Simulating the Martian environment on Earth requires reproducing Mars’s thin, cold, CO2-rich atmosphere inside a controlled chamber. This enables testing of equipment, chemical processes, and even biological organisms under realistic Mars conditions. Key factors include achieving the extremely low pressure (~6 mbar, about 0.6% of Earth’s atmospheric pressure), controlling temperatures down to Martian lows (around –60 °C on average, with extremes from –140 °C up to 30 °C), and using the correct gas mixture which is approximately 95% CO2, 3% N2, 1.6% Argon, plus trace Oxygen and Water.
We will outline methods and best practices for each aspect, as well as considerations in choosing chamber materials (acrylic vs. stainless steel). We will also highlight examples of Mars simulation facilities that have achieved these conditions.
Achieving and Maintaining Low Pressure
Reaching 6 mbar pressure (4.5 Torr) inside a chamber essentially means creating a partial vacuum. This is typically done in two stages: pump down the chamber to fully remove Earth’s air, then backfill or regulate the chamber with the Martian gas mix to reach the target pressure. In practice, a vacuum pump system is used to evacuate the chamber to well below 6 mbar, and then gas is introduced to raise the pressure up to 6 mbar.
A simple setup might use a roughing vacuum pump (rotary vane or scroll pump) to draw the chamber down; 6 mbar is within the capability of many roughing pumps (some can reach 1–0.01 mbar). For more precise control, facilities often use a combination of pumps and automated valves. For example, NASA’s Mars simulation chamber at Kennedy Space Center uses a vacuum pump plus a throttle valve regulated by an electronic controller to maintain any set pressure from ambient down to 0.1 mbar
At Sanatron, the best way to go about this is to pump the vacuum chamber down to 0.1 Torr (0.13 mbar) and then backfill the chamber with CO2. Since the Martian atmosphere is 95% CO2, it is good approximation and simply use 100% CO2 mixture to keep things simple and cost effective. After the chamber has been backfilled with 100% CO2 Gas, it now needs to be pumped down to 6mbar (4.5 Torr).
Maintaining Martian Simulation Pressure
Maintaining Martian pressure for long durations can be challenging due to leaks and outgassing. No chamber is perfectly sealed; tiny leaks (through valve seals, feedthroughs, or the material itself) will allow external air in or chamber gas out. Outgassing (release of adsorbed gases from internal surfaces) can also raise pressure over time.
Best practice is to use high-quality gaskets (e.g. Viton O-rings) and vacuum-rated fittings, and to test the leak rate of the chamber beforehand. Stainless steel chambers with welded seams and metal seals have very low leak rates, while acrylic chambers may allow more permeation.
Even in well-built systems, one may need to periodically pump down and refill the chamber or continuously bleed in gas while pumping to maintain composition. For instance, engineers suggest that if a chamber is simply sealed at low pressure, over time air will seep in and dilute the mix; thus, experiments often involve actively adding the correct gas mix or re-evacuating occasionally.
At Sanatron, we use Viton O-Rings and Vacuum Rated Acrylic and Stainless-Steel Vacuum Chamber which have the ability to hold Martian pressure for weeks (even months) without oxygen contamination.
It’s wise to include a pressure relief or safety valve as well, to avoid over-pressurizing the chamber when backfilling (6 mbar is low, but mistakes in gas control could accidentally overfill). Additionally, calibrate your pressure gauges for the low end (~0–10 mbar range) to ensure accuracy when reading Mars-like pressures.
Temperature Control and Extreme Martian Temperatures Mars’s surface temperature varies widely, often around negative 60 degrees Celsius but dropping below negative 120 degrees Celsius at night near the poles and rising up to about 20 Degrees Celsius in daytime equatorial regions.
Simulating this range requires a chamber that can be actively cooled and heated. A common solution for Mars chambers is using cryogenic cooling with liquid nitrogen (LN2) to reach the lowest temperatures, combined with electric heaters for warming.
For example, the appropriate Mars simulation chamber uses a cold plate inside the chamber cooled by liquid nitrogen, includes liquid nitrogen feedthroughs, allowing temperatures anywhere from negative 100 °C up to positive 160 °C to be programmed (including diurnal cycles)
By cooling the chamber walls or a thermal platform, the thin gas inside is also cooled to the set temperature. At ~6 mbar, convective heat transfer is minimal (the gas doesn’t carry much heat), so cooling the walls/plate effectively cools the whole environment by radiation and by the small amount of gas conduction.
