Astronomy Practice Exam

How does the density of Mars' atmosphere compare to Earth's?

1. Denser

2. Similar

3. Much less dense

4. More variable

The correct answer is: Much less dense

The density of Mars' atmosphere is much less dense than that of Earth's atmosphere, making it the correct choice. Mars' atmosphere is composed primarily of carbon dioxide (about 95.3%), with only traces of oxygen and nitrogen, resulting in a very thin atmosphere. In comparison, Earth has a much more complex atmosphere, rich in nitrogen (about 78%) and oxygen (about 21%), along with various other gases that contribute to its density. The atmospheric pressure on Mars is only about 0.6% of Earth's, which corresponds to a density that is significantly lower. This low density has important implications for weather, temperature variations, and the ability to support life as we know it. The thin Martian atmosphere leads to rapid temperature changes and makes it difficult for liquid water to exist on the surface for extended periods, contrasting with Earth's much thicker atmosphere that helps regulate temperatures and supports a variety of life forms. Therefore, understanding this stark difference in atmospheric density is crucial in comparative planetology and can provide insights into the climate and geological history of both planets.