- 1.) moons came out of their parent planet
- 2.) moons were debris which were captured by their parent planet
- 3.) that a planet and its moon(s) formed together out of the primordial nebula, as shown in the picture on the next page
Many of the moons surrounding other planets are really captured asteroids. One sign that a moon is really a captured asteriod is that it has a non-spherical shape, that is, an angular shape like a rock and not rounded like a planet. Moons such as these are the two moons of Mars; Phobos and Diemos. Another sign that a moon may be captured is if it orbits in a direction opposite to that of the mother planet. An example of a moon of this kind is Neptune's moon Neried.
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