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Across 1. The region between the orbits of Mars and Jupiter in which most asteroids are found. 4. The latitudes where the Hadley and Ferrel cells meet. 6. The study of the upper atmosphere of the Earth or another planet. 7. A circulation cell which forms at the mid-latitudes of a rotating planet to balance the transport by the Hadley and polar cells. 8. A liquid-giant planet whose atmosphere is composed of hydrogen and helium, with methane, ammonia, H2S, and water as condensable aerosols. 11. The portion of Saturn's rings on either side of the planet. 16. A class of asteroids with Earth-crossing orbits. 17. What a meteorite is called as it is falling through the sky. 18. One of the four cells created by convection currents on a rotating planet. 19. The closest planet to the Sun.

Down 1. The explosion of an asteroidal meteorite which has entered the Earth's atmosphere before it reaches the ground. 2. The appearance of a dark band connecting Venus and the Sun during the beginning and end of transits. 3. Caused when the Earth passes through the dust of a comet's tail. 5. A protoplanetary disk. 9. Tidal forces cause orbits to go to a state of lowest energy while conserving angular momentum. 10. A class of asteroids with Mars-crossing orbits. 12. The region of the Earth's atmosphere from roughly 80-500 km altitude. It includes the ionosphere. 13. A law giving the approximate distances of the planets from the Sun 14. A weakly ionized region of the Earth's atmosphere which conducts electricity 15. The periapsis of an elliptical orbit around the Earth.