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Cassini Finds an Atmosphere on Saturn's Moon Enceladus




The Cassini spacecraft's two close flybys of Saturn's icy moon Enceladus have revealed that the moon has a significant atmosphere. Scientists, using Cassini's magnetometer instrument for their studies, say the source may be volcanism, geysers, or gases escaping from the surface or the interior.

When Cassini had its first encounter with Enceladus on Feb. 17 at an altitude of 1,167 kilometers (725 miles), the magnetometer instrument saw a striking signature in the magnetic field. On March 9, Cassini approached to within 500 kilometers (310 miles) of Enceladus' surface and obtained additional evidence.

The observations showed a bending of the magnetic field, with the magnetospheric plasma being slowed and deflected by the moon. In addition, magnetic field oscillations were observed. These are caused when electrically charged (or ionized) molecules interact with the magnetic field by spiraling around the field line. This interaction creates characteristic oscillations in the magnetic field at frequencies that can be used to identify the molecule. The observations from the Enceladus flybys are believed to be due to ionized water vapor.

"These new results from Cassini may be the first evidence of gases originating either from the surface or possibly from the interior of Enceladus," said Dr. Michele Dougherty, principal investigator for the Cassini magnetometer and professor at Imperial College in London. In 1981, NASA's Voyager spacecraft flew by Enceladus at a distance of 90,000 kilometers (56,000 miles) without detecting an atmosphere. It's possible detection was beyond Voyager's capabilities, or something may have changed since that flyby.

This is the first time since Cassini arrived in orbit around Saturn last summer that an atmosphere has been detected around a moon of Saturn, other than its largest moon, Titan. Enceladus is a relatively small moon. The amount of gravity it exerts is not enough to hold an atmosphere very long. Therefore, at Enceladus, a strong continuous source is required to maintain the atmosphere.

The need for such a strong source leads scientists to consider eruptions, such as volcanoes and geysers. If such eruptions are present, Enceladus would join two other such active moons, Io at Jupiter and Triton at Neptune. "Enceladus could be Saturn's more benign counterpart to Jupiter's dramatic Io," said Dr. Fritz Neubauer, co-investigator for the Cassini magnetometer, and a professor at the University of Cologne in Germany.

Since the Voyager flyby, scientists have suspected that this moon is geologically active and is the source of Saturn's icy E ring. Enceladus is the most reflective object in the solar system, reflecting about 90 percent of the sunlight that hits it. If Enceladus does have ice volcanoes, the high reflectivity of the moon's surface might result from continuous deposition of icy particles originating from the volcanoes.

Enceladus' diameter is about 500 kilometers (310 miles), which would fit in the state of Arizona. Yet despite its small size, Enceladus exhibits one of the most interesting surfaces of all the icy satellites.

For images and information on the Cassini mission visit http://saturn.jpl.nasa.gov and http://www.nasa.gov/cassini .

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the Cassini-Huygens mission for NASA's Science Mission Directorate, Washington, D.C. The Cassini orbiter was designed, developed and assembled at JPL.

Contacts:
Carolina Martinez (818) 354-9382
Jet Propulsion Laboratory, Pasadena, Calif.

NEWS RELEASE: 2005-046


http://saturn.jpl.nasa.gov/news/press-r ... newsID=553
 
Cassini lines up close moon flyby


The Cassini spacecraft is heading towards its closest encounter with the Saturnian moon known as Enceladus.
It will pass a mere 175km (109 miles) from the surface of the icy body on Thursday, taking images and readings.

Enceladus has grown in interest since the US-European mission to the Saturn system arrived just over a year ago.

Cassini recently discovered a thin but significant atmosphere around the moon, which many scientists suspect may harbour ice volcanoes and geysers.

The atmosphere, composed of ionised water vapour, was detected by the orbiter's magnetometer instrument during flybys in February and March.

In those close encounters, Cassini's cosmic dust analyser also detected a shroud of icy particles around the moon.

Icy puzzle

Researchers are keen to follow up both these findings because they hint at previously unobserved activity on the satellite, where temperatures go down to -180C.

Enceladus measures some 500km (310 miles) in diameter and is described as the most reflective object in the Solar System, throwing back about 90% of the sunlight that hits it.

Orbiting Saturn at a distance of approximately 237,400km (147,500 miles), it sits in the middle of the outermost ring - the E ring.

This is composed of tiny ice particles that only last for hundreds of years. So, researchers believe there has to be a source of them and that source is most probably Enceladus.

Likewise, with the atmosphere, Enceladus does not possess the gravitational attraction necessary to hold on to a cloud of water ions, so this must be being replenished also.

Four-year low

Ice volcanoes would be a compelling solution to the puzzle and the continuous deposition on the surface of icy particles might explain the high reflectivity of Enceladus

Dark spots previously pictured on the surface may mark places of upwelling or outgasing.

Theoretical study, too, has suggested where the energy comes from to drive activity: from tidal heating as Saturn's gravitation field pulls on Enceladus as it moves around an eccentric orbit.

"But this is all speculation right now; all we have is the circumstantial evidence," said Cassini imaging scientist Professor Carl Murray of Queen Mary, University of London, UK.

"As yet, we haven't seen any activity. We've seen these dark spots on the surface and these are perhaps points of weakness where material comes out. But even if it is active, Enceladus may not be active right now. It's all a bit of a puzzle," he told the BBC News website.

The 14 July encounter was to have been at an altitude of 1,000km (620 miles), but the mission team has become so intrigued by the moon that a decision was taken to lower the height of the pass.

In fact, Thursday's encounter will be Cassini's lowest-altitude flyby of any object during its nominal four-year tour.

The $3.2bn Cassini-Huygens mission is a joint venture between the US space agency (Nasa), the European Space Agency (Esa) and the Italian Space Agency (Asi).

http://news.bbc.co.uk/1/hi/sci/tech/4676069.stm
 
Not Titan but the Cassini probe has taken images of Enceladus.

Saturn moon delights and baffles


Space scientists say their discoveries about Saturn's moon Enceladus are stunning, if just a little baffling.

Using the instrument-packed Cassini probe, they have confirmed that the 500km-wide world has an atmosphere.

They have also seen a "hotspot" at the icy moon's south pole, which is riven with cracks dubbed "tiger stripes".

But the US and European scientists told a London meeting they could not yet explain fully the energetic processes driving all the activity on Enceladus.

"There were signs from a long time ago that Enceladus was a strange moon," said Dr Carolyn Porco, leader of Cassini's imaging team, "but it is just so gratifying and fabulous to see all the results come together and clearly point to a specific region on the surface which seems to be the origin of a lot of that peculiarity."

'Strange' world

The moon has become a major target of interest since the Cassini mission to the Saturn system arrived just over a year ago.

Enceladus orbits the ringed planet at a distance of approximately 237,400km and is described as the most reflective object in the Solar System; its icy surface throws back about 90% of the sunlight that hits it.

The spacecraft made a special low pass of the moon on 14 July, crossing a mere 173km above the surface at its closest approach.

This allowed Cassini to make observations of unprecedented detail; and they backed up data obtained by the probe's magnetometer instrument on previous flybys that hinted at the presence of a water vapour atmosphere.

But that was just the start of what is now proving to be a fascinating and evolving story.

"We confirmed the signature that there was an atmosphere but it is strange atmosphere," Professor Michele Dougherty, from the UK's Imperial College and the lead scientist for the magnetometer instrument, told BBC News.

"It seems to be concentrated at the south pole and the best way to match our observations is that you have almost a cometary jet coming off the south pole."

'Hard to understand'

High-resolution imagery shows the southern polar region to be relatively smooth - usually a good indicator of recent activity - but cut by a number of long, dominant cracks. These are the so-called tiger stripes.

They are about 130km long and roughly parallel to one another, spaced about 40km apart.

Cassini's composite infrared spectrometer shows the region to be much warmer than expected.

Whereas temperatures near the equator are a frigid 80 Kelvin (minus 193C), the south polar average reaches 85K (minus 188C). Small areas of the pole, concentrated near the tiger stripe fractures, are even warmer: well over 110K (minus 163C) in some places.

"The amount of heat there is really hard to understand as being due to just sunlight warming the surface," said Dr John Spencer, from the Southwest Research Institute in Colorado, US.

"It shouldn't be that warm at the pole. It would be like flying past the Earth and finding that Antarctica was warmer than equatorial regions - that strange.

"This is only the second place in the Solar System beyond Earth that we've seen signs of heat coming out of the interior - the other being Jupiter's moon Io."

The scientists think the cracks may act like vents, spewing out water vapour and very fine water-ice particles. Some have suggested there could be ice geysers and even ice volcanoes at the stripe locations - but these have not been imaged directly.

