Chapter 8- Atmospheres of Terrestial Planets

Question 1

Primary atmospheres

Answer 1

H, He parts of original solar nebula. Some captured by inner planets before nebular gases dispersed by eruptions of growing protosun. But these light gases were soon lost.

Question 2

Escape speed

Answer 2

Minimum speed for gas molecule to become unbound from planet

Question 3

Distribution of molecular speeds

Answer 3

Temperature determines distribution of molecular speeds for molecules in atmosphere. Lighter molecules have higher speeds for same temperature than do heavier molecules. If a significant fraction of molecules have speeds near the escape speed, atmosphere will escape.

Jupiter: massive (high escape speed) and cold (low molecular speeds) has retained its atmosphere.
Moon: low mass (low escape speed) has lost its atmosphere.
Mercury: low mass, high temp – almost no atmosphere.

Question 4

Secondary atmospheres

Answer 4

Volcanism supplies gases trapped in interior materials(water vapor, carbon dioxide, sulfur dioxide, nitrogen).

Impacts from comets might bring in water vapor, carbon monoxide, methane, ammonia (decomposed by sunlight into hydrogen [escapes], nitrogen)

Question 5

Greenhouse effect

Answer 5

Solar radiation passes through atmosphere and strikes Earth,re-radiated as infrared. IR is absorbed by greenhouse gasses (CO2, H20) and changed to heat.