What Mars asks of a building
Every choice in the habitat answers one of these numbers.
3.73 m/s². Everything weighs 38% of its Earth weight, which eases the dead load on a stacked cluster.
About 0.6% of Earth's sea-level pressure. Each module is a pressure vessel first and a room second, so its walls are pushed outward from inside.
Daily swing measured at the Viking 1 lander site.
Plus 2.59% nitrogen and 1.94% argon. A feedstock for oxygen and fuel, not something to breathe.
Close to Earth's, so crew schedules can follow a familiar rhythm.
Distance makes resupply slow, so the habitat should be repairable on site.
Figures: NASA Goddard, Mars Fact Sheet (NSSDC).
Why hexagons
Shared walls
Hexagons tile a plane with no gaps. Every wall two modules share is a wall that never faces the outside, so the cluster needs less shell and loses less heat as it grows.
Stacking
Modules sit on top of one another two or three levels high. In 0.38 g, ladders and stairs are easy, and a tall cluster keeps the footprint and site preparation small.
Raised on legs
Legs lift the habitat clear of the surface and leave room for rovers below. Whether printed legs can carry every load is an open question.
One part, many uses
The same hexagonal shell becomes sleeping quarters, a lab, a greenhouse or an airlock. One production line, one set of spare parts, one repair manual.
The question has been asked in orbit. In April 1984, about 3,300 honeybees flew on Shuttle mission STS-41C in a student experiment designed by Dan Poskevich of Tennessee Tech, built to test whether bees would build comb without gravity and keep the hexagonal shape. During the flight the astronauts reported on live video that the bees had adapted and built a "great big old honeycomb." The article does not report the later measurements of the cells. UPI, 9 April 1984 · Smithsonian, Bee Enclosure Module.
Built from Mars
The habitat is built and supplied from Mars itself. Shells come from regolith, the loose rock and dust that covers the surface, and breathing oxygen comes from the carbon dioxide air. Earth sends only the machines and the parts Mars cannot make.
The buildings are 3D printed. The plan is for robotic printers to lay down regolith wall by wall, with lasers or other heat sources fusing the grains, before any crew arrive. These are design choices. No habitat has been printed on Mars yet, by anyone.
What ships from Earth
3D printers and sintering lasers, construction robots, airtight inner liners, windows, hatches, life support and power. Small, dense cargo that fits a launch fairing.
What Mars provides
Thick hexagonal walls, floors and the legs that lift each cluster. Heavy material that would be expensive to launch is already on the ground. An airtight liner inside carries the pressure, because printed regolith is expected to be weak in tension.
Air from the atmosphere
The plan is to split crew oxygen out of the 95% carbon dioxide atmosphere on site. This has been demonstrated only at small scale. A crew-sized system has not been built.
Why it suits the hexagon
A repeated six-sided cell gives the printer one wall shape to print again and again. Regolith walls also put mass between the crew and space radiation. How thick they must be is still open.
Precedent, on Earth: NASA's 3D-Printed Habitat Challenge (2015–2019) had teams build one-third-scale structures from recyclables and materials that could be found on deep-space destinations, then tested them for material mix, leakage, durability and strength. AI SpaceFactory of New York won the $500,000 first prize in May 2019. This shows subscale printing on Earth, not a printed habitat working on Mars. NASA release.
Precedent, on Mars: MOXIE, on NASA's Perseverance rover, made 122 grams of oxygen from Mars' carbon dioxide over 16 runs, reaching 12 grams per hour at 98% purity or better. NASA reported its final run in September 2023. MOXIE was a technology demonstration, far below what a crew would need. NASA release.
Hexagonal Mars habitats printed from local material are not a new idea. Team Zopherus placed first in the 2018 virtual modeling stage of NASA's Challenge, with a design that secondary reporting describes as modular and hexagonal, built from materials found on Mars. What this concept adds, stacking on legs, still needs a prior-art search before anyone calls it new. NASA results, July 2018.
Cluster planner
Tap cells to add or remove modules. The readout shows how much floor you gain and how many walls end up shared.
Hexagon floor area = 2.598 × side². Outside wall area assumes 3 m per level. Example layout, not a final plan.
A Brazilian take
Brazil already has an architecture for most of what the habitat needs: buildings raised off the ground, screen walls that filter sun, porches where daily life happens, and a tradition of building together. This section borrows that language. It changes how the habitat looks and is lived in. It does not change the engineering above.
The legs become a public floor
Brazilian modernism made raised buildings normal, from the Ministry of Education building in Rio to Lina Bo Bardi's MASP in São Paulo, which leaves a plaza under the museum. Here the space under the cluster is the free span where the crew meets, repairs equipment and parks the rovers.
The stilt house as ancestor
The Amazon's stilt houses lift homes above shifting ground and floodwater. A habitat on legs above drifting dust follows the same instinct.
Screen walls on the outer skin
The perforated block from Recife lets light and air through while cutting sun. Printed into the outer regolith skin, a cobogó pattern gives texture and shade on decks. It cannot cut through a pressurized wall, and perforated shells already appear in the Zopherus design, so this is a look, not a new idea.
