Download Homework 5 1 Orbital Observations 2 Surface Roughness 3 Lunar

The Solar System
Homework 5
Homework 5
Due Wednesday, June 20 at the start of class
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Orbital Observations
The year is 3030, and a space probe sent to a mystery planet in orbit around a distant star nearly
identical to our Sun has finally arrived. The planet is the size of Venus, rotates with the same
orbital period as Mars, and orbits at 1.2AU from its star. The spacecraft will orbit the planet and
take detailed observations to be sent back to distant Earth.
1. Based on the planetary parameters, describe in detail the intensity of each of the four basic
geological processes you expect to see on this planet. Give your answers by comparison to
Solar System Planets. Here’s a nonsense example: “I would expect this planet to experience
more impacts than Mars, but fewer than the Earth, because it spins slower than Earth but
faster than Mars.” If you can’t estimate with the information available, say what additional
information you would need to make a decision.
2. Without landing on the planet, what measurements could you make to determine whether
this planet has a metallic core?
3. The instruments designed to study the planet’s atmosphere fell off on the way. Can you
tell via photographs whether this planet has an atmosphere? What kinds of features would
provide definitive proof?
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Surface Roughness
Express the height of Olympus Mons (26 km tall) and Valles Marineris (7 km deep) as percentages
of Mars’s radius. Do the same for Mt. Everest (9 km tall) and the Grand Canyon (1.8 km deep) on
Earth. What do you notice? Make a hypothesis that might explain the differences between Earth
and Mars.
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Lunar Footprints
Micrometeorites will eventually erase the footprints left on the Moon by the Apollo astronauts.
Let’s find out how long it will take. Assume that the Moon is hit by 30 million micrometeorites
per day (this is about the same number hitting the Earth’s atmosphere) and that these impacts
strike randomly around the Moon’s surface. (Hint: Use units to check that your answer for each
part makes sense.)
1. What is the surface area of the Moon in square centimeters?
2. On average, how many micrometeorites hit 1 square centimeter per day?
3. Estimate the size of a footprint (in cm2 ). From part 2, how many impacts hit this area per
day?
4. Using an estimate of 20 hits to erase a footprint, how many years would it take to erase a
footprint on the Moon?
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The Solar System
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Homework 5
Explanations
The following are example quiz questions. Write down a 2-3 sentence explanation or answer for 4
of the following 8 questions. Indicate which question you’re answering before you answer.
1. What are the three sources of planetary heat? One lasts much longer than the others. Describe
why.
2. What are the three ways a planet loses heat? Provide an everyday example not discussed in
your textbook or in class for each of them.
3. How do we know that the Earth has an iron core? How do we know whether other planets
have iron cores?
4. What is differentiation? Give an example of an object that experienced it, and an object that
did not. What’s the key difference between these two objects?
5. What is meant by the phrase “surface area to volume ratio”? Why is it so important in
determining planetary geology?
6. Why are some parts of the Moon darker than others? Give an example of how at least two
of the four geologic processes are different between the light and dark areas of the Moon.
7. How does cratering depend on the three fundamental planetary properties? Describe how
you can use this knowledge to date planetary surfaces.
8. Describe how the presence or absence of an atmosphere affects each of the four basic geological
processes.
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Homework feedback
This question is ungraded, but I would really like your opinion. On a scale of 1-10, how difficult
was this homework? On the same scale, rank how much you think you learned. Write down the
number of hours you spent on this homework. Feel free to give verbose feedback: what did you like
or dislike? What was confusing or especially difficult?
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