Saturn’s Moon Enceladus

New Organic Compounds Found in Enceladus Ice Grains

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Gretchen McCartney
Jet Propulsion Laboratory, Pasadena, Calif.
gretchen.p.mccartney@jpl.nasa.gov

Alana Johnson
NASA Headquarters, Washington
alana.r.johnson@nasa.gov

PIA09761_hires
In this image captured by NASA’s Cassini spacecraft in 2007, the plumes of Enceladus are clearly visible. The moon is nearly in front of the Sun from Cassini’s viewpoint.Credit: NASA/JPL/Space Science Institute

New kinds of organic compounds, the ingredients of amino acids, have been detected in the plumes bursting from Saturn’s moon Enceladus. The findings are the result of the ongoing deep dive into data from NASA’s Cassini mission.

Powerful hydrothermal vents eject material from Enceladus’ core, which mixes with water from the moon’s massive subsurface ocean before it is released into space as water vapor and ice grains. The newly discovered molecules, condensed onto the ice grains, were determined to be nitrogen- and oxygen-bearing compounds.

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Gretchen McCartney
Jet Propulsion Laboratory, Pasadena, Calif.
gretchen.p.mccartney@jpl.nasa.gov

Alana Johnson
NASA Headquarters, Washington
alana.r.johnson@nasa.gov

PIA09761_hires
In this image captured by NASA’s Cassini spacecraft in 2007, the plumes of Enceladus are clearly visible. The moon is nearly in front of the Sun from Cassini’s viewpoint.Credit: NASA/JPL/Space Science Institute

New kinds of organic compounds, the ingredients of amino acids, have been detected in the plumes bursting from Saturn’s moon Enceladus. The findings are the result of the ongoing deep dive into data from NASA’s Cassini mission.

Powerful hydrothermal vents eject material from Enceladus’ core, which mixes with water from the moon’s massive subsurface ocean before it is released into space as water vapor and ice grains. The newly discovered molecules, condensed onto the ice grains, were determined to be nitrogen- and oxygen-bearing compounds.

Read the rest of this entry »

Water Vapor Plumes Discovered on Jupiter’s Moon Europa

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Written by George McGinn
Cosmology and Space Research
September 27, 2016 at 4:32pm EST

This composite image shows suspected plumes of water vapor erupting at the 7 o’clock position off the limb of Jupiter’s moon Europa. The plumes, photographed by NASA’s Hubble’s Space Telescope Imaging Spectrograph, were seen in silhouette as the moon passed in front of Jupiter. Hubble’s ultraviolet sensitivity allowed for the features — rising over 100 miles (160 kilometers) above Europa’s icy surface — to be discerned. The water is believed to come from a subsurface ocean on Europa. The Hubble data were taken on January 26, 2014. The image of Europa, superimposed on the Hubble data, is assembled from data from the Galileo and Voyager missions. Credits: NASA/ESA/W. Sparks (STScI)/USGS Astrogeology Science Center


In one of the most promising places in the Solar System where life may exist, astronomers using NASA’s Hubble Space Telescope have photographed what appears to be water vapor plumes escaping Jupiter’s moon Europa.

The team from the Space Telescope Science Institute (STScI) in Baltimore saw finger-like projections when viewing Europa as it past in front of Jupiter, according to team leader William Sparks.

The discovery occurred by accident as the team’s original proposal was to observe Europa to determine if it had an atmosphere or exosphere.

An exosphere of neon was detected on Earth’s Moon on August 17, 2015 based on study the data from the Lunar Atmosphere and Dust Environment Explorer (LADEE) spacecraft.

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Saturn’s Geyser Moon Shines in Close Flyby Views

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NASA’s Cassini spacecraft has begun transmitting its latest images of Saturn’s icy, geologically active moon Enceladus, acquired during the dramatic Oct. 28 flyby in which the probe passed about 30 miles (49 kilometers) above the moon’s south polar region. The spacecraft will continue transmitting its data from the encounter for the next several days.

