According to the NASA JPL video linked below the top five gases comprising the martian atmosphere include CO₂, O₂ and CO. Do the proportions reflect some chemical equilibrium? Are sunlight or chemical reactions involved in maintaining these proportions?

component     fraction
   CO2          95.9%
   Ar            2.0%
   N2            1.9%
   O2            0.14%
   CO            0.06%

Mars Atmospheric gases composition

The NASA JPL video Crazy Engineering: Making Oxygen on Mars with MOXIE is linked in How many square meters of solar panel to power a MOXIE-like oxygen source per person?


1 Answer 1


This is actually a very difficult question to answer, and one that is being actively studied. Made even more difficult is that there is a considerable variability in the day-to-day for some of these gasses, and particularly year round.

Carbon Dioxide will freeze at certain times of the year. This is a chart of Viking 1's pressure over a season, this is primarily due to the CO2 freezing.

enter image description here

Oxygen is a much more challenging gas. There has been some measurement of the variability of O2. The pattern doesn't quite fit what is predicted in the mold.

enter link description here

I haven't seen anything directly about CO. Argon and Nitrogen are pretty stable long term.

All that being said, there are some losses of all of these gas. All of the gasses are being lost to some extent, although the amount is pretty small, and they seem fairly stable. Wikipedia does a good job of explaining all of the various ways that gases can be lost.


Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.