Crossword Speed Challenge

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Across
  1. 4. Chemical element with symbol O
  2. 6. One thousand years
  3. 10. Natural satellite of Earth
  4. 12. Opposite of "rare" when referring to steak
  5. 13. Coldest continent
  6. 15. Rome's famous gladiatorial arena
  7. 17. Opposite of "false"
  8. 19. A Mars rover launched in 2020
  9. 20. Italian city known for canals
  10. 21. Study of living organisms
Down
  1. 1. Earth's largest ocean
  2. 2. Strong metal alloy of iron and carbon
  3. 3. Capital of Japan
  4. 5. Device that sends email
  5. 7. Music tempo marking meaning "slow"
  6. 8. Your future title
  7. 9. Word meaning "before noon"
  8. 11. Main gas in Earth's atmosphere
  9. 14. Country known for kangaroos
  10. 16. Author of The Shining
  11. 18. A polygon with five sides