“Cassini’s stunning images are providing us a quick look at Enceladus from this ultra-close flyby, but some of the most exciting science is yet to come,” said Linda Spilker, the mission’s project scientist at NASA’s Jet Propulsion Laboratory in Pasadena, California.

Researchers will soon begin studying data from Cassini’s gas analyzer and dust detector instruments, which directly sampled the moon’s plume of gas and dust-sized icy particles during the flyby. Those analyses are likely to take several weeks, but should provide important insights about the composition of the global ocean beneath Enceladus’ surface and any hydrothermal activity occurring on the ocean floor. The potential for such activity in this small ocean world has made Enceladus a prime target for future exploration in search of habitable environments in the solar system beyond Earth.

In addition to the processed images, unprocessed, or “raw,” images appear on the Cassini mission website at: http://saturn.jpl.nasa.gov/mission/flybys/enceladus20151028

Cassini’s next and final close Enceladus flyby will take place on Dec. 19, when the spacecraft will measure the amount of heat coming from the moon’s interior. The flyby will be at an altitude of 3,106 miles (4,999 kilometers).

Additional information and multimedia products for Cassini’s final Enceladus flybys are available at: http://solarsystem.nasa.gov/finalflybys

The Cassini-Huygens mission is a cooperative project of NASA, ESA (European Space Agency) and the Italian Space Agency. NASA’s Jet Propulsion Laboratory in Pasadena, California, manages the mission for the agency’s Science Mission Directorate in Washington. JPL is a division of the California Institute of Technology in Pasadena. The Cassini imaging operations center is based at the Space Science Institute in Boulder, Colorado.

For more information about Cassini, visit: http://www.nasa.gov/cassini or http://saturn.jpl.nasa.gov

NASA’s Cassini spacecraft has begun transmitting its latest images of Saturn’s icy, geologically active moon Enceladus, acquired during the dramatic Oct. 28 flyby in which the probe passed about 30 miles (49 kilometers) above the moon’s south polar region. The spacecraft will continue transmitting its data from the encounter for the next several days.

“Cassini’s stunning images are providing us a quick look at Enceladus from this ultra-close flyby, but some of the most exciting science is yet to come,” said Linda Spilker, the mission’s project scientist at NASA’s Jet Propulsion Laboratory in Pasadena, California.
Researchers will soon begin studying data from Cassini’s gas analyzer and dust detector instruments, which directly sampled the moon’s plume of gas and dust-sized icy particles during the flyby. Those analyses are likely to take several weeks, but should provide important insights about the composition of the global ocean beneath Enceladus’ surface and any hydrothermal activity occurring on the ocean floor. The potential for such activity in this small ocean world has made Enceladus a prime target for future exploration in search of habitable environments in the solar system beyond Earth.
In addition to the processed images, unprocessed, or “raw,” images appear on the Cassini mission website at: http://saturn.jpl.nasa.gov/mission/flybys/enceladus20151028

Cassini’s next and final close Enceladus flyby will take place on Dec. 19, when the spacecraft will measure the amount of heat coming from the moon’s interior. The flyby will be at an altitude of 3,106 miles (4,999 kilometers).
Additional information and multimedia products for Cassini’s final Enceladus flybys are available at: http://solarsystem.nasa.gov/finalflybys

The Cassini-Huygens mission is a cooperative project of NASA, ESA (European Space Agency) and the Italian Space Agency. NASA’s Jet Propulsion Laboratory in Pasadena, California, manages the mission for the agency’s Science Mission Directorate in Washington. JPL is a division of the California Institute of Technology in Pasadena. The Cassini imaging operations center is based at the Space Science Institute in Boulder, Colorado.

