Our Solar System

4. The most distant of the gas giants.
5. Pluto, Charon, Eris, and Sedna are all icy dwarf planets found in this part of the outer solar system
9. A short period comet that we can see ~ every 76 years.
14. One of the largest of the asteroids. Was originally considered a planet.
15. A moon of Pluto
17. A dwarf planet that is one reason why Pluto is no longer a planet.
18. A terrestrial planet with the thickest atmosphere.

1. One reason why Venus and Earth are warmer than they should be.
2. The largest of the gas giants.
3. A moon of Saturn that has the thickest atmosphere of any moon.
6. Our moon.
7. Useful for finding the relative age of a planet (or moon's) surface.
8. A terrestrial planet with an extremely thin atmosphere. Some would say it hasn't got one.
10. The rings of this gas giant were first observed by Galileo.
11. A vast swarm of comets on the outskirts of our solar system.
12. The fourth rock from the Sun.
13. A moon of Jupiter that may have a liquid water ocean underneath its icy crust.
16. A moon of Jupiter that has active volcanism.