The NEIU NASA/UNCF Project

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NEIU Earth Science Department

Exploring Crystal Form in Space

The exercises below are part of a series of interdisciplinary learning modules created by
geologists, chemists, physicists, and mathematicians to infuse a core curriculum with space science concepts.
This module is designed as an exercise in Mineralogy/ Crystallography.

 What is crystal form and symmetry?

 How can we examine crystal form of minerals from other bodies in space?

 What kinds of minerals occur on the moon? Are they similar to minerals on Earth?

 How are crystal form and symmetry affected by lower gravity or different atmospheres?

 Can any of the minerals in "outer space" be useful resources for our dwindling supply?

  Crystal Form and Symmetry
  Well-formed crystals can be classified by the shape, or form, which they exhibit.  
  Crystal FORM is defined as a group of crystal faces, all having the same relationship to the elements of
            symmetry of a given crystal system. 
 
  The macroscopic elements of symmetry in crystals include: 
          mirror plane (REFLECTION), 
          proper axis (ROTATION), 
          improper axis (ROTO-INVERSION), and 
          center of symmetry (INVERSION).
  The form of a specific mineral is an external reflection of the mineral's internal atomic structure.


  Read this introduction to crystal forms.  

             What factors would influence the shape of a euhedral mineral crystal?
  
  Simple (open) crystal forms include:
          pinacoids, domes, sphenoids, prisms, and pyramids.
  Forms present are a function of the symmetry element and the relationship of a specific face to that element
          (whether inclined or parallel)
  
  Examine the photos of mineral crystals below.  For each mineral photo, do the following:
            List the simple crystal forms that are present
            Identify the symmetry elements which are present
            Decide which crystal system is represented
  
           Can you guess, based on compositional information from the moon, what minerals these could be?

 
 Scanning electron micrograph from Apollo 15 mission sample.  [Photo from NASA/ JPL]

Scanning electron micrograph from Apollo 15 mission.  [More images at NASA/ JPL] 

  Thin Section Views
  Check out these images of meteorites in thin section.  Can you identify any of the minerals present?  
  What characteristics of individual mineral crystals are most useful to make identifications?

	image of Apollo 12 sample; NASA JSC Digital Image Collection
	link here to more lunar sample images: University of Arkansas Geology page J. Ryan, University of South Florida, Dept. Geology  Kurt Hollocher, Geology Dept, Union College
more images available at Apollo Image Gallery

The composition of the moon is known through samples of lunar soil and rocks recovered from Apollo mission landings in which samples were physically collected.  These samples are from specific sites on the moon, close to the landing sites of the respective missions.

In addition, "fly-by" missions, such as Galileo, Lunar Prospector, and Clementine, have yielded information about the elemental composition of the moon, as well as of other planets.
Information about chemical composition of space bodies yield clues as to their origin and possible resources in space.

The table in this link compares lunar to earth composition, with respect to key elements.  [Visit the page, scroll to the bottom to view the table, and then use your browser's 'back' button to return here.]

QUESTION 1:  What are the possible resource materials, as indicated in this list?

QUESTION 2:  What are the possible sources of error in this data, and how would that affect your  assessment of the potential for resources?

QUESTION 3: What are the most abundant elements in the earth's crust?  What elements are present in the earth's interior, but not abundant in the crust?  [For help, refer to link].  

QUESTION 4: Do we expect the moon and the earth to have similar compositions?  What would the similarity or difference indicate about the formation of the moon?  Theories about the formation of the moon are diverse:  see [links].  Which of these theories would account for the comparative composition of the moon and the earth? 
.