For more information about Cassini, visit: http://www.nasa.gov/cassini or http://saturn.jpl.nasa.gov

Saturn Moon’s Activity Could Be ‘Curtain Eruptions’

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Recent research suggests much of the eruption activity on the surface of Saturn’s moon Enceladus could be in the form of broad, curtain-like eruptions, rather than discrete jets. Image credit: NASA/JPL-Caltech/SSI/PSI
 


New research using data from NASA’s Cassini mission suggests most of the eruptions from Saturn’s moon Enceladus might be diffuse curtains rather than discrete jets. Many features that appear to be individual jets of material erupting along the length of prominent fractures in the moon’s south polar region might be phantoms created by an optical illusion, according to the new study.

The research is being published on Thursday, May 7, in the journal Nature.

“We think most of the observed activity represents curtain eruptions from the ‘tiger stripe’ fractures, rather than intermittent geysers along them,” said Joseph Spitale, lead author of the study and a participating scientist on the Cassini mission at the Planetary Science Institute in Tucson, Arizona. “Some prominent jets likely are what they appear to be, but most of the activity seen in the images can be explained without discrete jets.”

In analyzing Cassini’s images of the eruptions on Enceladus, Spitale and colleagues took particular note of the faint background glow present in most images. The brightest eruption features, which appear to be discrete jets, look to them to be superimposed intermittently upon this background structure.

The researchers modeled eruptions on Enceladus as uniform curtains along the tiger stripe fractures. They found that phantom brightness enhancements appear in places where the viewer is looking through a “fold” in the curtain. The folds exist because the fractures in Enceladus’ surface are more wavy than perfectly straight. The researchers think this optical illusion is responsible for most of what appear to be individual jets.

“The viewing direction plays an important role in where the phantom jets appear,” said Spitale. “If you rotated your perspective around Enceladus’ south pole, such jets would seem to appear and disappear.”

Phantom jets in simulated images produced by the scientists line up nicely with some of the features in real Cassini images that appear to be discrete columns of spray. The correspondence between simulation and spacecraft data suggests that much of the discrete-jet structure is an illusion, according to the researchers.

Curtain eruptions occur on Earth where molten rock, or magma, gushes out of a deep fracture. These eruptions, which often create spectacular curtains of fire, are seen in places such as Hawaii, Iceland and the Galapagos Islands.

“Our understanding of Enceladus continues to evolve, and we’ve come to expect surprises along the way,” said Linda Spilker, Cassini project scientist at NASA’s Jet Propulsion Laboratory, Pasadena, California, who was not involved in the study. “This little ice world is becoming more exciting, not less, as we tease out new details about its subsurface ocean and astonishing geophysical activity.”

The Cassini-Huygens mission is a cooperative project of NASA, ESA (European Space Agency) and the Italian Space Agency. NASA’s Jet Propulsion Laboratory in Pasadena, California, manages the mission for the agency’s Science Mission Directorate in Washington. The Cassini imaging operations center is based at the Space Science Institute in Boulder, Colorado.

For more information about Cassini, visit: http://www.nasa.gov/cassini and http://saturn.jpl.nasa.gov

Icy Tendrils Reaching into Saturn Ring Traced to Their Source

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This collage, consisting of two Cassini images of long, sinuous, tendril-like features from Saturn’s moon Enceladus and two corresponding computer simulations of the same, illustrates how well the structures, and the sizes of the particles composing them, can be modeled by tracing the trajectories of tiny, icy grains ejected from Enceladus’ south polar geysers. Credit: NASA/JPL-Caltech/Space Science Institute
 

Long, sinuous, tendril-like structures seen in the vicinity of Saturn’s icy moon Enceladus originate directly from geysers erupting from its surface, according to scientists studying images from NASA’s Cassini spacecraft.

This result is published online today in a study in the Astronomical Journal, along with additional insights into the nature of the structures.

“We’ve been able to show that each unique tendril structure can be reproduced by particular sets of geysers on the moon’s surface,” said Colin Mitchell, a Cassini imaging team associate at the Space Science Institute in Boulder, Colorado, and lead author of the paper. Mitchell and colleagues used computer simulations to follow the trajectories of ice grains ejected from individual geysers. The geysers, which were discovered by Cassini in 2005, are jets of tiny water ice particles, water vapor and simple organic compounds.

