Only proven technology to produce oxygen on Mars is Moxie unit installed on Perseverance Mars Rover since 2021. MOXIE (the Mars Oxygen In-Situ Resource Utilization Experiment) produces oxygen using solid-oxide electrolysis of carbon dioxide. Here’s the chemistry clearly and precisely.

2 CO2  →  2 CO+O2

This reaction splits carbon dioxide, releasing molecular oxygen.

MOXIE operates at ~800 °C using a solid oxide electrolysis cell (SOEC) made with a ceramic electrolyte (yttria-stabilized zirconia).

1. CO₂ intake

Mars’ atmosphere (~95% CO₂) is filtered, compressed, and heated.

2. Cathode reaction (CO₂ reduction)

At the cathode: CO2+2e−  →  CO+O2−

• CO₂ gains electrons
• Carbon monoxide is released
• Oxygen ions move through the solid electrolyte

3. Oxygen ion transport

• O2− ions migrate through the ceramic electrolyte under an electric field.

4. Anode reaction (oxygen formation)

At the anode: 2 O2−  →  O2+4e−   

• Oxygen gas is released
• Electrons are returned to the circuit

Net electrochemical process: 2 CO2  →electric power  2 CO+O2   

Key point:
This reaction is not spontaneous. It requires:

• High temperature
• Electrical energy
• Specialized materials

This is why bombs can’t replace MOXIE—you need controlled electrochemistry, not brute force.

In MOXIE:

• CO is vented back into the Martian atmosphere

In future systems:

• CO could be used as:
  • Fuel feedstock
  • Carbon source for plastics
  • Reactant for methane synthesis (Sabatier process)

MOXIE produced up to 12 g of O₂ per hour, enough to show scalability.

Energy required to produce 1 kg of O₂ from CO₂

Theoretical minimum

≈ 4 kWh per kg of O₂

This is the thermodynamic minimum set by electrochemistry.

Practical / real-world value

≈ 15–25 kWh per kg of O₂

This is what you should expect for an actual Mars system like MOXIE or its scaled-up successors.

1. Electrochemical minimum

MOXIE uses this reaction:

2 CO2→2 CO+O2

 4 electrons per O₂ molecule

• Minimum electrical energy ≈ 463 kJ per mole of O₂
• 1 kg O₂ = 31.25 moles
• Result:

≈4.0 kWh/kg O₂ 

This assumes:

• Perfect efficiency
• No losses
• No compression or heating costs

Which never happens.

2. Real system losses

MOXIE must also:

• Compress Mars’ thin atmosphere
• Heat CO₂ to ~800 °C
• Overcome electrical resistance
• Maintain thermal stability
• Run pumps, valves, control electronics

All of that costs energy.

MOXIE’s demonstrated performance

From published mission data:

• Power: ~300–400 W
• Oxygen output: up to 12 g/hour
• Scaling that up:

MOXIE-equivalent systems ≈  20 kWh/kg O₂  

This matches expectations for early-generation solid oxide electrolysis.

Cost of breathing in Mars

• One astronaut: ~ 0.8 kg O₂/day
• Energy needed: 20 kWh/day per person
• Considering $75 / kWh as energy costs to take solar panels from Earth, breathing Mars oxygen will cost $1,500 per day.

Ultimately by building solar panels & scaling up production in Mars, this will be a fraction of costs.