Interest index

The puzzle for researchers is how to explain such an energetic system on Enceladus.

As the moon moves around an eccentric orbit of Saturn, gravitational forces should subject the tiny world to some tidal heating. Radioactive isotopes in its rocky core may also be a source of some warming.

But scientists are struggling to make the numbers add up and are frankly baffled as to why the activity they see should be so concentrated in just the one region.

"One of the most fascinating aspects of Enceladus is that it's so very small as icy moons go, but so very geophysically active," said Dr Bob Brown, from the University of Arizona, US, and team leader for Cassini's visual and infrared mapping spectrometer.

"It's hard for a body as small as Enceladus to hold onto the heat necessary to drive such large-scale geophysical phenomena, but it had done just that.

"Enceladus and its incredible geology is a marvellous puzzle for us to figure out."

Certainly, what the Cassini data has done is thrust Enceladus up the interest index of objects in the Solar System that demand further investigation.

Scientists may not be able to explain the "boiler" at the south pole but they are already talking up the possibility that conditions there could allow for liquid water below the surface - with all the implications that might have.

"It's quite likely that this moon will now join the ranks of Mars and Jupiter's moon Europa where you might have liquid water - and the biologists could start getting interested in this being a place were life might possibly arise," enthused Dr Torrence Johnson, a Cassini scientist from Nasa's Jet Propulsion Laboratory in California.

"It moves Enceladus from being a small denizen of the outer Solar System - a frozen iceberg - to something that's more of an active type world that we're interested in exploring."

Cassini discoveries at Enceladus include:

presence of a strange atmosphere concentrated at the south pole
atmosphere mostly (91%) water vapour, but with some nitrogen, carbon dioxide and other simple carbon-based molecules (organics)
large crevasse features at south pole dubbed tiger stripes
intriguing hotspot at south pole - anomalous warmth in the area of the tiger stripes
presence of "orderly" water-ice at south pole, especially within tiger stripe features, indicates region must have been very hot, be very young, or both
presence of simple organics along the fractures
indication that water vapour and fine material are being ejected from tiger stripes
fine ice material is probably the significant and sustaining source of ice particles that make up Saturn's outermost ring - its E ring
Cassini scientists are meeting in London this week ahead of a major conference of the American Astronomy Society in Cambridge next week.
The $3.2bn Cassini-Huygens mission is a joint venture between the US space agency (Nasa), the European Space Agency (Esa) and the Italian Space Agency (Asi).

http://news.bbc.co.uk/1/hi/sci/tech/4197686.stm

 
Cassini snapshot reveals Saturn?s volcanic moon

NASA's Cassini spacecraft has captured unique views of two of Saturn's moons. The probe?s first close encounter with the large moon Rhea was somewhat eclipsed by a sidelong snapshot of the moon Enceladus, revealing active volcanic plumes above its surface.

On a previous, much closer pass by Enceladus, Cassini detected that the south pole of Enceladus is spewing out a vast plume of water vapour that stretches hundreds of kilometres from the moon's surface and keeps Saturn's E-ring topped up ? but it has now captured the first images of this activity. On Sunday, 27 November, Cassini was positioned so that the Sun was behind the moon, causing one side of Enceladus to be illuminated as a fine crescent, with its volcanic plumes backlit.

Enceladus is only the third body in the solar system to show signs of active volcanism, besides Earth and Io, Jupiter's moon. Even though this volcanism is exceptionally gentle, planetary scientists cannot yet work out what is driving it. The new pictures could help by revealing the muzzle velocity of the moon's plumes.

Evil twin
A day earlier, on 26 November, Cassini flew just 500 kilometres from the surface of Rhea. At 1500 kilometres across, Rhea is Saturn's second largest moon. From a first look at the raw images, there are few surprises ? the landscape is the same wasteland seen during more distant flybys, featuring craters up to 400 km wide. But revelations may still come from a more careful analysis.

"It was good to finally get a decent look at Tirawa, Rhea's largest crater, and its 'evil twin' directly to the northeast," says outer-moon expert William McKinnon of Washington University in St. Louis, US. A minor surprise is that neither of these craters has rings around its centre from the impacts which created them, which is to be expected given their size.

"Tirawa was first spotted in Voyager images, but the twin remained a secret until Cassini," McKinnon adds. "Both basins appear to be similarly old, and I conjecture that they may be the result of a binary impact, like East and West Clearwater in Canada."

http://www.newscientistspace.com/article.ns?id=dn8386
 
Cassini Images Reveal Spectacular Evidence Of An Active Moon


Jets of fine, icy particles streaming from Saturn's moon Enceladus were captured in recent images from NASA's Cassini spacecraft. The images provide unambiguous visual evidence that the moon is geologically active.
"For planetary explorers like us, there is little that can compare to the sighting of activity on another solar system body," said Dr. Carolyn Porco, Cassini imaging team leader at the Space Science Institute in Boulder, Colo.

"This has been a heart-stopper, and surely one of our most thrilling results."

The Cassini images clearly show multiple jets emanating from the moon's south polar region. Based on earlier data, scientists strongly suspected these jets arise from warm fractures in the region. The fractures, informally dubbed "tiger stripes," are viewed essentially broadside in the new images.

The fainter, extended plume stretches at least 186 kilometers (300 miles) above the surface of Enceladus, which is only 186 kilometers wide. Cassini flew through the plume in July, when it passed a few hundred kilometers above the moon.

During that flyby, Cassini's instruments measured the plume's constituent water vapor and icy particles.

Imaging team members analyzed images of Enceladus taken earlier this year at similar viewing angles. It was a rigorous effort to demonstrate that earlier apparitions of the plumes, seen as far back as January, were in fact real and not due to imperfections in the camera.

The recent images were part of a sequence planned to confirm the presence of the plumes and examine them in finer detail. Imaging team member Dr. Andrew Ingersoll from the California Institute of Technology, said, "I think what we're seeing are ice particles in jets of water vapor that emanate from pressurized vents. To form the particles and carry them aloft, the vapor must have a certain density, and that implies surprisingly warm temperatures for a cold body like Enceladus."

Imaging scientists are comparing the new views to earlier Cassini data in hopes of arriving at a more detailed, three-dimensional picture of the plumes and understanding how activity has come about on such a small moon. They are not sure about the precise cause of the moon's unexpected geologic vitality.

"In some ways, Enceladus resembles a huge comet," said Dr. Torrence Johnson, imaging team member from NASA's Jet Propulsion Laboratory.

"Only, in the case of Enceladus, the energy source for the geyser-like activity is believed to be due to internal heating by perhaps radioactivity and tides rather than the sunlight which causes cometary jets." The new data also give yet another indication of how Enceladus keeps supplying material to Saturn's gossamer E ring.

Cassini's Photo Album From A Season Of Icy Moons
Pasadena CA (JPL) Dec 07 - Wrapping-up a phenomenally successful year of observing Saturn's icy moons, the Cassini mission is releasing a flood of new views of the moons Enceladus, Dione, Rhea, Hyperion, and Iapetus.

The moons and their intricacies are being highlighted today at a news briefing held today at the American Geophysical Union meeting in San Francisco, Calif.

Several new images of Rhea, a moon measuring 1,528 kilometers (949 miles) across, were taken during Cassini's most recent close flyby on November 26. During the encounter, Cassini dipped to within 500 kilometers (310 miles) of Rhea's surface.

Additional new images include two "zoomable" mosaics of Rhea and Hyperion at high resolution; false-color views revealing compositional variation on the surfaces of Hyperion, Dione and Rhea; two movies reproducing Cassini's exciting encounters with Iapetus and Hyperion; and dazzling new images of the plumes of Enceladus, including a time-lapse movie.

http://www.spacedaily.com/news/cassini-05zzzzd.html
 
NASA'S CASSINI DISCOVERS POTENTIAL LIQUID WATER ON ENCELADUS
Thu Mar 09 2006 11:21:33 ET

**Exclusive**

NASA's Cassini spacecraft may have found evidence of liquid water reservoirs that erupt in Yellowstone-like geysers on Saturn's moon Enceladus. The rare occurrence of liquid water so near the surface raises many new questions about the mysterious moon.

"We realize that this is a radical conclusion - that we may have evidence for liquid water within a body so small and so cold," said Carolyn Porco, Cassini imaging team leader at the Space Science Institute, Boulder, Colo. "However, if we are right, we have significantly broadened the diversity of solar system environments where we might possibly have conditions suitable for living organisms."

