What Makes a World Habitable?

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Across
  1. 1. Life requires this liquid to be available.
  2. 2. This molecule of life requires a temperature range that is not too hot or not too cold.
  3. 7. Earth and Mars have very similar chemical ________ (ingredients).
  4. 8. Earth's atmosphere is a great insulator for temperatures, provides certain nutrients, and even provides a magnetic and chemical ______ for life.
  5. 10. Comparing Earth to this neighbor.
  6. 11. Our home planet.
  7. 13. Earth's average surface ______ is 15 degrees Celsius.
  8. 15. Many processes exist on Earth to ____ nutrients such as plate tectonics.
Down
  1. 1. Earth's water exists in all three states creating this.
  2. 3. This provides important protection and a source of biochemicals.
  3. 4. Water on mars almost always exists in this state.
  4. 5. Mars in on the edge of this zone.
  5. 6. Mars' atmosphere is too thin to insulate or protect the surface and is mostly made of this gas.
  6. 9. They make almost all of the food chains on Earth possible.
  7. 12. Mars's average surface temperature is far below _______.
  8. 14. Organisms need light, heat, or chemicals to gain this to live.