Niemeyer's curves on a hexagonal grid
The hexagon stays, because it does the geometric work. Corners soften, stair ramps curve, and the skyline of the cluster rises and falls instead of stepping.
A porch for every module, a yard in the middle
Each module faces out onto a sheltered porch. The shared central cell is the backyard, with a greenhouse where the mango tree would be.
Gardens laid out like landscape
Greenhouse cells are food production first, planned with the curving beds Roberto Burle Marx used in his gardens and promenades, instead of rows of racks.
Built together
A mutirão is a collective work party where neighbors build a house together. On Mars the printers raise the shells and the crew finishes the interiors together, cell by cell.
Names to choose from
Grows like a cajueiro
The hive grows by one rule, applied again and again. A cluster sends out walkways, and at the end of each walkway a new cluster sets down its own legs. Then the new cluster does the same. The model is the Cajueiro de Pirangi, the giant cashew tree near Natal, whose branches grow sideways, reach the ground and take root, so one tree spreads like a small forest.
Rule: each new cluster sends two walkways, turned 60° left and right of the one it came from. Branches stop where they would run into existing cells. A layout sketch, not a structural design.
Every branch puts its feet down
The araucária, the Paraná pine, is the other famous Brazilian branching tree, but its branches are long arms held out from a trunk. Built in printed regolith, arms like that would be cantilevers with tension along their tops, which the material is expected to handle poorly. The cajueiro sets its branches down and roots again, so each cluster stands on its own legs and walkways only span short gaps.
Each generation is one building season
The printers finish one generation of clusters before starting the next. The settlement is usable at every stage, and it can stop growing at any generation without being left half built.
A tree has only one path
In a pure branching pattern there is one route between any two clusters, so a damaged walkway cuts off everything beyond it. Real cajueiro branches cross and touch. The habitat would need cross-links between neighboring branches, which breaks the pure tree but adds escape routes.
About the tree: Brazilian press reports put the Cajueiro de Pirangi in Pirangi do Norte, Parnamirim, Rio Grande do Norte, covering more than 8,500 m², and attribute its spread to a genetic trait that sends branches sideways to the ground, where they root. NSC Total, 20 Feb 2025 (news report; the genetic explanation is not sourced there).
Batata-doce in the walls
Each module grows its food in a ring between the outer shell and the people. Sweet potato is the first crop: it is on NASA's life-support crop list and on the list Brazil's Space Farming network chose, it grows from cuttings without pollinators, and both its roots and its leaves are eaten. The beds of wet growing medium add mass between the crew and space.
The beds sit inside the airtight liner, because plants need air too. Light is artificial.
Life support that also shields
NASA's Water Walls concept (Michael Flynn, NIAC Phase I, 2012) built waste processing, air revitalization and food growth into wall cells that also serve as radiation shielding. This page borrows that idea and swaps algae bags for sweet potato beds. Food-producing shielding is not a new idea.
How much it shields
The protection comes from the water and growing medium, not the plants. How many centimetres of wet medium the ring needs, and how much dose it removes, has not been calculated. Until it is, the ring counts as a garden, not as shielding.
What could go wrong
The plants take the radiation before the crew does, and sweet potato's tolerance is untested. Wet beds against the liner risk hidden leaks and mould, so the liner needs inspection access. Harvests remove some mass, so beds are harvested in turn, never all at once. The water has to come from Mars.
Crop lists: Wheeler, "Plants for Human Life Support in Space: From Myers to Mars," Gravitational and Space Biology 23(2), 2010 (NASA's shared candidates: wheat, soybean, potato, rice, sweet potato, lettuce, peanut). Brazil's first crops (sweet potato and chickpea) as reported in Brazilian press, April 2026. NASA NIAC: Water Walls.
How it grows
A draft order of build-out. None of these steps has been tested.
Seed cluster
Printers land ahead of the crew and print one airlock module and a core ring on legs from local regolith. Liners go in and the cluster is pressurized before anyone arrives.
Second level
Lab and sleeping modules stacked on the core, with outside decks and stairs down to the rover bay.
Neighbor clusters
Additional honeycombs nearby, linked by covered walkways, so a failure in one cluster does not have to shut down the others.
What would run it
A pressurized cluster needs power all the time, so the open question is where the power comes from.
On 8 October 2026 NASA and the Department of Energy signed an agreement on space nuclear power and propulsion, effective 1 November 2026. The release says nuclear power will be essential for the energy needs of future Mars missions and describes Lunar Reactor-1, a fission system for the Moon Base, as a step toward that. It gives no Mars reactor design, schedule or power level, and it says nothing about this habitat. Treat it as context: the cluster in this draft is not sized to any power source, and that sizing is still to do.
Source: NASA release 26-084, 8 Oct 2026, as pasted by the author; not re-checked against the NASA page.
Decisions still to make
- Wall thickness needed on the upper levels for radiation shielding.
- Which fusing method suits the regolith at the chosen site (laser, microwave or binder), and how airtight liners seal against printed walls.
- Whether the legs can be printed too, since printed regolith is expected to be weak in tension, as concrete is.
- Crew size and mission length the first cluster is sized for.
- Power source and demand for the cluster, including how it would be kept running through dust storms and long nights.
- Water source: where the nearest subsurface ice is, and how it is mined.