High-resolution Cassini images show icy jets and towering plumes ejecting huge quantities of particles at high speed. Scientists examined several models to explain the process. They ruled out the idea the particles are produced or blown off the moon's surface by vapor created when warm water ice converts to a gas. Instead, scientists have found evidence for a much more exciting possibility. The jets might be erupting from near-surface pockets of liquid water above 0 degrees Celsius (32 degrees Fahrenheit), like cold versions of the Old Faithful geyser in Yellowstone.

"We previously knew of at most three places where active volcanism exists: Jupiter's moon Io, Earth, and possibly Neptune's moon Triton. Cassini changed all that, making Enceladus the latest member of this very exclusive club, and one of the most exciting places in the solar system," said John Spencer, Cassini scientist, Southwest Research Institute, Boulder.

-more--2-

"Other moons in the solar system have liquid-water oceans covered by kilometers of icy crust," said Andrew Ingersoll, imaging team member and atmospheric scientist at the California Institute of Technology, Pasadena, Calif. "What's different here is that pockets of liquid water may be no more than tens of meters below the surface."

"As Cassini approached Saturn, we discovered the Saturnian system is filled with oxygen atoms. At the time we had no idea where the oxygen was coming from," said Candy Hansen, Cassini scientist at NASA's Jet Propulsion Laboratory (JPL) in Pasadena. "Now we know Enceladus is spewing out water molecules, which break down into oxygen and hydrogen."

Scientists still have many questions. Why is Enceladus so active? Are other sites on Enceladus active? Might this activity have been continuous enough over the moon's history for life to have had a chance to take hold in the moon's interior?

In the spring of 2008, scientists will get another chance to look at Enceladus when Cassini flies within 350 kilometers (approximately 220 miles), but much work remains after the spacecraft's four-year prime mission is over.

"There's no question, along with the moon Titan, Enceladus should be a very high priority for us. Saturn has given us two exciting worlds to explore," said Jonathan Lunine, Cassini interdisciplinary scientist, University of Arizona, Tucson, Ariz.

Mission scientists report these and other Enceladus findings in this week's issue of Science.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency.

JPL, a division of the California Institute of Technology
 
Very significant find 8) Source

NASA Makes Announcement
Earth has been the only place known with running water until now. Scientists announced a startling discovery on Enceladus, one of Saturn's moons. Scientists say that moon is shooting out massive jets of cold water, from the moon's South Pole.

It's Enceladus's cold-water version of Old Faithful. Saturn's moon Enceladus is roughly a 300-mile wide planet, about the size of Great Britain.

Oceanographer Dr. George Maul told us, "That would suggest there's some heating from below, much like you see the plumes coming out of Old Faithful."

NASA's possible discovery of cold running water on another body in the solar system is a huge find for the agency. Because scientists say where there is water, there is always the possibility of life.

"We've always associated liquid water with life," Maul said.

Dr. Maul says the oceanography community is excited to add to what NASA scientists are finding.

Dr. Maul has learned after more than four decades studying Earth's water that in all different water conditions, life can be found on Earth. Now that search will extend to Saturn's moon.

"It's above zero, above freezing, and whenever you find above freezing water temperatures on earth, you find life someplace in that. So one would expect, and perhaps hope to find that there is something in these other planets," Maul said.

However, there is no evidence of life in this possible cold-water find. It's impossible for anyone to tell if life will be found at all.
 
Saturn moon 'may have an ocean'

Saturn's moon Enceladus could harbour a liquid water ocean beneath its icy crust, according to data sent back by the Cassini spacecraft.
Until Cassini reached Saturn, the tiny moon had received little attention.

But Enceladus is now the focus of intensive study following the discovery that it is geologically active.

Enceladus may possess reservoirs of near-surface liquid water that erupt to form geysers - and where there's water, there may be life, scientists argue.

These jets have been observed erupting from a "hot spot" in the moon's south polar region.

Scientists on the mission have likened them to the kinds of geysers found in Yellowstone National Park in the US.


Click here to see how activity may be generated on Enceladus
"We realise that this is a radical conclusion - that we may have evidence for liquid water within a body so small and so cold," said Dr Carolyn Porco, Cassini imaging team leader at the Space Science Institute in Boulder, US.

"However, if we are right, we have significantly broadened the diversity of Solar System environments where we might possibly have conditions suitable for living organisms. It doesn't get any more exciting than this."

Dr Jeffrey Kargel, from the US Geological Survey in Flagstaff, Arizona, US, believes that shifting, glacier-like tectonic plates and tidal forces could generate and trap heat to produce the activity seen on Enceladus.

His modelling also allows for a deep liquid water ocean saturated with gases such as carbon dioxide (CO2). This CO2 may either be locked up in the icy crust or may exist as an icy clathrate seafloor below the hypothesised ocean.

Other researchers on the Cassini mission say the plume at the south pole may be erupting from near-surface pockets of liquid water above 0C (32 F), like cold versions of the Old Faithful geyser in Yellowstone Park.

"There are other moons in the Solar System that have liquid water oceans covered by kilometres of icy crust," said Dr Andrew Ingersoll from the California Institute of Technology (Caltech) in Pasadena.

"What's different here is that pockets of liquid water may be no more than 10 metres below the surface."

Jupiter's icy moon Europa is also thought to host a briny ocean beneath its crust of ice. Neptune's moon Triton has an icy volcanic surface from which break forth plumes of nitrogen.

http://news.bbc.co.uk/1/hi/sci/tech/4790126.stm
 
NASA's Cassini Discovers Potential Liquid Water on Enceladus


NASA's Cassini spacecraft may have found evidence of liquid water reservoirs that erupt in Yellowstone-like geysers on Saturn's moon Enceladus. The rare occurrence of liquid water so near the surface raises many new questions about the mysterious moon.

"We realize that this is a radical conclusion -- that we may have evidence for liquid water within a body so small and so cold," said Dr. Carolyn Porco, Cassini imaging team leader at Space Science Institute, Boulder, Colo. "However, if we are right, we have significantly broadened the diversity of solar system environments where we might possibly have conditions suitable for living organisms."

High-resolution Cassini images show icy jets and towering plumes ejecting large quantities of particles at high speed. Scientists examined several models to explain the process. They ruled out the idea that the particles are produced by or blown off the moon's surface by vapor created when warm water ice converts to a gas. Instead, scientists have found evidence for a much more exciting possibility -- the jets might be erupting from near-surface pockets of liquid water above 0 degrees Celsius (32 degrees Fahrenheit), like cold versions of the Old Faithful geyser in Yellowstone.

Mission scientists report these and other Enceladus findings in this week's issue of Science.

"We previously knew of at most three places where active volcanism exists: Jupiter's moon Io, Earth, and possibly Neptune's moon Triton. Cassini changed all that, making Enceladus the latest member of this very exclusive club, and one of the most exciting places in the solar system," said Dr. John Spencer, Cassini scientist, Southwest Research Institute, Boulder, Colo.

"Other moons in the solar system have liquid-water oceans covered by kilometers of icy crust," said Dr. Andrew Ingersoll, imaging team member and atmospheric scientist at the California Institute of Technology, Pasadena, Calif. "What's different here is that pockets of liquid water may be no more than tens of meters below the surface."

Other unexplained oddities now make sense. "As Cassini approached Saturn, we discovered that the Saturnian system is filled with oxygen atoms. At the time we had no idea where the oxygen was coming from," said Dr. Candy Hansen, Cassini scientist at NASA's Jet Propulsion Laboratory in Pasadena. "Now we know that Enceladus is spewing out water molecules, which break down into oxygen and hydrogen."

Scientists are also seeing variability at Enceladus. "Even when Cassini is not flying close to Enceladus, we can detect that the plume's activity has been changing through its varying effects on the soup of electrically-charged particles that flow past the moon," said Dr. Geraint H. Jones, Cassini scientist, magnetospheric imaging instrument, Max Planck Institute for Solar System Research, Katlenburg-Lindau, Germany.

Scientists still have many questions. Why is Enceladus currently so active? Are other sites on Enceladus active? Might this activity have been continuous enough over the moon's history for life to have had a chance to take hold in the moon's interior?

"Our search for liquid water has taken a new turn. The type of evidence for liquid water on Enceladus is very different from what we've seen at Jupiter's moon Europa. On Europa the evidence from surface geological features points to an internal ocean. On Enceladus the evidence is direct observation of water vapor venting from sources close to the surface," said Dr. Peter Thomas, Cassini imaging scientist, Cornell University, Ithaca, N.Y.

In the spring of 2008, scientists will get another chance to look at Enceladus when Cassini flies within 350 kilometers (approximately 220 miles), but much work remains after Cassini¿s four-year prime mission is over.

