ESA: Enceladus rains water onto Saturn

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ESA: Enceladus rains water onto Saturn

Post by bystander » Wed Jul 27, 2011 5:53 am

Enceladus rains water onto Saturn
ESA Space Science | 2011 July 26
ESA’s Herschel space observatory has shown that water expelled from the moon Enceladus forms a giant torus of water vapour around Saturn. The discovery solves a 14-year mystery by identifying the source of the water in Saturn’s upper atmosphere.

Herschel’s latest results mean that Enceladus is the only moon in the Solar System known to influence the chemical composition of its parent planet.

Enceladus expels around 250 kg of water vapour every second, through a collection of jets from the south polar region known as the Tiger Stripes because of their distinctive surface markings.

These crucial observations reveal that the water creates a doughnut-shaped torus of vapour surrounding the ringed planet.

The total width of the torus is more than 10 times the radius of Saturn, yet it is only about one Saturn radius thick. Enceladus orbits the planet at a distance of about four Saturn radii, replenishing the torus with its jets of water.

Despite its enormous size, it has escaped detection until now because water vapour is transparent to visible light but not at the infrared wavelengths Herschel was designed to see.

Saturn's atmosphere is known to contain traces of gaseous water in its deeper layers. A particular enigma has been the presence of water in its upper atmosphere.

First reported in 1997 by teams using ESA’s Infrared Space Observatory, the source of this water was unknown until now. Computer models of these latest Herschel observations show that about 3-5% of the water expelled by Enceladus ends up falling into Saturn.

“There is no analogy to this behaviour on Earth,” says Paul Hartogh, Max-Planck-Institut für Sonnensystemforschung, Katlenburg-Lindau, Germany, who led the collaboration on the analysis of these results.

“No significant quantities of water enter our atmosphere from space. This is unique to Saturn.”

Although most of the water from Enceladus is lost into space, freezes on the rings or perhaps falls onto Saturn’s other moons, the small fraction that does fall into the planet is sufficient to explain the water observed in its upper atmosphere.

It is also responsible for the production of additional oxygen-bearing compounds, such as carbon dioxide.

Ultimately, water in Saturn's upper atmosphere is transported to lower levels, where it will condense but the amounts are so tiny that the resulting clouds are not observable.

“Herschel has proved its worth again. These are observations that only Herschel can make,” says Göran Pilbratt, ESA Herschel Project Scientist.

“ESA’s Infrared Space Observatory found the water vapour in Saturn’s atmosphere. Then NASA/ESA’s Cassini/Huygens mission found the jets of Enceladus. Now Herschel has shown how to fit all these observations together.”

Direct detection of the Enceladus water torus with Herschel - P Hartogh et al
Geysers of Enceladus
CICLOPS Art Release | 2011 July 26

"The geysers of Enceladus are seen here up close. They are believed to be caused by Saturn's gravitational pull and the tidal flexure of Enceladus that results from it. This is enough to melt water inside Enceladus. Pressure in the liquid water chambers ejects fine water droplets to form the geysers found in the southern hemisphere, in an area known as "The South Polar Terrain." A small fraction of the ejected ice crystals is captured by Saturn's gravity and forms its E ring.

Enceladus is one of only two moons in the solar system where geysers have directly been detected.

From the surface of Enceladus, Saturn appears more than 50 times larger on the sky than our full moon does from Earth. In this illustration, along with some moons, the rings are visible as a line cutting through the center of Saturn."

Credit: Fahad Sulehria and Brian Christensen © 2011

Herschel confirms Enceladus as primary water supply for Saturn's atmosphere
ESA | Science & Technology | Herschel | 2011 July 26

Mystery Solved: Water on Saturn Comes From Icy Moon 'Rain'
Space.com | Denise Chow | 2011 July 26

Saturn weather forecast: rings, with light rain from Enceladus
Discover Blogs | Bad Astronomy | 2011 July 26

Enceladus Rains Water on Saturn
Universe Today | Nancy Akinson | 2011 July 26

Water from a Saturnian Moon Rains Down on the Ringed Planet
Scientific American | John Matson | 2011 July 26
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Re: ESA: Enceladus rains water onto Saturn

