Why is the Martian atmosphere 96% CO2?

There are numerous factors that can have an impact on the composition of a planet's atmosphere. In general, the primary (original) source for atmospheric gases tends to be from volcanic activity. read more

They each have about 95–96% CO2, 2–3% nitrogen, 1–2% argon, and traces of a bunch of other stuff. Venus, being the larger and more active of the two, has a much, much thicker atmosphere, but for the most part they have very similar makeups. read more

2) Mars' atmosphere is actually much thinner than the Earth's due to the absence of carbonate recycling- due to our tectonics (volcanic eruptions) the carbonate is recycled into co2, contributing to constant levels of the greenhouse gas. read more

The atmosphere of Mars is a resource of known composition available at any landing site on Mars. It has been proposed that human exploration of Mars could use carbon dioxide (CO 2) from the Martian atmosphere to make rocket fuel for the return mission. read more