PTYS/ASTR 206 – Section 3 – Homework 3 – Assigned 2/26/09NAME:______________________________________________(PRINT CLEARLY)- Homework is due in class on Thursday March 5th.- Late homeworks can be turned in class on Tuesday March 10th for 50% credit.- Homeworks turned in later than this receive 0%.- Students are encouraged to discuss approaches to solving homework problemswith each other; however, all work submitted must be the student’s own. Donot turn in identical homeworks! See the syllabus for moreinformation.______________________________________________________________________Hint: Each of these questions should be quick to answer. If you find yourself engagedin a long chain of complicated reasoning or more than a few lines of math thensomething is probably wrong! Make sure to start this early and talk to the TA or myselfwith any questions.Question 1: Planetary interiorsGive two reasons why we know the core of the Earth is at least partly liquid?When rocks rise up through the Earth’s mantle why do they partly melt?Volcanoes with very viscous lavas have very explosive eruptions. Give three reasonswhy some lavas are more viscous than others.PTYS/ASTR 206 – Section 3 – Homework 3 – Assigned 2/26/09You might already have heard about the Mount St. Helens eruption during 1980 inWashington State. Do a little web research on this eruption, what kind of volcano isthis? The mountain itself was badly damaged in the eruption – what will happen to thisvolcano in the future?Question 2: Atmospheres of terrestrial planetsThe surface pressure of the martian atmosphere is about 0.006 times that of the Earthand the scale height of Earth’s atmosphere is about 8km. Is the top of Mount Everest atlower or higher pressure than the surface of Mars (elevation of Mount Everest is8.8km)?PTYS/ASTR 206 – Section 3 – Homework 3 – Assigned 2/26/09Both Earth and Titan have mostly nitrogen atmospheres at roughly the same pressure.Temperature on Titan is 90K and on the Earth 300K. How dense is Titan’s atmospherecompared to the Earth?How do we know there is ice in Mercury’s polar regions? Why is it stable there despiteMercury being such a hot planet?Question 3: Atmospheric CirculationWhat latitudes contain most of the deserts on the Earth? What causes this?PTYS/ASTR 206 – Section 3 – Homework 3 – Assigned 2/26/09Which way do winds at Earth’s equator blow? (Sketch a picture). Where does this aircome from and why do these winds blow in this direction?How does the greenhouse effect work? Why does adding more CO2 to the atmospherechange the climate? Why did Venus’s greenhouse effect run away while the Earth’s iskept in check?Question 4: The MoonMost people now believe that the Moon formed in a giant collision between the Earthand a passing Mars-sized planet. Give two pieces of evidence to support this.PTYS/ASTR 206 – Section 3 – Homework 3 – Assigned 2/26/09An old formation theory involved the Moon and Earth splitting apart from a rapidlyspinning parent body. Why doesn’t this work?What are the dark low-land plains on the Moon composed of? Why do they have muchfewer impact craters than the bright lunar highlands? Why are these dark plainsconcentrated on the side of the Moon that faces the Earth?Question 5: VenusMost volcanoes on Venus produce lava that is not at all viscous. Suggest a reason whythe viscosity of the Venusian lavas is so low.PTYS/ASTR 206 – Section 3 – Homework 3 – Assigned 2/26/09Venus is 0.72 AU from the Sun. Assume Venus had no atmosphere and that its baresurface reflected 50% of the sunlight that hit it. How much solar power would it absorbon each square meter? If the temperature was stable then this absorption would bebalanced by emitted energy. What would be the temperature in this case?[Hint: you solved a problem almost just like this in the last homework]What is the actual surface temperature on Venus? How big of an effect is theatmosphere
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