What if we're all from Mars? AFP/Getty Images hide caption

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This may look like a mad scientist's garage sale, but it's actually the most precise clock ever built. Jim Burrus/NIST hide caption

itoggle caption Jim Burrus/NIST

This artist rendering provided by NASA shows Voyager 1 at the edge of the solar system. AP hide caption

itoggle caption AP

Mission to Mars: Six explorers lived in this simulated Mars habitat in Hawaii for four months, part of a NASA study to test the role of cooking and food on an extended space mission. Sian Proctor/NASA HI-SEAS hide caption

itoggle caption Sian Proctor/NASA HI-SEAS

An artist's illustration of Kepler-22b, a planet that circles its star in the "goldilocks" zone. Ames/JPL-Caltech/NASA/Getty Images hide caption

itoggle caption Ames/JPL-Caltech/NASA/Getty Images