Solar System

4. A bowl-shaped depression at the top of a volcano or at the mouth of a geyser.
6. Small, rocky bodies orbit close to the sun.
9. The third planet from the Sun.
10. The fourth planet from the Sun.
11. The eighth planet from the Sun and the fourth largest.
12. The central of the Earth, lying below the mantle.
13. The second planet from the Sun.

1. An object that produces a coma.
2. Any of the large, low-lying dark areas on the Moon or on Mars or other inner planets.
3. The seventh planet from the Sun and the third largest.
5. The planet closest to the Sun and the smallest in the solar system.
7. A compound containing two oxygen atoms per molecule.
8. The fifth planet from the Sun and the largest.
10. The layer of the Earth between the crust and the core.
12. The solid, outermost layer of the Earth, lying above the mantle.