which people cannot breathe.
Carbon dioxide: more than 95 percent of Mars's air.
…CO₂, at 95.1 percent; O₂ is only 0.16 percent.
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What did NASA's MOXIE make on Mars?
What did NASA's MOXIE machine make from Mars's air?
What did MOXIE produce from Martian CO₂?
- Oxygen
- Water
- Food
Show the answer
Oxygen
Oxygen, the gas we breathe!
Oxygen: 122 grams in all, from carbon dioxide.
Molecular oxygen, 122 g over 16 runs, by separating it from CO₂.
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Why do space travelers need fresh food?
Why do long space missions need fresh food, not just packets?
What problem does growing crops on long missions address?
- Vitamins in packaged food break down over time
- Packets are too heavy to open
- Astronauts do not like packets
Show the answer
Vitamins in packaged food break down over time
Packet food slowly loses its vitamins.
Vitamins in prepackaged food break down over time.
Vitamin degradation in prepackaged food over months or years without resupply.
Experiments to try
- Watch Try it What If? Lab What if you lived on Mars? You would be made of exactly the same amount of stuff on Mars, but Mars pulls on you less than Earth does. In our model, a bathroom scale there would show only a little over a third of your Earth reading, and your jumps would go more than twice as high.
- Watch What If? Lab What if cars drove themselves? Self-driving cars use cameras, radar, lidar and maps, plus computers that decide when to steer, speed up and brake. Today most cars can only help a human driver, and cars that drive themselves work only in certain places. Explore how these cars see, how they decide, and what sharing the street with them could mean.
- Watch Try it What If? Lab What if an electric plane carried more batteries? An electric plane needs batteries to fly, and more batteries could store more energy. But batteries are heavy. In our model, a small plane weighing 1,100 kg flies at 55 meters per second with lift to spare. Load it up to 1,500 kg and, at the same speed and wing tilt, its wings make only 88 percent of the lift it needs.
- Watch What If? Lab What if we could print a house? Giant 3D printers already build walls by squeezing out concrete one layer at a time, like icing from a piping bag. In 2026, a U.S. Army base in Texas opened the first of ten printed buildings for soldiers, and in 2022 a university in Maine printed a small house from wood fibers. What if we printed lots of our buildings? Explore how printed homes are made and whether they are really faster.
- Watch What If? Lab What if we built a space elevator? Rockets burn huge amounts of fuel to reach space. A space elevator would be a cable stretching from the equator about 35,786 kilometers up to a special orbit, with robot climbers riding up and down. NASA studies say it might cut the cost of reaching orbit hugely, but it needs a material far stronger than anything we can make in long lengths today. Explore the cable, the materials and the ride.
- Watch What If? Lab What if Mars had oceans again? Mars is a cold, dusty desert today, but rovers have found dry riverbeds, deltas and an ancient lake. Its air is now so thin that liquid water can't last on the surface. Imagine a blue Mars, find out what it would need, and see a possible clue to past life that NASA's Perseverance rover has found.
Explore next
- Watch Try it What If? Lab What if you lived on Mars? You would be made of exactly the same amount of stuff on Mars, but Mars pulls on you less than Earth does. In our model, a bathroom scale there would show only a little over a third of your Earth reading, and your jumps would go more than twice as high.
- Watch What If? Lab What if cars drove themselves? Self-driving cars use cameras, radar, lidar and maps, plus computers that decide when to steer, speed up and brake. Today most cars can only help a human driver, and cars that drive themselves work only in certain places. Explore how these cars see, how they decide, and what sharing the street with them could mean.
- Watch Try it What If? Lab What if an electric plane carried more batteries? An electric plane needs batteries to fly, and more batteries could store more energy. But batteries are heavy. In our model, a small plane weighing 1,100 kg flies at 55 meters per second with lift to spare. Load it up to 1,500 kg and, at the same speed and wing tilt, its wings make only 88 percent of the lift it needs.
- Watch What If? Lab What if we could print a house? Giant 3D printers already build walls by squeezing out concrete one layer at a time, like icing from a piping bag. In 2026, a U.S. Army base in Texas opened the first of ten printed buildings for soldiers, and in 2022 a university in Maine printed a small house from wood fibers. What if we printed lots of our buildings? Explore how printed homes are made and whether they are really faster.
- Watch What If? Lab What if we built a space elevator? Rockets burn huge amounts of fuel to reach space. A space elevator would be a cable stretching from the equator about 35,786 kilometers up to a special orbit, with robot climbers riding up and down. NASA studies say it might cut the cost of reaching orbit hugely, but it needs a material far stronger than anything we can make in long lengths today. Explore the cable, the materials and the ride.
- Watch What If? Lab What if Mars had oceans again? Mars is a cold, dusty desert today, but rovers have found dry riverbeds, deltas and an ancient lake. Its air is now so thin that liquid water can't last on the surface. Imagine a blue Mars, find out what it would need, and see a possible clue to past life that NASA's Perseverance rover has found.
- Watch Try it What If? Lab What if a home ran on a big battery? A big home battery in our model stores 13,500 watt hours. Running a small 500-watt load, it lasts more than a day; switch on a 2,000-watt heater and it is empty in under seven hours. The secret is dividing the energy stored by how fast it is used.
- Watch What If? Lab What if cities floated on the sea? Floating buildings already exist: in Rotterdam, in the Netherlands, a three-story office floats in a harbor on concrete pontoons. Designers have also planned a floating neighborhood off Busan, South Korea, for up to 12,000 people. But a floating city would need to stay afloat, cope with waves and storms, and find fresh water in the middle of salty sea. Explore each challenge.
For parents & teachers
What children will learn
- Mars has thin, cold, carbon dioxide air that people cannot breathe.
- A home there would need to supply air, water, food, warmth and protection.
- NASA has tested making oxygen on Mars and growing food in space.
- Practice missions on Earth help scientists learn how people cope far from home.
Recommended ages: 7 to 17 · About 15 minutes
Talk about it
- What things does Earth give us for free that we would have to make on Mars?
- Would you rather bring supplies from Earth or make them on Mars? Why?
- What would be hardest about living in a small practice habitat for a year?
Try at home or in class
- Design a Mars base on paper: label where air, water, food, power and sleeping areas would go.
- Grow lettuce or cress seeds on a windowsill and keep a diary, like a space gardener.
Key vocabulary: habitat, atmosphere, carbon dioxide, radiation, in-situ resource utilization, analog mission
Where these facts come from
- What Is Mars? (Grades 5-8) , NASA
- Mars: Facts , NASA Science
- Mars Fact Sheet , NASA Goddard Space Flight Center
- NASA's Oxygen-Generating Experiment MOXIE Completes Mars Mission , NASA
- Growing Plants in Space , NASA
- Crew Health and Performance Exploration Analog (CHAPEA) , NASA
- Radiation Exposure Comparisons with Mars Trip Calculation , NASA Science
- Earth Fact Sheet , NASA Goddard Space Flight Center
Checked, not yet human-reviewed. Last updated October 24, 2026. Spotted a mistake? Tell us.