Inner and Outer Planets

4. a long, steep slope or cliff on a planetary surface, often formed by tectonic forces like faulting when a planet's crust shrinks or is pushed together.
6. a system for detecting the presence, direction, distance, and speed of aircraft, ships, and other objects, by sending out pulses of high-frequency electromagnetic waves that are reflected off the object back to the source.
7. the four large, outer planets of our solar system.
9. the smaller, outer moon of Mars, named after the Greek god of dread, son of Ares (Mars).
12. the four largest moons of Jupiter.
13. when the external tidal forces on an object become greater than the internal forces that hold it together.
15. the largest impact basin on Mercury.
16. a large, continent-sized highland region or "terra" located in the northern hemisphere of Venus.
17. the larger, innermost, and irregularly shaped moon of Mars.
18. a disk-like structure of countless small particles (dust, ice, rock) orbiting a celestial body.

1. a system of canyons located just south of the Martian equator.
2. a rocky, Earth-like planet with a solid surface, primarily composed of silicate rocks and metals.
3. the largest moon of Saturn.
5. the process where a molecule breaks apart into smaller atoms or fragments after absorbing a photon of light.
8. the largest moon of Jupiter.
10. a colossal shield volcano on Mars and the largest volcano and tallest mountain in the entire solar system.
11. when relatively narrow bands of strong wind in the upper levels of the atmosphere.
14. the largest moon of Neptune.