Tag: Enceladus

Io’s volcanoes get their lava from separate magma chambers, not a global underground ocean of magma

11:11 am

Io's interior as presently theorized
Click for original animation.

Using data collected from Juno’s multiple fly-bys of the Jupiter moon Io, scientists now hypothesize that the moon does not have a global underground ocean of magma, feeding its many volcanoes, but that instead each volcano is fed its lava from a separate magma chamber.

The graphic to the right illustrates the present conclusion. You can read the paper here [pdf]. From the press release:

The Juno team compared Doppler data from their two flybys with observations from the agency’s previous missions to the Jovian system and from ground telescopes. They found tidal deformation consistent with Io not having a shallow global magma ocean.

“Juno’s discovery that tidal forces do not always create global magma oceans does more than prompt us to rethink what we know about Io’s interior,” said lead author Ryan Park, a Juno co-investigator and supervisor of the Solar System Dynamics Group at JPL. “It has implications for our understanding of other moons, such as Enceladus and Europa, and even exoplanets and super-Earths. Our new findings provide an opportunity to rethink what we know about planetary formation and evolution.” [emphasis mine]

The highlighted words indicate the significance of this data. It possibly suggests that the underground oceans of water that have been theorized for these other moons — where life could possibly exist — might be mistaken. Instead, they might have smaller pockets of water, similar to Io’s many magma chambers.

Everything here however is uncertain, including these new conclusions about Io. We just don’t have enough data from any of these moons to make any definitive conclusions.

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Scientists detect evidence of phosphorus coming from the interior of Enceladus

9:13 am

Using archival data from the Cassini orbiter, scientists have now detected the first evidence of phosphorus – a key element in the development of life on Earth – coming from the interior of the Saturn moon Enceladus.

The small moon is known to possess a subsurface ocean, and water from that ocean erupts through cracks in Enceladus’ icy crust as geysers at its south pole, creating a plume. The plume then feeds Saturn’s E ring (a faint ring outside of the brighter main rings) with icy particles.

During its mission at the gas giant from 2004 to 2017, Cassini flew through the plume and E ring numerous times. Scientists found that Enceladus’ ice grains contain a rich array of minerals and organic compounds – including the ingredients for amino acids – associated with life as we know it.

Phosphorus, the least abundant of the essential elements necessary for biological processes, hadn’t been detected until now. The element is a building block for DNA, which forms chromosomes and carries genetic information, and is present in the bones of mammals, cell membranes, and ocean-dwelling plankton. Phosphorus is also a fundamental part of energy-carrying molecules present in all life on Earth. Life wouldn’t be possible without it.

“We previously found that Enceladus’ ocean is rich in a variety of organic compounds,” said Frank Postberg, a planetary scientist at Freie Universität Berlin, Germany, who led the new study, published on Wednesday, June 14, in the journal Nature. “But now, this new result reveals the clear chemical signature of substantial amounts of phosphorus salts inside icy particles ejected into space by the small moon’s plume. It’s the first time this essential element has been discovered in an ocean beyond Earth.”

You can read the paper here. It is very important to emphasize that though phosphorus is essential for life, life in the underground ocean of Enceladus has not been discovered. The scientists have merely found evidence of this specific ingredient needed for life, suggesting that these ingredients are common in our solar system. Going from a list of ingredients to a finished dish one can eat is something else entirely.

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Webb detects large water plume released from Saturn’s moon Enceladus

9:10 am

Water vapor plume seen by Webb
Click for original image.

Using the infrared cameras on the Webb Space Telescope, astronomers have detected a surprisingly long and large plume of water vapor erupting from the tiger stripe fractures on Saturn’s moon Enceladus that scientists for years have detected vapor plumes.

The false color image to the right shows that plume.

A water vapor plume from Saturn’s moon Enceladus spanning more than 6,000 miles – nearly the distance from Los Angeles, California to Buenos Aires, Argentina – has been detected by researchers using NASA’s James Webb Space Telescope. Not only is this the first time such a water emission has been seen over such an expansive distance, but Webb is also giving scientists a direct look, for the first time, at how this emission feeds the water supply for the entire system of Saturn and its rings.