"There's no question that, along with the moon Titan, Enceladus should be a very high priority for us. Saturn has given us two exciting worlds to explore," said Dr. Jonathan Lunine, Cassini interdisciplinary scientist, University of Arizona, Tucson, Ariz.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. JPL, a division of the Caltech, manages the mission for NASA's Science Mission Directorate. The Cassini orbiter was designed, developed and assembled at JPL.

http://saturn.jpl.nasa.gov/news/press-r ... newsID=639
 
Saturn's moon 'best bet for life'
By Richard Black
Environment Correspondent, BBC News website



Saturn's tiny moon Enceladus may be the best place to look for life elsewhere in the Solar System.
That is the view of a senior scientist working on the Cassini spacecraft, which has been studying Saturn and its moons for nearly two years.

Dr Bob Brown told a major conference in Vienna, Austria, Enceladus contains simple organic molecules, water and heat, the ingredients for life.

He raised the possibility of future missions to probe inside the moon.

Other research presented at the European Geosciences Union (EGU) annual meeting suggests that Enceladus may have a core of molten rock reaching temperatures of 1,400K (above 1,100C).

Jets and rings

In July 2005 Cassini completed a spectacularly close flyby of Enceladus, passing just 173km above its surface.

From this flyby came confirmation that the moon has an atmosphere, and strong evidence that the gases which make up the atmosphere are coming from cracks in the surface, nick-named "tiger stripes", near the south pole.


It appears that the gases are being forced through the surface, as they emerge in jets which shoot upwards for hundreds of kilometres before dispersing, eventually forming Saturn's E-ring.
Most of the gas is water vapour, suggesting strongly that liquid water lies under the moon's icy surface.

From his base at the University of Arizona, Tucson, Bob Brown leads the scientific team for Cassini's visual and infrared mapping spectrometer (Vims) which analysed the chemical composition of Enceladus's atmosphere and mapped the distribution of various gases.

"We very clearly saw water; there's water everywhere on Enceladus, it's 99.9% water ice in general at the surface, and we've known that for years, so it wasn't a big surprise," he told the BBC News website.

"But when we started looking at our spectra we saw absorption bands from a compound that had to have carbon and hydrogen bonded together.


Enceladus in a very real sense becomes a stronger candidate for life than [Jupiter's moon] Europa
Bob Brown, University of Arizona, Tucson

"And when we mapped the location, it was right in these 'tiger stripes' - right where the jets are coming out, and right where it's hot - and it's pretty hard to imagine it's getting there from anywhere but inside."
The organic molecules appear to be quite simple, he said, probably largely methane.

The jets also contain nitrogen; and putting all this together means, said Dr Brown, that Enceladus contains all the ingredients necessary for the development of life, or of precursors to it.

"What you need to put microbes together of the kind that we're familiar with is carbon, hydrogen, nitrogen and oxygen, and water to act as an intermediary for metabolism," he said.

"You've got a rock core that's hot as hell; you've got all the conditions that we think gave rise to the first self-replicating molecules and eventually to life on this planet.


"So Enceladus in a very real sense becomes a stronger candidate for life than [Jupiter's moon] Europa, for instance."

One of the puzzling facets of Enceladus is how and why it is hot enough that it can generate liquid water and spew vapour into space.

Most of its surface has a temperature of about 80 Kelvin (minus 193C). But in the "tiger stripes" it soars to 140 Kelvin (minus 123C), and the interior must be considerably hotter.

Computer models have been produced which try to explain just how hot the interior needs to be, and examine the processes which could produce and maintain the temperatures observed today.

Dr Dennis Matson from Nasa's Jet Propulsion Laboratory (JPL) took EGU delegates through a model which envisages energy coming from two sources, radioactive decay and tidal heating, where differences in the gravitational forces exerted by a nearby body (in this case the giant planet Saturn) cause churning inside the moon, producing heat through friction.

"Down here [in the centre] we have molten magma," he said. "In this model, in the present day, it's entering a cooling phase which may go on for another billion years or so; but at depth you still have high temperatures."

Temperatures at the centre could reach 1,400 Kelvin, he said.

But there are still puzzles. Radioactive decay would have produced the vast majority of its heat shortly after the solar system's formation; somehow, Enceladus has retained some of that energy.

"We think there's a thermostatic mechanism going on in the magma," observed Dr Matson.

If the magma were to cool, he said, it would become more viscous, increasing friction from tidal churning and so producing more heat. But if temperatures veered higher, the magma would flow more easily, and tidal heat production would reduce accordingly.

Exceptional world

Along with all the other Cassini mission findings, the research presented here emphasises what an unexpected treasure trove of scientific novelty researchers have discovered on Enceladus.

Its tiger stripes amount to a "water volcano", the only one seen in the solar system other than on Earth.

Among our neighbours, it is the only known geophysically active world other than Jupiter's moon Io.

But as always with space missions, one set of answers leads to another set of questions.

The way to answer some is a further flyby in about two years' time, shortly before the end of Cassini's scheduled mission, which could take the $3.2bn craft just 25km above the tiger stripes and through their jets.

"There's a little bit of a danger, because observations suggest that the particles get larger as you get in closer," said Dr Brown.

"If they're only 20 or 30 microns [in diameter] they won't hurt the spacecraft; but if they're a millimetre or two, and hit the spacecraft in the wrong place, we're dead."

If there is enough fuel left on board Cassini and enough money in the coffers of its masters, the US, European and Italian space agencies (Nasa, Esa and Asi), the mission may gain an extension to its scheduled life, which could yield further flybys of the tiny moon.

But investigations aimed at looking for self-replicating molecules or even primitive forms of life would have to wait for a further mission.

For Europa, landers have been proposed which would burrow down through the top layer of ice into liquid water below, perhaps using heat from radioactive decay to penetrate the surface.

The same approach could potentially work on Enceladus; but Bob Brown believes there may be another, simpler way in.

"You could target the cracks; they clearly give you a way to get down inside, into the reservoir," he said.

"Now whether we can make something smart enough to do that robotically I don't know. But if there are bugs, they don't have to be in the ocean; they could live inside the vents, they just have to be somewhere where it's hot enough and they have enough energy to conduct metabolism.


"My guess is that if stuff has evolved in this ocean, it's figured out a way to work itself up into these vents; and maybe it's not completely crazy to think some of this stuff is sitting there near the surface."

ENCELADUS 'COLD GEYSER'



Story from BBC NEWS:
http://news.bbc.co.uk/go/pr/fr/-/1/hi/s ... 895358.stm

Published: 2006/04/10 09:44:12 GMT

© BBC MMVI
 
Enceladus: Nasa discovers new evidence that Saturn moon 'may contain life'
New evidence that liquid water lies beneath the surface on the Saturn moon of Enceladus has been discovered by Nasa scientists, suggesting that life may exist.
By Andrew Hough
Published: 12:29AM GMT 09 Feb 2010

Nasa's Cassini spacecraft flew through icy plumes created by ice volcanoes and detected negatively charged water molecules, in a clear sign an underground sea exists.

On Earth this short-lived type of ion is produced where water is moving, such as in waterfalls or crashing ocean waves.

British scientists, reporting in the journal Icarus, say it is known that the jets contained water but it was not clear before whether this might be liquid.

If there is liquid water on Enceladus, Nasa scientists believe Saturn's sixth-largest moon could have the conditions necessary to sustain life.

High-resolution images already taken by the Cassini spacecraft show that the icy surface of Enceladus has a spreading Earthlike crust that has changed over time.

On Earth the spreading of the sea floor is driven by molten rock and Nasa scientists speculated that the liquid beneath the south pole of Enceladus may be water

Cassini scientist Andrew Coates said the evidence gathered by Cassini pointed to other constituents for life, such as carbon, plus a source of heat to keep the water liquid.

"While it's no surprise that there is water there, these short-lived ions are extra evidence for subsurface water," said Dr Coates, from University College London's Mullard Space Science Laboratory.

"And where there's water, carbon and energy, some of the major ingredients for life are present.

“The surprise for us was to look at the mass of these ions. There were several peaks in the spectrum, and when we analysed them we saw the effect of water molecules clustering together one after the other.”

Similar negatively charged ions have been found on another satellite of Saturn, Titan, which is the only moon in the solar system with a thick atmosphere.

The data from Enceladus's icy spray was collected by an instrument on Cassini called a plasma spectrometer.

It measured the density, temperature and speed of ions and electrons it collected as it flew through the jets.

Cassini is a project of Nasa, the European Space Agency and the Italian Space Agency.

It has been a major success for U.S. and European scientists since the spacecraft began orbiting Saturn and studying its rings and moons since 2004.

Nasa has just extended the mission's life by seven years. :D

But the British scientists have been told to abandon their research thanks to swingeing cuts in science spending by the government. :evil:

http://www.telegraph.co.uk/science/spac ... -life.html
 
More Cassini news, it could be a while before theres a full analysis of the data though.