Post by neufer » Wed Jul 27, 2011 1:06 pm

bystander wrote:Enceladus rains water onto Saturn
ESA Space Science | 2011 July 26
Herschel’s latest results mean that Enceladus is the only moon in the Solar System known to influence the chemical composition of its parent planet. Enceladus expels around 250 kg of water vapour every second, through a collection of jets from the south polar region known as the Tiger Stripes because of their distinctive surface markings. These crucial observations reveal that the water creates a doughnut-shaped torus of vapour surrounding the ringed planet. The total width of the torus is more than 10 times the radius of Saturn, yet it is only about one Saturn radius thick. Enceladus orbits the planet at a distance of about four Saturn radii, replenishing the torus with its jets of water. Despite its enormous size, it has escaped detection until now because water vapour is transparent to visible light but not at the infrared wavelengths Herschel was designed to see. Saturn's atmosphere is known to contain traces of gaseous water in its deeper layers. A particular enigma has been the presence of water in its upper atmosphere.
The only moon?
http://en.wikipedia.org/wiki/Io_%28moon%29 wrote: Io plays a significant role in shaping the Jovian magnetic field. The magnetosphere of Jupiter sweeps up gases and dust from Io's thin atmosphere at a rate of 1 tonne per second. This material is mostly composed of ionized and atomic sulfur, oxygen and chlorine; atomic sodium and potassium; molecular sulfur dioxide and sulfur; and sodium chloride dust. These materials ultimately have their origin from Io's volcanic activity, but the material that escapes to Jupiter's magnetic field and into interplanetary space comes directly from Io's atmosphere. These materials, depending on their ionized state and composition, ultimately end up in various neutral (non-ionized) clouds and radiation belts in Jupiter's magnetosphere and, in some cases, are eventually ejected from the Jovian system.

Surrounding Io (up to a distance of 6 Io radii from the moon's surface) is a cloud of neutral sulfur, oxygen, sodium, and potassium atoms. These particles originate in Io's upper atmosphere but are excited from collisions with ions in the plasma torus (discussed below) and other processes into filling Io's Hill sphere, which is the region where the moon's gravity is predominant over Jupiter. Some of this material escapes Io's gravitational pull and goes into orbit around Jupiter. Over a 20-hour period, these particles spread out from Io to form a banana-shaped, neutral cloud that can reach as far as 6 Jovian radii from Io, either inside Io's orbit and ahead of the satellite or outside Io's orbit and behind the satellite. The collisional process that excites these particles also occasionally provides sodium ions in the plasma torus with an electron, removing those new "fast" neutrals from the torus. However, these particles still retain their velocity (70 km/s, compared to the 17 km/s orbital velocity at Io), leading these particles to be ejected in jets leading away from Io.

Io orbits within a belt of intense radiation known as the Io plasma torus. The plasma in this doughnut-shaped ring of ionized sulfur, oxygen, sodium, and chlorine originates when neutral atoms in the "cloud" surrounding Io are ionized and carried along by the Jovian magnetosphere. Unlike the particles in the neutral cloud, these particles co-rotate with Jupiter's magnetosphere, revolving around Jupiter at 74 km/s. Like the rest of Jupiter's magnetic field, the plasma torus is tilted with respect to Jupiter's equator (and Io's orbital plane), meaning Io is at times below and at other times above the core of the plasma torus. As noted above, these ions' higher velocity and energy levels are partly responsible for the removal of neutral atoms and molecules from Io's atmosphere and more extended neutral cloud. The torus is composed of three sections: an outer, "warm" torus that resides just outside Io's orbit; a vertically extended region known as the "ribbon", composed of the neutral source region and cooling plasma, located at around Io's distance from Jupiter; and an inner, "cold" torus, composed of particles that are slowly spiraling in toward Jupiter. After residing an average of 40 days in the torus, particles in the "warm" torus escape and are partially responsible for Jupiter's unusually large magnetosphere, their outward pressure inflating it from within. Particles from Io, detected as variations in magnetospheric plasma, have been detected far into the long magnetotail by New Horizons. To study similar variations within the plasma torus, researchers measure the ultraviolet-wavelength light it emits. While such variations have not been definitively linked to variations in Io's volcanic activity (the ultimate source for material in the plasma torus), this link has been established in the neutral sodium cloud.

During an encounter with Jupiter in 1992, the Ulysses spacecraft detected a stream of dust-sized particles being ejected from the Jupiter system. The dust in these discrete streams travel away from Jupiter at speeds upwards of several hundred kilometres per second, have an average size of 10 μm, and consist primarily of sodium chloride. Dust measurements by Galileo showed that these dust streams originate from Io, but the exact mechanism for how these form, whether from Io's volcanic activity or material removed from the surface, is unknown.

