1. astronaut
2. universe
3. plate tectonics
4. continental drift
5. meteoroid
6. asteroid
7. vertical
8. horizontal
9. considerate
10. sensible
11. similar
12. possible
13. assemble
14. initial
15. exceptions
Challenge words
1. explanation
2. opportunity
3. pleasantly
4. dreary
5. irregular
Extra challenge words
1. expurgate
2. interpolate
3. lugubrious
4. notarize
5. parameter