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| 1. | These objects are also known as minor planets. |
| 2. | This planet has two prominent rings, which are very bright. |
| 3. | Pluto's orbit sometimes crosses the orbit of this planet. |
| 4. | When air in the atmosphere is warmed, air pressure ____. |
| 5. | This planet is the densest planet in the Solar System. |
| 6. | the fastest moving planet in the Solar System |
| 7. | The atmosphere of Venus is mostly carbon _________. |
| 8. | This is the only planet in the Solar System that has not yet been visited by a spacecraft. |
| 9. | the number of seasons that Mercury has |
| 10. | Earth is the only planet known to support _________. |
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| 6. | Uranus' blue color is a result of this gas in the atmosphere. |
| 11. | Jupiter is composed mostly of _________ and is known as a _________ giant. |
| 12. | The temperature in Earth's _________ is estimated to be as high as 7500 K. |
| 13. | Warm air is ____ dense than cold air, which is why a hot-air balloon rises. |
| 14. | In comparison to the direction that the Earth rotates, _________ rotates in the opposite direction. |
| 15. | Two Viking spacecrafts landed on this planet in 1976. |
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