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 Ο δορυφόρος του Κρόνου Εγκέλαδος : Saturn's moon Enceladus

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ΔημοσίευσηΘέμα: Απ: Ο δορυφόρος του Κρόνου Εγκέλαδος : Saturn's moon Enceladus   18.02.10 11:45

Zooming in on Enceladus - Mosaic



As it swooped past the south pole of Saturn's moon Enceladus on July 14, 2005 , Cassini acquired high resolution views of this puzzling ice world. From afar, Enceladus exhibits a bizarre mixture of softened craters and complex, fractured terrains.

This large mosaic of 21 narrow-angle camera images have been arranged to provide a full-disk view of the anti-Saturn hemisphere on Enceladus. This mosaic is a false-color view that includes images taken at wavelengths from the ultraviolet to the infrared portion of the spectrum, and is similar to another, lower resolution false-color view obtained during the flyby (see NASA's Planetary Photojournal -- PIA06249). In false-color, many long fractures on Enceladus exhibit a pronounced difference in color (represented here in blue) from the surrounding terrain.

A leading explanation for the difference in color is that the walls of the fractures expose outcrops of coarse-grained ice that are free of the powdery surface materials that mantle flat-lying surfaces.

The original images in the false-color mosaic range in resolution from 350 to 67 meters (1,148 to 220 feet) per pixel and were taken at distances ranging from 61,300 to 11,100 kilometers (38,090 to 6,897 miles) from Enceladus.

Credit: NASA/JPL/Space Science Institute


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ΔημοσίευσηΘέμα: Απ: Ο δορυφόρος του Κρόνου Εγκέλαδος : Saturn's moon Enceladus   18.02.10 11:47

Enceladus and the Search for Water



Based on data from Cassini spacecraft instruments, researchers are now arguing that liquid water reservoirs exist only tens of meters below the surface of Saturn's small (500 kilometer diameter) but active moon Enceladus.

The exciting new results center around towering jets and plumes of material erupting from the moon's surface.
The plumes originate in the long tiger stripe fractures of the south polar region pictured here.

Detailed models suport conclusions that the plumes arise from near-surface pockets of liquid water at temperatures of 273 kelvins (0 degrees Celsius), even though Enceladus has a surface temperature of about 73 kelvins (-200 degrees Celsius).

Clearly an important step in the search for water and the potential for the origin of life beyond planet Earth, such near-surface reservoirs of water would be far more accessible than, for example, the internal ocean detected on the Jovian moon Europa.

Credit: Cassini Imaging Team, SSI, JPL, ESA, NASA


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ΔημοσίευσηΘέμα: Απ: Ο δορυφόρος του Κρόνου Εγκέλαδος : Saturn's moon Enceladus   18.02.10 11:54

Labtayt Sulci on Saturn's Enceladus



Do some surface features on Enceladus roll like a conveyor belt? A leading interpretation of recent images taken of Saturn's most explosive moon indicate that they do.

This form of asymmetric tectonic activity, very unusual on Earth, likely holds clues to the internal structure of Enceladus, which may contain subsurface seas where life might be able to develop.

Pictured above is a composite of 28 images taken by the robotic Cassini spacecraft in October just after swooping by the ice-spewing orb. Inspection of these images show clear tectonic displacements where large portions of the surface all appear to move all in one direction.

Near the top of the image appears one of the most prominent tectonic divides: Labtayt Sulci, a canyon about one kilometer deep.

Credit: Cassini Imaging Team, SSI, JPL, ESA, NASA


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ΔημοσίευσηΘέμα: Απ: Ο δορυφόρος του Κρόνου Εγκέλαδος : Saturn's moon Enceladus   18.02.10 12:00

Fresh Tiger Stripes on Saturn's Enceladus



Do underground oceans vent through the tiger stripes on Saturn's moon Enceladus?
Long features dubbed tiger stripes are known to be spewing ice from the moon's icy interior into space, creating a cloud of fine ice particles over the moon's South Pole and creating Saturn's mysterious E-ring.
Evidence for this has come from the robot Cassini spacecraft now orbiting Saturn.

Pictured above, a high resolution image of Enceladus is shown from a close flyby.
The unusual surface features dubbed tiger stripes are visible in false-color blue.

Why Enceladus is active remains a mystery, as the neighboring moon Mimas, approximately the same size, appears quite dead.
Most recently, an analysis of dust captured by Cassini found evidence for sodium as expected in a deep salty ocean.

Conversely however, recent Earth-based observations of ice ejected by Enceladus into Saturn's E-Ring showed no evidence of the expected sodium.
Such research is particularly interesting since such an ocean would be a candidate to contain life.

Credit: Cassini Imaging Team, SSI, JPL, ESA, NASA


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ΔημοσίευσηΘέμα: Απ: Ο δορυφόρος του Κρόνου Εγκέλαδος : Saturn's moon Enceladus   18.02.10 12:01

Enceladus Ice Volcanos



In this stunning Saturnian vista - one in a series of artist's visions of volcanos on alien worlds - icy geysers erupt along narrow fractures in inner moon Enceladus.

The majestic plumes were actually discovered by instruments on the Cassini Spacecraft during close encounters with bright and shiny Enceladus last year.
Researchers now suspect the plumes originate from near-surface pockets of liquid water with temperatures near 273 kelvins (0 degrees C) - hot when compared to the distant moon's surface temperature of 73 kelvins (-200 degrees C).

A dramatic sign that tiny, 500km-diameter Enceladus is surprisingly active, these ice volcanos hold out another potential site in the search for water and origin of life beyond planet Earth.

