Chapter 21

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Across
  1. 3. when a planets atmosphere traps solar energy and causes the surface tempature to increase
  2. 4. Millions of small rocky objects
  3. 5. A small rocky particle that moves through space .
  4. 7. Planets closest to the sun that are made of rocky materials
  5. 8. a round depression formed on the surface of a planet or moon
  6. 11. The avergae distance from the earth to the sun.
  7. 12. a streak of light in earth s atmosphere made by a glowing meteoroid
Down
  1. 1. the time it takes an object to complete one rotation
  2. 2. The time it takes for an object to travel once around the sun
  3. 6. A meteoroid that strikes a planet or a moon
  4. 9. The 4 largest moons of jupiter
  5. 10. An object made of gas and dust that orbits the sun