Petrographic and mineralogical studies are the sine qua non for understanding the nature, origin, and history of many types of astromaterials. It is through petrographic examination that such materials are identified, classified, and understood. Moreover, most other types of chemical, spectroscopic, and isotopic studies rely on petrographic and mineralogical studies to provide information about the nature of the sample and the host phases of constituent elements.

The ARES Electron Microbeam Laboratories contain instruments for studying the petrography and mineralogy of samples at scales ranging from millimeters to nanometers. Instruments include:

• An optical petrographic microscope with an automated stage, a digital camera, and software for image processing and analysis.


• A Cameca SX100 electron microprobe with 5 wavelength dispersive x-ray spectrometers and an energy dispersive x-ray analysis system. This instrument analyzes micrometer-sized regions on the surface of polished samples. It can accurately determine the concentration of elements present in concentrations of a few hundredths of a weight per cent or greater. In addition, it can map the spatial distribution of those elements across the surface of the sample. This information can be used to identify the minerals in the sample and compute their abundances.


• A JEOL 6340f Field Emission Gun Scanning Electron Microscope with an energy dispersive x-ray analysis system. This instrument is used to collect images of the surfaces of samples, and can resolve features ranging in size from millimeters to 2.5 nanometers. It can also be used to obtain chemical analyses of sub-micrometer sized regions on sample surfaces.


• A JEOL 2000fx Scanning Transmission Electron Microscope with an energy dispersive x-ray analysis system. This instrument examines ultra-thin slices of samples by directing an electron beam through the slice. In addition to determining the textures and morphologies of minerals within the sliced sample, it can determine the crystal structure within nanometer-scale volumes and thus unambiguously identify the mineral constituents. It can also image crystal lattices at atomic scale resolution.