1. Moons of our Solar System by Mr. McKinsey, November, 2007

2. A Moon for Every Planet? Most planets have moons. Even dwarf planets have moons. Only Mercury and Venus do not have moons. Moons vary in size, in composition, and in many other ways.

3. Gravity The sun’s gravity keeps planets, moons, comets and asteroids in our solar system. Each planet’s gravity keeps its moon or moons in orbit around the planet. The pull of gravity depends on the size of the objects and their distance from each other. Close objects pull harder than distant ones.

4. Moon Characteristics Atmosphere Moon diameter Surface appearance Distance from host planet Size compared to host planet Amount of reflected light (albedo)

5. Comparing Moons Moons of our Solar System are large and small, smooth and rough, near and far.

6. Moon Atmospheres MoonAtmosphere? Earth’s MoonNo PhobosNo IoYes! GanymedeNo TritonYes!

7. Jupiter’s Galilean moons Io has an atmosphere.

8. Moon Diameters MoonDiameter in Kilometers Earth’s Moon3,476.2 Phobos22.4 (average) Io3,643.2 Ganymede5,262.4 Triton2,706.8

9. Earth’s Moon and Neptune’s Triton to the same scale.

10. Largest moon in the solar system Ganymede - 8th largest world

11. Io 12th largest world

12. Surface Appearance MoonSurface Appearance Earth’s MoonRocky, cratered Mars’ PhobosRocky, smooth Jupiter’s IoRocky, volcanic Jupiter’s GanymedeCratered, icy, grooved TritonIcy, volcanic

13. Phobos, moon of Mars Phobos photographed from Mars

14. Io has active volcanoes.

15. Io’s Volcanoes Volcanic eruptions change Io’s surface

16. Ganymede Ganymede’s complex surface has grooves, craters, lava flows, mountains, and water ice.

17. Neptune's Triton from a distance of 530,000 kilometers (330,000 miles).

18. Distance from Moon to Planet MoonDistance from Moon to Planet in Kilometers Moon 384,467 Phobos 6,000 Io 421,600 Ganymede1,070,400 Triton 354,760

19. Neptune (top) and its moon, Triton (bottom)

20. Ratio of Moon Diameter to Planet Diameter, as % of Planet Diameter Moon Ratio Expressed as a % Earth’s Moon27.37% Mars’ Phobos0.33% Jupiter’s Io2.60% Jupiter’s Ganymede3.76% Triton5.52%

21. Jupiter seen below its moon, Io

22. Reflected Sunlight (Albedo) MoonPercent of Sunlight Reflected by Moon Surface (Albedo) Earth’s Moon7% (0.07) Phobos6% (0.06) Io61% (0.61) Ganymede42% (0.42) Triton7% (0.07)