Crossword 5

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