The primary substance in the atmosphere of Mars is carbon dioxide (CO2), which makes up about 95% of its atmosphere. Mars has a very thin atmosphere compared to Earth, with a surface pressure less than 1% that of Earth. The Martian atmosphere consists primarily of carbon dioxide, nitrogen, argon, and traces of oxygen and water vapor. This composition contributes to the planet's cold temperatures and has significant implications for potential habitability, exploration, and the search for signs of past life. Understanding Mars' atmosphere is crucial for future missions aimed at human exploration and colonization.