Enceladus' ice volcanos also likely produce Saturn's faint but extended E ring.

Illustration Credit & Copyright: Michael Carroll




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ΔημοσίευσηΘέμα: Απ: Ο δορυφόρος του Κρόνου Εγκέλαδος : Saturn's moon Enceladus   18.02.10 13:57

© Brian Smallwood 2010



One of the innermost moons of Saturn, Enceladus is believed to have ice geysers which may be responsible for sustaining Saturn's E ring's supply of micrometer-sized particles.

At some depth beneath the surface, the temperatures are possibly hot enough for water to become liquid, which then, under pressure, escapes to the surface in a geyser.

The surface of Enceladus is also cross-cut by numerous faults.


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ΔημοσίευσηΘέμα: Απ: Ο δορυφόρος του Κρόνου Εγκέλαδος : Saturn's moon Enceladus   18.02.10 16:43

Saturn from the surface of Enceladus



This is how Saturn may appear from the icy surface of Enceladus, one of Saturn's eight major satellites. At a distance of 148 thousand miles, Saturn would subtend an angle of 29º in Enceladus' sky, about the same width as 58 Earth moon's lined up side-by-side.

While the surface of Enceladus is as reflective as new fallen snow, it would probably appear leaden about an hour before sunrise with a crescent Saturn as the only source of illumination. Like all of Saturn's major satellites, Enceladus always keeps the same side facing its host planet. From the perspective of a stationary observer on Enceladus, Saturn would always appear in the same position in the sky, cycling through its phases in about one-and-half Earth days.

This image also illustrates a phenomenon only recently discovered by NASA's Cassini probe: sunlight reflecting off of Saturn's rings casts a faint glow onto the cloud tops of Saturn's night side. The illumination is about the same as three of Earth's full moon combined.

Special thanks to Björn Jónsson for his Saturn clouds map and rings data.

Copyright © Walter Myers


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ΔημοσίευσηΘέμα: Απ: Ο δορυφόρος του Κρόνου Εγκέλαδος : Saturn's moon Enceladus   18.02.10 17:04

Water geyser on Enceladus



Liquid water reaches the surface of Enceladus' south pole and drives a massive plume of ice crystals into the sky. The combination of Enceladus' low surface gravity and the geyser's force accelerate the crystals to escape velocity, where sunlight breaks the water molecules down into their constituent atoms of hydrogen and oxygen. Saturn itself appears low on the horizon due to the proximity to Enceladus' pole.

The small object immediately to Saturn's left is another icy moon named Mimas. Somewhat smaller than Enceladus and closer to Saturn, Mimas sprints around Saturn in slightly less than one Earth day.

In March 2006 NASA's Cassini probe revealed evidence of water-driven geysers on the surface of Enceladus. At first glance Enceladus doesn't seem to be a likely host for liquid water as the surface is extremely cold, about -330° F. However, tidal forces from Saturn's massive gravity alternately pull and push on Enceladus' interior, creating enough heat to melt the water ice immediately beneath the surface. This water is believed to periodically break through the surface as geysers, similar to Yellowstone's Old Faithful.

There are only three other places in the Solar System where this kind of geologic activity is known to exist: our own Earth, Jupiter's satellite Io, and Neptune's satellite Triton. What makes Enceladus especially interesting is that this the most compelling evidence yet for liquid water--a requirement for life--on any world beyond the Earth.

Special thanks to Björn Jónsson for his Saturn clouds map.

Copyright © Walter Myers


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ΔημοσίευσηΘέμα: Απ: Ο δορυφόρος του Κρόνου Εγκέλαδος : Saturn's moon Enceladus   18.02.10 17:08

A geyser on Enceladus with Saturn & Titan



Liquid water breaches the floor of a crevasse and is propelled into the frigid vacuum of space as a jet of ice crystals.

The perspective is from Enceladus' south pole. Saturn rests low on the horizon, its rings seen edge-on as a thin line.

Saturn's largest satellite Titan appears as an orange dot on the right just above the horizon.

Special thanks to Björn Jónsson for his Saturn clouds map.

Copyright © Walter Myers




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ΔημοσίευσηΘέμα: Απ: Ο δορυφόρος του Κρόνου Εγκέλαδος : Saturn's moon Enceladus   18.02.10 20:58

Fountains of Enceladus



Enceladus is one of Saturn’s inner most moons and is composed primarily of fresh clean water ice.

Its southern polar region vents plumes of ice particles, water vapor and trace organic compounds out into space, a process called ‘cryovolcanism’.

The ejecta from the icy volcanoes feed Saturn’s tenuous E Ring as it orbits the planet.
This is an indication that the moon is still geologically active, a process supported through tidal friction with Saturn.

Christian Joore


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ΔημοσίευσηΘέμα: Απ: Ο δορυφόρος του Κρόνου Εγκέλαδος : Saturn's moon Enceladus   18.02.10 21:00

Enceladus, Earth, and Earth's Moon Compared



Enceladus is considered one of Saturn's major satellites, however it is quite diminutive when compared with the Earth and Earth's Moon.

With a radius of only 160 miles, Enceladus could rest in the Gulf of Mexico with plenty of room to spare.

Enceladus is one of the brightest objects in the Solar System.

Where Earth's Moon has a surface reflectively about the same as charcoal, Enceladus is covered in water ice that reflects sunlight like freshly fallen snow.

Copyright © Walter Myers


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Ο δορυφόρος του Κρόνου Εγκέλαδος : Saturn's moon Enceladus
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