Final answer:
The statement that the atmosphere of Mars is composed of mostly carbon dioxide along with some nitrogen is true as the atmosphere of Mars is mostly composed of carbon dioxide (95%), with some nitrogen (3%), and argon (2%).
Step-by-step explanation:
The Martian atmosphere has a surface pressure of less than 0.01 bar and is primarily composed of carbon dioxide (95%), with the remainder consisting of about 3% nitrogen and 2% argon. This atmospheric composition means that Mars has a very thin atmosphere, with air so rarefied that it resembles conditions found at an altitude of about 30 kilometers above Earth's surface.
Carbon dioxide and nitrogen are common atmospheric gases within our solar system. On Earth, carbon dioxide is present in much smaller quantities due to the presence of water and life, which have led to a different atmospheric composition with more oxygen and nitrogen.
In contrast, without life and with little to no water vapor, Mars retains a high percentage of carbon dioxide, with nitrogen making up a few percent of the atmosphere. As for what other compositions are in Mars, the Martian atmosphere also contains trace amounts of argon, as well as occasional dust clouds, water ice clouds, and carbon dioxide (dry ice) clouds, especially prevalent around the polar ice caps.