…The length of the plume was not the only characteristic that intrigued researchers. The rate at which the water vapor is gushing out, about 79 gallons per second, is also particularly impressive. At this rate, you could fill an Olympic-sized swimming pool in just a couple of hours. In comparison, doing so with a garden hose on Earth would take more than 2 weeks.

Though that rate of release sounds large, we must remember it is being released from a moon 313 miles across. From that perspective the rate of flow is quite reasonable.

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Scientists: Enceladus’ tiger stripes come from underground ocean

9:58 am

The uncertainty of science: Using a new computer model, scientists now think they have shown how on the Saturn moon Enceladus pressure from an underground ocean can push through cracks to produce geysers on the surface.

Rudolph and his colleagues ran a physics-based model to map the conditions that could allow the cracks from the surface to reach the ocean and cause the eruptions. The model accounts for cycles of warming and cooling that last on the scale of a hundred million years, associated with changes in Enceladus’ orbit around Saturn. During each cycle, the ice shell undergoes a period of thinning and a period of thickening. The thickening happens through freezing at the base of the ice shell, which grows downward like the ice on a lake, Rudolph said.

The pressure exerted by this downward-expanding ice on the ocean below is one possible mechanism researchers have proposed to explain Enceladus’ geysers. As the outer ice shell cools and thickens, pressure increases on the ocean underneath because ice has more volume than water. The increasing pressure also generates stress in the ice, which could become pathways for fluid to reach the surface 20-30 kilometers away.

You can read the paper here.

Be warned: This is only a model. Moreover, its conclusions suggest that this mechanism will not work on Jupiter’s moon Europa, which has many planet-wide crack-like features that suggest (as yet unconfirmed) a bubbling up from below.

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A hint of unexpected fresh ice on Enceladus

11:53 am

Two views of Enceladus
Click for full image.

Using data collected by Cassini while it orbited Saturn for thirteen years, scientists have found that there might be more relatively fresh ice on the surface of the moon Enceladus than previously believed.

Cassini scientists discovered in 2005 that Enceladus – which looks like a highly reflective, bright white snowball to the naked eye – shoots out enormous plumes of ice grains and vapor from an ocean that lies under the icy crust. The new spectral map shows that infrared signals clearly correlate with that geologic activity, which is easily seen at the south pole. That’s where the so-called “tiger stripe” gashes blast ice and vapor from the interior ocean.

But some of the same infrared features also appear in the northern hemisphere. That tells scientists not only that the northern area is covered with fresh ice but that the same kind of geologic activity – a resurfacing of the landscape – has occurred in both hemispheres. The resurfacing in the north may be due either to icy jets or to a more gradual movement of ice through fractures in the crust, from the subsurface ocean to the surface.

The image above, cropped, reduced, and rearranged to post here, shows two views of Enceladus. On the left we are looking at one hemisphere, with the south pole at the bottom. On the right we are looking straight down at the south pole. The red areas are where scientists think there is relatively fresh ice. While the new ice is very pronounced at the south pole, where the tiger-striped vents have been found, the northern ice is much less evident, though clearly there.

That northern fresh ice however might not come from the planet’s interior, as suggested by the press release. It might also be new ice deposited from space that came from those very active tiger stripes. At the present time the data doesn’t allow for any solid conclusions.

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More organics detected in Enceladus’ plumes

10:23 am

Using Cassini archived data scientists have detected evidence of new organic molecules in the water-ice plumes coming from the tiger stripe fissures on Saturn’s moon Enceladus.

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.

On Earth, similar compounds are part of chemical reactions that produce amino acids, the building blocks of life. Hydrothermal vents on the ocean floor provide the energy that fuels the reactions. Scientists believe Enceladus’ hydrothermal vents may operate in the same way, supplying energy that leads to the production of amino acids.

For clarity I should point out that I am using the term “organics” as chemists do. It refers not to life, but to any molecule that is formed using carbon.

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The never-ending snowstorm circling Saturn

10:21 am

New data suggests that the water being spewed out of Enceladus’s tiger stripes is depositing so much snow and ice on Saturn’s three inner moons, Mimas, Enceladus and Tethys, that these moons, as well as Enceladus, are about twice as bright in radar than previously thought.