Practicality of Martian Temperature Control
Achieving negative 140 °C is at the edge of what many systems can do. It likely requires ample Liquid Nitrogen flow or multiple stages of cooling. You may not need to reach the absolute Martian minimum unless you’re focusing on extreme polar night conditions.
This is why many experiments target a more moderate range (e.g. -80 °C to +30 °C). And some, even disregard temperature control and simply focus on only absolute pressure.
However, designing your system for at least -120 °C gives a good safety margin. Insulating the chamber externally (to limit heat leak from the room) will help in maintaining such low temperatures efficiently.
Internally, surfaces might accumulate frost if any moisture is present, so chambers are often pre-dried by vacuum baking or by purging with dry gas to prevent ice buildup that could alter the atmosphere’s composition.
For heating, standard resistive heaters or heat lamps can raise and hold the chamber at warmer temperatures. In fact, some Mars chambers double as ovens for sterilization tests.
In your case, reaching +20–30 °C is straightforward once the chamber is sealed. The challenge will be mostly with cooling. Use PID temperature controllers with thermocouples at key points (on the cold plate and in the ambient gas) to regulate the temperature.
Best practice is to cycle the temperature slowly to avoid thermal shocks to the chamber material or the instruments inside. Mars has roughly 55 Kelvin temperature swings between day and night in many regions. Chambers often mimic this by ramping temperature over a few hours. Ensure that any chamber windows or feedthroughs can handle the temperature extremes (for example, glass viewports should be made of a material like quartz or borosilicate that tolerates rapid cooling without cracking).
Replicating Martian Gas Composition
The Atmosphere is ~95% carbon dioxide with a balance of N2, Ar and trace gases. Even though in most cases a 100% Carbon Dioxide mixture will be good enough, there are instances where a more accurate gas mixture representation is needed.
To simulate this, you need to introduce the correct gas mixture into the chamber. The most convenient method is to use a pre-mixed tank of “Mars air” – gas suppliers can provide certified mixtures (one NASA chamber used a mix of 95.54% CO2, 2.7% N2, 1.6% Ar, 0.13% O2, 0.03% H2O by volume, which closely matches Martian composition). With a premix cylinder, you simply feed the gas in until the chamber reaches the target pressure (using a mass flow controller or a fine metering valve to avoid overshooting). This was the approach in the KSC Mars simulator: a tank with Martian atmosphere gas was connected through a mass-flow controller to continuously supply the chamber.
If a premixed gas isn't available, you can mix gases manually using separate cylinders of CO2, N2, Ar, and a small O2 source. The procedure would be: evacuate the chamber, then introduce CO2 until pressure is ~95% of 6 mbar, add N2 to reach ~2 to 3% of 6 mbar, etc. (For 6 mbar total, roughly 5.7 mbar CO2, 0.16 mbar N2, 0.1 mbar Ar, and a few tens of microns of O2 and H2O). Because these partial pressures are very low, it’s difficult to measure them directly with standard gauges.
Instead, calculate the required volume or use flow controllers calibrated for low pressure. Mass spectrometers or residual gas analyzers can verify the composition if needed. In research settings, FTIR spectroscopy has been used to monitor gas composition inside a Mars chamber in real time. For most engineering tests, though, knowing the mix proportions going in (and ensuring no significant leaks of air) is sufficient evidence that the atmosphere is Mars-like.
Including the trace gases (O2, H2O) is optional depending on your goals. Trace oxygen at 0.13% is a double-edged sword: it can slightly oxidize materials over long periods, but at 6 mbar the amount is tiny. Water vapor on Mars is extremely low (equivalent to ~0.03% at 6 mbar, though it varies with season).
If your test involves biological samples, you might want a trace of water for realism. But be careful: at cold temperatures that water may condense as frost. One way to add trace water is to humidify the CO2/N2/Ar mix slightly (e.g. pass a small portion of the gas through a water bubbler at controlled temperature).
