planets crosspuzzle

1. retrograde motion, in astronomy, actual or apparent motion of a body in a direction opposite to that of the (direct)
3. solid piece of debris from an object in space
5. metal with composition of alloy with low melting point
7. region of space where most of the asteroids reside
8. small rocky or metallic body in outer space
10. long cliffs on mercury's surface
11. a celestial body resembling a small planet.
12. a chemical that can be used to store, move, and deliver energy
14. other planets in our solar system with compact, rocky surface like Earth's terra firma
15. measure of how non-circular the orbit of a body is
16. region of the solar system, believed to contain many small bodies
18. small icy solar system body
19. habitable area around a star where life can form

2. a unit of measurement used for space
4. small body of matter from outer space that enters the earth's atmosphere
6. when a number of small bodies pass close to earths atmosphere
9. large planet with low density; mostly gas
13. Any of innumerable small bodies of accreted gas and dust thought to have orbited the Sun during the formation of the planets
17. the locus of all points such that the sum of the distances from two foci to any point on the ellipse is a constant