Cassini spacecraft makes Saturn moon flyby
http://www.bbc.co.uk/news/science-environment-17526723
By Paul Rincon
Science editor, BBC News website

The pass enabled Cassini to sample the jets from Enceladus' south pole

Related Stories

Probe to end mission in ring gap
Icy Saturn moon ‘may be active’
Enceladus water story reinforced

The Cassini spacecraft has made its lowest pass yet over the south pole of Enceladus, an active moon of Saturn which may harbour a liquid water ocean.

The flyby, at an altitude of 74km (46mi), allowed Cassini to "taste" the jets of ice and water vapour that gush from the moon's polar region.

Several lines of evidence suggest these jets are fed by a liquid water ocean beneath Enceladus' outer icy shell.

The spacecraft's closest approach took place at 1930 GMT on Tuesday.

The scientists are using Cassini's Ion and Neutral Mass Spectrometer instrument to learn more about the composition, density and variability of the plumes from Enceladus.

Scientists previously detected salts in these jets, which suggested the sub-surface liquid water ocean was probably in contact with Enceladus' rocky core.

This makes Enceladus an even more important target in the search for life elsewhere in the Solar System, as rocks could furnish the ocean with the chemical ingredients thought essential for life.

The plumes erupt from fissures at the south pole known as "tiger stripes".

Last week, scientists presented evidence of a connection between the jet activity on Enceladus and the way Saturn's gravity stretches and stresses the fissures.

The results were outlined by Terry Hurford, from Nasa's Jet Propulsion Laboratory (JPL), at the Lunar and Planetary Science Conference (LPSC) in The Woodlands, Texas.

However, about 35% of the observations could not be explained by tension in the jets' source regions.

Continue reading the main story

Enceladus experiences tidal contortions as it orbits its parent planet
This energy is producing a "hotspot" at the satellite's southern pole
Big cracks (L) are 100 degrees warmer than the surrounding ice surface
These so called tiger stripes are the source of immense plumes (R)
Enceladus moves around Saturn in a distorted, oval-shaped orbit rather than a circular one. This causes the moon to be pulled and squeezed by Saturn's gravity, inducing the heat that enables geological activity on the icy moon.

Cassini's closest approach to any part of Enceladus occurred in October 2008, when it flew within about 25km (16 mi) of the surface.

A flyby in October 2015 will bring Cassini about 25km closer to the moon.

[email protected]. and follow me on Twitter
 
Wonderful! Images at link.

Cassini spacecraft captures Saturn moon geyser images
http://www.bbc.co.uk/news/science-environment-17550834
By Paul Rincon
Science editor, BBC News website

The jets emanate from hot fissures known as "tiger stripes" at the south pole

Related Stories

Probe to end mission in ring gap
Icy Saturn moon ‘may be active’
Enceladus water story reinforced

The Cassini spacecraft has captured striking images from flying by three moons of Saturn, including new pictures of Enceladus's gushing geysers.

Cassini made its lowest pass yet over the south pole of Enceladus, at at an altitude of 74km (46 miles).

This allowed it to "taste" the jets of water vapour and ice that the moon spews forth into space.

The Nasa probe also made relatively close flypasts of two other Saturnian satellites: Dione and Janus.

The observations were made over 27 and 28 March.

The encounter was primarily designed for Cassini's ion and neutral mass spectrometer instrument, which sampled the composition of Enceladus's south polar plume.


Abundant evidence of geological activity criss-crosses Enceladus's surface
Other instruments, including the Cassini plasma spectrometer and composite infrared spectrometer, also took measurements.

Before the closest approach to Enceladus, Cassini's onboard cameras captured images of the geysers, which contain organic compounds along with the ice and vapour.

The jets erupt from cracks, or hot fissures, at the south pole known as "tiger stripes".


Dione's surface has hints of past or present activity, but at a lower level than on Enceladus
Several lines of evidence suggest the jets are fed by a liquid water ocean beneath Enceladus' outer icy shell.

Scientists have previously detected salts in these jets, which suggests the ocean is probably in contact with the moon's rocky core.

"Cassini has flown several times now through this spray and has tasted it. And we have found that aside from water and organic material, there is salt in the icy particles. The salinity is the same as that of Earth's oceans," said Dr Carolyn Porco, head of the imaging team on Cassini.

As the spacecraft passed Enceladus, the cameras made a nine-frame mosaic of the surface of Enceladus's leading hemisphere.

Cassini then flew by the small moon Janus with a closest approach distance of 44,000km. The planet was in the background in some of these views.

On 28 March, the spacecraft passed Dione at roughly the same distance and captured, among other observations, a nine-frame mosaic depicting the side of the moon that faces away from Saturn.

Continue reading the main story

Start Quote

It sounds crazy but it could be snowing microbes on the surface of this little world”

Dr Carolyn Porco
Space Science Institute
Scientists recently presented evidence that Dione has features resembling tiger stripes and a cryovolcano, which erupts water-ammonia or methane instead of molten rock.

It is unclear whether there is current geological activity at Dione, but, if so, it is almost certainly at a lower level than on Enceladus.

The discovery that Enceladus probably harbours an ocean in contact with the rocky core makes this moon an even more important target in the search for life elsewhere in the Solar System. The rocks could furnish the ocean with the chemical ingredients thought essential for life.

"The kind of ecologies Enceladus might harbour could be like those deep within our own planet," Dr Porco said in an interview with Nasa's science website.


Janus is one of the inner satellites of Saturn, measuring some 200km across
The habitable zone on Enceladus might be comparatively easy to access by future robotic space missions. Dr Porco added: "It's erupting out into space where we can sample it. It sounds crazy but it could be snowing microbes on the surface of this little world.

"In the end, it's the most promising place I know of for an astrobiology search. We don't even need to go scratching around on the surface. We can fly through the plume and sample it. Or we can land on the surface, look up and stick our tongues out."

The source of Enceladus's heat appears to be Saturn itself. The moon moves around Saturn in a distorted, oval-shaped orbit rather than a circular one.

This causes it to be pulled and squeezed by Saturn's gravity, inducing the heat that enables geological activity on the icy moon.

Enceladus experiences tidal contortions as it orbits its parent planet
This energy is producing a "hotspot" at the satellite's southern pole
Big cracks (L) are 100 degrees warmer than the surrounding ice surface
These so called tiger stripes are the source of immense plumes (R)
 
Cassini spacecraft captures Saturn moon geyser images
By Paul Rincon, Science editor, BBC News website

The Cassini spacecraft has captured striking images from flying by three moons of Saturn, including new pictures of Enceladus's gushing geysers.
Cassini made its lowest pass yet over the south pole of Enceladus, at at an altitude of 74km (46 miles).
This allowed it to "taste" the jets of water vapour and ice that the moon spews forth into space.

The Nasa probe also made relatively close flypasts of two other Saturnian satellites: Dione and Janus.

The observations were made over 27 and 28 March.
The encounter was primarily designed for Cassini's ion and neutral mass spectrometer instrument, which sampled the composition of Enceladus's south polar plume.
Other instruments, including the Cassini plasma spectrometer and composite infrared spectrometer, also took measurements.

Before the closest approach to Enceladus, Cassini's onboard cameras captured images of the geysers, which contain organic compounds along with the ice and vapour.
The jets erupt from cracks, or hot fissures, at the south pole known as "tiger stripes".
Several lines of evidence suggest the jets are fed by a liquid water ocean beneath Enceladus' outer icy shell.
Scientists have previously detected salts in these jets, which suggests the ocean is probably in contact with the moon's rocky core.

"Cassini has flown several times now through this spray and has tasted it. And we have found that aside from water and organic material, there is salt in the icy particles. The salinity is the same as that of Earth's oceans," said Dr Carolyn Porco, head of the imaging team on Cassini. Careful it doesn't go rusty! ;)

As the spacecraft passed Enceladus, the cameras made a nine-frame mosaic of the surface of Enceladus's leading hemisphere.
Cassini then flew by the small moon Janus with a closest approach distance of 44,000km. The planet was in the background in some of these views.
On 28 March, the spacecraft passed Dione at roughly the same distance and captured, among other observations, a nine-frame mosaic depicting the side of the moon that faces away from Saturn.

Scientists recently presented evidence that Dione has features resembling tiger stripes and a cryovolcano, which erupts water-ammonia or methane instead of molten rock.
It is unclear whether there is current geological activity at Dione, but, if so, it is almost certainly at a lower level than on Enceladus.

The discovery that Enceladus probably harbours an ocean in contact with the rocky core makes this moon an even more important target in the search for life elsewhere in the Solar System. The rocks could furnish the ocean with the chemical ingredients thought essential for life. "The kind of ecologies Enceladus might harbour could be like those deep within our own planet," Dr Porco said in an interview with Nasa's science website.

