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-----------------------------1901 - Moons around the planets.
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- Review #1900 discussed the moons in our Solar System and the forces that keep them in orbit. This Review #1901 discusses each of the planets with their respective moons that are all outside the Roche Limit.
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- There are only 3 natural moons orbiting the 4 inner planets. Earth has one and Mars has two. Our Moon was created by an enormous collision that the Earth had with a Mars-size object some 4.6 billion years ago. Mars on the other hand captured its two moons as orbiting asteroids, Phobos and Deimos.
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- Like our moon, Phobos and Deimos are tidally locked to Mars, always showing the same face as they orbit. These two captured asteroids were once part of the Asteroid Belt. Phobos is only 14 miles in diameter and Deimos only 7.8 miles in diameter. Phobos’ orbit is at 5,287 miles. Deimos farther out at 14,577 miles taking 30.35 hours to complete a single orbit.
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- These are the inner Rocky Planet moons. Beyond the Asteroid Belt things get much different for the four gaseous planets:
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- Jupiter has 67 known moons, but, if you count smaller “ moonlets” the count is over 200 satellites. The 4 largest moons can be seen with binoculars under good conditions. They were first discovered in 1610 by Galileo using his first telescope.
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----------------- Io is the most volcanically active.
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----------------- Europa likely has a massive subsurface ocean.
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----------------- Ganymede is the largest moon in our Solar System. Even larger than the planet Mercury.
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----------------- Callisto is also thought to have a subsurface ocean.
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- Jupiter’s inner smaller moons have diameters less than 124 miles. These orbit within 124,000 miles of the surface. The outer moons are irregular satellites with more eccentric orbits captured by Jupiter’s intense gravity.
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- Saturn has at least 150 moons and moonlets. 53 or Saturn’s moons have names. 34 of these are less than 6.2 miles in diameter. The inner large moons are Mimas, Enceladus, Tethys, and Dions. These moons have rocky cores but are composed of mostly water ice.
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- Titan is Saturn’s largest moon at 3,200 miles diameter. Titan is large enough to have its own atmosphere, which is primarily nitrogen. There are recordings of hydrocarbons and methane ice crystals in this nitrogen atmosphere. There are liquid methane-ethane lakes at the poles.
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- Uranus has 27 known moons. Titania is the largest at 981 miles diameter. Miranda at 293 miles. Miranda is primarily ammonia and carbon dioxide ice.
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- Neptune has 14 known moons, Triton is the larges at 1,678 miles diameter. It orbits 220,427 miles form Neptune, about the same distance our Moon orbits Earth.
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- Past Neptune are the Dwarf Planets, Pluto’s orbit and beyond. Pluto has the large moon Charon first discovered in 1978. The two smaller moons Nix and Hydra discovered in 2005. The 5th moon Styx discovered in 2012.
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- Charon is so large that Pluto and Charon orbit each other, and are tidally locked together. Ammonia hydrates and water crystals on the surface of Charon suggest active cryo-geysers. Pluto may have a subsurface ocean as well.
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- Other Dwarf Planets include Eris, Haumea, Makemake, and Sedna. Haumea has 2 known moons. Eris has one known moon.
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- More satellites will surely be found in the future. Ganymede is by far the largest, even larger than the planet Mercury. On the smaller size satellites have been found orbiting Jupiter that are only 0.6 miles diameter.
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- Other reviews available upon request on this subject:
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- Review # 1899 - Moon - far-side and rainbows. Also lists 8 more reviews about the moon
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----- 707-536-3272 ---------------- Wednesday, August 24, 2016 -----
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