Few things are as important to explorers as good maps. For a planetary explorer, one of the most important types of maps is a geological map. A geological map shows what types of terrains or rocks one is likely to encounter on a planetary surface, and in what order they were created. Since our ability to go to different planetary surfaces is limited, planetary scientists must do most of their exploring and mapping by studying images from spacecraft.

Anybody can look at a pretty picture of a planetary surface and say "That's Mars", or "That's the Moon". A planetary scientist can take that picture and interpret what is there and reconstruct the history of that surface. Recognizing various landforms on spacecraft images and being able to determine their relative ages is an important component of this class.

The Identity of the various landforms can be ascertained by comparing known images with what you see (and by asking your TA), while the relative ages of the various features can be determined by using the Principle of Superposition. Nicholas Steno, a seventeenth century physician, is first credited with stating this simple but powerful geological principle. He wrote that "... at the time when the lowest stratum was being formed, none of the upper strata existed." or in its modern restatement: Young formations overlap old formations.

In this lab we will act as planetary scientists and interpret what we see by creating a geological map and writing a description of a selected region of the Moon. Our materials will be the same primary data the Apollo program scientists used when they were first trying to both understand the lunar surface and find interesting landing spots for the Apollo missions. The photographs are from the Lunar Orbiter missions that were flown around the Moon in 1966 and 1967.

Pick an interesting region on your Lunar Orbiter image. You do not have to map the entire photograph. The region you do pick should have at least 4 different features whose relative ages you can determine. Feel free to pick and label a region with many more features, but not so many that it would take you a week to draw the map.

The figure below should give you some idea as to what we want to do. On the left is an image taken from the command module of Apollo 15. The image is of the area surrounding the ghost crater Prinz. In the center is my geological map of the region identifying the different landforms, and labeling my determination of the relative ages for 4 features. You should label the relative ages with numbers, with (1) being the oldest features and (4) being the younger features. On the right is the key to the different landforms on my geological map. You do not need to use my shading scheme, colors work really nice.

A reader of your map should be able to understand what the various surface features are in the photograph, and in what order they were formed. Often it is not clear what a surface feature is or when it was formed. Be bold and make a guess, we are not going to go the Moon in the near future, so it is hard to tell if you are wrong.

You need to turn in your geological map and a paragraph describing the features you mapped. Your paragraph should both describe the features and indicate their relative ages. Please refer explicitly to the 4 features you labeled on your map indicating them by number. For example, a description of the example images might go along the lines of:

"The oldest features in this image are the highland mountains and the ghost crater (1). It is not possible to tell the relative ages of the two features. They may actually be part of the same feature and have the same age. A lava flow (mare surface) fills in much of the image and overlays and abuts the mountains and ghost crater (2. Lava channels overlay the lava flow in numerous places indicating a younger age. In particular one of them (3) cuts across the highland mountains. All of the lava channels seem to have the same relative age since they overlay the same features. Simple impact craters dot the mare surface. A few craters seems to partially cover lava channels, indicating they are younger. One of the impact craters (4) looks very sharp and fresh so may be very young. The rest of the impact craters on the mare do not intersect the channels, so their relative ages cannot be determined. My guess is that they are probably younger than the lava channels based on their fresh appearance."