Under certain lighting conditions, Cassini’s wide-view images showing icy material erupting from Enceladus reveal faint, finger-like features, dubbed “tendrils” by the imaging team. The tendrils reach into Saturn’s E ring — the ring in which Enceladus orbits — extending tens of thousands of miles (or kilometers) away from the moon. Since the tendrils were discovered, scientists have thought they were the result of the moon’s geysering activity and the means by which Enceladus supplies material to the E ring. But the ghostly features had never before been traced directly to geysers on the surface.

Because the team was able to show that tendril structures of different shapes correspond to different sizes of geyser particles, the team was able to zero in on the sizes of the particles forming them. They found the tendrils are composed of particles with diameters no smaller than about a hundred thousandth of an inch, a size consistent with the measurements of E-ring particles made by other Cassini instruments.

As the researchers examined images from different times and positions around Saturn, they also found that the detailed appearance of the tendrils changes over time. “It became clear to us that some features disappeared from one image to the next,” said John Weiss, an imaging team associate at Saint Martin’s University in Lacey, Washington, and an author on the paper.

The authors suspect that changes in the tendrils’ appearance likely result from the cycle of tidal stresses — squeezing and stretching of the moon as it orbits Saturn — and its control of the widths of fractures from which the geysers erupt. The stronger the tidal stresses raised by Saturn at any point on the fractures, the wider the fracture opening and the greater the eruption of material. The authors will investigate in future work whether this theory explains the tendrils’ changing appearance.

There is even more that can be extracted from the images, the scientists say. “As the supply lanes for Saturn’s E ring, the tendrils give us a way to ascertain how much mass is leaving Enceladus and making its way into Saturn orbit,” said Carolyn Porco, team leader for the imaging experiment and a coauthor on the paper. “So, another important step is to determine how much mass is involved, and thus estimate how much longer the moon’s sub-surface ocean may last.” An estimate of the lifetime of the ocean is important in understanding the evolution of Enceladus over long timescales.

Because of its significance to the investigation of possible extraterrestrial habitable zones, Enceladus is a major target of investigation for the final years of the Cassini mission. Many observations, including imaging of the plume and tendril features, and thermal observations of the surface of its south polar geyser basin, are planned during the next couple of years.

The Cassini-Huygens mission is a cooperative project of NASA, ESA (European Space Agency) and the Italian Space Agency. NASA’s Jet Propulsion Laboratory in Pasadena, California, manages the mission for the agency’s Science Mission Directorate in Washington. JPL is a division of the California Institute of Technology in Pasadena. The Cassini imaging operations center is based at the Space Science Institute in Boulder, Colo.

New images released today can be found at:

http://www.ciclops.org/view_event/205

More information about Cassini, visit:

http://www.nasa.gov/cassini

http://saturn.jpl.nasa.gov

The Solar System and Beyond is Awash in Water

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NASA is exploring our solar system and beyond to understand the workings of the universe, searching for water and life among the stars. Image credit: NASA

As NASA missions explore our solar system and search for new worlds, they are finding water in surprising places. Water is but one piece of our search for habitable planets and life beyond Earth, yet it links many seemingly unrelated worlds in surprising ways. 

“NASA science activities have provided a wave of amazing findings related to water in recent years that inspire us to continue investigating our origins and the fascinating possibilities for other worlds, and life, in the universe,” said Ellen Stofan, chief scientist for the agency. “In our lifetime, we may very well finally answer whether we are alone in the solar system and beyond.”

The chemical elements in water, hydrogen and oxygen, are some of the most abundant elements in the universe. Astronomers see the signature of water in giant molecular clouds between the stars, in disks of material that represent newborn planetary systems, and in the atmospheres of giant planets orbiting other stars. 

