Exploration of the Solar System

Topic 6

Week 5

What We Learned From the Surface of the Moon

 

 

 

The Moon as Seen by the Apollo Spacecraft

The following PowerPoint presentation gives spectacular pictures from the Apollo 11 (first) and Apollo 17 (last) missions.  You can peruse the Johnson Spaceflight Center collection of images at the following WebSite:

http://images.jsc.nasa.gov/

This lecture serves as an introduction to the pictures you will see, so that they (hopefully) make more sense,  and you will appreciate their significance.  I will discuss the scientific ramifications of the Apollo  missions.  The most important results came from analysis of the 400 kilograms of rock samples returned from those missions.  There is no substitute for seeing these rocks up close.  It is amazing to see these ordinary,  unremarkable-looking rocks,  and realize that for eons they lay on the surface of the Moon.

 

Characteristics of Lunar Rock Samples

The most valuable aspect of the Apollo mission was analysis of lunar rock samples.  What was particularly important was dating the age of formation of the rocks via the technique of radioisotope dating. 

 

            The following results were obtained.

  1. All lunar rocks are igneous; no sedimentary, no metamorphic.  The rocks of the lunar highlands are of a sort called anorthosite, the rocks in the maria are basalts.
  2. Radioisotope dating showed the lunar rocks (normal ones you would pick up on the surface of the Moon) to be extremely old, older than all rocks on the Earth.
  3. The ages of lunar rocks range from 3.3 to 4.5 billion years. But there is more to say. 
  4. The Mare rocks are from 3.2 to 3.8 billion years.
  5. The Terrae rocks are from 3.8 to 4.5 billion years.
  6. There is therefore a difference in the age of formation of the terrae and the maria.  The difference is small compared to the age of the Moon, but significant.
  7. Combining the realization that craters were caused by impacts, and the fact that the terrae are heavily cratered while the maria are quite smooth, leads to a fascinating conclusion about the early history of the solar system

 

OK, Wake Up:  Here’s a question.  Think about it.

Given the above findings about the moon rocks from the different locations,  and the appearance of the Moon as shown on the picture from the first lecture ,

http://www.oarval.org/MoonMapen.htm

 what can you say about the geological history of the Moon?