The history of planetary exploration clearly shows that investigations by space probes are required if we are to learn about the interior structures, geological evolution, and possible habitability of the planets in our own Solar System, and so it seems clear that advanced spacecraft will eventually be needed for the investigation of other planetary systems as well. America stands today at the opening of a second Space Age. On tonight's show, Clyde Lewis talks about SENTINEL: THE GUARDIAN OF THE GALAXY.

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