Exploratour - Evolution of the Solar System
This story explains the forming planets, but what of their moons? There are three theories about how moons came to be in place:
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- 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 is not round. That is, a moon may be shaped like a rock. 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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