The habitable zone on Enceladus might be comparatively easy to access by future robotic space missions. Dr Porco added: "It's erupting out into space where we can sample it. It sounds crazy but it could be snowing microbes on the surface of this little world.
"In the end, it's the most promising place I know of for an astrobiology search. We don't even need to go scratching around on the surface. We can fly through the plume and sample it. Or we can land on the surface, look up and stick our tongues out." :D

The source of Enceladus's heat appears to be Saturn itself. The moon moves around Saturn in a distorted, oval-shaped orbit rather than a circular one.
This causes it to be pulled and squeezed by Saturn's gravity, inducing the heat that enables geological activity on the icy moon.

http://www.bbc.co.uk/news/science-environment-17550834
 
Another possibility of Life on a far off Moon. But will Life On Enceladus be a hit?

Saturn's Enceladus moon hides 'great lake' of water
By Jonathan Amos
Science correspondent, BBC News
http://www.bbc.com/news/science-environment-26872184

Enceladus

Jets of water-ice are blasted thousands of km above the surface of Saturn's tiny moon Enceladus

The evidence for an "ocean" of water under the surface of Saturn's moon Enceladus appears to be overwhelming.

The little world has excited scientists ever since jets of icy material were seen squirting into space from a striped region at its south pole.

Now, exquisite measurements using Nasa's Cassini probe as it flew over the moon have allowed researchers to detect the water's gravitational signal.

Science magazine reports the details.

"The measurements that we have done are consistent with the existence of a large water reservoir about the size (volume) of Lake Superior in North America," Prof Luciano Iess told BBC News.

A European comparison would be 245 times the water mass of Lake Garda in Italy.

The findings of Prof Iess and his team will boost the view that the 500km-wide moon would be one of the best places beyond Earth to go look for the existence of microbial life.

Lake Superior
Lake Superior has a volume of 12,000 cu km. The amount of liquid on Enceladus would be somewhat similar
Cassini's data suggests the liquid volume lies about 40km under Enceladus's ice crust.

This would put it directly on top of the moon's layered, rocky interior.

The case for a subglacial ocean has been growing ever since Cassini first sensed a diffuse atmosphere at the moon in 2005.

Subsequent observations pinned the source of this atmosphere to mineral-rich streams of water vapour flowing away from surface fractures dubbed "tiger stripes" for their resemblance to the markings on a big cat.

Cassini even flew through the plumes to "taste" their load of salts and organic (carbon-rich) molecules.

Continue reading the main story

Start Quote

I think Enceladus has gone to the top of the charts in terms of a place where there could be life”

Prof Andrew Coates
UK Cassini scientist
Enceladus's orbit around Saturn is highly eccentric - it is a big ellipse. The giant planet's gravity should therefore be expected to squeeze and stretch the little moon as it travels this path, heating some of its ices and melting them.

Some of the resulting liquid could then be hurled into space through the deep tiger fractures, although quite how this happens is not yet fully understood.

Nonetheless, the new work reinforces this general picture.

It has involved measuring tiny changes in the speed of Cassini as it passed through Enceladus's own gravitational field.

These changes in velocity were as small as 20 millionths of a metre per second.

They enabled Prof Iess and colleagues to map variations in the distribution of mass on the moon.

The large anomaly they spotted in the data at the southern pole is best explained by the presence of a big volume of water.

"What we see is consistent with a water pocket of about 8-10km in depth, and this pocket can extend up to southern latitudes of 50 degrees around the pole," the Sapienza University of Rome researcher explained.

Stripes
The moon has long fractures in its ice surface that have been dubbed tiger stripes
There is strong evidence to suspect the existence of sub-glacial oceans at a number of Solar System moons.

Saturn's largest satellite, Titan, probably has one. Similarly, the Jupiter moons Europa, Ganymede and Callisto would fall into this class; and perhaps even Triton at Neptune.

Of these, Enceladus and Europa draw the most interest because it is more likely that their water would be in contact with rock.

This could make for some interesting chemistry - the sort of reactions that might facilitate the emergence of life.

Prof Andrew Coates, of the UK's UCL-Mullard Space Science Laboratory, commented: "I think Enceladus has gone to the top of the charts in terms of a place where there could be life.

"It's got several of the things which you need for life - there's certainly the presence of heat, there's liquid water in this ocean, there's organics and that type of chemistry going on.

"The only question is, has there been enough time for life to develop?"

Prof David Stevenson, from the California Institute of Technology, added: "We don't have an answer to that, but there are some theoretical ideas.

"First, let me say that the ocean that we have found could keep things going for tens of millions of years, maybe 100 million years, but, of course, we don't know whether the ocean is being added to at present or is freezing up.

"And, maybe, Enceladus does go through cycles and those cycles would be related to the eccentricity of the orbit. It's possible that the orbit has not always had the same eccentricity."

Impression of interior

An impression of the moon's interior with the water concentrated at the south pole

[email protected]. and follow me on Twitter: @BBCAmos
 
Saturn's Enceladus moon hides 'great lake' of water
By Jonathan Amos, Science correspondent, BBC News

The evidence for an "ocean" of water under the surface of Saturn's moon Enceladus appears to be overwhelming.
The little world has excited scientists ever since jets of icy material were seen squirting into space from a striped region at its south pole.
Now, exquisite measurements using Nasa's Cassini probe as it flew over the moon have allowed researchers to detect the water's gravitational signal.
Science magazine reports the details.

"The measurements that we have done are consistent with the existence of a large water reservoir about the size (volume) of Lake Superior in North America," Prof Luciano Iess told BBC News.
A European comparison would be 245 times the water mass of Lake Garda in Italy.

The findings of Prof Iess and his team will boost the view that the 500km-wide moon would be one of the best places beyond Earth to go look for the existence of microbial life.

Cassini's data suggests the liquid volume lies about 40km under Enceladus's ice crust.
This would put it directly on top of the moon's layered, rocky interior.

The case for a subglacial ocean has been growing ever since Cassini first sensed a diffuse atmosphere at the moon in 2005.
Subsequent observations pinned the source of this atmosphere to mineral-rich streams of water vapour flowing away from surface fractures dubbed "tiger stripes" for their resemblance to the markings on a big cat.

Cassini even flew through the plumes to "taste" their load of salts and organic (carbon-rich) molecules.

Enceladus's orbit around Saturn is highly eccentric - it is a big ellipse. The giant planet's gravity should therefore be expected to squeeze and stretch the little moon as it travels this path, heating some of its ices and melting them.

Some of the resulting liquid could then be hurled into space through the deep tiger fractures, although quite how this happens is not yet fully understood.
Nonetheless, the new work reinforces this general picture.

It has involved measuring tiny changes in the speed of Cassini as it passed through Enceladus's own gravitational field.
These changes in velocity were as small as 20 millionths of a metre per second.
They enabled Prof Iess and colleagues to map variations in the distribution of mass on the moon.
The large anomaly they spotted in the data at the southern pole is best explained by the presence of a big volume of water.

"What we see is consistent with a water pocket of about 8-10km in depth, and this pocket can extend up to southern latitudes of 50 degrees around the pole," the Sapienza University of Rome researcher explained.

There is strong evidence to suspect the existence of sub-glacial oceans at a number of Solar System moons.
Saturn's largest satellite, Titan, probably has one. Similarly, the Jupiter moons Europa, Ganymede and Callisto would fall into this class; and perhaps even Triton at Neptune.

Of these, Enceladus and Europa draw the most interest because it is more likely that their water would be in contact with rock.
This could make for some interesting chemistry - the sort of reactions that might facilitate the emergence of life.

Prof Andrew Coates, of the UK's UCL-Mullard Space Science Laboratory, commented: "I think Enceladus has gone to the top of the charts in terms of a place where there could be life.
"It's got several of the things which you need for life - there's certainly the presence of heat, there's liquid water in this ocean, there's organics and that type of chemistry going on.
"The only question is, has there been enough time for life to develop?"

Prof David Stevenson, from the California Institute of Technology, added: "We don't have an answer to that, but there are some theoretical ideas.
"First, let me say that the ocean that we have found could keep things going for tens of millions of years, maybe 100 million years, but, of course, we don't know whether the ocean is being added to at present or is freezing up.
"And, maybe, Enceladus does go through cycles and those cycles would be related to the eccentricity of the orbit. It's possible that the orbit has not always had the same eccentricity."

http://www.bbc.co.uk/news/science-environment-26872184
 
Scientists are about to get their best look ever at the ocean that sloshes beneath the surface of Saturn's icy moon Enceladus.

