General instructions for assignments
All responses must be typed.
All calculations must be shown in full.
All graphs must be electronically produced.
All references must be cited using Chicago Manual of Style conventions.
Sharing of phrasing or formatting with other students is prohibited.
This work is the intellectual property of the instructor and Washington State University. All reproduction or retransmission in whole or in part is strictly prohibited.
NO TITLE PAGE.
Ref: Gas retention simulator (authored by the Columbia Center for New Media Teaching and Learning; Columbia University; hosted on github)
https://ccnmtl.github.io/astro-simulations/gas-retention-simulator/ (Links to an external site.)
Ref: NASA Planetary fact sheet – metric
https://nssdc.gsfc.nasa.gov/planetary/factsheet/index.html (Links to an external site.)
In this exercise we will simulate planetary atmospheres: their composition, temperature, and escape conditions.
In your favorite browser, navigate to the simulation and spend a few minutes playing with the controls. Orient yourself to the display: the box on the upper left is a chamber in which a gas will be contained; the gas particles (atoms or molecules) are represented by little colored balls that move about, and the shade (darker or lighter) of color of each ball indicates how quickly it is moving. The display at upper right shows a histogram of the number of gas particles at a particular speed at any instant.
When you are ready, Reset the simulation (top right).
Pull down the menu entitled Select gases to add and select Xenon. Leave the other settings at their default values. Then select Start simulation. Focus upon a single gas atom and follow it for several seconds. Does it always move at the same speed? If not, what causes its speed to change?
Look at the distribution plot. In the previous question we established that a given particle speeds up and slows down. Why does the distribution plot NOT change over time?
Reset the simulation. Now simulate the atmosphere of Earth as it was 4.5 billion years ago. Add three gases: hydrogen, water, and carbon dioxide. Set the temperature to 288 kelvin (from the NASA fact sheet, Earth’s mean T = 15 C; 15 celcius 273 = 288 kelvin). Check on the box beside Allow escape from chamber. Set the escape speed to 1/8 of Earth’s escape speed, 11.2/8 = 1.4 km/s = 1400 m/s. Start the simulation and wait at least 60 seconds. Which gases escape? Which are retained? Do your results verify what you expected; if so then how, and if not then how not?
Reset the simulation. Now simulate Mars: record here Mars’s mean temperature (kelvin) and 1/8 escape speed (m/s). Add hydrogen, water, and carbon dioxide to the chamber. Start the simulation and wait at least 60 seconds. Does the end result resemble the composition of Mars’s atmosphere today?
Reset the simulation. Now simulate Venus. Record your initial conditions. Record your results. Write a sentence or two of interpretation of your results.
Generalize your results: under what conditions will a gas escape from a planet’s atmosphere? Under what conditions will a gas be retained in a planet’s atmosphere?
Grading: all questions are weighted equally. Total points = [30].
