Crossword 5

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Across
  1. 3. natural satellite of Earth
  2. 4. study of earthquakes
  3. 7. three-quarters of moon
  4. 8. a piece of rock from outer space
  5. 11. a part of the thermosphere
  6. 13. person trained to travel in spacecraft
Down
  1. 1. a natural calamity
  2. 2. hottest planet of solar system
  3. 3. an important greenhouse gas
  4. 5. meteoroids burn up in this layer
  5. 6. this gas comprises 78% of air
  6. 9. sudden shaking of Earth
  7. 10. layer in which jet planes fly
  8. 12. hot molten rocks inside Earth