NASA instrument on the Perseverance rover that produced oxygen from Martian atmospheric carbon dioxide by solid oxide electrolysis. First production was on 20 April 2021 (about 5 grams); by its 16th and final run on 7 August 2023 it had produced 122 grams in total, with a peak rate of 12 grams per hour at 98% purity or better, per NASA. Hoffman et al. (2022) describe it as "the first demonstration of ISRU on another planet".
Objective. Demonstrate production of oxygen from the carbon dioxide of the Martian atmosphere as a technology precursor for propellant and life-support oxygen.
This is one instrument. Its evidence and outcome are its own and are not the carrier mission's result.
NASA names MIT's Michael Hecht as principal investigator and JPL, OxEon Energy and Air Squared as developers. Only NASA and OxEon have participant records here; MIT, JPL and Air Squared are not separately admitted in this batch. OxEon's payload_builder role is limited to its solid-oxide electrolysis stack contribution, not ownership, prime contractorship or sole construction of MOXIE.
Record history
changes to this record's facts, newest first
Changed
Field
Was
Now
Reason
Source
2026-11-01
participants
Only NASA payload ownership recorded.
OxEon added for its electrolysis-stack contribution; other developers remain named in the caveat.
Since Perseverance landed on Mars in 2021, MOXIE has generated a total of 122 grams of oxygen – about what a small dog breathes in 10 hours. At its most efficient, MOXIE was able to produce 12 grams of oxygen an hour – twice as much as NASA’s original goals for the instrument – at 98% purity or better.
NASA Jet Propulsion LaboratoryGovernment recordPublished 2023-09-06Accessed 2026-09-25Supports: open evidence gaps
After the instrument proved far more successful than its creators at the Massachusetts Institute of Technology (MIT) expected, its operations are concluding.
In this first operation, MOXIE’s oxygen production was quite modest – about 5 grams, equivalent to about 10 minutes worth of breathable oxygen for an astronaut.
Quote matched the source text when accessed.
Cite this record
SpaceMiningData, “MOXIE (Mars Oxygen In-Situ Resource Utilization Experiment)”, dataset version a00fa2c68a45, built 2026-11-11, https://spaceminingdata.com/missions/nasa-moxie.html. Record checked 2026-10-05.
How MOXIE made oxygen
MOXIE made oxygen from carbon dioxide in Mars's air, on NASA's Perseverance rover: 122 g of oxygen in total, by the 16th and final run on 7 August 2023. On this site's evidence ladder this counts as a processing demo, the step before commercial delivery. It worked on air, not on material dug from the ground, and its oxygen was released to the atmosphere, not delivered. No commercial delivery in this dataset.
All 11 steps with their quotes, the 2021 runs and the chemistryThe stages in the order the paper gives them: the filter, the scroll pump, heating and the SOXE assembly (step 1's first quote). This layout is schematic: component positions and gas routing are simplified for reading. Select a stage to go to its step.
Inspect the parts (3D)
Illustrative layout. The paper's Figure 1 and NASA/JPL's 'Components of MOXIE' illustration show the real arrangement; this model is not traced from them. Positions, sizes, shapes and orientation inside the published 23.9 × 23.9 × 30.9 cm chassis dimensions are schematic, and the drawn inlet port and outlets extend beyond them. Only the 10 cells in two halves, and the heater plates above and below the stack, follow the paper.
Step 1 Martian air in
MOXIE takes in Martian air, which is about 95% carbon dioxide, through a dust-trapping HEPA filter.
MOXIE takes in martian atmosphere through a dust-trapping HEPA filter, compresses the atmosphere via a scroll pump, heats it to 800°C
An experiment inside NASA’s Mars 2020 Perseverance rover, MOXIE has successfully produced oxygen from the carbon dioxide that comprises ~95% of the martian atmosphere.
A scroll pump compresses the thin air, and its speed sets how much comes in; its maximum speed is 3,500 rpm. Separately, a generic run starts with the speed set to take in 55 g/hour of Martian air, which is also the most MOXIE can reliably take in at that maximum speed when the air is least dense in the Martian year.
