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Across 1. The apparent westward drift of planets. 6. Made observations of Mars that were far more precise than any others made. 8. Soil-like layer of the moon that is composed of igneous rocks, glass beads and lunar dust (2 Words) 9. The science that studies the universe. 10. Greeks had the belieft that the Earth was the center of the universe. 12. He discovered three laws of planetary motion. 13. Dark, smooth area on the moon's surface 14. He concluded that Earth is a planet. 15. Splash marks left by young craters

Down 2. The oval shaped path that Mars follows. 3. Long channels that are associated with maria 4. The average distance between Earth and Sun. (2 Words) 5. Most important contributions were his decriptions of the behavior of moving objects 7. In this model Earth and other planets orbit the sun. 11. Round depressions in the surface of the moon.