Another way is simply to rely on outgassing from the chamber or sample to provide a minimal H2O background. In fact, achieving a perfectly dry chamber is hard and unless you bake it out, there will be a few Pascals of water vapor from moist surfaces. This often suffices to represent Martian humidity. If needed, you can dry the chamber by pumping it to high vacuum and perhaps gently heating it, then fill with the dry gas mix to minimize water content.
To keep the gas composition stable, it’s important to prevent contamination from air. This circles back to maintaining pressure: any leak will mostly bring in N2/O2 from Earth’s air, skewing the ratios. Continuous flushing with the correct mix can mitigate this (i.e. flowing a slow bleed of Mars gas through the chamber while pumping out, which ensures any leak is countered by excess Mars gas flow).
However, continuous flow at 6 mbar can be tricky and wasteful. Most setups, including research chambers, operate in a static mode: fill and seal, then run the experiment, which is fine for shorter tests.
However, for multi-day experiments, monitoring composition is advisable. The use of all-metal vacuum rated valves and clean materials helps to avoid introducing contaminants. In summary, replicating the Martian atmosphere involves careful gas handling: use high-purity CO2 (and other gases) to avoid reactive impurities, measure out the correct proportions, and consider using an internal fan or small circulation pump (if feasible at low pressure) to ensure the gases mix uniformly. Diffusion will mix them given time, but if you introduce gases sequentially, allow some time or slight heating to encourage mixing.
Selecting your Vacuum Chamber Material: Acrylic vs. Stainless Steel
When building or choosing a Mars simulation chamber, material selection affects durability, vacuum quality, and gas purity. Stainless steel is the standard in most professional vacuum chambers, whereas acrylic (plexiglass) is sometimes used in smaller, low-vacuum setups for its transparency. Each has pros and cons:
Vacuum Performance & Leak Tightness:
Stainless steel chambers offer superior vacuum integrity. They can be welded for an almost hermetic seal and have very low outgassing. Stainless steel is the most common choice for high and ultra-high vacuum systems. They can easily hold 6 mbar (and far lower) with negligible leak rates.
Acrylic chambers can hold moderate vacuum if properly designed. For example, a 1-inch (2.5 cm) thick acrylic chamber build by Sanatron can sustain a near-full vacuum (~0.006 mbar absolute) for 72 hours without much leaks. And a few Torr of vacuum loss over the course of weeks.
Acrylic is inherently more gas-permeable than metal and joints are usually sealed with gaskets or adhesives which may slowly leak over time. Expect a higher leak rate with acrylic. One test of an 18-inch acrylic chamber found that after isolating the pump, pressure rose from 0.37 Torr to 0.62 Torr in 11 minutes due to slight leakage/outgassing. This is equivalent to ~1.38 Torr/hour leakage rate. Keep in mind that this is initial leak rate and that it will subdue and level off slowly as the chamber pressure settles.
In a Mars simulation (4.5 Torr target), that kind of leak would noticeably alter the pressure in an hour or two. Stainless steel, by contrast, can be sealed to have leak rates on the order of 10^−9 Torr L/s (essentially negligible for our purposes). Bottom line: if you need long, unattended experimental runs or very stable conditions, stainless is far better for holding a low pressure without drift.
Outgassing and Purity of Vacuum Chambers:
Metals (especially stainless steel, when properly cleaned) have low outgassing rates, meaning they won’t significantly contaminate your low-pressure atmosphere. Plastics like acrylic contain more volatile substances and will release absorbed water and monomers under vacuum.
This can introduce unwanted gases (often water or organic vapors) into your chamber, which could interfere with sensitive chemical experiments or sensor tests. You can mitigate acrylic outgassing by pre-pumping the chamber for a long time or storing it in a dry environment, but you can’t bake it at high temperature (as is often done with metal chambers to drive off moisture) because acrylic would deform.
For high-fidelity simulations of Mars air chemistry (trace reactive gases, etc.), a stainless-steel chamber that you can bake and fully evacuate is preferred. If using acrylic, consider that its outgassing might add a tiny amount of organic vapor; likely not a big issue for most equipment tests, but possibly a concern for delicate chemistry or biology experiments.
