Class Activity: Europa Wedges
The recent NASA Galileo mission brought back to Earth exciting, new images of the surface of Jupiter’s icy moon, Europa. These images show a variety of fascinating geological features, such as wedges, fractures, flows produced by ice volcanism, low ridges and pits. These features not only suggest that Jupiter’s moon may be geologically active, but may hold evidence that a liquid ocean exists or once existed under Europa’s icy crust.
Step 1: Background:
To understand how scientists interpret these features on Europa, you will first need to learn more about geologic processes on Earth, such as plate tectonics, sea floor spreading, and crosscutting relationships. Europa is unique in that it is the only other solar system body in the solar system to exhibit these features. To understand these features and learn how to identify them visit the USGS website.
Step 2: Explore Europa:
Visit Europa’s geology and identify Europa’s surface features, understand how they were formed, determine their relative age, and reconstruct the surface of Europa.
Step 3: Investigation
Now, you will examine a specific area of Europa’s frozen ocean. Click on the following link and open the image in a separate tab in your Internet browser.
PIA00518: Ridges on Europa: This view of Jupiter’s moon Europa shows a portion of the surface that has been highly disrupted by fractures and ridges. This picture covers an area about 238 kilometers (150 miles) wide by 225 kilometers (140 miles). Symmetric ridges in the dark bands suggest that the surface crust was separated and filled with darker material, somewhat analogous to spreading centers in the ocean basins of Earth. Although some impact craters are visible, their general absence indicates a youthful surface. The youngest ridges, such as the two features that cross the center of the picture, have central fractures, aligned knobs, and irregular dark patches. These and other features could indicate cryovolcanism, or processes related to eruption of ice and gases.
Step 4: Analysis:
Scientists are always fine-tuning their research so it is very important to take detailed notes in order to advance existing theories or develop new ones. Using these notes, answer the following questions about this area of Europa’s surface.
1. List the types of motion along plate boundaries that were used to shift the older geological units together. Use the USGS information your studied earlier to guide your analysis.
2. What do these types of motion suggest about the physical properties of the material beneath the surface (brittle, soft, fluid, solid, etc.)? Why would this type of material allow the plate boundary movement you listed in the previous question.
3. Now that you have made a geologic map of the area, can you figure out which unit is oldest and which is youngest? One way to determine relative age is to look for crosscutting relationships. Like a cake that is sliced, the surface can be broken by fractures or faults. The unit (or slice) which cuts through the rock (or cake) is always younger than the rock itself. In other words, you can’t cut something unless it’s already there! Using the shade (i.e. white, light gray or dark gray) as the name for each geologic unit, arrange them in order of their relative age in the space below.
Oldest————————————————————————————————-Youngest
4. If a new geologic unit were to form in this region of Europa’s surface, would you predict it to be bright or dark? Explain your reasoning.
5. Explain how the youngest geologic units that you identified might have formed (i.e., where did the material come from?) Give evidence for your answer.
6. Answer the following questions based on the theory of plate tectonics:
a. If new ice or crust is being created in this region of Europa’s surface, and we find that the moon is not expanding or forming mountains, then what must be occurring elsewhere?
b. Describe at least one way in which this might occur.
