Answer to Question 1
Venus rotates very slowly; therefore, her circulation patterns are not broken into smaller cyclonic systems. Earth rotates relatively fast; therefore, circulation patterns break circulation patterns into cyclonic (spiral) disturbances.
Venus's cloud layers are much higher and more stable than those on Earth. These cloud layers are highly stable because the atmospheric circulation on Venus is much more regular than that on Earth. Convection circulates this gas toward the dark side of the planet and the poles, where it cools and sinks.
Answer to Question 2
The abundant presence of deuterium in the atmosphere. Deuterium is 5.5 times more abundant than normal (light) hydrogen in the atmosphere of Mars, suggesting that Mars once had about 20 times more water than it has now. Presumably, much of the water was broken up and the normal hydrogen mostly lost to space.