Dr Le Gall and a team of researchers from France and the US have analysed 60 radar observations of Saturn’s inner moons, drawing from the full database of observations taken by the Cassini mission between 2004 and 2017. They found that previous reporting on these observations had underestimated the radar brightness by a factor of two.

Unprotected by any atmospheres, Saturn’s inner moons are bombarded by grains of various origins which alter their surface composition and texture. Cassini radar observations can help assess these effects by giving insights into the purity of the satellites’ water ice.

The extreme radar brightness is most likely related to the geysers that pump water from Enceladus’s internal ocean into the region in which the three moons orbit. Ultra-clean water ice particles fall back onto Enceladus itself and precipitate as snow on the other moons’ surfaces.

Dr Le Gall, of LATMOS-UVSQ, Paris, explained: “The super-bright radar signals that we observe require a snow cover that is at least a few tens of centimetres thick. However, the composition alone cannot explain the extremely bright levels recorded. Radar waves can penetrate transparent ice down to few meters and therefore have more opportunities to bounce off buried structures. The sub-surfaces of Saturn’s inner moons must contain highly efficient retro-reflectors that preferentially backscatter radar waves towards their source.”

While the new results suggest that the surfaces of these moons are much brighter that expected, I find the circumstances they describe far more fascinating: a never-ending snow storm in the orbits around Saturn and landing continually on these moons.

My, isn’t the universe wonderful?

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Complex carbon molecules from within Enceladus

9:11 am

Scientists have determined, using Cassini data, that there are complex carbon molecules spewing from the tiger stripes on Saturn’s moon Enceladus.

Putting it all together, the scientists concluded that the Cassini spacecraft was encountering dust particles rich in carbon in large, complex “macromolecular structures”. The only place this material could have come from was the interior of Enceladus, from which ice, dust and gas is jetting out in geyser-like plumes. These plumes are fed by vapours escaping from a sub-surface ocean.

“So this is a direct sample of the Enceladus ocean,” Khawaja says.

What exactly the newly discovered organic materials are is open for debate, although Khawaja believes they most likely are made of large numbers of ring-like structures cross-linked by hydrocarbon chains. An important hint comes from the fact that the organic-rich grains don’t contain much water, implying that the materials in them don’t easily mix with water. Khawaja hypothesises that they formed deep inside Enceladus, then rose to the top of its underwater ocean, where they formed a thin film akin to an earthly oil slick.

Just to be very clear, they have not discovered life. What they have found however increases the chances that there is life within Enceladus’s underground ocean.

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Methane detected on Enceladus could come from microbes

8:38 am

The uncertainty of science: New research has found that the methane that Cassini detected being released from Enceladus’s interior could conceivably come from at least one Earth-type microbe.

Using various mixtures of gases held at a range of temperatures and pressures in enclosed chambers called “bioreactors,” Rittmann and his co-authors cultivated three microorganisms belonging to the oldest branch of Earth’s tree of life, known as Archaea. In particular, they focused on Archaean microbes that are also methanogens, which are able to live without oxygen and produce methane from that anaerobic metabolism. The team examined the simplest types of microbes, which could be the primary producers of methane at the base of a possibly more complex ecological food chain within the moon.

They tried to simulate the conditions that could exist within and around Enceladus’s hydrothermal vents, which are thought to resemble those found at a few deep-sea sites on Earth, often near volcanically active mid-oceanic ridges. According to their tests, only one candidate, the deep-sea microbe Methanothermococcus okinawensis, could grow there—even in the presence of compounds such as ammonia and carbon monoxide, which hinder the growth of other similar organisms.

There are a lot of fake news stories today trumpeting this result as proof that alien microbes can exist on Enceladus. The data does no such thing. All it shows that one methane producing microbe could possibly live in an environment that researchers guess might somewhat resemble the situation on Enceladus. However, as the article admits,

Scientists do not really know the precise conditions on Enceladus yet, of course. And in any case it is possible any life there, if it exists, is nothing like any DNA-based organism on our planet, rendering our Earth-based extrapolations moot. What’s more, these findings only show microbial life might exist in one particular subset of possible environments within the moon’s dark ocean.

