One of the cool things about NASA is that in the last 10 years they have become a little less anal about their work product. They have opened an entire resource library dedicated to 3D visualizations. Everything from highly realistic graphic 3D models of the Eta Carinae Homunculas nebula (Clearly they are still working on creating cool names for space stuff) to an exact topographical map of the mars surface including rover paths which can be 3D printed.

Barring the usual open source limitations, all of the materials are royalty free and available for download just in time for your kid's next science project.

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