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National Aeronautics and Space AdministrationEarth’s MoonEarthCallistoIoEuropaGanymedeEnceladusTritonDioneIapetusTethysTitaniaTitanMimasRheaCharonOberonMirandaMoons of the Solar System
Moons — also called satellites — come in many shapes, sizes,and types. They are generally solid bodies, and few have atmo-spheres. Most of the planetary moons probably formed from thediscs of gas and dust circulating around planets in the early solarsystem. Some moons are large enough for their gravity to causethem to be spherical, while smaller moons appear to be cap-tured asteroids, not related to the formation and evolution of thebody they orbit. The International Astronomical Union lists 146moons orbiting planets in our solar system — this number doesnot include the moons awaiting official recognition and naming,the eight moons of the dwarf planets, nor the tiny satellites thatorbit some asteroids and other celestial objects.Of the terrestrial (rocky) planets of the inner solar system, neitherMercury nor Venus has any moons at all, Earth has one, andMars has its two small moons. In the outer solar system, the gasgiants (Jupiter, Saturn) and the ice giants (Uranus and Neptune)have numerous moons. As these huge planets grew in the earlysolar system, they were able to capture objects with their largegravitational fields.Earth’s Moon probably formed when a large body about the sizeof Mars collided with Earth, ejecting material from our planet intoorbit. This material accumulated to form the Moon approximately
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Term
Fall
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Tags
Solar System, Planet, Pluto, Dwarf planet, Natural satellite

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