This result is interesting, but it really proves nothing about Enceladus itself.

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Billionaire Yuri Milner considering funding mission to Enceladus

9:21 pm

Capitalism in space: Billionaire Yuri Milner, who already funds several astronomy projects aimed at interstellar travel, is now considering funding a planetary probe to the Saturn moon Enceladus.

At the moment all he is doing is holding workshops with scientists and engineers to see if such a mission can be done for an amount he can afford. Considering that Elon Musk’s first concept to send a private probe to Mars, before SpaceX existed, was stopped because of high launch costs, thus becoming the inspiration for SpaceX itself in order to lower those costs, Milner’s private effort might actually be affordable now.

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Cassini says goodbye to Saturn

9:27 am

Saturn, October 2016

Cool image time! The picture above, reduced in resolution to show here, was taken in October 2016 during one of Cassini’s last distant orbits that gave it a global view of Saturn and its rings. Since it began its dives close to the gas giant such views have not been possible.

The mission ends this coming Saturday with a dive into Saturn. It was launched in October 1997, and after a seven year journey has spent the last thirteen years in orbit around the planet, providing us the first long term glimpse of a gas giant as its seasons evolved.

Cassini has been orbiting Saturn for nearly a half of a Saturnian year but that journey is nearing its end. This extended stay has permitted observations of the long-term variability of the planet, moons, rings, and magnetosphere, observations not possible from short, fly-by style missions.

When the spacecraft arrived at Saturn in 2004, the planet’s northern hemisphere, seen here at top, was in darkness, just beginning to emerge from winter (see Cassini’s Holiday Greetings​). Now at journey’s end, the entire north pole is bathed in the continuous sunlight of summer.

The spacecraft was also able to observe the seasonal changes that occurred to Titan. It also studied the plumes coming from the tiger stripe cracks on Enceladus, shown below the fold in a movie created by Cassini over a 14 hour time period in August 2017.

I expect that scientists will be exploring Cassini’s data archive for decades, finding many things not noticed in their initial viewing. Unfortunately, we will not have another spacecraft taking new pictures in orbit around Saturn to compare with Cassini’s past images for many decades to come. On Saturday, we go blind.
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Pole of Saturn’s moon Enceladus shifted 55 degrees in the past

2:41 pm

Data from Cassini now suggests that the moon Enceladus shifted its pole as much as 55 degrees sometime in the past, possibly due to an impact.

Whether it was caused by an impact or some other process, Tajeddine and colleagues think the disruption and creation of the tiger-stripe terrain [at south pole] caused some of Enceladus’ mass to be redistributed, making the moon’s rotation unsteady and wobbly. The rotation would have eventually stabilized, likely taking more than a million years. By the time the rotation settled down, the north-south axis would have reoriented to pass through different points on the surface — a mechanism researchers call “true polar wander.”

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Water plumes on Europa plus hydrogen in Enceladus plumes

4:31 am

Scientists have detected more evidence of underground oceans on both Europa (orbiting Jupiter) and Enceladus (orbiting Saturn).

In the case of Europa, the Hubble Space Telescope has once again detected plumes of water ice being shot up from cracks in the moon’s surface. This second detection confirms the first from two years ago.

In the case of Enceladus, Cassini data has detected the presence of hydrogen in the plumes totaling 1% of the total material in the plumes.

The Europa story is significant, in that it confirms that the moon is still active geologically, and that the underground ocean is interacting with the outside world by ejecting material from it to the surface. This increases the odds that there will be some very intriguing chemistry in that ocean, including the possibility of organic life.

The Enceladus story puzzles me. We already know that the plumes there are made of water, which in itself is one third hydrogen. Why should anyone be surprised that a portion of that water gets split so that some of the hydrogen gets released as an atom instead of part of the water molecule. In fact, this discovery does not seem to me to be much of a discovery at all, but simply a confirmation that the plumes have the materials from the water ocean below the surface. That NASA has pushed it this week so hard in conjunction with their future Europa Clipper mission suggests that this part of the press story is really about lobbying for funds and has little to do with science.