Temperature Resistance of Vacuum Chambers:
The wide temperature range of Martian conditions is a major deciding factor. Stainless steel remains robust at cryogenic temperatures and high heat. It won’t crack at -140 °C, and it can be heated (it will expand, but uniformly). Acrylic, on the other hand, becomes brittle at low temperatures, many plastics may not be able to handle cryogenic temperatures without losing strength.
An acrylic chamber cooled to -60 °C might survive if the cooling is uniform, but at -140 °C there is a real risk of the material cracking or the sealed joints failing. Also, if you ever need to heat parts of the chamber (even to 50–60 °C to simulate a warm day or to purge gases), keep in mind that acrylic starts to lose material strength after 40 Degrees Celsius. It cannot withstand sterilization temperatures or a wide hot-cold swing.
Thermal cycling is another issue. Stainless steel can handle repeated cooling and heating cycles (it’s used in space simulation chambers that go from cryo to high heat regularly). Acrylic will develop micro-cracks or crazing over repeated thermal cycles, especially if exposed to extreme colds.
If your experiments only run near room temperature or mildly cold ( -20 °C), acrylic is fine, but true Mars conditions push it to its limits. In summary, Stainless steel is strongly recommended if you plan to use the full Martian temperature range or do many temp cycles. Acrylic could be used for a narrower range (e.g. 0 °C to maybe -60 °C) with caution, but going lower may be risky. Acrylic is recommended for its cost effectiveness.
Chemical Compatibility of Chambers:
Both stainless steel and acrylic are compatible with the main Martian gases (CO2, N2, Ar). CO2 is not corrosive at low temperature and pressure, and N2/Ar are inert. Trace O2 might oxidize steel over years, but that’s negligible (plus stainless is oxidation-resistant).
Acrylic doesn’t react with CO2 or N2. However, if you introduce Martian dust or conduct chemical experiments, consider that acrylic is easier to scratch and may absorb or react with certain chemicals. Stainless steel’s passive oxide layer handles most chemicals well and can be cleaned by solvents.
If biological experiments involve nutrients or acids, stainless can be sterilized and cleaned thoroughly. Acrylic might absorb stains or even be weakened by harsh chemicals or UV exposure. Also, Mars simulation often involves UV light to mimic sunlight, acrylic blocks UVC and most UVB, so it would not transmit the full Mars UV spectrum.
If UV experiments are planned, a steel chamber with a quartz window is a better design. Acrylic material transparency is great for visible observation but not for transmitting deep UV. Over time, intense UV can also discolor acrylic.
Visibility and Accessibility:
A big advantage of acrylic is that it’s transparent. Being able to see the experiment inside the chamber is useful, especially for biological tests or for adjusting equipment. If you use a stainless-steel chamber, you’ll likely need viewports (typically small diameter glass or quartz windows bolted onto the chamber).
Those give limited views and are additional potential leak sources. For a 2ft x 2ft acrylic chamber, you could have an entirely clear enclosure to observe the whole setup. Many researchers compromise by using metal chambers with one or two large windows (sometimes even an entire side made of thick glass, mostly acrylic) – this yields better vacuum performance than all-acrylic, while retaining some visibility.
If constant observation is crucial, as in watching live organisms or real-time instrument readings, acrylic might be justified, but remember you can always add cameras inside a metal chamber as well. There are vacuum-compatible cameras or you can feed a fiber optic camera through a port.
Durability and Structural Strength:
Stainless steel is extremely durable under vacuum. A welded steel chamber can last decades and handle thousands of pump-down cycles. It also handles any accidental bumps or instrument mounting with ease (you can weld or bolt fixtures to it).
Acrylic is structurally strong for its weight, but in a 2ft span it will flex under atmospheric pressure if not thick enough or reinforced. Typically, thick acrylic panels or a cylindrical design (to distribute stress) are used to prevent implosion. The margins for safety are smaller with acrylic, you must ensure no cracks and use thick material. Also, if you plan to integrate feed-throughs for electrical connections, gas lines, or sensors, with stainless you can weld in metal ports or use standard vacuum flanges.
With acrylic, you’ll need to machine holes and use sealing fittings, which can be tricky and potential leak sites. Fortunately, Sanatron makes leak-tight vacuum rated feedthroughs for Acrylic Vacuum Chambers which allow for full vacuum performance without compromising the vacuum.
