Preview: Saturn's Mysterious Moons
- uploaded: Apr 9, 2011
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Preview: Saturn's Mysterious Moons
Uploaded by SpaceRip on Apr 8, 2011
This video previews an expanded-updated 1080p version of our popular Cosmic Journeys episode. Some 900 million miles from the Sun, orbiting the planet Saturn, lies a mysterious world. Enceladus is enveloped in ice. Because nearly all of the sunlight that manages to hit its surface is reflected back into space, it's one of the brightest objects in the solar system.
At its equator, the temperature is --315 degrees Fahrenheit. But, at the poles, the temperature is at least 15 degrees warmer... and as much as 65 degrees warmer in grooves that stretch across the south like tiger stripes.
In 2005, the Cassini spacecraft spotted a complex plume of water vapor shooting out into space from several locations near the south pole. That may mean that Enceladus harbors a remarkable secret below its frigid surface:
A liquid ocean... and maybe... some forms of life. This discovery was the culmination of a search that began over three decades ago. Back in 1979, the outer planets of the solar system lined up in such a way that mission planners were able to dispatch the Voyager spacecraft to fly past each of them.
The two Voyagers sent back tens of thousands of images... of planetary realms more diverse than anyone had imagined. These long-distance marathon flyers - both now headed out towards interstellar space - made discoveries about the planetary chemistry that make these gas giants appear to us as gigantic works of abstract art.
The Voyagers disclosed new details about their magnetic fields, atmospheres, ring systems, and even the nature of their inner cores. Voyager turned up some surprising new mysteries too: a huge dark spot -- a storm in fact - on Neptune. They found that Uranus is tipped 90 degrees to one side. That Saturn is less dense than water; if you had a bathtub big enough, Saturn would float!
And that you'd need the mass of three Saturns to make just one Jupiter! But what really knocked the scientists' socks off were the moons that orbit these gas giants. All of them have been pummeled over the millennia by wayward asteroids and comets.
But a few appear to also be sculpted by forces below their icy surfaces. Neptune's largest moon Triton has few craters. It's marked with circular depressions bounded by rugged ridges that may mean the icy surface is collapsing. There are also grooves and folds in the land that stretch for dozens of miles, a sign of fracturing and deforming.
Triton has geysers too. But these are not spurts of water. On frigid Triton -- so far from the Sun -- the liquid that spouts some five miles above the planet is nitrogen. No one yet knows exactly what drives them. Tiny Miranda... one of 27 known moons that orbit Uranus... wears a jumbled skin that's been shaped and reshaped. Most likely, its outer crust is slipping and sliding on a molten core.
The moon called Io -- orbiting perilously close to giant Jupiter is literally turning itself inside out! Rivers of sulfurous lava roll down from open craters that are constantly erupting. What was causing these tiny moons to generate so much energy from within? The answer may well be here... on Jupiter's Europa -- just slightly smaller than Earth's Moon.
Voyager saw no signs of volcanic activity, but --but instead documented a complex network of criss-crossing grooves and ridges. In the 1990s, the Galileo spacecraft was sent back to get a closer look at Europa and its sister moons. .
It found that Europa's surface is a crazy quilt of fractured plates, cliff faces and gullies... amid long grooves like a network of superhighways. How did it get like this?
Well, as it orbits around Jupiter in a nearly circular ellipse, the massive planet's gravity constantly tugs at Europa's rocky core. The friction of rock rubbing on rock causes that core to heat up. That heat rises up through an ocean of liquid water... then cracks and spreads the icy surface in a thousand different ways.
Callisto and Ganymede also show such features... suggesting they have -- or perhaps once had --liquid oceans below their surfaces too! Crossing outward to the Saturn system, Voyager's images from the late 1970's showed that the moon Enceladus had a similar surface...
The same was presumed of Saturn's by far largest moon, Titan... enshrouded in heavy clouds. So when the Cassini spacecraft arrived in 2004 to scrutinize the kingdom of Saturn, it came ready to answer a range of burning questions.
Can such moons really have liquid oceans beneath their surfaces... and do those oceans have the ability to cook up and then support life?