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New model for Enceladus’s subsurface ocean

4:03 pm

A new model proposes that the subsurface liquid water ocean of Saturn’s moon Enceladus is possible only 3 miles below the surface near its south pole.

In order to reconcile the different constraints [created by the known data], the researchers propose a new model in which the top two hundred meters of the ice shell acts like an elastic shell. According to this study, Enceladus is made up successively of a rocky core with a radius of 185 km, and an internal ocean approximately 45 km deep, isolated from the surface by an ice shell with a mean thickness of around 20 km, except at the south pole where it is thought to be less than 5 km thick. In this model, the ocean beneath the ice makes up 40% of the total volume of the moon, while its salt content is estimated to be similar to that of Earth’s oceans.

Need I mention that this is only a computer model, and should therefore be considered with great skepticism?

Posted from warm and dry Tucson, Arizona, where I am home at last!

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The jets of Enceladus

9:09 am

Enceladus's jets

Cool image time! The image above, taken in June by Cassini, shows the night side of Saturn’s moon Enceladus, framed by Saturn’s rings, and faintly showing the jets of water coming from its south pole. To show it here I have cropped it and reduced it somewhat, as well as brightened the jets to make them more visible.

The release notes how the image compares the frozen water of Saturn’s rings and the liquid activity of Enceladus’s jets. I note how the image is simply beautiful. Be sure to click on the link to see the full resolution image.

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Enceladus rises over Dione

10:13 am

Enceladus rising behind Dione

Cool image time! The image on the right was taken by Cassini in September 2015, and shows two Saturn moons, bright Enceladus partly blocked by darker and nearer Dione.

Although Dione (near) and Enceladus (far) are composed of nearly the same materials, Enceladus has a considerably higher reflectivity than Dione. As a result, it appears brighter against the dark night sky.

The surface of Enceladus (313 miles or 504 kilometers across) endures a constant rain of ice grains from its south polar jets. As a result, its surface is more like fresh, bright, snow than Dione’s (698 miles or 1123 kilometers across) older, weathered surface. As clean, fresh surfaces are left exposed in space, they slowly gather dust and radiation damage and darken in a process known as “space weathering.”

The image doesn’t contain any earth-shattering discoveries. It is simply beautiful. And in these dark times, seeing beauty is sometimes the most important thing one can do.

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An Enceladus close look

11:28 pm

Enceladus at 77 miles

Cool image time! The image on the right is the first processed close-up image released from Cassini’s fly-by of Saturn’s moon Enceladus on Wednesday. The resolution is about 50 feet per pixel, taken from about 77 miles away. This surface, in the general area where Enceladus vents lie, reminds me of a thick field of snow that has begun to melt away.

Since the fly-by got within 30 miles, even higher resolution images should follow.

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Enceladus flyby images begin arriving

10:38 am

Enceladus

Cool image time! The first images from Cassini’s close flyby of Saturn’s moon Enceladus on Wednesday have started to arrive.

None have yet been processed, though the press release above provided a distant view of the moon’s plumes as the spacecraft approached. The image on the right, showing the moon itself, is one of the flyby I pulled off from the raw image website. Expect some interesting views to appear there throughout the day, with a more detailed press release tomorrow.

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Fractures on Enceladus’s north pole

6:02 pm

Enceladus's North Pole

The Cassini science team has released the first image from Wednesday’s flyby of the Saturn moon Enceladus.

Scientists expected the north polar region of Enceladus to be heavily cratered, based on low-resolution images from the Voyager mission, but the new high-resolution Cassini images show a landscape of stark contrasts. “The northern regions are crisscrossed by a spidery network of gossamer-thin cracks that slice through the craters,” said Paul Helfenstein, a member of the Cassini imaging team at Cornell University, Ithaca, New York. “These thin cracks are ubiquitous on Enceladus, and now we see that they extend across the northern terrains as well.”

To see more you can browse the raw images here.

The next flyby later this month will be especially interesting as they will dip to within 30 miles of the surface.