On Wednesday (Oct. 28), NASA's Cassini spacecraft will zoom just 30 miles (50 kilometers) above Enceladus, flying through and sampling the plume of material that erupts from the satellite's south polar region.

This plume is thought to originate from Enceladus' underground liquid-water ocean, so Cassini's onboard sample analysis should shed light on the moon's potential to host life, mission team members said. [Watch how Cassini will sail through Enceladus' icy plumes]

"On Wednesday, we will plunge deeper into the magnificent plume coming from the south pole than we ever have before, and we will collect the best samples ever from an ocean beyond Earth," Curt Niebur, Cassini program scientist at NASA Headquarters in Washington, D.C., said during a news conference today (Oct. 26).

http://www.scientificamerican.com/article/nasa-probe-to-dive-through-saturn-moon-s-icy-plume/
 
The Cassini spacecraft took a daring plunge into the icy geysers of Saturn's moon Enceladus this week in search of telltale signs of a habitable environment.

The plume continuously jets thousands of miles into space from tiger stripe fissures in the moon's south pole, carrying particles from the vast salty ocean sloshing just beneath the icy surface.

Cassini's sweep though the icy fountain completes its second of three Enceladus flyby missions this year and is NASA's best shot at determining whether this small moon has the right ingredients to harborlife.

The encounter with the mysterious plume lasted only tens of seconds as Cassini hurtled past at a speed of about 19,000 miles per hour, yet in these critical moments up to 10,000 particles per second were sampled and identified using the probe's cosmic dust analyzer. Analysis of this data over the coming weeks could provide the most promising signs of habitability yet in the decade since Cassini's initial flyby of the moon in 2005.

"Cassini's instruments do not have the capability to detect life itself," Cassini project scientist Linda Spilker, told Astrobiology Magazine. "Those instruments can, however, make powerful measurements about the ocean and its potential habitability."

Earl Maize, Cassini's deputy program manager at NASA's Jet Propulsion Laboratory, further clarified the probe's abilities.


“llustration of the interior of Saturn’s moon Enceladus showing a global liquid water ocean between its rocky core and icy crust. Thickness of layers shown here is not to scale.” Credit: NASA/JPL-Caltech
"Cassini has instruments that are capable of detecting complex organic molecules which could possibly be fragments of even larger molecules," he told Astrobiology Magazine, "However, the instruments are not capable of determining whether the processes are biological or geological."

NASA confirmed the existence of a global ocean sandwiched beneath Enceladus' icy crust and rocky core this year when scientists measured a slight gravitational wobble between the north and south pole, an unsteady movement that could only be accounted for by a hidden liquid layer. But what is keeping the underground water liquid and what is the driving force of these plumes? Today's flyby took us one step closer to that answer.

"There's some heat source that has caused a lot of that water-ice to melt and form liquid water," Curt Niebur, program scientist for the Cassini mission, told Astrobiology Magazine. "Our best guess and the most likely culprit is tidal heating from the interaction of Enceladus and the nearby moons and Saturn."

http://phys.org/print365409620.html
 
Enceladus: Does this moon hold a second genesis of life?
Jonathan Amos Science correspondent

The mighty Cassini probe has made many great discoveries at Saturn, but none top its extraordinary revelations at Enceladus.
What the plutonium-powered satellite has seen at this 500km-wide, ice-crusted moon is simply astounding.
Cassini has pictured huge jets of water vapour and other materials spewing from cracks at its south pole.

It's quite a spectacle, and it's unique in the Solar System, according to Carolyn Porco, who runs the camera system on the big spacecraft.
"It became a joke on our team that we had found the Enceladus Interplanetary Geyser Park, and that future generations may go there just for vacation," she tells me in a Discovery programme all about Enceladus which goes out on the BBC World Service on Monday.

But researchers are not laughing when they say this little world is among the best places to search for life beyond Earth.
The plumbing for the jets leads to a vast body of water that may be 30-40km deep in places. And Cassini's instruments have been able to show, by flying through and sampling the emissions, that the conditions and - importantly - the chemistry in this subterranean ocean could support microbial life.
There are strong indications that the water is interacting with rock at the ocean bed, to produce the sort of nutrient cocktail on which simple bugs could dine.

Chris McKay is an astrobiologist with Nasa: "I've been interested in the search for life in the Solar System for decades and I'm still flabbergasted by what we're seeing on Enceladus. It's such a small world so far from Earth, putting out such a wealth of organics and water and indications of habitability - it's astounding, and the samples are right there, free for the taking."

But as capable as Cassini is, its 1980s/90s technology cannot definitely prove the case for microbes under the icy surface of Enceladus.
For that we'd need a different kind of satellite with specialised sensors.

Cassini will make one final close flyby of the moon next week to acquire a last batch of detailed surface pictures.
It will then move across the Saturnian system to prepare for some end-of-mission observations of the ringed planet itself.
So, we're about to bid farewell to Enceladus, and of course that's prompted people to start talking up how we might return one day with far more capable instrumentation.

etc...

http://www.bbc.co.uk/news/science-environment-34963515
 
Delicate space nets. Probes landing with the force of a bomb. Ice-burrowing tunnellers. These are a few of the robots poised to grab the baton from NASA’s Cassini orbiter in the search for alien life on Saturn’s icy moon Enceladus.

As Cassini prepares for a death dive into Saturn next year, planetary scientists met in Boulder, Colorado, last week to discuss its possible successors.

Enceladus has a massive global ocean under its frozen surface, and cracks in its exterior spew plumes of water into space. The plumes continually add icy material to one of Saturn’s rings, and offer a tantalising taste of the water within. But Cassini can’t test them. Its instruments aren’t detailed enough to analyse the water, because when it was built, no one knew the plumes were there.

“That is a very fine example of why it’s so hard to design space missions,” says Alexis Bouquet, a PhD student at the Southwest Research Institute in San Antonio, Texas. “By definition, we are going to an object that we don’t know much about. So we always get surprises.”

As Cassini flew through Enceladus’s plumes a handful of times in the past 11 years, its instruments were flooded with hydrogen molecules, which are a possible smoking gun for hydrothermal vents in the oceans. If confirmed, those vents would have major implications for life beneath the ice.

But it’s unclear whether the hydrogen molecules came from Enceladus or from Cassini itself. That’s because when ice grains in the plumes smack into Cassini’s instruments they break apart, like insects on a car windshield. “They are smashing so fast that they can actually chip the windshield and form tiny craters,” says Bouquet. This releases titanium into Cassini’s instruments, which steals oxygen from the icy water to release hydrogen molecules.

At the meeting in Boulder, Bouquet presented computer simulations he is using to figure out how much water is really there and how much is the instrument’s confusion – although he hasn’t come to a conclusion yet.

To improve matters, a future Enceladus plume sampler could use gold sensors, which wouldn’t react in the same way as the titanium ones. Or it could use a soft, spongy net, similar to the capture devices developed for the Stardust mission, which grabbed a few specks of cosmic dust from interstellar space in 2006.

A net about 12 square centimetres in area would be big enough to capture a few micrograms of plume spray, saysRichard Mathies, a chemist at the University of California at Berkeley. While that’s not a lot, the proposed lab-on-a-chip Enceladus Organic Analyzer — new details of which Mathies’s collaborators presented in Boulder — can sniff out one organic molecule in a billion others, Mathies says.

Landers and drills would be able to get an even closer look at the subsurface sea. But to enter they would have to crash with immense force or melt the ice, disturbing anything living there even as they tried to detect it. Tests on the EOA’s instruments suggest it could still do its job after an impact with an energy 50,000 times greater than Earth’s gravitational pull, which is a greater g-force than that felt by an artillery shell.

At the meeting, Amanda Stockton at the Georgia Institute of Technology presented design concepts with optical instruments in the centre of a lander, which would make them more likely to survive impact.

One other robot concept could break more than just ice grains. A proposed Enceladus Explorer mission could set up a robotic base station near the moon’s southern pole, where the plumes are thought to originate. A robot drill called the IceMole would both melt ice and ram through it, reaching down about 100 to 200 metres to the ocean below the surface. ...

https://www.newscientist.com/articl...ts-could-hunt-for-life-on-icy-moon-enceladus/
 
Saturn moon 'able to support life'
By Jonathan AmosBBC Science Correspondent
  • 13 April 2017
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Image copyrightNASA/JPL-CALTECH/SSI
Image captionEasy to sample: Jets of water spew from the south pole of Enceladus.
Saturn's ice-crusted moon Enceladus may now be the single best place to go to look for life beyond Earth.

The assessment comes on the heels of new observations at the 500km-wide world made by the Cassini probe.

It has flown through and sampled the waters from a subsurface ocean that is being jetted into space.