There are several worlds thought to possess liquid water beneath their surfaces, and many more that have water in the form of ice or vapor. Water is found in primitive bodies like comets and asteroids, and dwarf planets like Ceres. The atmospheres and interiors of the four giant planets — Jupiter, Saturn, Uranus and Neptune — are thought to contain enormous quantities of the wet stuff, and their moons and rings have substantial water ice.

Perhaps the most surprising water worlds are the five icy moons of Jupiter and Saturn that show strong evidence of oceans beneath their surfaces: Ganymede, Europa and Callisto at Jupiter, and Enceladus and Titan at Saturn. 

Scientists using NASA’s Hubble Space Telescope recently provided powerful evidence that Ganymede has a saltwater, sub-surface ocean, likely sandwiched between two layers of ice. 

Europa and Enceladus are thought to have an ocean of liquid water beneath their surface in contact with mineral-rich rock, and may have the three ingredients needed for life as we know it: liquid water, essential chemical elements for biological processes, and sources of energy that could be used by living things. NASA’s Cassini mission has revealed Enceladus as an active world of icy geysers. Recent research suggests it may have hydrothermal activity on its ocean floor, an environment potentially suitable for living organisms. 

NASA spacecraft have also found signs of water in permanently shadowed craters on Mercury and our moon, which hold a record of icy impacts across the ages like cryogenic keepsakes.

While our solar system may seem drenched in some places, others seem to have lost large amounts of water. 

On Mars, NASA spacecraft have found clear evidence that the Red Planet had water on its surface for long periods in the distant past. NASA’s Curiosity Mars Rover discovered an ancient streambed that existed amidst conditions favorable for life as we know it.

More recently, NASA scientists using ground-based telescopes were able to estimate the amount of water Mars has lost over the eons. They concluded the planet once had enough liquid water to form an ocean occupying almost half of Mars’ northern hemisphere, in some regions reaching depths greater than a mile (1.6 kilometers). But where did the water go? 

It’s clear some of it is in the Martian polar ice caps and below the surface. We also think much of Mars’ early atmosphere was stripped away by the wind of charged particles that streams from the sun, causing the planet to dry out. NASA’s MAVEN mission is hard at work following this lead from its orbit around Mars. 

The story of how Mars dried out is intimately connected to how the Red Planet’s atmosphere interacts with the solar wind. Data from the agency’s solar missions — including STEREO, Solar Dynamics Observatory and the planned Solar Probe Plus — are vital to helping us better understand what happened.

Understanding the distribution of water in our solar system tells us a great deal about how the planets, moons, comets and other bodies formed 4.5 billion years ago from the disk of gas and dust that surrounded our sun. The space closer to the sun was hotter and drier than the space farther from the sun, which was cold enough for water to condense. The dividing line, called the “frost line,” sat around Jupiter’s present-day orbit. Even today, this is the approximate distance from the sun at which the ice on most comets begins to melt and become “active.” Their brilliant spray releases water ice, vapor, dust and other chemicals, which are thought to form the bedrock of most worlds of the frigid outer solar system.

Scientists think it was too hot in the solar system’s early days for water to condense into liquid or ice on the inner planets, so it had to be delivered — possibly by comets and water-bearing asteroids. NASA’s Dawn mission is currently studying Ceres, which is the largest body in the asteroid belt between Mars and Jupiter. Researchers think Ceres might have a water-rich composition similar to some of the bodies that brought water to the three rocky, inner planets, including Earth.

The amount of water in the giant planet Jupiter holds a critical missing piece to the puzzle of our solar system’s formation. Jupiter was likely the first planet to form, and it contains most of the material that wasn’t incorporated into the sun. The leading theories about its formation rest on the amount of water the planet soaked up. To help solve this mystery, NASA’s Juno mission will measure this important quantity beginning in mid-2016.

Looking further afield, observing other planetary systems as they form is like getting a glimpse of our own solar system’s baby pictures, and water is a big part of that story. For example, NASA’s Spitzer Space Telescope has observed signs of a hail of water-rich comets raining down on a young solar system, much like the bombardment planets in our solar system endured in their youth. 