Jupiter's magnetic field lines, which Io crosses, couples Io's atmosphere and neutral cloud to Jupiter's polar upper atmosphere through the generation of an electric current known as the Io flux tube. This current produces an auroral glow in Jupiter's polar regions known as the Io footprint, as well as aurorae in Io's atmosphere. Particles from this auroral interaction act to darken the Jovian polar regions at visible wavelengths. The location of Io and its auroral footprint with respect to the Earth and Jupiter has a strong influence on Jovian radio emissions from our vantage point: when Io is visible, radio signals from Jupiter increase considerably. The Juno mission, planned for the next decade, should help to shed light on these processes. The Jovian magnetic field lines that do get past Io's ionosphere also induce an electric current, which in turn creates an induced magnetic field, within Io's interior. Io's induced magnetic field is thought to be generated within a partially molten, silicate magma ocean 50 kilometers beneath the moon's surface. Similar induced fields were found at the other Galilean satellites by Galileo, generated within liquid water oceans in the interiors of those moons.>>
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Re: ESA: Enceladus rains water onto Saturn

Post by Beyond » Wed Jul 27, 2011 1:53 pm

neufer wrote:The dust in these discrete streams travel away from Jupiter at speeds upwards of several hundred kilometres per second, have an average size of 10 μm, and consist primarily of sodium chloride.
So.... Jupiter is the 'salt' of the solar system. Who would have thought.
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Re: ESA: Enceladus rains water onto Saturn

Post by neufer » Wed Jul 27, 2011 2:09 pm

Beyond wrote:
neufer wrote:
The dust in these discrete streams travel away from Jupiter at speeds upwards of several hundred kilometres per second, have an average size of 10 μm, and consist primarily of sodium chloride.
So.... Jupiter is the 'salt' of the solar system. Who would have thought.
Jupiter is the 'IO-dized salt' of the solar system.
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Re: ESA: Enceladus rains water onto Saturn

Post by bystander » Wed Jul 27, 2011 2:13 pm

neufer wrote:Jupiter is the 'IO-dized salt' of the solar system.
So, is Saturn the Sea salt?
http://asterisk.apod.com/viewtopic.php?f=31&t=24569
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seasilt saltsick of Saturn's Enceladus

Post by neufer » Wed Jul 27, 2011 2:44 pm

bystander wrote:
neufer wrote:
Jupiter is the 'IO-dized salt' of the solar system.
So, is Saturn the Sea salt?
http://asterisk.apod.com/viewtopic.php?f=31&t=24569
Finnegans Wake (last page)

And it's old and old it's sad and old it's sad and weary
I go back to you, my cold father, my cold mad father,
my cold mad feary father, till the near sight of the
mere size of him, the moyles and moyles of it, moananoaning,
makes me seasilt saltsick and I rush, my only, into your arms
.
http://en.wikipedia.org/wiki/History_of_salt wrote:
<<There have been two main sources for salt: sea water and rock salt. Rock salt occurs in vast beds of sedimentary evaporite minerals that result from the drying up of enclosed lakes, playas, and seas. Salt beds may be up to 350 m thick and underlie broad areas. In the United States and Canada extensive underground beds extend from the Appalachian basin of western New York through parts of Ontario and under much of the Michigan basin. Other deposits are in Texas, Ohio, Kansas, New Mexico, Nova Scotia, and Saskatchewan. In the United Kingdom underground beds are found in Cheshire and around Droitwich. Salzburg, Austria was named "the city of salt" for its mines. Tuzla in Bosnia and Herzegovina were named "place of salt" by Turks.

Salt's ability to preserve food was a foundation of civilization. It eliminated the dependence on the seasonal availability of food and it allowed travel over long distances. However, salt was difficult to obtain, and so it was a highly valued trade item. Many salt roads, such as the via Salaria in Italy, had been established by the Bronze age. Aside from being a contributing factor in the development of civilization, salt was also used in the military practice of salting the earth by various peoples, beginning with the Assyrians.

It is commonly believed that Roman soldiers were at certain times paid with salt. (They say the soldiers who did their job well were "worth their salt.)" This, however, is debatable: 'salary' derives from the Latin word salārium, possibly referring to money given to soldiers so they could buy salt. The Roman Republic and Empire controlled the price of salt, increasing it to raise money for wars, or lowering it to be sure that the poorest citizens could easily afford this important part of the diet.

