Question

Choose the best answer to each of the following. Explain your reasoning with one or more complete sentences. Mars's seasonal winds are driven primarily by (a) dust; (b) sublimation of carbon dioxide ice; (c) sublimation of water ice.

Short answer

(b) Sublimation of carbon dioxide ice.

Step-by-step solution

Understanding the Factors

To determine which factor primarily drives Mars's seasonal winds, we must consider how changes in temperature and phase transitions in Mars's environment contribute to air movement on the planet.

Evaluating Dust Influence

Dust on Mars plays a significant role in weather phenomena, including dust storms. While dust can affect wind patterns by absorbing sunlight and warming the atmosphere, it is not the initial trigger of seasonal winds.

Analyzing Carbon Dioxide Sublimation

Mars is known for its large polar ice caps made primarily of carbon dioxide (CO2), which sublime (change from solid to gas) during the Martian spring and summer. This sublimation causes large pressure differences, initiating strong seasonal winds as the CO2 gas spreads across the planet.

Considering Water Ice Sublimation

While Mars has some water ice, its sublimation is less significant compared to that of carbon dioxide ice. Water ice contributes to local weather patterns but does not have as strong an influence on Mars's seasonal winds due to its limited presence and lower sublimation rate.

Conclusion: Identifying the Primary Driver

Based on the analysis, the sublimation of carbon dioxide ice is the main factor driving Mars's seasonal winds due to its large-scale impact on atmospheric pressure and temperature changes.

Key concepts

Carbon Dioxide Sublimation

Carbon dioxide sublimation is a critical process on Mars that significantly influences the planet's seasonal winds. Unlike Earth, where water plays a dominant role, Mars has polar ice caps primarily consisting of solid CO extsubscript{2}. During the warmer Martian spring and summer, these deposits undergo sublimation. Sublimation is the phase change where a substance transitions from a solid directly to a gas, without passing through the liquid phase.
Key points about carbon dioxide sublimation:

• As the ice sublimates, it turns into carbon dioxide gas.
• This gas spreads from the polar regions, causing shifts in atmospheric pressure.
• These pressure changes result in strong winds, helping drive seasonal atmospheric patterns.

The amount of carbon dioxide involved and the rapidity of its phase transition allow it to dominate Martian weather patterns. Overall, carbon dioxide sublimation is a powerful driver of Mars's seasonal winds.

Martian Atmosphere

Mars's atmosphere plays a pivotal role in understanding how winds and weather patterns develop on the planet. Although it is much thinner than Earth's, comprising mostly of carbon dioxide, it is sufficient to allow weather phenomena. The characteristics of the Martian atmosphere include:

• The atmosphere is about 100 times less dense than Earth's, making it very thin.
• It is primarily composed of carbon dioxide (95.3%) with small amounts of nitrogen and argon.
• The thinness means less heat retention, leading to more extreme temperature variations.

These features contribute to unique meteorological events, like dust storms and the generation of seasonal winds by pressure differences caused by carbon dioxide sublimation. Understanding these atmospheric dynamics is crucial for studying Martian weather and its effects on the planet's surface conditions.

Polar Ice Caps

The polar ice caps on Mars are fascinating features that undergo significant seasonal transformations. They primarily consist of carbon dioxide ice, unlike Earth's, which are made of water. Main aspects of Martian polar ice caps:

• These ice caps expand and recede dramatically over the Martian year due to sublimation and deposition cycles.
• During the Martian winter, CO extsubscript{2} freezes out of the atmosphere, forming extensive ice caps.
• In warmer seasons, the CO extsubscript{2} sublimates, thinning the ice cap and releasing gas into the atmosphere.

The cyclical nature of these ice caps directly impacts the atmospheric pressure differences across the planet, resulting in seasonal winds. By studying these polar regions, scientists gain insights into the climate and atmospheric processes on Mars.

Temperature Changes

Temperature changes on Mars have a profound effect on its weather and atmospheric dynamics. Mars experiences wide temperature fluctuations, both daily and seasonally. How temperature affects Mars:

• The planet's surface temperatures can range from -125°C (-193°F) during winter nights to 20°C (68°F) in equatorial areas during midday.
• These temperature variations are pronounced due to the thin Martian atmosphere, lacking a thick blanket to retain heat.
• Temperature changes trigger the sublimation of carbon dioxide in the polar regions, which in turn leads to atmospheric pressure differences.

Understanding these temperature variations is key to comprehending the drivers behind Martian seasonal winds. The significant temperature shifts fuel the dynamic atmospheric processes, including the exchange of gases between polar and equatorial regions.