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Cassini’s last flybys of Enceladus

2:04 pm

As Cassini approaches the end of its decade-long mission at Saturn it will begin its last series of flybys of the moon Enceladus starting October 14.

Images will arrive a day or two afterward. The last two flybys will take place in late October and then in December, with the second October flyby getting closest, only 30 miles from the surface.

Beginning next year they will shift the spacecraft’s orbit so that it can get a better look at Saturn’s poles during its last two years. In that orbit flybys of the moons cannot be done.

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Giant global ocean inside Saturn’s moon Enceladus

1:53 pm

Using data from seven years of flybys by Cassini of Enceladus scientists now think they have confirmed the existence of a global ocean of liquid water beneath the moon’s icy crust.

Cassini scientists analyzed more than seven years’ worth of images of Enceladus taken by the spacecraft, which has been orbiting Saturn since mid-2004. They carefully mapped the positions of features on Enceladus — mostly craters — across hundreds of images, in order to measure changes in the moon’s rotation with extreme precision. As a result, they found Enceladus has a tiny, but measurable wobble as it orbits Saturn. Because the icy moon is not perfectly spherical — and because it goes slightly faster and slower during different portions of its orbit around Saturn — the giant planet subtly rocks Enceladus back and forth as it rotates.

The team plugged their measurement of the wobble, called a libration, into different models for how Enceladus might be arranged on the inside, including ones in which the moon was frozen from surface to core. “If the surface and core were rigidly connected, the core would provide so much dead weight the wobble would be far smaller than we observe it to be,” said Matthew Tiscareno, a Cassini participating scientist at the SETI Institute, Mountain View, California, and a co-author of the paper. “This proves that there must be a global layer of liquid separating the surface from the core,” he said.

Previous data had suggested a lens-shaped ocean under the south pole. This new data suggests the ocean in global.

As always, the possibility of liquid water suggests the possibility of life. None has been found, but with water and energy it is certainly possible.

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Tiny grains from the interior ocean of Enceladus

5:16 pm

Using Cassini scientists have detected tiny grains of rock orbiting Saturn that they think were formed on the floor of the interior ocean of Enceladus and then spewed out its vents into space.

They believe that these silicon-rich grains originate on the seafloor of Enceladus, where hydrothermal processes are at work. On the seafloor, hot water at a temperature of at least 90 degrees Celsius dissolves minerals from the moon’s rocky interior. The origin of this energy is not well understood, but likely includes a combination of tidal heating as Enceladus orbits Saturn, radioactive decay in the core and chemical reactions.

As the hot water travels upward, it comes into contact with cooler water, causing the minerals to condense out and form nano-grains of ‘silica’ floating in the water. To avoid growing too large, these silica grains must spend a few months to several years at most rising from the seafloor to the surface of the ocean, before being incorporated into larger ice grains in the vents that connect the ocean to the surface of Enceladus. After being ejected into space via the moon’s geysers, the ice grains erode, liberating the tiny rocky inclusions subsequently detected by Cassini.

Additional data suggest that the interior of Enceladus is very porous, which means that interior ocean might not be one large bubble but a complex liquid-filled cave.

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Planet of geysers

2:54 pm

Using Cassini data assembled over the past seven years, scientists have now identified 101 distinct geysers erupting on the surface of the Saturn’s moon Enceladus.

Over a period of almost seven years, Cassini’s cameras surveyed the south polar terrain of the small moon, a unique geological basin renowned for its four prominent “tiger stripe” fractures and the geysers of tiny icy particles and water vapor first sighted there nearly 10 years ago. The result of the survey is a map of 101 geysers, each erupting from one of the tiger stripe fractures, and the discovery that individual geysers are coincident with small hot spots. These relationships pointed the way to the geysers’ origin.

The really important discovery here however is this:
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Is it snowing microbes on Enceladus?

8:22 pm

Is it snowing microbes on Enceladus?

“More than 90 jets of all sizes near Enceladus’s south pole are spraying water vapor, icy particles, and organic compounds all over the place,” says Carolyn Porco, an award-winning planetary scientist and leader of the Imaging Science team for NASA’s Cassini spacecraft. “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.”

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