Final answer:
Nitrogen is the most abundant gas in Titan's atmosphere, being the primary atmospheric constituent of Saturn's largest moon, Titan.
Step-by-step explanation:
The most abundant gas in Titan's atmosphere is nitrogen. Titan, the largest moon of Saturn, has a complex atmosphere composed predominantly of nitrogen, similar to Earth's atmosphere. Although other gases are present, such as methane (CH4), ethane (C2H6), and various hydrogen compounds, nitrogen stands out as the primary component. Studies indicate that this atmospheric composition is due to the presence of sufficient volatiles, such as ammonia, methane, and nitrogen, which have led to Titan's substantial atmosphere. Titan's cold temperatures prevent common volatiles such as carbon dioxide or water from being in vapor form, thus allowing nitrogen to become the primary atmospheric constituent over time.