Already in the early years of the Roman Republic, with the growth of the city of Rome, roads were built to make transportation of salt to the capital city easier. An example was the Via Salaria (originally a Sabine trail), leading from Rome to the Adriatic Sea. The Adriatic Sea, having a higher salinity due to its shallow depth, had more productive solar ponds compared with those of the Tyrrhenian Sea, much closer to Rome.

During the late Roman Empire and throughout the Middle Ages salt was a precious commodity carried along the salt roads into the heartland of the Germanic tribes. Caravans consisting of as many as forty thousand camels traversed four hundred miles of the Sahara bearing salt to inland markets in the Sahel, sometimes trading salt for slaves: Timbuktu was a huge salt and slave market.

In the Old Testament, Mosaic law called for salt to be added to all burnt animal sacrifices (Lev. 2:13). The Book of Ezra (550 BC to 450 BC) associated accepting salt from a person with being in that person's service. In Ezra 4:14, the servants of Artaxerxes I of Persia explain their loyalty to the King. When translated, it is either stated literally as "because we have eaten the salt of the palace" or more figuratively as "because we have maintenance from the king". Salt is used as a metaphor in the Bible. In the New Testament, Matthew 5:13, Jesus said, "You are the salt of the earth". He added that if the salt loses its flavor, it is good for nothing but to be trampled. Jesus said this in order to show his disciples how valuable they were and this saying is commonly used today to describe someone who is of particular value to society. In addition, the preservative quality of salt is in view here to show how the disciples were called to preserve the society and the world around them from moral decay. On another occasion, according to the Gospels, Jesus commanded his followers to "have salt within them".

Salt has played a prominent role in determining the power and location of the world's great cities. Liverpool rose from just a small English port to become the prime exporting port for the salt dug in the great Cheshire salt mines and thus became the entrepôt for much of the world's salt in the 19th century. Wich and wych are names associated (but not exclusively) with brine springs or wells in England. Originally derived from the Latin vicus, meaning place, by the 11th century use of the 'wich' suffix in placenames was associated with places with a specialised function including that of salt production. Several English places carry the suffix and are historically related to salt, including the four Cheshire 'wiches' of Middlewich, Nantwich, Northwich and Leftwich (a small village south of Northwich), and Droitwich in Worcestershire. Middlewich, Nantwich, Northwich and Droitwich are known as the Domesday Wiches due to their mention in the Domesday Book, "an indication of the significance of the salt-working towns in the economy of the region, and indeed of the country".

Salt created and destroyed empires. The salt mines of Poland led to a vast kingdom in the 16th century, only to be destroyed when Germans brought in sea salt (to most of the world, considered superior to rock salt). Venice fought and won a war with Genoa over salt. However, Genoese Christopher Columbus and Giovanni Caboto would later destroy the Mediterranean trade by introducing the New World to the market.

Cities, states and duchies along the salt roads exacted heavy duties and taxes for the salt passing through their territories. This practice even caused the formation of cities, such as the city of Munich in 1158, when the then Duke of Bavaria, Henry the Lion, decided that the bishops of Freising no longer needed their salt revenue.

The gabelle—a hated French salt tax—was enacted in 1286 and maintained until 1790. Because of the gabelles, common salt was of such a high value that it caused mass population shifts and exodus, attracted invaders and caused wars.

In American history, salt has been a major factor in outcome of wars. In the Revolutionary War, the British used Loyalists to intercept Rebel salt shipments and interfere with their ability to preserve food. During the War of 1812, salt brine was used to pay soldiers in the field, as the government was too poor to pay them with money. Before Lewis and Clark set out for the Louisiana Territory, President Jefferson in his address to Congress mentioned a mountain of salt supposed to lie near the Missouri River, which would have been of immense value, as a reason for their expedition. (By 1810, new discoveries along the Kanawha and Sandy Rivers had greatly reduced the value of salt.)

During more modern times, it became more profitable to sell salted food than pure salt. Thus sources of food to salt went hand in hand with salt making. The British controlled saltworks in the Bahamas as well as North American cod fisheries. This may have added to their economic clout during their 19th century imperial expansion period. The search for oil in the late 19th and early 20th centuries used the technology and methods pioneered by salt miners, even to the degree that they looked for oil where salt domes were located.>>
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Saturn's Moon Enceladus Spreads Its Influence

Post by bystander » Wed Sep 21, 2011 6:06 pm

Saturn's Moon Enceladus Spreads Its Influence
NASA JPL-Caltech | Cassini Solstice Mission | 2011 Sept 21
Chalk up one more feat for Saturn’s intriguing moon Enceladus. The small, dynamic moon spews out dramatic plumes of water vapor and ice -- first seen by NASA’s Cassini spacecraft in 2005. It possesses simple organic particles and may house liquid water beneath its surface. Its geyser-like jets create a gigantic halo of ice, dust and gas around Enceladus that helps feed Saturn’s E ring. Now, thanks again to those icy jets, Enceladus is the only moon in our solar system known to influence substantially the chemical composition of its parent planet.

