Questions from the lecture on Monday, December 2. Advice for submitting study guide answers is here.

(167)

One possible explanation for the lack of water on Venus is that Venus never had much water to begin with, compared to the Earth. Explain two reasons why this explanation is not plausible (in other words, why we think the original atmospheres of Earth and Venus were similar).

(168)

What evidence in Venus' atmosphere tells us that the original water in the atmosphere likely did not leave the atmosphere by either condensing or through chemical reactions, going into the ground?

(169)

Although Venus started with an atmosphere that was probably very similar in mass and composition compared with the Earth, various differences between Earth and Venus led to a gradual loss of water vapor on Venus, combined with an enormous increase in the carbon dioxide content. Describe the positive feedback mechanism (Runaway Greenhouse Effect) by which water is lost and the atmosphere thickened.

(170)

Name and briefly explain the significance of two important differences between Venus and Earth that led Venus to undergo the Runaway Greenhouse process while Earth did not.

(171)

What evidence on the surface of Mars indicates Mars once had a thicker, warmer Earth-like atmosphere? Explain.

(172)

Explain how the loss of internal heating on Mars about 2-3 billion years ago may have led to the gradual loss of the Martian atmosphere.