Cassini’s chemistry analysis strongly suggests the Enceladean seafloor has hot fluid vents - places that on Earth are known to teem with life.

To be clear: the existence of such hydrothermal systems is not a guarantee that organisms are present on the little moon; its environment may still be sterile. But the new results make a compelling case to return to this world with more sophisticated instrumentation - technologies that can re-sample the ejected water for clear evidence that biology is also at play.

"We're pretty darn sure that the internal ocean of Enceladus is habitable and we need to go back and investigate it further," said Cassini scientist Dr Hunter Waite from the Southwest Research Institute in San Antonio, Texas.

"If there is no life there, why not? And if there is, all the better. But you certainly want to ask the question because it's almost as equally as interesting if there is no life there, given the conditions," he told BBC News.

_95631544_1-extremeshrim.jpg
Image copyrightWHOI/NSF/NASA
Image captionOn Earth, the microbes at vents support a range of more complex organisms
The sub-surface ocean on Enceladus is thought to be many kilometres deep, kept liquid by the heat generated from the constant gravitational squeezing the moon receives from the mighty Saturn.

Cassini has already established that this voluminous liquid is in contact with the rock bed from the types of salts and silica that have also been detected in the jets.

But what scientists really wanted to know is if a particular interactive process seen at Earth was taking place in the distant abyss - something called serpentinisation.

At the mid-ocean ridges on our planet, seawater is drawn through, and reacts with, hot upwelling rocks that are rich in iron and magnesium. As the minerals in these rocks incorporate H2O molecules into their crystal structure, they release hydrogen - a byproduct that can be used by some microbes as an energy source to drive their metabolism.

It is the definitive signal for molecular hydrogen in the plumes of Enceladus that Cassini has now confirmed.

"If you were a micro-organism, hydrogen would be like candy - it's your favourite food," explained Dr Chris McKay, an astrobiologist with the US space agency (Nasa).

"It's very good energetically; it can support micro-organisms in grand style. Finding hydrogen is certainly a big plus; icing on the cake for the habitability argument, and a very tasty one at that."

The type of microbes described by Dr McKay are called methanogens because they make methane as they react the hydrogen with carbon dioxide.

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Image copyrightSOURCE: NASA
Nasa, which leads the Cassini mission, was due to make the hydrogen announcement a couple of months after the probe's last fly-through of the moon's jets in October 2015. But the agency held off.

One of the concerns was that the Ion and Neutral Mass Spectrometer on the satellite can actually make molecular hydrogen inside itself if water enters the instrument in a particular way.

Dr Waite's group has spent a year analysing the data to make sure the hydrogen signal is intrinsic to the jets and not merely some artefact of the INMS's operation. And although serpentinisation is arguably the best explanation for the signal, it is possible to produce the gas also from the heating of very primitive (meteoritic) rock.

The Cassini mission is coming to a close. Having spent 12 years circling Saturn, it is now running low on fuel and will be dumped in the atmosphere of the ringed planet in September - to ensure it cannot collide with Enceladus at some future date and contaminate it.

_94954328_mediaitem94954327.jpg
Image copyrightNASA/JPL-CALTECH/SETI INSTITUTE
Image captionEuropa holds a vast, salty ocean beneath its fractured ice shell
As brilliant as the probe's instruments are, they were never designed to make a direct life detection at the bright white moon. This would need a whole new class of spectrometers. A proposal is being put together to fly them in 2026.

Nasa has already green-lit a mission to Europa, an ocean moon of Jupiter. It very likely has serpentinisation going on as well. But its ice shell is very much thicker and it could be that very little of the water escapes to space.

The appeal of Enceladus is the ease with which its subsurface can be studied because of the material carried into space by its network of geysers. A probe only needs fly through the emission to make the investigation.

"The Cassini mission has really brought Enceladus to the fore in terms of the search for life elsewhere in the Solar System," commented British Cassini scientist Dr Andrew Coates.

“The top three now I would say are about equal. There's Mars, which may have had life 3.8 billion years ago when conditions were very different to what they are now. There's Europa, which has a subsurface ocean; and now Enceladus. Those three may have, or had, the right conditions for life."

Dr Waite added: “For life, you need liquid water, organics, and the CHNOPS elements (carbon, hydrogen, nitrogen, oxygen, phosphorus, sulphur). OK, we haven't yet measured phosphorus and sulphur at Enceladus. But you also need some kind of metabolic energy source, and the new Cassini results are an important contribution in that regard."

A paper describing the work of Dr Waite's group is published in the journal Science.

http://www.bbc.co.uk/news/science-environment-39592059
 
Cassini has been studying Saturn and its moons since 2004; some of its many discoveries include finding at least 101 water geysers spouting from the moon Enceladus and discovering evidence of prebiotic chemistry on the moon Titan. ...

https://www.space.com/38135-cassini..._medium=social&utm_campaign=2016twitterdlvrit

Vids at link.

Life On Enceladus?

Microbes that produce methane may already be living on Enceladus, a moon of Saturn which is tipped to host life because it boasts a liquid water ocean beneath a crust of solid ice, and strange atmospheric plumes of water. That’s the implication of research showing that an earthbound organism which also produces methane can happily survive in conditions known to exist on Enceladus, from observations by the Cassini space probe before its mission ended last year.

Isolated from deep sea vents almost 1000 metres deep in the Okinawa Trough off Japan, Methanothermococcus okinawensis was subjected to gruelling physical and chemical conditions found on Enceladus for more than five years.

https://www.newscientist.com/articl...m=SOC&utm_source=Twitter#link_time=1519812211
 
Interesting discoveries from Cassini

Saturn moon a step closer to hosting life
By Mary HaltonScience reporter, BBC News


_102232268_r4000099-enceladus-spl.jpg
Image copyrightNASA
Scientists have found complex carbon-based molecules in the waters of Saturn's moon Enceladus.

Compounds like this have only previously been found on Earth, and in some meteorites.

They are thought to have formed in reactions between water and warm rock at the base of the moon's subsurface ocean.

Though not a sign of life, their presence suggests Enceladus could play host to living organisms.

The discovery came from data gathered by the Cassini spacecraft.

etc

https://www.bbc.co.uk/news/science-environment-44630121
 
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NEW KINDS OF ORGANIC COMPOUNDS’ FOUND ON ALIEN MOON ENCELADUS, SAYS NASA

Source: Independent Newspaper
Date: 2 October, 2019

"New kinds of organic compounds" have been found on an alien moon, Nasa says, in a major breakthrough in the search for extraterrestrial life.

The compounds found on Saturn's moon Enceladus are the ingredients of amino acids, the building blocks of life.

https://www.independent.co.uk/life-...n-organic-compounds-amino-acids-a9133336.html
 
Mysterious stripes on alien world that are ‘like nothing else in our solar system’ finally explained by scientists

Scientists have finally explained the "tiger stripes" that cover the surface of the mysterious moon Enceladus.

Saturn's icy moon is one of the most interesting places in the solar system for scientists. It is not only one of the prime candidates for being home to extraterrestrial life – because of the ocean that hides beneath its surface – but also because it remains so mysterious.

One of those mysteries are the four stripes that cover its south pole, which are like nothing else known in our solar system. Now researchers have revealed the physics behind the fissures that open up and spill ocean water out of the icy surface, and create those stripes.

Scientists did not even know that Enceladus had the stripes until recently, when Nasa's Cassini mission flew past Saturn and took in Enceladus as it did.

"First seen by the Cassini mission to Saturn, these stripes are like nothing else known in our Solar System," lead author Hemingway explained. "They are parallel and evenly spaced, about 130 kilometers long and 35 kilometers apart.
(c) The Independent '19

There a video (with sound track) so turn your vol. down a notch.
 
Further analysis of Cassini data indicates Enceladus is more dynamic than we originally through, and it may be continually resurfacing itslef with ice.
Breathtaking Images Suggest There's Fresh Ice on One of Saturn's Moon

To human eyes, Saturn's moon Enceladus looks relatively plain. Shift the wavelength away from the optical, however, and Enceladus starts to look a lot more interesting, as new images amply demonstrate.

Although its surface is scored with deep chasms and gorges, Enceladus seems fairly uniform otherwise, with a glistening white ice shell, like a giant snowball in space.

In infrared wavelengths, astronomers have discovered that much of the ice over the entirety of the moon is fresh, suggesting there might be global internal activity resurfacing the moon. ...

FULL STORY :
https://www.sciencealert.com/infrared-eyes-see-new-ice-on-the-surface-of-saturn-s-moon-enceladus

PUBLISHED RESEARCH ARTICLE:
https://www.sciencedirect.com/science/article/abs/pii/S0019103520302293?via=ihub#!
 
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