RELATIVE DATING OF FEATURES

 (This observing exercise is geared for elementary, middle, and high school students.)

 

Individual Lunar Features

1. One way to deduce whether a crater is old or young is to investigate the amount of erosion that has occurred. Although the Moon does not have water erosion, there is an erosional process that occurs. Countless number of micro-meteoroids (particles smaller than grains of sand) are continuously beating into the surface since the Moon does not have an atmosphere to protect itself. Over time, the relentless pulverizing causes crater rims to degrade from sharp (young craters) to rounded (old ones). Can you date some of the craters you have seen as either young or old? Why?

 

2. Two very large craters (named for famous astronomers) are Copernicus and Tycho. Are they young or old craters? Why?

 

3. Near the time of Full Moon, it is easy to see surface features called rays. These look like white “fingers” pointing away from some of the craters. How do you think rays were formed?

 

4. Do all craters have rays? If not, describe which types of craters have rays? (For example, are they old or young craters, or are they large versus small ones).

 

5. Does the Moon have many or only a few rays? If many, how do you think they were formed, and are they young or old features? If only a few, what do you think has happened to them?

 

Overlying Lunar Features

1. As you look at the surface of the Moon, can you find any regions where there is one feature on top of another? For example can you find a crater on top of another crater? Even better, can you find three features that are on top of each other? In all of these cases, which feature had to have formed first and which one last? Why? (Reverse the order and see if you would get the same result on the Moon's surface.)

 

2. The way the maria look to us today is not how they first appeared. Initially there was an explosive impact throwing out debris and creating a large basin. Over time the basin was filled with lava. Examine a maria and look carefully at the features near and on it. Can you describe the order of events that created these features?

 

James Sowell, 2013