Environmental studies

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Across
  1. 4. many stars together
  2. 5. Object orbiting a planet and made of ice and dust
  3. 9. our star
  4. 10. Movement of water to the atmosphere
  5. 13. biggest planet of the system solar
  6. 14. Main constituant of the air
  7. 15. Top part of the Earth
  8. 17. closest planet to the sun
Down
  1. 1. Represent about 20% of the air we breath
  2. 2. big object orbiting a star
  3. 3. all the living organisms on Earth
  4. 6. Layer of earth under the Crust
  5. 7. essential Life element which is part of a cycle
  6. 8. Object orbiting a planet
  7. 11. object orbiting a star and made of rock and metal
  8. 12. lower part of the atmosphere
  9. 15. gas causing climate change
  10. 16. Inner part of the Earth made of Iron and Nickel