March 4 - March 17
In this module, we examine the features and processes that characterize the surfaces of solid worlds.
Introduction & Perspective:
First we'll learn about solid surfaces, the features on them, and the processes that change them. We'll ignore most aspects of atmospheres for now (that's M6), and will deal with energy and the world as a system later (M5). Chapter 9 gives the basics (for now, just skim the part about the interiors), but only applies the results to the terrestrial worlds. We have to collect the other worlds from other chapters. The key is to understand that it's very very cold in the outer Solar System, and what are called "ices" (including water ice, but also frozen carbon dioxide and other chemicals) make the same patterns that rock does on the warmer worlds.
Over the past decade or so, as we've gotten more and more detail about worlds, planetary scientists have classified the surface processes on worlds into four broad categories. These are now almost set, but you may still find some differences in naming or where exactly certain processes are listed. Tectonics (note, this is not just plate tectonics but any distortion of crust by stresses from the mantle below) is pretty set. Volcanism is also pretty set, but the oozing of lava into an impact crater is not always classified the same way. What the text calls "erosion" should be a broader category - the processes involving surface or near-surface volatiles. That would include, for example, the collapse of a rocky surface as ices or fluids escape from below, changes wrought by polar caps, chemical changes, etc. - not just actions of wind and sand and water. Impact cratering is pretty much set as a category, except for the connection to lava oozing.
Although we're not focusing on interiors right now, know that the first three processes are mostly characteristic of worlds that are warm inside - if a world is geologically inactive, then the passive process of impact cratering will tend to dominate. The cratering record can tell us how long a surface has been sitting around doing nothing else except getting hit.
Answers due at the end of the first week of the module:
1. What part of Earth's crust is (a) the youngest? (b) the oldest? (c) How do we determine the relative ages of surfaces on most worlds?
2. In Fig. 9.24a, there is a medium-sized crater near the center and a ridge running through it. Did the impact that formed the crater happen before or after the cliff formed? (While you're at it, try to find at least one set of three craters where you can tell which impact happened first, second, and third.)
1. Read the assigned readings.
2. Contribute to the main discussion.
3. Contribute to your group's discussion.
4. Answer the study questions by the end of the first week.
5. Submit homework - individually - by the end of the second week. It should contain:
These questions are to be discussed in the Module 4 Conference Folder
Questions will be posted at the beginning of the module.
last updated 5/5/02