How much percentage of carbon dioxide is present in the atmosphere of Venus and Mars?

The atmospheres of both Venus and Mars are predominantly composed of carbon dioxide, though they differ vastly in density. Venus possesses a thick, dense atmosphere where carbon dioxide accounts for approximately 96% to 96.5% of the total volume [1]. This high concentration, combined with extreme atmospheric pressure, creates a powerful greenhouse effect [3]. Similarly, the Martian atmosphere is primarily carbon dioxide, with concentrations typically cited between 95% and 96% [3]. Specifically, Mars' atmosphere contains about 95.3% to 95.97% carbon dioxide, along with smaller amounts of nitrogen and argon [2]. Despite this high CO2 percentage, Mars remains cold because its atmosphere is extremely thin compared to Earth and Venus [3]. Therefore, the range of 95–97% accurately represents the carbon dioxide levels found on both planets.

Sources

1. [1] Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 2: The Solar System > Venus > p. 28
2. [3] Science ,Class VIII . NCERT(Revised ed 2025) > Chapter 13: Our Home: Earth, a Unique Life Sustaining Planet > Table 13.2: Planets in our solar system > p. 214
3. [2] Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 2: The Solar System > Mars > p. 30