Cost and Practicality:
An acrylic chamber is generally cheaper and faster to construct for small sizes. Stainless steel chambers are more expensive upfront and heavier a 2ft steel cube with flanges will weigh a lot and take a long time to be built.
There’s also the matter of the pump-down time: a metal chamber can be more thoroughly evacuated, even to high vacuum if needed, whereas acrylic might limit you to rough vacuum levels.
If you foresee expanding the setup (adding better vacuum pumps, doing high-vacuum experiments, etc.), a stainless chamber leaves that possibility open. Many existing Mars simulation chambers in research are stainless steel specifically for the reliability and versatility reasons discussed
In summary, stainless-steel is typically the material of choice for a durable, vacuum-tight Mars simulation chamber, especially for rigorous testing and long-term use. Acrylic chambers can work for simulating Mars in a simpler setup, they have been used in various projects and small-scale experiments, but they require careful handling and are limited in extreme conditions.
If you do opt for acrylic, for budget, availability or visibility, use a thick-walled design, limit the temperature extremes, and be prepared to actively manage pressure stability, perhaps by more frequent re-pumping. A hybrid approach is also possible: for instance, use a stainless-steel chamber but add an acrylic window panel for observation, combining strength with visibility.
Examples and Additional Considerations
Multiple research facilities have built chambers to simulate Martian conditions, offering guidance on best practices. The Mars Environmental Simulation Chamber (MESCH) in Spain, for instance, was designed to test meteorological instruments for Mars: it operates from 1000 mbar down to 10^−6 mbar, controls gas composition, and ranges in temperature from 108 K to 423 K (about -165°C to +150°C) using LN2 cooling.
It even includes a UV source and Mars dust dispersion system to mimic dust storms. NASA’s Mars simulation chamber at the Kennedy Space Center, simulates not just pressure, temperature, and gas, but also Martian sunlight and dust loading, for any latitude or season. The chamber is stainless steel and uses the methods described such as a vacuum pump with throttle control, a Mars-gas mix supply, and an LN2-cooled cold plate.
Another example, the Open University’s “Mars Chamber”, is used for astrobiology experiments; it can automate daily temperature cycles at 6 mbar CO2/N2 and expose samples to Mars-like UV radiation. These examples underscore the importance of automation and materials that can handle the extremes.
When designing your own setup, also consider safety and instrumentation. Vacuum chambers at 6 mbar have a large pressure differential (nearly 1 atm). You must ensure the chamber, especially if acrylic, is built to withstand this to avoid implosion risk. Do not try to DIY a vacuum chamber as that is not safe and always reach out to Sanatron if you are looking for a quality vacuum chamber.
Incorporate multiple sensors: at least a pressure gauge such as capacitive manometer for accuracy in the mbar range and temperature sensors. If doing biological tests, you might want a residual gas analyzer to monitor any changes in composition. For example, detecting if microbes produce trace gases like methane.
Plan for how to insert and remove samples or equipment: a convenient solution is a load-lock or a simple valve to a small antechamber, so you don’t have to vent the entire chamber every time. This is more critical for high-vacuum work, but if you need repetitive tests, it saves time. For biology, also consider that Mars’s low pressure can cause dehydration, you might design holders that keep samples in a soil simulant or gel to retain moisture, or run shorter experiments to observe immediate effects.
Other Considerations
Note that Mars’s gravity is about 0.38g, which you obviously can’t simulate with pressure and temperature alone. If your equipment tests are sensitive to gravity (e.g. dust settling, fluid behavior), you may need additional strategies. Some tests use horizontal setups or even drop towers, but those are beyond the scope of this article. However, for most chemical and biological tests, gravity differences are secondary compared to the atmospheric conditions you will simulate.
Summary
If you are looking for a simple setup, use Acrylic Vacuum Chamber and simply pump it down to 4.5 Torr. This keeps it simple and matches the pressure.
The next step would be to match chemistry and atmosphere composition by introducing Carbon Dioxide into the mix.
Finally, the third step is to match pressure, chemistry, and temperature by switching to a Stainless-Steel Chamber with liquid nitrogen cooling ability and an acrylic door for visibility.