Following the reference segment, a generic MOXIE run steps the compressor up to its 3500 rpm maximum speed, implements another V - I sweep,
To save mass, volume and complexity, passive flow control devices in the cathode and anode channels take the place of true pressure regulators. About 6% of the CO-rich cathode exhaust goes back to the intake, a design that mitigates the risk of the nickel in the cathode oxidizing.
To reduce mass, volume, and complexity, the cathode and anode flow channels are equipped with passive viscous flow control devices rather than true pressure regulators.
Early oven tests suggested 800 °C as an optimal compromise between efficient operation and the risk of damaging heat-sensitive materials. In the rover, volume and power limits ruled out an oven, so two heater plates at the top and bottom of the stacks do the heating, with insulation partly covering the sides; the centre cells run up to 10 °C cooler than those nearer the heaters.
Initial tests of the SOXE, performed in an oven, suggested that an operating temperature of 800°C is an optimal compromise between efficient operation and the risk of damaging heat-sensitive materials.
Inside the Perseverance rover, however, volume and power constraints precluded an oven, so, instead, MOXIE’s SOXE is heated by two heater plates at the top and bottom of the electrolysis stacks with insulation partially covering its sides.
This configuration results in thermal gradients of up to 10°C between the cooler cells in the center of the stack and the warmer cells nearer the heaters.
In the solid oxide electrolysis (SOXE) assembly, CO₂ flows over a nickel-based catalyzed cathode and decomposes into oxygen ions and CO (carbon monoxide). The scandia-stabilized zirconia ceramic electrolyte selectively passes the oxygen ions to the anode, where they recombine into O₂; overall, 2CO₂ → 2CO + O₂.
sends it through a solid oxide electrolysis (SOXE) assembly, where CO 2 flows over a nickel-based catalyzed cathode and decomposes into oxygen ions and CO.
The scandia-stabilized zirconia ceramic electrolyte selectively passes oxygen ions to the anode, where the ions recombine into O 2 , which is measured for quantity and purity before being released to the Mars atmosphere.
The SOXE uses a stack of 10 electrolysis cells wired in series, with a centre tap so that they can be controlled as two five-cell halves, top and bottom. Manifolds for the cathode inlet and exhaust and for the oxygen exhaust are shared by all 10 layers, and thin Inconel leads connect the stack to MOXIE's voltage control circuitry.
The SOXE uses a stack of 10 electrolysis cells, electrically wired in series with a center tap such that they can be controlled as two five-cell stacks, referred to as top (T) and bottom (B).
FM OC12 was designed to estimate the resistance ( R L ) of the thin Inconel leads connecting the MOXIE voltage control circuitry to the stack of electrolysis cells that comprise the SOXE.
Another reaction, 2CO → 2C + O₂, would form carbon, so in the main segment of a generic run (step 10) the estimated electrolysis voltage is kept at least 0.1 V below the Nernst potential for carbon formation. Cooler cells have both a higher resistance and a smaller safe voltage zone, so they are at greater risk of coking.
sets the current to as high a value as possible for this maximum gas intake while keeping the estimated electrolysis voltage at least 0.1 V below the Nernst potential for carbon formation.
The oxygen is measured for quantity and purity before it is released to the Mars atmosphere. Purity is judged by an infrared sensor that watches for trace CO₂ in the anode exhaust, one of four gas-specific sensors, and pressure sensors sit at the anode and cathode exhausts.
The scandia-stabilized zirconia ceramic electrolyte selectively passes oxygen ions to the anode, where the ions recombine into O 2 , which is measured for quantity and purity before being released to the Mars atmosphere.
Purity is determined by a commercial nondispersive infrared (NDIR) CO 2 sensor that monitors trace CO 2 (0 to 5%) in the anode exhaust. This is one of four gas-specific sensors.