In June, the European Space Agency announced that its Herschel Space Observatory, which has important NASA contributions, had found a huge donut-shaped cloud, or torus, of water vapor created by Enceladus encircling Saturn. The torus is more than 373,000 miles (600,000 kilometers) across and about 37,000 miles (60,000 kilometers) thick. It appears to be the source of water in Saturn’s upper atmosphere.

Though it is enormous, the cloud had not been seen before because water vapor is transparent at most visible wavelengths of light. But Herschel could see the cloud with its infrared detectors. "Herschel is providing dramatic new information about everything from planets in our own solar system to galaxies billions of light-years away,” said Paul Goldsmith, the NASA Herschel project scientist at NASA's Jet Propulsion Laboratory, Pasadena, Calif.

The discovery of the torus around Saturn did not come as a complete surprise. NASA’s Voyager and Hubble missions had given scientists hints of the existence of water-bearing clouds around Saturn. Then in 1997, the European Space Agency’s Infrared Space Observatory confirmed the presence of water in Saturn’s upper atmosphere. NASA’s Submillimeter Wave Astronomy Satellite also observed water emission from Saturn at far-infrared wavelengths in 1999.

While a small amount of gaseous water is locked in the warm, lower layers of Saturn’s atmosphere, it can’t rise to the colder, higher levels. To get to the upper atmosphere, water molecules must be entering Saturn’s atmosphere from somewhere in space. But from where and how? Those were mysteries until now.

Build the model and the data will come.

The answer came by combining Herschel’s observations of the giant cloud of water vapor created by Enceladus’ plumes with computer models that researchers had already been developing to describe the behavior of water molecules in clouds around Saturn.

One of these researchers is Tim Cassidy, a recent post-doctoral researcher at JPL who is now at the University of Colorado’s Laboratory for Atmospheric and Space Physics, Boulder. “What’s amazing is that the model,” said Cassidy, “which is one iteration in a long line of cloud models, was built without knowledge of the observation. Those of us in this small modeling community were using data from Cassini, Voyager and the Hubble telescope, along with established physics. We weren’t expecting such detailed ‘images’ of the torus, and the match between model and data was a wonderful surprise.”

The results show that, though most of the water in the torus is lost to space, some of the water molecules fall and freeze on Saturn’s rings, while a small amount -- about 3 to 5 percent -- gets through the rings to Saturn’s atmosphere. This is just enough to account for the water that has been observed there.

Herschel’s measurements combined with the cloud models also provided new information about the rate at which water vapor is erupting out of the dark fractures, known as “tiger stripes,” on Enceladus’ southern polar region. Previous measurements by the Ultraviolet Imaging Spectrograph (UVIS) instrument aboard the Cassini spacecraft showed that every second the moon is ejecting about 440 pounds (200 kilograms) of water vapor.

“With the Herschel measurements of the torus from 2009 and 2010 and our cloud model, we were able to calculate a source rate for water vapor coming from Enceladus,” said Cassidy. “It agrees very closely with the UVIS finding, which used a completely different method.”

“We can see the water leaving Enceladus and we can detect the end product -- atomic oxygen -- in the Saturn system,” said Cassini UVIS science team member Candy Hansen, of the Planetary Science Institute, Tucson, Ariz. “It’s very nice with Herschel to track where it goes in the meantime.”

While a small fraction of the water molecules inside the torus end up in Saturn’s atmosphere, most are broken down into separate atoms of hydrogen and oxygen. “When water hangs out in the torus, it is subject to the processes that dissociate water molecules,” said Hansen, “first to hydrogen and hydroxide, and then the hydroxide dissociates into hydrogen and atomic oxygen.” This oxygen is dispersed through the Saturn system. “Cassini discovered atomic oxygen on its approach to Saturn, before it went into orbit insertion. At the time, no one knew where it was coming from. Now we do.”

“The profound effect this little moon Enceladus has on Saturn and its environment is astonishing,” said Hansen
Know the quiet place within your heart and touch the rainbow of possibility; be
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