With the study of exoplanets — planets that orbit other stars — we are closer than ever to finding out if other water-rich worlds like ours exist. In fact, our basic concept of what makes planets suitable for life is closely tied to water: Every star has a habitable zone, or a range of distances around it in which temperatures are neither too hot nor too cold for liquid water to exist. NASA’s planet-hunting Kepler mission was designed with this in mind. Kepler looks for planets in the habitable zone around many types of stars.

Recently verifying its thousandth exoplanet, Kepler data confirm that the most common planet sizes are worlds just slightly larger than Earth. Astronomers think many of those worlds could be entirely covered by deep oceans. Kepler’s successor, K2, continues to watch for dips in starlight to uncover new worlds. 

The agency’s upcoming TESS mission will search nearby, bright stars in the solar neighborhood for Earth- and super-Earth-sized exoplanets. Some of the planets TESS discovers may have water, and NASA’s next great space observatory, the James Webb Space Telescope, will examine the atmospheres of those special worlds in great detail. 

It’s easy to forget that the story of Earth’s water, from gentle rains to raging rivers, is intimately connected to the larger story of our solar system and beyond. But our water came from somewhere — every world in our solar system got its water from the same shared source. So it’s worth considering that the next glass of water you drink could easily have been part of a comet, or an ocean moon, or a long-vanished sea on the surface of Mars. And note that the night sky may be full of exoplanets formed by similar processes to our home world, where gentle waves wash against the shores of alien seas.

 

JPL: Saturn Moon’s Ocean May Harbor Hydrothermal Activity

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This cutaway view of Saturn’s moon Enceladus is an artist’s rendering that depicts possible hydrothermal activity that may be taking place on and under the seafloor of the moon’s subsurface ocean, based on recently published results from NASA’s Cassini mission.


Spacecraft Data Suggest Saturn Moon’s Ocean May Harbor Hydrothermal Activity

Fast Facts:

› Cassini finds first evidence of active hot-water chemistry beyond planet Earth

› Findings in two separate papers support the notion

› The results have important implications for the habitability of icy worlds

NASA’s Cassini spacecraft has provided scientists the first clear evidence that Saturn’s moon Enceladus exhibits signs of present-day hydrothermal activity which may resemble that seen in the deep oceans on Earth. The implications of such activity on a world other than our planet open up unprecedented scientific possibilities.

“These findings add to the possibility that Enceladus, which contains a subsurface ocean and displays remarkable geologic activity, could contain environments suitable for living organisms,” said John Grunsfeld, astronaut and associate administrator of NASA’s Science Mission Directorate in Washington. “The locations in our solar system where extreme environments occur in which life might exist may bring us closer to answering the question: are we alone in the universe.”

Hydrothermal activity occurs when seawater infiltrates and reacts with a rocky crust and emerges as a heated, mineral-laden solution, a natural occurrence in Earth’s oceans. According to two science papers, the results are the first clear indications an icy moon may have similar ongoing active processes.

The first paper, published this week in the journal Nature, relates to microscopic grains of rock detected by Cassini in the Saturn system. An extensive, four-year analysis of data from the spacecraft, computer simulations and laboratory experiments led researchers to the conclusion the tiny grains most likely form when hot water containing dissolved minerals from the moon’s rocky interior travels upward, coming into contact with cooler water. Temperatures required for the interactions that produce the tiny rock grains would be at least 194 degrees Fahrenheit (90 degrees Celsius).

“It’s very exciting that we can use these tiny grains of rock, spewed into space by geysers, to tell us about conditions on — and beneath — the ocean floor of an icy moon,” said the paper’s lead author Sean Hsu, a postdoctoral researcher at the University of Colorado at Boulder.

Cassini’s cosmic dust analyzer (CDA) instrument repeatedly detected miniscule rock particles rich in silicon, even before Cassini entered Saturn’s orbit in 2004. By process of elimination, the CDA team concluded these particles must be grains of silica, which is found in sand and the mineral quartz on Earth. The consistent size of the grains observed by Cassini, the largest of which were 6 to 9 nanometers, was the clue that told the researchers a specific process likely was responsible.

