Scholars Online Astronomy - Chapter 10: The Moon
Reading: Astronomy, Chapter 10: The Barren Moon
Study Notes: notes on your assigned reading from the text
- 10.1 Lunar motions include the Moon's orbit (revolution) around Earth and its rotation around its own axis. These motions are governed by the laws of gravity and conservation of momentum and energy, which over time have locked the Moon in a synchronized orbit-rotation, one rotation per orbit. The combination of motions and apparent wobble (libration) allow us to see slightly more than half the Moon's surface. Thus the Moon has a "far side" not visible from Earth, but no "dark side" which is never in sunlight.
Surface features of the Moon include craters and maria. Theories of crater origins include both impact by meteors and asteroids, and volcanic activity. Most craters appear to be the result of impact. Most maria appear to be the result of lava-type upwelling from below the lunar crust. There are no current erosion forces since the Moon has no atmosphere, or liquid surface water (with the possible exception of ice in polar craters; however these would not be a major erosive force). The Moon also has a single crust unit; there are no tectonic plates.
- 10.2 Manned exploration of the Moon took several phases. Unmanned mapping expeditions included a series of missions: Ranger - US, Lunas - USSR, Manned surveys without landing included the Apollo 8-10 missions, and manned landings included Apollo 10-17. Recent unmanned surveys by the Clementine and Lunar Prospector craft have discovered indications of surface ice, enough to support a lunar colony.
- 10.3 Evidence for the internal structure of the Moon rests on magnetosphere and moonquake data and supports the model of a small iron-rich core, lower mantle plastic asthenosphere, and a solid lithosphere upper mantle beneath a think crust. The mantle is nearly 4/5 of the radius of the Moon. Moonquakes are the result of deformation due to Earth's tidal forces.
- 10.4 Lunar rock samples reveal only igneous processes: mare rock is primarily basalt, highlands are anorthosite, and impact brescias are scattered during cratering events. By dating craters, we can determine conditions in the inner solar system at different periods since the formation of the Moon.
- 10.5 Theories of lunar formation include the capture theory, the fission theory, and the collisional ejection theory (the latter is the current front-runner). Current measurements show the Moon slowly receding from Earth.
Key Formulae to Know
Read the following weblecture before chat: Earth's Moon
- Set Stellarium to December 19, 2021, at 18:00. Find the moon in the southeastern sky and zoom in. What features can you identify?
- Find Venus on the western horizon and do a "Contol-G" to move to Venus as your viewing location. Swing the sky around until you can find Earth (near the East horizon from this viewing location. Double-click on Earth to center it and then zoom in until you can see the Moon. Double-click on the Moon to center it and zoom in. You should see the same face more or less as you did from Earth, since the Moon is near full.
- Back the time up to December 6, when the Moon is near new relative to the Earth. You should now see the "far side" of the Moon. What features do ou notice? How are the two sides of the Moon different?
In The Nine Planets Solar System Tour (web application), load the application, then click on Earth. Back out and click on the Moon, then on "Visit". The model will show the Moon's current position. Can you determine the Moon's phase at the time you observe it from its position relative to Earth and the Sun? Can you determine the Moon's phase from the portion of lunar surface in sunlight?
From above the surface of the Moon, investigate the following locations:
- Mare Tranquilitatis (Sea of Tranquility)
- Tycho crater (near side)
- Crookes crater (far side)
See how many features mentioned in the text you can identify, including surface features and core (if the application supports structure diagrams).
Use the simulator at the Earth Space Lab to explore Earth's ocean tides as a result of lunar motion.
Google Maps has a Moon site that is fun to explore, especially if you want to "walk around" the Apollo landing sites.
Chat Preparation Activities
- Essay question: The Moodle forum for the session will assign a specific study question for you to prepare for chat. You need to read this question and post your answer before chat starts for this session.
- Go over the list of Key Words and Key Ideas at the end of the chapter. If you don't remember the definition of the key word, review its use (the page number on which it is explained is given).
- Read through the Review Questions and be prepared to discuss them in class. If any of them confuses you, ask about it!
- Mastery Exercise: The Moodle Mastery exercise for the chapter will contain sections related to our chat topic. Try to complete these before the chat starts, so that you can ask questions.
- Required: Complete the Mastery exercise with a passing score of 85% or better.
- Go to the Moodle and take the quiz for this chat session to see how much you already know about astronomy!
Read through the lab for this week; bring questions to chat on any aspect of the lab, whether you intend not perform it or not. If you decide to perform the lab, be sure to submit your report by the posted due date.
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