At the University of Arizona’s Biosphere 2, the Space Analog for the Moon and Mars, better known as SAM, operates as a sealed habitat where air, water and food are measured and recycled as if it were far from Earth’s croplands and life-sustaining atmosphere.

SAM’s research informs the future of astronaut life-support systems while advancing a broader goal: positioning the facility as a critical testing ground for next-generation space habitats.

The SAM facility is built around Biosphere 2’s original 1987 Test Module, a prototype designed to determine whether humans could survive inside a sealed environment on Earth. The module was later abandoned until Kai Staats, SAM’s director of research, led a reconstruction effort. After years of restoration, the original pressure vessel was expanded and now includes a crew quarters with a kitchen, bath, engineering bay, airlock, carbon dioxide scrubber and life support monitors. Together, they form a pressurized habitat analog capable of hosting long-duration missions with up to four crew.

Testing life support with crops – and one human

SAM’s most recent mission sealed a single crew member, Matthias Beach, a member of the SAM development and operations team, inside the habitat with 144 dwarf pea plants to test whether crops could help sustain human life in isolation. The experiment lays a foundation for future off-world missions.

Conducted over two weeks in October 2025, the dwarf pea experiment tracked how efficiently plants sequester carbon dioxide and return oxygen in a confined environment. Initially, every breath Beach exhaled inside SAM was captured by the plants through photosynthesis and converted back into breathable air. On Day 8, with Beach still inside, the peas were harvested so the team could observe the level of carbon dioxide and record a precise measurement of how much carbon each plant had been removing from the air.

The test demonstrated how a relatively small number of crops could become part of a closed air system to support life on future lunar or Martian settlements. For the crew member inside, the experiment was also a deeply personal experience.

“When I harvested the plants, it was actually kind of sad,” Beach said. “I took pictures of a few that I thought were adorable, and I really missed them afterward. I missed hearing the pumps cycle on and off every half hour, the glow of the lights and that smell – the humidity and the green. Without it, the habitat felt more like a spaceship.”

Additional crops are slated for testing inside SAM through 2026, contributing to a growing database documenting how 20 or more food species might support air revitalization in a sealed habitat. Those crops include peas, wheat, rice, barley, lettuce, cabbage, spinach, sweet potatoes and white potatoes, Staats said. The dataset will help determine how many square meters of crops are needed to support long duration, human-crewed missions and how much carbon those crops can recycle.

Building a database for space agriculture

Inside the SAM Test Module, hydroponic racks – managed with support from the U of A’s Controlled Environment Agriculture Center – regulate plant growth through controlled lighting, nutrient delivery, humidity and temperature. Sensors embedded within each of SAM’s four compartments continuously monitor carbon dioxide, oxygen, humidity, temperature and vapor-pressure deficit, a measure of how much moisture the air holds relative to how much it can hold when saturated. That metric is critical to plant health and carbon sequestration rates.

The data streams in real time to SIMOC Live, an air-quality monitoring platform developed by Staat’s team, that connects globally participating habitats in the World’s Biggest Analog project into a shared repository. Those measurements are also fed into SAM’s digital twin, SIMOC – an agent-based computer model that uses mission data to refine predictions and improve future habitat performance. 

SIMOC is now available for use by anyone in the world, equipped with a working, virtual model of the original 1991-93 and 1994 Biosphere 2 missions, as well as SAM and a Mars habitat of customizable design. 

Testing machines and plants side by side

Additionally, while the dwarf pea trial focused on what researchers call “bioregenerative” air revitalization, SAM’s team is also developing a complementary “physicochemical” system. Construction is now complete on the Experimental Air Revitalization Laboratory, or EARL, a four-bed molecular-sieve carbon dioxide scrubber modeled after the system used on the International Space Station and developed under a technology license with NASA.

Designed in partnership with James Knox, a spacecraft carbon dioxide removal systems expert, the scrubber allows the SAM team to test mechanical and biological life-support methods side by side, switching between them or operating in parallel while humans are sealed inside the habitat. Researchers will be able to evaluate which approach works best for specific mission scenarios and how hybrid systems can balance power demands and environmental control.

“SAM is the only facility on Earth that can study both machine-based and plant-based processes with humans in the loop in a pressurized facility,” Staats said. “We have the closest thing to an actual Mars habitat running on Earth. No one else – not even NASA or the International Space Station – has that today.”

Practicing missions on a simulated Mars

The SAM habitat is immediately adjacent to an indoor Mars yard – a geologically accurate landscape featuring ancient riverbed deposits, a lava tube, a scree slope and a reduced gravity simulator designed for rovers and crewed exploration. Researchers train in pressure suits while testing procedures and mobility under reduced-gravity conditions, allowing scientists and industry partners to evaluate systems and protocols before launching them into orbit or deploying them on planetary surfaces.

A new surgical bay is also under construction inside of the SAM crew quarters. Led by practicing surgeon and SAM team member Dr. Bindhu Oommen, the SAM Med Bay has engaged a growing collaboration of space medical professionals, including former NASA flight surgeons, the APEX fellowship based at Banner Health in Phoenix and the University of Florida.

With its expanding capabilities, SAM is positioned to serve as a primary test site for commercial space companies, government agencies and academic institutions interested in validating new tools, rovers, medical systems and life-support hardware. Its integration with the Mars yard makes it a natural training environment for teams preparing missions that require realistic operational testing.