On Earth, the most common way to form silica grains of this size is hydrothermal activity under a specific range of conditions; namely, when slightly alkaline and salty water that is super-saturated with silica undergoes a big drop in temperature.

“We methodically searched for alternate explanations for the nanosilica grains, but every new result pointed to a single, most likely origin,” said co-author Frank Postberg, a Cassini CDA team scientist at Heidelberg University in Germany.

Hsu and Postberg worked closely with colleagues at the University of Tokyo who performed the detailed laboratory experiments that validated the hydrothermal activity hypothesis. The Japanese team, led by Yasuhito Sekine, verified the conditions under which silica grains form at the same size Cassini detected. The researchers think these conditions may exist on the seafloor of Enceladus, where hot water from the interior meets the relatively cold water at the ocean bottom.

The extremely small size of the silica particles also suggests they travel upward relatively quickly from their hydrothermal origin to the near-surface sources of the moon’s geysers. From seafloor to outer space, a distance of about 30 miles (50 kilometers), the grains spend a few months to a few years in transit, otherwise they would grow much larger.

The authors point out that Cassini’s gravity measurements suggest Enceladus’ rocky core is quite porous, which would allow water from the ocean to percolate into the interior. This would provide a huge surface area where rock and water could interact.

The second paper, recently published in Geophysical Research Letters, suggests hydrothermal activity as one of two likely sources of methane in the plume of gas and ice particles that erupts from the south polar region of Enceladus. The finding is the result of extensive modeling to address why methane, as previously sampled by Cassini, is curiously abundant in the plume.

The team found that, at the high pressures expected in the moon’s ocean, icy materials called clathrates could form that imprison methane molecules within a crystal structure of water ice. Their models indicate that this process is so efficient at depleting the ocean of methane that the researchers still needed an explanation for its abundance in the plume.

In one scenario, hydrothermal processes super-saturate the ocean with methane. This could occur if methane is produced faster than it is converted into clathrates. A second possibility is that methane clathrates from the ocean are dragged along into the erupting plumes and release their methane as they rise, like bubbles forming in a popped bottle of champagne.

The authors agree both scenarios are likely occurring to some degree, but they note that the presence of nanosilica grains, as documented by the other paper, favors the hydrothermal scenario.

“We didn’t expect that our study of clathrates in the Enceladus ocean would lead us to the idea that methane is actively being produced by hydrothermal processes,” said lead author Alexis Bouquet, a graduate student at the University of Texas at San Antonio. Bouquet worked with co-author Hunter Waite, who leads the Cassini Ion and Neutral Mass Spectrometer (INMS) team at Southwest Research Institute in San Antonio.

Cassini first revealed active geological processes on Enceladus in 2005 with evidence of an icy spray issuing from the moon’s south polar region and higher-than-expected temperatures in the icy surface there. With its powerful suite of complementary science instruments, the mission soon revealed a towering plume of water ice and vapor, salts and organic materials that issues from relatively warm fractures on the wrinkled surface. Gravity science results published in 2014 strongly suggested the presence of a 6-mile- (10-kilometer-) deep ocean beneath an ice shell about 19 to 25 miles (30 to 40 kilometers) thick.

The Cassini-Huygens mission is a cooperative project of NASA, ESA (European Space Agency) and the Italian Space Agency. NASA’s Jet Propulsion Laboratory in Pasadena, California, manages the mission for the agency’s Science Mission Directorate in Washington. The Cassini CDA instrument was provided by the German Aerospace Center. The instrument team, led by Ralf Srama, is based at the University of Stuttgart in Germany. JPL is a division of the California Institute of Technology in Pasadena.

More information about Cassini, visit:

http://www.nasa.gov/cassini

and

http://saturn.jpl.nasa.gov