Oxygen leaves from the anode side, while the cathode exhaust is a mixture of CO₂, CO and inert atmospheric gases, mainly argon and nitrogen.
The scandia-stabilized zirconia ceramic electrolyte selectively passes oxygen ions to the anode, where the ions recombine into O 2 , which is measured for quantity and purity before being released to the Mars atmosphere.
A generic run, as described in the 2022 paper (runs OC10, OC11, OC14, OC15)
The paper calls runs OC10, OC11, OC14 and OC15 generic runs, essentially identical except for the time of sol and the season's air density; choose a phase to see the parts involved. Two diagnostic runs, carried out to study uncertainties in the cell voltage and the oxygen's purity, differed and are not shown here.
OC10, OC11, OC14, and OC15 were generic runs, essentially identical except for the time of sol they were run and the seasonal atmospheric density.
In addition to the generic runs just discussed, two diagnostic runs were carried out to shed light on uncertainties associated with determining the actual voltage across the cells and assessing the purity of the O 2 product.
Compressor up to its 3,500 rpm maximum, then another V–I sweep quote
Current as high as possible while the estimated voltage stays at least 0.1 V below the carbon limit quote
End check· Scroll compressor, SOXE stack
5 min back at the reference compressor speed and current quote
Cool-down· Heater plates (off)
Laboratory tests showed that heating and cooling between cycles, not starting and stopping oxygen production, cause the degradation quote
Quotes for the phases
Initial tests of the SOXE, performed in an oven, suggested that an operating temperature of 800°C is an optimal compromise between efficient operation and the risk of damaging heat-sensitive materials.
The reference segment starts with a 16-min “equilibration” step with 2-A electrolysis current (6 g/hour of oxygen), during which time, the internal operating temperature stabilizes.
This is followed by 3.5-min steps at 1.6 A and 1.2 A (4.8 and 3.6 g/hour of oxygen, respectively), providing a voltage-current ( V - I ) sweep to determine the internal resistance of the SOXE
The current returns to 2 A to end the reference segment. Running identical reference segments at the beginning of every MOXIE run allows for tracking changes in MOXIE performance.
sets the current to as high a value as possible for this maximum gas intake while keeping the estimated electrolysis voltage at least 0.1 V below the Nernst potential for carbon formation.
At the end of a run, the compressor speed and electrolysis current are reset for 5 min to the values used in the reference segment to compare the system behavior at the beginning and at the end of the run.
Previous laboratory tests have demonstrated that it is the cooling and heating between cycles rather than the start-up and shutdown of the oxygen production process that causes this degradation, suggesting that it is likely associated with differential thermal stress.
In seven oxygen production runs through 2021, at night and by day, MOXIE made about 50 g of oxygen and met its requirements for oxygen generation rate and purity. Reducing the stack's wear from cycle to cycle was a primary development focus, and operation on Mars so far indicated that it was highly successful; the rover's energy limits did not allow testing over the thousands of hours of continuous operation that a human mission will require.
In seven oxygen production runs through 2021, MOXIE successfully produced ~50 g of oxygen and definitively demonstrated that it meets requirements for oxygen generation rate and purity despite design compromises demanded by severe constraints on mass, power, volume, and cost.
Reduction in cycle-to-cycle SOXE degradation was a primary development focus, and operation so far on Mars indicates that the outcome was highly successful.
the energy constraints of Perseverance do not allow testing of longevity over the thousands of hours of continuous operation that will be required in support of a human mission,
Totals to the end of the mission, from this record:
122 g of oxygen in total, by the 16th and final run on 7 August 2023This record's summary, from the NASA/JPL release of 6 September 2023 that it cites; dated 7 August 2023.
First production was on 20 April 2021 (about 5 grams); by its 16th and final run on 7 August 2023 it had produced 122 grams in total,
This record, Record summary
Since Perseverance landed on Mars in 2021, MOXIE has generated a total of 122 grams of oxygen
This record, NASA/JPL release of 6 September 2023, quoted in source [1]
9.8 g on that 16th runThe NASA/JPL release of 6 September 2023, as quoted in this record; dated 7 August 2023.
