The atmosphere of Mars is 96% CO₂, with a pressure of approximately 6 x 10⁻³ atm at the surface. Based on measurements taken over a period of several years by the Rover Environmental Monitoring Station (REMS), the average daytime temperature at the REMS location on Mars is –5.7°C (22°F), while the average nighttime temperature is –79°C (–109°F). This daily variation in temperature is much larger than what we experience on Earth. What factor plays the largest role in this wide temperature variation, the composition or the density of the atmosphere?