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Planetary Ponderings - Part 6 of 9: Saturn

by Perry Pezzolanella, MVAS

Saturn is the most beautiful planet to ponder; the simple thought of it conjures up vivid images of beautiful rings. Saturn is the most inspiring planet to view through any telescope regardless of its size.

  • Saturn is the sixth planet from the Sun with an average distance of 885 million miles. It can get as close as 835 million miles or as far as 934 million miles.

  • Saturn is the second largest planet with an equatorial diameter of 73,966 miles and has 48 known moons.

  • A day on Saturn is the second shortest of all planets lasting only 10 hours and 39 minutes, but a year lasts 29.46 Earth years.

  • Saturn's rapid rotation flattens the planet at the poles so that its polar diameter is 66,774 miles, or about 7200 miles less than at the equator.

  • Saturn can come within 740 million miles of Earth, appear as large as 20.6 arc-seconds, and shine as bright as magnitude -0.5.

  • Because Saturn orbits farther from the Sun than Earth, it can never appear less than 99% lit.

  • Saturn is a huge ball of mainly gas surrounding a liquid hydrogen mantle and a small rocky core, The atmosphere is thousands of miles deep and is 92% hydrogen, 8% helium, and less than 1% of all other trace elements.

  • The huge amount of hydrogen makes Saturn so light that it would float in a tub of water.

  • Saturn is completely cloudy with sulfides giving it a butterscotch hue, but an ammonia haze obscures the finer details.

  • Saturn's cloud tops are as cold as -280 F, but heat from within stirs up huge thunderstorms.

  • The Great White Spots of 1933 and 1990 are huge thunderstorms larger than Earth towering high above the haze. In the intense cold, these clouds may be enormous, Earth-swallowing ammonia blizzards!

  • There is no surface on Saturn. The atmosphere thickens into a slush with increasing depth, pressure, and heat, and eventually into metallic hydrogen like Jupiter.

  • The molten iron core creates a powerful magnetic field (though much weaker than Jupiter's), and aurora, but at least spacecraft can tolerate the radiation better than at Jupiter.

  • Saturn is surrounded by thousands of rings that are created by tidal forces.

  • The rings are made up of millions of pieces of dirty ice ranging in size from a grain of sand to icebergs as large as a small house.

  • The rings are over 200,000 miles across, but are less than 100 feet thick.

  • The rings are so thin that they appear invisible every 15 to 17 years when they become edge-on as seen from Earth.

  • Saturn has strange braided rings and spokes that levitate above and below the main ring plane.

  • Saturn has nine major moons: Mimas, Enceladus, Tethys, Dione, Rhea, Titan, Hyperion, Iapetus, and Phoebe.

  • Mimas looks like Darth Vader's Death Star with a crater so huge that it nearly shattered the moon.

  • Enceladus is the brightest moon in the Solar System reflecting nearly 90% of the Sun's light and is emitting particles of water ice through enormous fissures.

  • Tethys has a huge canyon that stretches nearly three quarters of the way around the moon and many softened craters that hint at a history of glacial flows.

  • Dione has several bright wispy streaks on its surface that are long ridges of reflective water ice.

  • Rhea has so many craters that new ones can only form by destroying old ones and yet only a select few have frost deposits within them.

  • Hyperion appears like a battered hockey puck and wobbles badly, hinting at a possibly recent catastrophic collision that shattered the moon.

  • Iapetus has one side as bright as snow and the other as dark as tar with a huge mountain range straddling the equator. Is the bright material splashed onto Iapetus or did the dark material ooze up from within?

  • Phoebe is a dark cratered moon, possibly a captured asteroid that rotates once every nine hours unlike the other moons that keeps the same face towards Saturn.

  • Titan is completely covered with orange organic smog that is 1.6 times thicker than Earth's atmosphere. It is composed mainly of nitrogen with some methane and other organic compounds.

  • Titan may have seas or lakes of liquid ethane. Organic compounds may rain or snow from the gloomy sky above. Huygens has revealed numerous drainage channels, deltas, and dark lakebeds along with very moist soil indicating it recently rained.

  • Temperatures are as cold as -290 F on the surface of Titan and daylight is no brighter than a moonlit night on Earth.

The arrival of Cassini last year along with the stunning discoveries of Huygens give so much to ponder regarding Saturn, its rings, Titan, and its many moons, that a book could easily be dedicated to this most beautiful gem of the Solar System. The best may be yet to come.