On its 16th run, on Aug. 7, the instrument made 9.8 grams of oxygen.
This record, NASA/JPL release of 6 September 2023, quoted in source [2]
Five runs were at night and two by day. OC9 to OC13 ran in a high-density season, OC14 as the density was falling and OC15 near the yearly minimum. Sols are Martian days, counted from the landing. The paper's table does not say what its pressure and temperature columns measure.
Table 1 of Hoffman et al. 2022
Run
Sol
Date
Time
Pressure (Pa)
Temperature (K)
O₂ minutes
O₂ (g)
Running total (g)
Average (g/hour, derived)
FM OC9
60
20 April 2021
Night
751
201
59
5.4
5.4
5.49
FM OC10
81
12 May 2021
Night
768
199
74
6.9
12.3
5.59
FM OC11
100
1 June 2021
Day
757
256
71
6.9
19.2
5.83
FM OC12
155
27 July 2021
Night
737
201
96
8.9
28.1
5.56
FM OC13
176
17 August 2021
Night
720
199
82
8.1
36.2
5.93
FM OC14
241
24 October 2021
Night
651
206
73
6.9
43.1
5.67
FM OC15
276
29 November 2021
Day
631
253
74
6.8
49.9
5.51
The last column is derived here (grams ÷ minutes × 60); the paper does not give it.
Runs FM OC9 to OC13 were performed at a semiannual high-density season (northern hemisphere spring). FM OC14 was executed as the atmospheric density was decreasing, and OC15 took place near the annual minimum density.
2CO → 2C + O₂Carbon formation, which must be avoided
MOXIE must run above the Nernst potential of the oxygen-producing reaction, the voltage above which a reaction can be initiated, and below that of carbon formation. Carbon deposition (coking) in the cathode raises the cells' resistance and may possibly fracture the cathode.
MOXIE [Mars Oxygen In Situ Resource Utilization (ISRU) Experiment] is the first demonstration of ISRU on another planet, producing oxygen by solid oxide electrolysis of carbon dioxide in the martian atmosphere.
The latter process must be avoided to prevent coking (carbon deposition) in the SOXE cathode, which raises the resistance of cells by reducing their active area and may possibly fracture the cathode, causing an inability to produce oxygen.
Different time spans. The paper covers seven oxygen runs to the end of 2021, about 50 g in all (49.9 g in its table); the record gives 122 g up to the 16th and final run on 7 August 2023. Every total here is dated for that reason.
In seven oxygen production runs through 2021, MOXIE successfully produced ~50 g of oxygen and definitively demonstrated that it meets requirements for oxygen generation rate and purity despite design compromises demanded by severe constraints on mass, power, volume, and cost.
First production was on 20 April 2021 (about 5 grams); by its 16th and final run on 7 August 2023 it had produced 122 grams in total,
This record, Record summary
Different run counts. The paper's OC numbers count every heating cycle, including seven on Earth (OC1 to OC7) and a heating checkout on Mars with no oxygen (OC8), so its seven 2021 runs on Mars are OC9 to OC15. NASA, as quoted in the record, calls the run of 7 August 2023 the 16th; these sources do not say what that count includes or which OC number it matches.
Note that the OC number increments every time MOXIE undergoes a heating cycle, whether or not oxygen is produced.
The first seven cycles, flight model (FM) OC1 to OC7 were run in laboratories on Earth as part of preflight testing and qualification. FM OC8 was a heating cycle checkout with no oxygen production.
SpaceMiningData record msn-nasa-moxie, sources [1] and [2] aboveLicence: Record data CC BY 4.0; quoted excerpts belong to their publishers
Quoted excerpts belong to their publishers. The paper's figures are images and are not reproduced here.
Every statement above rests on the quotes printed with it, from the flight paper by Hoffman et al. and from this record; where they are silent, the text says so. The 3D model is illustrative.
How MOXIE made oxygenOpen the live view