The Sun and Planets
Homework 3.
Spring Semester 2017
Prof Dr Ravit Helled
Due by: 16.03.2017
TURN IN YOUR SOLUTIONS NEXT WEEK IN CLASS
or
EMAIL THEM AS A PDF
Exercise 1.
Planetary Geology
a) What are the three major heat sources in planets? Provide a brief explanation of
each source and explain when is each is important.
b) What are the three types of heat transport in planets? Briefly explain how each
type functions.
c) All terrestrial planets have layers. Identify and describe the three density layers
found in terrestrial planets. What rock types are found in each layer? Try to
illustrate (simply—no need for the Mona Lisa) how these layers are ordered.
d) What are the three basic requirements for a global magnetic field in terrestrial planets? Do all of the terrestrial planets in the solar system meet these requirements?
e) What are the four main geologic processes operating on the terrestrial planets?
Describe each briefly and list the major geologic features and rock types associated
with each process.
Exercise 2.
Plate Tectonics
Typical motions of one plate relative to another are 1 centimeter per year. At this rate,
how long would it take for two continents 3’000 kilometers apart to collide? What are
the global consequences of motions like this?
Exercise 3.
Internal versus External Heating
In daylight, the Earth’s surface absorbs about 400 watts per square meter. Earth’s internal
radioactivity produces a total of 3 trillion (3 × 1012 ) watts that leak out through our
planet’s entire surface (recall that the surface area of a sphere with radius r is A = 4πr2 ).
Calculate the amount of heat from radioactive decay that flows outward through each
square meter of Earth’s surface (your answer should have units of watts per square meter).
Compare quantitatively to solar heating, and comment on why internal heating drives
geologic activity.
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