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Resource: The Virtual Microscope (downloadable software) includes samples/images of lunar and mars dust, meteorites, Costa Rican sand, stromatolites, and pyrites.
License: Image copyright is held by the Imaging Technology Group, part of the Beckman Institute for Advanced Science and Technology at the University of Illinois at Urbana-Champaign and the project was funded by NASA and the NSF. The materials are provided for educational use. The software is Open Source.
Additional info: Software is available for Windows, Mac, and Linux. Data sets are downloadable within the software. Additional training materials, tools, and information are available from the website. A separate website, COGS, includes lesson plans and other educational materials.